Molecular sieve abstract
The present invention relates to novel calix pyrroles and a process
for synthesis of calix (4) pyrroles by reacting pyrrole with cyclic
or acyclic ketones in dichloro methane (DCM) solvent over molecular
sieve catalysts which provides an eco-friendly, more economical
and selective heterogeneous method.
Molecular sieve claims
1. Novel compounds of substituted calix(4) pyrroles namely tetraspiro
cycloheptyl calix (4) pyrrole , tetraspiro cyclooctyl calix (4)
pyrrole and tetraspiro (2-methyl cyclohexyl) calix(4) pyrrole as
shown in structural formulae 6a, 7a and 8a of the accompanying drawings,
for use in many industrial applications particularly in biological
applications.
2. Novel compounds as claimed in claim 1 wherein the compounds
having following properties. i) tetraspiro cycloheptyl calix (4)
pyrrole (6a): .sup.1HNMR (200 MHz, CDCl.sub.3): .delta.=1.45-1.72
(m, 32H, cycloheptyl), 1.94-2.12 (m,16H, Cycloheptyl), 5.83 (br,
d,8H, pyrrole-.beta.H), 6.78-6.88 (br,s,4H,NH),; HR-MS (EI) for
C.sub.44H.sub.60N.sub.4: calcd: 644.4817 found: 644.4752; ii) tetraspiro
cyclooctyl calix (4) pyrrole (7a), .sup.1HNMR (200 MHz, CDCl.sub.3):
.delta.=1.18-1.82 (m, 56H, cyclooctyl), 5.93 (br,d,8H, pyrrole-.beta.H),
6.91-6.99 (br,s,4H, pyrrole-NH); HR-MS (EI) for C.sub.48N.sub.68N.sub.4:
calcd; 700.5443 found: 700.5456; and iii) tetraspiro (2-methyl
cyclohexyl) calix(4)pyrrole (8a): HR-MS (EI) for C44H60N.sub.4:
calcd: 644.4817 found 644.4847.
3. A method for preparing substituted calix (4) pyrroles, said
method comprising reacting a pyrrole with a acyclic and cyclic ketones
over a mesoporus molecular sieve solid acid catalyst in presence
of a solvent, at reflux temperature of about 100.degree. C. for
period ranging from 10 to 72 hours, recovering the solid products
by filtration, washing with deionized water and drying in air and
calcined at 773K in air.
4. A method as claimed in claim 3 wherein, the catalyst is selected
from MCM-41 HZSM-5 (30), H.beta., HY and SAPO-5.
5. A method as claimed in claim 3 wherein, the amount of catalyst
used is ranging from 0.1 g to 1.0 g.
6. A method as claimed in claim 3 wherein, the catalysts used are
having the following surface area and pore size as given below.
14 Surface area Catalyst (m.sup.2/g) Pore size (.degree. A) MCM-41
980-1200 30-100 HY 525-625 6-8 HZSM-5 (30) 275-340 5-7.5 SAPO-5
175-240 6.5-8.4 H.beta. 600-680 5.5 .times. 6.6 to 7.5 .times. 8.5
7. A method as claimed in claim 3 wherein, the pore size and surface
area of the catalysts used in the reaction are given in the following
table.
15 Catalyst Surface area (m.sup.2/g) Pore size (.degree. A) HY
593 7.3 HZSM-5 (30) 310 5.6 SAPO-5 207 7.4 H.beta. 640 6.5 .times.
7.6
8. A method as claimed in claim 3 wherein, the solvent used for
refluxing is selected from dichloromethane, methanol, and acetonitrile.
9. A method as claimed in claim 3 wherein, the molar ratio of pyrrole
to ketone is selected in between 1:1 to 1:4.
10. A method as claimed in claim 3 wherein, the cycloketone is
selected from the group comprising cyclohexanone, cycloheptanone,
cyclopentanone and cyclooctanone.
11. A method as claimed in claim 3 wherein acyclic ketone is selected
from the group comprising methyl ethyl ketone and 3-pentanone.
12. A method as claimed in claim 3 wherein, acyclic products are
obtained using the catalyst HY.
13. A method as claimed in claim 3 wherein, major amounts of liner
products are obtained using catalyst HZSM-5 (30).
14. A method as claimed in claim 3 wherein, the yield of the calix
(4) pyrrole is up to 70%.
15. A method as claimed in claim 3 wherein, the selectivity of
the calix (4) pyrrole is up to 90%.
16. A method as claimed in claim 3 wherein, the calix (4) pyrrole
obtained are: i) octamethyl calix (4) pyrrole (1a); ii) Tetraethyl
Tetra methyl calix (4) pyrrole (2a); iii) octaethyl calix (4) pyrrole
(3a); iv) tetraspiro cyclohexyl calix (4) pyrrole (4a); v) tetraspiro
cyclopentyl calix (4) pyrrole (5a); vi) tetraspiro cycloheptyl calix
(4) pyrrole (6a), vii) tetraspiro cyclooctyl calix (4) pyrrole (7a);
viii) (2-methyl cyclohexyl) calix (4) pyrrole (8a) and ix) dimer,
trimer and tetramers of pyrroles
17. A method for preparing calix (4) pyrroles or tetraspiro calix
(4) pyrroles, said method comprising mixing a pyrrole with a acyclic
or cyclic ketones over a molecular sieve solid acid catalyst and
subjecting the mixture to microwave radiation for 3 to 10 minutes
and optionally, refluxing using a solvent for extracting the compounds.
18. A method as claimed in claim 17 wherein, the solvent used for
refluxing is selected from dichloromethane, methanol, and acetonitrile.
19. A method as claimed in claim 17 wherein, the molar ratio of
pyrrole to ketone is 1:1.
20. A method as claimed in claim 17 wherein, in the reaction of
equimolar ratio of pyrrole and cyclohexanone, dichloromethane is
used as a solvent for refluxing to obtain cyclic products.
21. A method as claimed in claim 17 wherein, the catalyst used
is mesoporus molecular sieve catalyst (MCM-41).
22. A method as claimed in claim 17 wherein, the mesoporus catalyst
used in the reaction is having surface area ranging between 980-1200
m.sup.2/g.
23. A method as claimed in claim 17 wherein, the mesoporus catalyst
used in the reaction is having pore size ranging between 30-100.degree.
A.
24. A method as claimed in claim 17 wherein, the microwave heating
is carried out for a period ranging from 2 minutes to 15 minutes,
more preferably 3 to 10 minutes.
25. A method as claimed in claim 17 wherein, the microwave radiation
level is at about 2450 MHz.
26. A method as claimed in claim 17 wherein, the acyclic ketone
used is acetone.
27. A method as claimed in claim 17 wherein, the cyclic ketone
used is cyclohexanone.
28. A method as claimed in claim 17 wherein, the preparation of
calix (4) pyrroles or tetraspiro calix (4) pyrroles is a solvent
free process.
29. A method as claimed in claim 17 wherein, the calix (4) pyrrole
obtained are: i) octamethyl calix (4) pyrrole (1a); ii) Tetraethyl
Tetra methyl calix (4) pyrrole (2a); iii) octaethyl calix (4) pyrrole
(3a); iv) tetraspiro cyclohexyl calix (4) pyrrole (4a); v) tetraspiro
cyclopentyl calix (4) pyrrole (5a); vi) tetraspiro cycloheptyl calix
(4) pyrrole (6a), vii) tetraspiro cyclooctyl calix (4) pyrrole (7a);
viii) (2-methyl cyclohexyl) calix (4) pyrrole (8a); and ix) dimer,
trimer and tetramers of pyrroles
Molecular sieve description
FIELD OF THE INVENTION
[0001] The present invention relates to novel calix (4) pyrroles
and preparation of calix (4) pyrroles over zeolite molecular sieves.
More particularly, this invention relates to a method for synthesis
of calix (4) pyrroles directly from pyrroles and ketones in an eco-friendly
zeolite catalyzed heterogeneous method with high yields.
[0002] This invention provides a non-corrosive eco-friendly process,
where the catalyst is recyclable and reused many times, no work
up procedure, no-wastage of the compounds (i.e. high atom selectivity),
simple sample extraction and high selectivity of products.
BACKGROUND AND PRIOR ART REFERENCES
[0003] Calix pyrroles represent a subset of class of macrocycles
that was previously termed as porphyrinogens. Porphyrinogens are
non-conjugated macrocyclic species composed of four pyrrole rings
linked to the position via sp.sup.3 hybridized carbon atoms. Porphyrinogens
that carry meso-hydrogen atoms are prone to oxidation to the corresponding
phorphyrins and renamed the term porphyrinogen as calixpyrrole due
to the analogues properties of calixarenes. Fully meso non-hydrogen
substituted phorphyrongens are generally stable crystalline materials.
The first such macrocycle, meso octamethyl calix (4) pyrrole was
reported over a century ago by Bayer (Ber. Disctz. Chem. Ger. 1886
19 2184) using condensation between acetone and pyrrole catalyzed
by HCl, however, the structure of the molecule was not elucidated.
This method was refined by Dennstedt and Zimmerman (Ber. Disctz.
Chem. Ger. 1887 20 850) by replacing the HCl with "chlorzink"
and heating the reaction. Chelintzev and Toronov synthesized calix
(4) pyrrole by the method of condensing acetone and pyrrole, methyl
ethyl ketone and pyrrole, methyl hexyl ketone and pyrrole and a
mixture of acetone and methyl ethyl ketone with pyrrole (J. Russ.
Phys. Chem. Soc. 1916 48 1197; Chem Abstr. 1917 11 1418). Further,
Chelintzev, Tronov and Kurmunov reported the production of calixpyrroles
by condensing cyclohexanone with pyrrole and a mixture of acetone
and cyclohexanone with pyrrole (J. Russ. Phys. Chem. Soc. 1916
48 1210). Rothenmund and Gage refined Dennstedt and Zimmermann's
method by replacing the acid catalyst with methane sulphonic acid
(J. Am. Chem. Soc. 1955 55 3740). In 1971 Brown, Iluichioson
and Mackinon (Can. J. of Chem. 1971 49 4017) repeated the synthesis
of mesotetracyclohexyl calixpyrrole and assigned a tetrameric macrocyclic
structure. J. M. Lehn and coworkers have synthesized meso-octa-3-chloro
propyl calix (4) pyrrole by an unpublished procedure and converted
into meso-octa-3-cyano propyl calix pyrrole (B. Dietrich, P. Viout
and J. M. Lehn in macrocyclic chemistry, VCH, Publishers, Weinhein
1993 pg82). The metal cation binding of deprotanated calix (4)
pyrrole macrocyclics has been studied by Floriani and co-workers
(Chem. Commun. 1996 1257). Floriani has developed a method for
expanding the pyrrole rings of metal bound deprotanated calix (4)
pyrroles forming calix (1) pyridino (3) pyrroles and calix (2) pyridino
(2) pyrroles (J. Am. Chem. Soc. 1995 117 2793). A further a prior
art method reports using pyrrole, a C.sub.4-C.sub.6 saturated acyclic
ketone and an acid containing vinyl groups are triple bonds to form
a polymerized resin (WO 93/13150). In this case, the resulting products
are undefined, since it appears to be unknown where the modifying
group is attached to the product. By making use of calixarenes as
templates P. A. Gale et al synthesized Calixarene-calix pyrrole
dimers (calixarene capped-calixpyrrole) and expanded calixpyrroles
(Tet Lett 37(44), 19967881) and also reported the synthesis of
calixpyridino pyrroles and calix pyridines from calixpyrroles (Chem
corn 1998 1). Macrocycles have unexpected properties that make
them particularly useful. Calixpyrroles bind anion and neutral molecular
species in solution and in the solid state in such an effective
and selective way the anions or neutral molecular species can be
separated from other anions and neutral molecular species. Further
the affinity a macrocycle has for a particular species can be `tuned`
by strategic choice of electron-donating or electron-withdrawing
peripheral substituents for the synthesis of macrocycles.
[0004] According to W.O.Pat.No. 97/37995 various types of calixpyrroles
was synthesized using different ketones including tetrahydrothiopyran-4-o-
ne, diphenylacetone, 10-nonadecanone, acetyl ferrocenes and chiral
calixpyrroles by using chiral ketones. And also reported the synthesis
of expanded calixpyrroles, where n>4 (i.e. Calix (5) pyrrole,
Calix (6) pyrrole, calix (8) pyrroles), calix pyridino pyrroles,
calix pyridines and their applications. Application of these properties
for removal of biological ions or neutral molecule species for medical
uses, removal of undesirable ions or neutral molecule species from
environmental sources provides only a few of the practical and important
uses.
[0005] These calix (4) pyrroles can be used in the dialysis of
bodily fluids. Examples of dialyzable substrates include, but are
not limited to phosphate containing molecules or halide waste (i.e.
diabetes or drug overdoses and kidney dialysis).
[0006] Clean technology is fast replacing the various processes,
which were once catalyzed by highly corrosive liquid acids, due
to the growing concern for the environment. In these eco-friendly
processes, solid acids which are highly selective and active with
strong proton donating sites distributed uniformly within the pores,
have been found to be an attracting replacement for the non-reusable,
hazardous liquid acids. Porous materials created by nature or by
synthetic have found great utility in all aspects of human activity.
The pore structure of solids is usually formed in the stages of
crystallization or subsequent treatment. Depending on their predominant
pore size, the solid materials are classified as microporous, mesoporous
and macroporous materials. The only class of porous materials possessing
rigorously uniform pore sizes is that of Zeolites and related molecular
sieves. Zeolites are uniform porous crystalline aluminosilicates
and their lattice is composed by TO.sub.4 tetrahedral (T=Al and
Si) linked by sharing the apical oxygen atoms (Breck D. W., Zeolite
molecular sieves: Structure, Chemistry and Use; Wiley and Sons;
London 1974). As Zeolites act as sieves at the molecular level,
these are considered as a subclass of molecular sieves. Zeolites
have a number of interesting physical and chemical properties. The
classes of phenomena that are of greatest practical importance are
the availability to sorb organic and inorganic substances, to act
as cation exchangers and to catalyze a wide variety of reactions.
But due to the smaller pore size of these molecular sieves restricted
their wide range applications, especially in case of larger molecules.
But this has been overcome by the report of Mesoporous molecular
sieves by Mobil researchers (C. T. Kresge, M. E. Leonowicz, W. J.
Roth, J. C. Vartuli and J. S. Beck, Nature 359 (1992) 710) in 1992.
These Mesoporous molecular sieve (MCM-41) has been opened a new
era in the zeolite catalysis. Till then many reports have been published
on the applications of this material for the catalytic activity
towards oxidation, acylation and alkylation. And support material
for enzymes, whole cell immobilization, and nano particles.
[0007] The previous processes have the disadvantage that (a) in
all the cases mineral acids used as catalysts which are highly corrosive,
(b) in all the cases inert atmosphere should be maintained, (c)
in all the cases tedious work-up procedure is present, such as neutralization
of acid etc, (c) separation and reusability of the catalyst is not
possible, (d) in some cases more than a single step is carried out
to get a particular calix pyrrole selectively, and (e) in some cases
dry conditions should be maintained in order to obtain the corresponding
compound.
[0008] Increasing the applications of these calix pyrroles demands
an eco-friendly, environmentally clean, economical and free handling
process. The present invention provides an eco-friendly process,
which can overcome all the above drawbacks.
OBJECTS OF THE INVENTION
[0009] The main object of the present invention is to provide calix
(4) pyrroles over zeolite molecular sieves, which is an eco-friendly
heterogeneous catalytic method.
[0010] Another object of the present invention is to provide a
process for the synthesis of novel calix (4) pyrroles such as tetraspirocycloheptyl
calix (4) pyrrole, tetraspirocyclooctyl calix (4) pyrrole and tetraspiro
(2-methylcyclohexyl) calix (4) pyrrole with sufficiently good yields.
[0011] Still another object of the present invention is to synthesize
calix (4) pyrroles over molecular sieve catalysts under microwave
irradiation, which is a solvent free reaction.
[0012] Yet another object is to provide a method wherein the kind
and composition of calix (4) pyrrole can be varied within limits
by a proper selection of catalyst.
[0013] Yet another object of this invention is to provide an efficient
and economical method for synthesizing calix (4) pyrroles from pyrrole
and ketones over solid acid catalysts.
SUMMARY OF THE INVENTION
[0014] The present invention relates to novel calix (4) pyrroles
and a process for synthesis of calix (4) pyrroles as shown in FIGS.
1 to 8 of the accompanying drawings, from corresponding pyrrole
and ketone over mesoporous molecular sieves. Macrocycles of the
present invention can be selectively synthesized by taking the different
pore sizes of the zeolites and by varying the reaction conditions.
DETAILED DESCRIPTION OF INVENTION
[0015] The present invention relates to novel calix (4) pyrroles
and a process for synthesis of calix (4) pyrroles over mesoporous
molecular sieves. The invention particularly relates to heterogeneous
eco-friendly methodology for the synthesis of calix (4) pyrroles
by using pyrrole and ketone in dichloromethane solvent. Specifically,
the present invention relates to the synthesis calix (4) pyrroles
from corresponding pyrrole and ketone over mesoporous (Mesoporous
molecular sieve) MCM-41 molecular sieves with a high yield and selectivity.
In an embodiment of the invention, the catalyst is selected from
MCM-41 HZSM-5 (30), H.beta., HY and SAPO-5.
[0016] In another embodiment of the invention, the catalysts MCM-41
HZSM-5(30), H.beta., HY and SAPO-5 are conventional zeolite catalysts.
[0017] In another embodiment of the invention, the amount of catalyst
used is ranging from 0.1 g to 1.0 g.
[0018] In still another embodiment of the invention, the solvent
used for refluxing is selected from dichloromethane, methanol, and
acetonitrile.
[0019] In yet another embodiment of the invention, the catalysts
used are having the following surface area and pore size as given
in the table below.
1 Catalyst Surface area (m.sup.2/g) Pore size (.ANG.) MCM-41 980-1200
30-100 HY 525-625 6-8 HZSM-5 (30) 275-340 5-7.5 SAPO-5 175-240 6.5-8.4
H.beta. 600-680 5.5 .times. 6.6 to 7.5 .times. 8.5
[0020] In yet another embodiment of the invention, the pore size
and surface area of the catalysts used in the reaction are given
in the following table.
2 Catalyst Surface area (m.sup.2/g) Pore size (.ANG.) HY 593 7.3
HZSM-5 (30) 310 5.6 SAPO-5 207 7.4 H.beta. 640 6.5 .times. 7.6
[0021] In yet another embodiment of the invention, the molar ratio
of pyrrole to ketone is selected in between 1:1 to 1:4.
[0022] In yet another embodiment of the invention, the cycloketone
is selected from the group comprising cyclohexanone, cycloheptanone,
cyclopentanone and cyclooctanone.
[0023] In yet another embodiment of the invention, the acyclic
ketone is selected from the group comprising methyl ethyl ketone
and 3-pentanone.
[0024] In yet another embodiment of the invention, acyclic products
are obtained using the catalyst HY.
[0025] In yet another embodiment of the invention, major amounts
of liner products are obtained using catalyst HZSM-5 (30).
[0026] In yet another embodiment of the invention, the yield of
the calix (4) pyrrole is up to 70%.
[0027] In yet another embodiment of the invention, the selectivity
of the calix (4) pyrrole is up to 90%.
[0028] In one more embodiment of preparing calix (4) pyrroles or
tetraspiro calix (4) pyrroles, said method comprising mixing a pyrrole
with a acyclic or cyclic ketones over a molecular sieve solid acid
catalyst and subjecting the mixture to microwave radiation at a
radiation level of about 2450 MHz (Hl power) for 3 to 10 minutes
and optionally, refluxing using a solvent for extracting the compounds.
[0029] In another embodiment, the solvent used for refluxing is
selected from dichloromethane, methanol, and acetonitrile.
[0030] In yet another embodiment of the present invention, in the
equimolar reaction, the molar ratio of pyrrole to ketone is 1:1
and dichloromethane is used as a solvent for refluxing to obtain
cyclic products.
[0031] In yet another embodiment, the catalyst used is mesoporus
molecular sieve catalyst (MCM-41).
[0032] In yet another embodiment, the acyclic ketone used is acetone.
[0033] In yet another embodiment, the cyclic ketone used is cyclohexanone.
[0034] In yet another embodiment, the preparation of calix (4)
pyrroles or tetraspiro calix (4) pyrroles is a solvent free process.
[0035] The catalyst can be synthesized from the well known defined
methods. The starting materials used in the process are acyclic
and cyclic ketones, which are readily available. Reacting the pyrrole
with acyclic ketones, which are selected from acetone, methyl ethyl
ketone, and 3-pentanone leads to form octamethyl calix (4) pyrrole,
tetramethyl tetraethyl calix (4) pyrrole, and octaethylcalix (4)
pyrroles correspondingly.
[0036] In case of cyclic ketones, cyclohexanone, cyclopentanone,
cycloheptanone, 2-methylcyclochexanone, cyclo octanone forms tetraspirocyclochexyl
calix (4) pyrrole, tetraspirocyclopentyl calix (4) pyrrole, tetraspirocycloheptyl
calix (4) pyrrole, tetraspiro (2-methylcyclohexyl) calix (4) pyrrole
and tetraspirocyclooctyl calix (4) pyrrole correspondingly.
[0037] The catalyst MCM-41 (Mesoporous molecular sieve) prepared
by an aqueous solution of aluminum isopropoxide (0.38 g) and to
it an aqueous solution of sodium hydroxide (0.3 g) was added in
50 ml beaker and stirred in hot conditions, till a clear solution
was formed. Then 9.4 ml of tetraethyl ammonium hydroxide (TEAOH)
and Ludox colloidal silica (9.26 g) were added drop wise while stirring
at room temperature. Then hexadecyl tri-methylammonium bromide (10.55
g) was added slowly to the above solution. The pH of the mixture
was maintained at 11.0-11.5. Finally, the gel mixture was transferred
into an autoclave and heated at 100.degree. C. for 24 h. The solid
product was recovered by filtration, washed with deionized water
and dried in air. All the as-synthesized samples were calcined at
773K in air.
[0038] The catalyst weight can be varied in this reaction from
0.1 g to 1 g. The pyrrole to acetone molar ratio can be varied from
1:1 to 1:4.
[0039] In the reaction, an equimolar ratio of pyrrole and cyclohexanone
was refluxed in dichloromethane (DCM) for 10 h in presence of MCM-41
catalyst. Along with the cyclized product, tetraspirocyclo hexyl
calix (4) pyrrole 4a, the acyclic condensed products viz., dimer,
trimer and tetramer (4b, 4c and 4d) were also formed.
[0040] In place of MCM-41catalyst when HY was used, instead of
cyclic product only the acyclic products were formed.
[0041] When HZSM-5 (30) was used as catalyst, along with the cyclized
product calix (4) pyrrole, linear products also formed but the linear
products are in major.
[0042] When H.beta. was used as catalyst, along with the cyclized
product calix (4) pyrrole, linear products are also formed.
[0043] The reaction time will be varied depending upon the nature
of ketone and the catalyst. In the one of equimolar reaction, pyrrole
and acetone was mixed thoroughly and 0.5 gm of MCM-41 catalyst was
added and then subjected to microwave irradiation for 3 min at a
radiation level of about 2450 MHz and extract the compound by using
dichloromethane as solvent, resulting low selectivity of cyclic
product (1a). The reaction time is varied from 3 min to 10 min.
[0044] In another equimolar reaction, pyrrole and cyclohexanone
was mixed thoroughly and added 0.5 gm of MCM-41 catalyst and then
subjected to microwave irradiation for 3 min and extracted the compound
by using dichloromethane as solvent, resulting low selectivity of
cyclic product (4a). The reaction time is varied from 3 min to 10
min. The radiation level is maintained at about 2450 MHz.
[0045] Mixed calix pyrroles such as tetramethyl dicyclohexyl calix
(4) pyrrole, hexamethyl cyclohexyl calix (4) pyrrole, dimethyl tri
cyclohexyl calix (4) pyrrole has been obtained by reacting the acetone,
cyclohexanone in required molar ratio over MCM-41 catalyst in dicholoromethane
solvent by refluxing for 15 h.
[0046] Pore size and surface area of the catalysts plays a major
role in this reaction.
[0047] All the catalysts were characterized by X-ray diffraction,
Infrared spectroscopy, BET-surface area and NH.sub.3-Temperature
programmed desorption.
[0048] The inventors found that the dichloromethane (DCM) was better
solvent than other solvents like methanol, acetonitrile. Acetone
as solvent did not found the selectivity towards higher selectivity
of octamethyl calix (4) pyrrole.
[0049] After the reaction was completed the catalyst was separated
by filtration, then the solvent was vacuum evaporated and the residue
was mounted on the silica column and the products were separated
through n-hexane: ethylacetate (95:5) media and confirmed by H.sup.1
NMR, C.sup.13 NMR and Mass spectroscopy and for 1a, single crystal
XRD also.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[0050] FIG. 1 shows structure of octa alkyl substituted calix (4)
pyrrole, wherein
[0051] R.sub.1 and R.sub.2=CH.sub.3 for octamethyl calix (4) pyrrole
(1a),
[0052] R.sub.1=CH.sub.3 and R.sub.2=CH.sub.2CH.sub.3 for Tetraethyl
Tetra methyl calix (4) pyrrole (2a), and
[0053] R.sub.1=R.sub.2=CH.sub.2CH.sub.3 for octaethyl calix (4)
pyrrole (3a).
[0054] FIG. 2 shows structure of tetraspiro cyclohexyl calix (4)
pyrrole (4a).
[0055] FIG. 3 shows structure of tetraspiro cycloalkyl substituted
calix (4) pyrrole
[0056] wherein,
[0057] n=1 for tetraspiro cyclopentyl calix (4) pyrrole (5a),
[0058] n=2 for tetraspiro cycloheptyl calix (4) pyrrole (6a), and
[0059] n=4 for tetraspiro cyclooctyl calix (4) pyrrole (7a).
[0060] FIG. 4 shows structure of (2-methyl cyclohexyl) calix (4)
pyrrole (8a).
[0061] FIG. 5 shows structures of condensed products viz. dimer
(4b), trimer (4c) and tetrameter (4d).
[0062] FIG. 6 shows structure of alkyl substituted linear (dimer)
products, wherein
[0063] R.sub.1 and R.sub.2=CH.sub.3 for 1a, R.sub.1=CH.sub.3 and
R.sub.2=CH.sub.2CH.sub.3 for 2a, and
[0064] R.sub.1=R.sub.2=CH.sub.2CH.sub.3 for 3a.
[0065] FIG. 7 shows structure of cyclic products, wherein n=1 for
5b; n=3 for 6b and n=4 for 7b.
[0066] FIG. 8 shows structure of dimer product of 2-methylcyclohexyl
(8b).
[0067] The process of this invention is described in further detail
herein below by way of the following examples, which are only illustrative
and are not intended to limit the scope of this invention.
EXAMPLES
Example 1
[0068] Synthesis of Octamethyl Calix (4) Pyrrole
[0069] In a 50 ml round bottom flask, 20 ml of dichloromethane
(DCM) was introduced and 0.5 ml of pyrrole, 0.503 ml of acetone,
and 0.5 g of MCM-41 catalyst were added to it. Then the reaction
mixture was refluxed for 10 h. The cooled reaction mixture filtered,
washed with DCM (5.times.10 ml). Then the solvent DCM was removed
under reduced pressure and product was purified by column chromatography
on silicagel (hexane eluent) affording the product as a white powder.
The product was confirmed by NMR and Mass spectrometry. Yield of
octamethyl calix (4) pyrrole was 67.5%; Selectivity was 73.0; Conversion
of pyrrole was 92.4%. Selectivity was calculated as follows
Selectivity=Yield/Conversion
[0070] 1a: .sup.1HNMR (200 MHz, CDCl.sub.3): .delta.=1.49 (s, 24H,
--CH.sub.3), 5.85 (br, d, 8H; (pyrrole-.beta.H), 6.89-6.99 (br,
S, 4H, pyrrole-NH); HR-MS(EI): for calcd for C.sub.28 H.sub.36 N.sub.4:
calcd: 428.2939; found: 428.2938.
Example 2
[0071] In a 50 ml round bottom flask 20 ml of dichloromethane (DCM)
was introduced and 0.5 ml of pyrrole, 0.503 ml of acetone, and 0.5
g of HZSM-5 (30) catalyst were added to it. Then the mixture was
refluxed for 10 h. The cooled reaction mixture filtered, washed
with DCM (5.times.10 ml). Then the solvent DCM was removed under
reduced pressure and product was purified by column chromatography
on silicagel (hexane eluent) the products were confirmed by NMR
and estimation was done by high pressure thin layer chromatography
(HPTLC). The Results are as follows: Conversion of pyrrole is 81.4%.
3 Product Yield (wt %) Selectivity (%) Octamethyl calix(4)pyrrole
(1a) 40.0 49.2 Trimer + tetramer 29.8 36.6 Dimer (1b) 11.56 14.2
Example 3
[0072] In a 50 ml round bottom flask 20 ml of dichloromethane (DCM)
was introduced and 0.5 ml of pyrrole, 0.503 ml of acetone, and 0.5
g of HY catalyst was added to it. Then the mixture was refluxed
for 10 h. The cooled reaction mixture filtered, washed with DCM
(5.times.10 ml). Then the solvent DCM was removed under reduced
pressure and product was purified by column chromatography on silicagel
(hexane eluent) the products were confirmed by NMR and estimation
was done by high pressure thin layer chromatography (HPTLC). The
results as follows: conversion of pyrrole is 72.5%.
4 Product Yield (wt %) Selectivity (%) Octamethyl Calix(4)pyrrole
Trimer + tetramer 14.0 19.3 Dimer 58.5 80.7
[0073] 1b: .sup.1HNMR (200 MHz, CDCl.sub.3): .delta.=1.62 (s, 6H,
--CH.sub.3), 6.01-6.11 (m, 4H, pyrrole-.beta.H), 6.48-6.56 (m, 2H,
pyrrole-.alpha.H), 7.42-7.78 9br, s, 2H, NH), .sup.13C NMR (50 MHz,
CDCl.sub.3): .delta.=29.30 35.32 103.74 107.72 117.03 138.21;
HR-MS (EI) for C.sub.11H.sub.14N.sub.2: calcd: 174.1156; found:
174.1148
Example 4
[0074] Synthesis of Tetramethyl Tetraethyl Calix (4) Pyrrole
[0075] In a 50 ml round bottom flask 20 ml of dichloromethane (DCM)
was introduced and 0.5 ml of pyrrole, 0.65 ml of Methyl ethyl ketone,
and 0.5 g of Al-MCM-41 catalyst was added to it. Then the mixture
was refluxed for 72 h. The cooled reaction mixture filtered, washed
with DCM (5.times.10 ml). Then the solvent DCM was removed under
reduced pressure and product was purified by column chromatography
on silicagel (hexane eluent) the products were confirmed by NMR
and estimation was done by high pressure thin layer chromatography
(HPTLC). The results as follows: conversion of pyrrole is 48.0%.
5 Product Yield (wt %) Selectivity (%) Tetraethyl tetramethyl calix(4)pyrrole
(2a) 34.8 72.5 Trimer + tetramer 4.5 9.4 Dimer (2b) 8.7 18.1
[0076] 2a: .sup.1HNMR (200 MHz, CDCl.sub.3): .delta.=0.63-0.8 (t,
J(H,H)=2 Hz, 12H), 1.34-1.48 (br, s, 12H, -CH.sub.3 1.86-1.96 (q,
8H, CH.sub.2CH.sub.3), 5.85 (br, d, 8H), 6.89-7.09 (br, s, 4H, NH);
.sup.13C NMR (50 MHz, CDCl.sub.3): 137.26 103.75 39.18 33.21
26.04 8.65; HR-MS (EI) for C.sub.32H.sub.44N.sub.4: calcd: 484.3565
found: 484.3561.
[0077] 2b: .sup.1HNMR (200 MHz, CDCl.sub.3): .delta.=0.72-0.85
(t, J=8.37 3H. --CH.sub.2CH.sub.3), 1.53 (s, 3H, -CH.sub.3), 1.92-2.06
(q, J=4.65 6.97 Hz, 2H, --CH.sub.2CH.sub.3), 6.0-6.10 (m, 4H, pyrrole-.beta.H),
6.50-6.58 (m, 2H,pyrrole-.alpha.H), 7.6 (BR, S, 2H, pyrrole-NH).
.sup.13C NMR: 138.04 116.29 107.61 104.66 39.35 33.63 25.57
8.91; HR-MS (EI) for C.sub.12H.sub.16N.sub.2: calcd: 188.1313 found:
188.1317.
Example 5
[0078] Synthesis of Octaethyl Calix (4) Pyrrole
[0079] In a 50 ml round bottom flask 20 ml of dichloromethane (DCM)
was introduced and 0.5 ml of pyrrole, 0.73 ml of 3-Pentanone, and
0.5 g of Al-MCM-41 catalyst was added to it. Then the mixture was
refluxed for 5 days. The cooled reaction mixture filtered, washed
with DCM (5.times.10 ml). Then the solvent DCM was removed under
reduced pressure and product was purified by column chromatography
on silicagel (hexane eluent) the products were confirmed by NMR
and estimation was done by high pressure thin layer chromatography
(HPTLC). The results as follows: conversion of pyrrole is 77.0%.
6 Product Yield (wt %) Selectivity (%) Octaethyl calix(4)pyrrole
(3a) 10.1 13.1 Trimer + tetramer 4.8 6.2 Dimer (3b) 62.1 80.7
[0080] 3a: .sup.1HNMR (200 MHz, CDCl.sub.3): .delta.=5.85-5.93
(br, d, J (H,H)=2.27 Hz, 8H, pyrrole-.beta.H), 6.96-7.05 (br, s,
4H, pyrrole-NH); HR-MS (EI) for C.sub.36H.sub.52N.sub.4: calcd:
540.4191 found: 540.4194.
[0081] 3b: .sup.1HNMR (200 MHz, CDCl.sub.3): .delta.=0.68-0.76
(t, J=7.17 6H, CH.sub.2CH.sub.3), 1.88-2.01 (q, J=5.12 7.69 Hz,
4H, CH.sub.2CH.sub.3), 6.01-6.12 (br, s, 4H, pyrrole-.beta.H), 6.5-6.59
(br, s, 2H), 7.45-7.65 (br, s, 2H, pyrrole-NH); HR-MS (EI) for C.sub.13H.sub.19N.sub.2:
calcd: 202.1469 found: 202.1475.
Example 6
[0082] Synthesis of Tetraspiro Cyclohexyl Calix (4) Pyrrole
[0083] In a 50 ml round bottom flask 20 ml of dichloromethane (DCM)
was introduced and 0.5 ml of pyrrole, 0.75 ml of Cyclohexanone,
and 0.5 g of calcined and dried Al-MCM-41 catalyst was added to
it. Then the mixture was refluxed for 10 h The cooled reaction mixture
filtered, washed with DCM (5.times.10 ml). Then the solvent DCM
was removed under reduced pressure and product was purified by column
chromatography on silicagel (hexane eluent) the products were confirmed
by NMR and estimation was done by high pressure thin layer chromatography
(HPTLC). The results as follows: conversion of pyrrole is 95.0%.
7 Product Yield (wt %) Selectivity (%) Tetraspirocyclohexyl 70.3
74.0 calix(4)pyrrole (4a) Trimer + tetramer 12.4 13.0 Dimer (4b)
12.3 13.0
[0084] 4a: .sup.1H NMR (200 MHz, CDCl.sub.3): .delta.=1.38-1.68(m,24H,
cyclohexyl), 1.88-2.12(m,16H, cyclohexyl), 5.86 (br.d, 8H; pyrrole-.beta.H),
6.95 (br.s, 4H, pyrrole NH), .sup.13C NMR (50 MHz,CDCl.sub.3): .delta.=22.75
26.04 37.17 39.63 103.44 (pyrrole-.beta.H), 136.50(pyrrole-.alpha.H);
HR-MS(EI) for C.sub.40H.sub.52N.sub.4 (H.sup.+): calcd: 588.4191;
found: 588.4169.
Example 7
[0085] In a 50 ml round bottom flask 20 ml of dichloromethane (DCM)
was introduced and 0.5 ml of pyrrole, 0.75 ml of Cyclohexanone,
and 0.5 g of HZSM-5 (30) catalyst was added to it. Then the mixture
was refluxed for 10 h. The cooled reaction mixture filtered, washed
with DCM (5.times.10 ml). Then the solvent DCM was removed under
reduced pressure and product was purified by column chromatography
on silicagel (hexane eluent) the products were confirmed by NMR
and estimation was done by high pressure thin layer chromatography
(HPTLC). The results as follows: Conversion of pyrrole is 69.6%.
8 Product Yield (wt %) Selectivity (%) Tetraspirocyclohexyl 10.7
15.4 Calix(4)pyrrole Trimer + tetramer 5.9 8.5 Dimer 53.0 76.1
Example 8
[0086] In a 50 ml round bottom flask 20 ml of dichloromethane (DCM)
was introduced and 0.5 ml of pyrrole, 0.75 ml of Cyclohexanone,
and 0.5 g of HY catalyst was added to it. Then the mixture was refluxed
for 10 h. The cooled reaction mixture filtered, washed with DCM
(5.times.10 ml). Then the solvent DCM was removed under reduced
pressure and product was purified by column chromatography on silicagel
(hexane eluent) the products were confirmed by NMR and estimation
was done by high pressure thin layer chromatography (HPTLC). The
results as follows: conversion of pyrrole is 78.9%.
9 Product Yield (wt %) Selectivity (%) Tetraspirocyclohexylcalix
(4) pyrrole Trimer + tetramer 16.2 20.5 Dimer 62.7 79.5
[0087] 4b: .sup.1H NMR (200 MHz, CDCl.sub.3): .delta.=1.36-1.65(m,6H,
cyclohexyl),95-2.12(m,4H,cyclohexyl),6.01-6.12(m,4H,pyrrole-.beta.H),
6.45(br.d, 2H; pyrrole-.alpha.H), 7.32-7.68 (br.s, 2H, pyrrole NH);
.sup.13C NMR(50 MHz,CDCl.sub.3):.delta.=22.1726.3237.65 41.21
104.64 108.27116.99139.21; HR-MS(EI) for C.sub.14H.sub.18N.sub.2
(H.sup.+): calcd: 214.1469; found: 214.1460.M+: 214(100%), 171148
[0088] 4d: HR-MS (EI) for C H N: calcd: 508.3546; found=508.3565
Example 9
[0089] Synthesis of Tetraspiro Cyclopentyl Calix (4) Pyrrole
[0090] In a 50 ml round bottom flask 20 ml of dichloromethane (DCM)
was introduced and 0.5 ml of pyrrole, 0.64 ml of Cyclopentanone,
and 0.5 g of Al-MCM-41 catalyst was added to it. Then the mixture
was refluxed for 20 h. The cooled reaction mixture filtered, washed
with DCM (5.times.10 ml). Then the solvent DCM was removed under
reduced pressure and product was purified by column chromatography
on silicagel (hexane eluent) the products were confirmed by NMR
and estimation was done by high pressure thin layer chromatography
(HPTLC). The results as follows: conversion of pyrrole is 74.3%.
10 Product Yield (wt %) Selectivity (%) Tetraspiro cyclopentyl
62.7 84.4 calix(4)pyrrole (5a) Trimer + tetramer 7.3 9.8 Dimer 4.3
5.8
[0091] 5a: .sup.1HNMR (200 MHz, CDCl.sub.3): .delta.=1.55-1.8 (m,
16H, cyclopentyl), 1.85-2.01 (m, 16H, cyclopentyl), 5.8 (br, d,
J=0.38 Hz, 8H, pyrrole-.beta.H),7.0 (br, s, 4H, pyrrole-NH); .sup.13C
NMR: (50 MHz, CDCl.sub.3): 137.20 (pyrrole-.alpha.H), 103.04 (pyrrole-.beta.H),
46.93 39.02 23.91; HR-MS (EI) for C.sub.36H.sub.44N.sub.4: calcd:
532.3565 found: 532.6575.
Example 10
[0092] Synthesis of Tetraspiro Cycloheptyl Calix (4) Pyrrole
[0093] In a 50 ml round bottom flask 20 ml of dichloromethane (DCM)
was introduced and 0.5 ml of pyrrole, 0.85 ml of Cycloheptanone,
and 0.5 g of Al-MCM-41 catalyst was added to it. Then the mixture
was refluxed for 3 days. The cooled reaction mixture filtered, washed
with DCM (5.times.10 ml). Then the solvent DCM was removed under
reduced pressure and product was purified by column chromatography
on silicagel (hexane eluent) the products were confirmed by NMR
and estimation was done by high pressure thin layer chromatography
(HPTLC). The results as follows: conversion of pyrrole is 69.8%.
11 Product Yield (wt %) Selectivity (%) Tetraspiro cycloheptyl
26.7 38.3 calix(4)pyrrole (6a) Trimer + tetramer 15.7 22.5 Dimer
(6b) 27.4 39.2 6a: .sup.1HNMR (200 MHz, CDCl.sub.3): .delta. = 1.45-1.75
(m, 32H cycloheptyl), 1.94-2.12 (m, 16H, Cycloheptyl), 5.83 (br,
d, 8H, pyrrole-.beta.H), 6.78-6.88 (br, s, 4H, NH),; HR-MS (EI)
for C.sub.44H.sub.60N.sub.4: calcd: 644.4817 found: 644.4752. 6b:
.sup.1HNMR (200 MHz, CDCl.sub.3): .delta. = 2.12-2.26 (m, 8H, cycloheptyl),
2.42-2.58 (m, 4H, cycloheptyl), 6.01-6.13 (m, 4H, pyrrole-.beta.H),
6.52-6.61 (m, 2H, pyrrole-.alpha.H), 7.51-7.71 (br, s, 2H, pyrrole-NH);
HR-MS (EI) for C.sub.15H.sub.20N.sub.2: calcd: 228.1626 found:
228.1616.
[0094] 6a: .sup.1HNMR (200 MHz, CDCl.sub.3): .delta.=1.45-1.72
(m, 32H, cycloheptyl), 1.94-2.12 (m,16H, Cycloheptyl), 5.83 (br,
d,8H, pyrrole-.beta.H), 6.78-6.88 (br,s,4H,NH),; HR-MS (EI) for
C44H.sub.60N.sub.4: calcd: 644.4817 found: 644.4752.
[0095] 6b: .sup.1HNMR (200 MHz, CDCl.sub.3): .delta.=2.12-2.26(m,8H,cycloh-
eptyl), 2.42-2.58 (m,4H, cycloheptyl), 6.01-6.13 (m, 4H,pyrrole-.beta.H),
6.52-6.61 (m,2H, pyrrole-.alpha.H),7.51-7.71 (br,s,2H, pyrrole-NH);
HR-MS (EI) for C.sub.15H.sub.20N.sub.2: calcd: 228.1626 found 228.1616.
Example 11
[0096] Synthesis of Tetraspiro Cyclo Octyl Calix (4) Pyrrole
[0097] In a 50 ml round bottom flask 20 ml of dichloromethane (DCM)
was introduced and 0.5 ml of pyrrole, 0.9 ml of Cyclooctanone, and
0.5 g of Al-MCM-41 catalyst was added to it. Then the mixture was
refluxed for 5days. The cooled reaction mixture filtered, washed
with DCM (5.times.10 ml). Then the solvent DCM was removed under
reduced pressure and product was purified by column chromatography
on silicagel (hexane eluent) the products were confirmed by NMR
and estimation was done by high pressure thin layer chromatography
(HPTLC). The results as follows: conversion of pyrrole is 78.0%.
12 Product Yield (wt %) Selectivity (%) Tetraspiro cyclooctyl 8.3
10.6 calix(4)pyrrole (7a) Trimer + tetramer 23.7 30.4 Dimer (7b)
46.0 59.0 7a: .sup.1HNMR (200 MHz, CDCl.sub.3): .delta. = 1.18-1.82
(m, 56H cyclooctyl), 5.93 (br, d, 8H, pyrrole-.beta.H), 6.91-6.99
(br, s, 4H, pyrrole-NH); HR-MS (EI) for C.sub.48N.sub.68N.sub.4:
calcd; 700.5443 found: 700.5456. 7b: .sup.1HNMR (200 MHz, CDCl.sub.3):
.delta. = 1.42-1.80 (m, 10H, cyclooctyl), 2.09-2.21 (m, 4H, cyclooctyl),
5.99-6.16 (m, 4H, pyrrole-.beta.H), 6.48-6.57 (m, 2H, pyrrole-.alpha.H),
7.42-7.69 (br, s, 2H, pyrrole-NH),; HR-MS (EI) for C.sub.16N.sub.22N.sub.2:
calcd: 242.1782 found: 242.1777.
[0098] 7a: .sup.1HNMR (200 MHz, CDCl.sub.3): .delta.=1.18-1.82
(m, 56H, cyclooctyl), 5.93 (br,d,8H, pyrrole-.beta.H), 6.91-6.99
(br,s,4H, pyrrole-NH); HR-MS (EI) for C.sub.48N.sub.68N.sub.4: calcd;
700.5443 found: 700.5456.
[0099] 7b: .sup.1HNMR (200 MHz, CDCl.sub.3): .delta.=1.42-1.80(m,10H,
cyclooctyl), 2.09-2.21(m,4H, cyclooctyl), 5.99-6.16 (m,4H,pyrrole-.beta.H),
6.48-6.57 (m,2H,pyrrole-.alpha.H),7.42-7.69(br,s,- 2H,pyrrole-NH),;
HR-MS(EI) for C.sub.16N.sub.22N.sub.2: calcd: 242.1782 found: 242.1777.
Example 12
[0100] Synthesis of Tetraspiro (2-Methylcyclohexyl) Calix (4) Pyrrole
[0101] In a 50 ml round bottom flask 20 ml of dichloromethane (DCM)
was introduced and 0.5 ml of pyrrole, 0.875 ml of 2-Methyl cyclohexanone,
and 0.5 g of Al -MCM-41 catalyst was added to it. Then the mixture
was refluxed for 10 h. The cooled reaction mixture filtered, washed
with DCM (5.times.10 ml). Then the solvent DCM was removed under
reduced pressure and product was purified by column chromatography
on silicagel (hexane eluent) the products were confirmed by NMR
and estimation was done by high pressure thin layer chromatography
(HPTLC). The results as follows: conversion of pyrrole is 60.2%.
13 Product Yield (wt %) Selectivity (%) Tetraspiro 5.1 8.5 (2-methylcyclohexyl)
calix(4)pyrrole (8a) Trimer + tetramer 21.3 35.4 Dimer (8b) 33.8
56.1 8a: HR-MS (EI) for C.sub.44H.sub.60N.sub.4: calcd: 644.4817
found 644.4847. 8b: .sup.1HNMR (200 MHz, CDCl.sub.3): .delta. =
0.8 (d, 3H, J(H,H) = 7.2 Hz, CH.sub.3), 1.24-2.34 (m, 9H, cyclohexyl),
6.01-6.14 (m, 4H, pyrrole-.beta.H), 6.42-6.54 (m, 2H, pyrrole-.alpha.H),
748 (br, s, 2H, pyrrole-NH); HR-MS (EI) for C.sub.15H.sub.20N.sub.2:
calcd: 228.1626 found: 228.1634.
[0102] 8a: HR-MS (EI) for C.sub.44H.sub.60N.sub.4: calcd: 644.4817
found 644.4847.
[0103] 8b: .sup.1HNMR (200 MHz, CDCl.sub.3): .delta.=0.8(d,3H,J(H,H)=7.2
Hz,CH.sub.3), 1.24-2.34(m,9H,cyclohexyl), 6.01-6.14 (m,4H,pyrrole-.beta.H),
6.42-6.54 (m,2H,pyrrole-.alpha.H),7.48(br,s,2H,py- rrole-NH); HR-MS
(EI) for C.sub.15H.sub.20N.sub.2: calcd: 228.1626 found: 228.1634.
[0104] The Main Advantages of the Present Invention Are:
[0105] 1. The present invention is an improved process that comprises
environmentally clean technology with low wastage, easy separable
and reusability of the catalyst.
[0106] 2. This method provides a selective heterogeneous catalyst
with longer life.
[0107] 3. The catalysts used in this process are easily separable
by the simple filtration
[0108] 4. It also provides a method wherein the kind and composition
of calix (4) pyrrole can be varied within limits by a proper selection
of catalyst.
[0109] 5. Tetraspirocyclopentyl calix (4) pyrrole has been synthesized
for the first time over the heterogeneous method as well as homogeneous
method.
[0110] 6. Tetraspirocycloheptyl calix (4) pyrrole has been synthesized
for the first time over the heterogeneous method as well as homogeneous
method.
[0111] 7. Tetraspirocyclooctyl calix (4) pyrrole has been synthesized
for the first time over the heterogeneous method as well as homogeneous
method.
[0112] 8. Tetraspiro (2-Methylcyclohexyl) calix (4) pyrrole has
been synthesized for the first time over the heterogeneous method
as well as homogeneous method.
[0113] The Salient Futures of the Process are
[0114] i) the present invention provides an improved process that
comprises environmentally clean technology with low wastage, easy
separable and reusability of the catalyst,
[0115] ii) the catalysts used in this process are easily separable
by the simple filtration,
[0116] iii) this process provides an eco-friendly method with higher
selectivity,
[0117] iv) a method provides a selective heterogeneous catalyst
with longer life, and
[0118] v) a method wherein the kind and composition of calix(4)pyrrole
can be varied within limits by a proper selection of catalyst and
this invention provides an efficient and economical method for synthesizing
calix(4)pyrroles from pyrrole and ketones over solid acid catalysts.
|