Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2001-03-27
2002-12-10
Seaman, D. Margaret (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C546S350000, C546S352000
Reexamination Certificate
active
06492524
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for the synthesis of an aryl pyridine base using a zeolite catalyst. More particularly, the present invention relates to a method for synthesizing phenyl pyridines directly from acetophenone and allyl alcohol in an eco-friendly, zeolite catalyzed heterogeneous method with high yields and selectivity. This invention provides a non-corrosive, eco-friendly process, where the life time of the catalyst is longer, it can be recycled and reused for many times, no-wastage of compounds (i.e. high atom selectivity) and high selectivity of the products.
BACKGROUND OF THE INVENTION
Phenyl pyridines have emerged as the integral backbone of several potent azapeptide HIV protease inhibitors with anti HIV activity such as BMS-232632a. Strategies for the synthesis of these phenyl pyridines by condensation and substitution reactions frequently afford low yields and cannot facilitate the synthesis of the 2-position selectively. A few homogeneous catalysts like Rh(1) have been reported for use in the selective alkylation of phenyl pyridine with olefins.
Zeolites of ZSM series are available from Conteka (Sweden). The methods for producing them are described in detail in U.S. Pat. Nos. 3,702,886 (ZSM-5), 3,709,979 (ZSM-11). HY is available from (PQ Corporation USA). HBEA is available from (Sud Chemie, India). HX is available from Aldrich. The synthesis of MCM-41 is disclosed in J. S. Beck et al, Nature 359 (1992) 710.
It is known that crystalline alumino silicate (zeolite) is used as a catalyst for producing pyridine bases from an aliphatic aldehyde and/or ketone and ammonia. ( U.S. Pat. No. 4,220,783 and Japanese patent application kokai (Laid-open) No. 38,362/85).
However, there are no reports available for the production of phenyl pyridines over a solid acid catalyst, except Japanese patent JP 01261367A/98 which discloses the synthesis of 2-phenyl-6-methyl pyridine over Si:Al catalyst starting with acetophenone, formaldehyde and acetone. The selectivity towards the phenyl pyridines in this patent is low. Another disadvantage of the process disclosed in JP 01261367A/98 is that it suffers from the selective synthesis of 2-phenyl pyridine without methyl group. Although a process for the synthesis phenyl pyridine using benzaldehyde and acetaldehyde is described in Ullmann's encyclopaedia A22, the major yield was only 4-phenyl pyridine.
Prior art processes suffer from the following disadvantages:
(a) in all the cases mineral acids are used as catalysts that are highly corrosive,
(b) non-reusability of the catalyst,
(c) in all the cases tedious work-up procedure is required, such as neutralization of acid etc.,
(d) in some cases more than a single step is require to synthesize phenyl pyridines selectively.
Increasing applications of these phenyl pyridines demands an eco-friendly, economical and free handling process. The present invention provides a eco-friendly process which can overcome all the above drawbacks.
OBJECTS OF THE INVENTION
The main object of the present invention is to provide a process for the synthesis of phenyl pyridine bases by using a specific zeolite catalyst, which is an eco-friendly heterogeneous catalytic method.
Another object of the present invention is to improve selectivity of the product.
SUMMARY OF THE INVENTION
Accordingly the present invention relates to a process for the synthesis of an aryl pyridine base said process comprising reacting an aromatic ketone of the formula R
1
COR
2
wherein R
1
is phenyl or alkyl phenyl, R
2
is alkyl with 1 to 2 carbon atoms with the formula R
3
CH═CHCH
2
OH wherein R
3
is selected from the group consisting of hydrogen, methyl, ethyl and aryl, with ammonia in a gaseous phase, the mole ratio of the aromatic ketone to allylic alcohol being in the range of 1:1 to 1:5, the mole ratio of ammonia to aromatic aldehyde and/or ketone being in the range of 0.5 to 5.0, the reaction temperature is in the range of 350° C. to 500° C., in the presence of a catalyst consisting of modified or unmodified zeolite having an atomic ratio of Si to Al in the range of 2.5 to 12.5 with at least one ion of and/or at least one compound of a metal selected from lead and lanthanum to obtain sais aryl pyridine base.
In one embodiment of the invention, the aryl ketone used is selected from acetophenone and methyl acetophenone.
In one embodiment of the invention, the aromatic aldehyde is phenyl acetaldehyde.
In one embodiment of the invention, the allylic alcohol is selected from allyl alcohol and crotyl alcohol.
In one embodiment of the invention, the aromatic ketone used comprises acetophenone and the allylic alcohol used comprises allyl alcohol to obtain 2-Phenyl pyridine.
In a further embodiment of the invention, the molar ratio of Acetophenone:allyl alcohol: ammonia is in the range of 1:1-3:0.5-5.
In one embodiment of the invention, the aromatic ketone used comprises acetophenone and is reacted with acrolein to obtain 2-phenyl pyridine.
In one embodiment of the invention, the aromatic aldehyde used comprises phenyl acetaldehyde and the allylic alcohol used comprises allyl alcohol to obtain 3-phenyl pyridine.
In one embodiment of the invention, the aromatic aldehyde used comprises phenyl acetaldehyde and is reacted with acrolein to obtain 3-phenyl pyridine.
In one embodiment of the invention, acetophenone is reacted with crotyl alcohol to yield 2-phenyl 4-methyl pyridine.
In one embodiment of the invention, acetophenone is reacted with crotonaldehyde to yield 2-phenyl 4-methyl pyridine.
In a further embodiment of the invention, methanol is added to the starting materials in an amount of up to 0.5 mole per mole of acetaldehyde.
In another embodiment of the invention, the zeolite used is in alkali ion form or ammonium ion form or proton form.
In a further embodiment of the invention, the alkali ion form of the zeolite is selected from sodium and potassium.
In a further embodiment of the invention, the zeolite catalyst is ion exchanged with a metal ion of a metal selected from the group consisting of lanthanum, thallium, lead and cobalt.
In yet another embodiment of the invention, the zeolite catalyst used is treated with at least one compound of a metal selected from the group consisting of lanthanum, lead and cobalt by impregnation, immersion, deposition or evaporation to dryness.
In yet another embodiment of the invention, the metal compound of lanthanum, lead and/or cobalt is at least one metal compound selected from the group consisting of oxides, halides, sulfates and phosphates.
In a further embodiment of the invention, the metal compound of lanthanum, lead and/or cobalt comprise oxides.
In yet another embodiment of the invention, the content of the metal compound of lanthanum, thallium, lead and/or cobalt is 0.1 to 5 wt % equivalent per g of the zeolite.
In yet another embodiment of the invention, crotyl alcohol is used as the allylic alcohol to obtain aryl picoline.
In another embodiment of the invention, the proportion of Si to Al in the zeolite is in the range of 2.5 to 140.
In yet another embodiment of the invention, the zeolite is selected from the group consisting of ZSM-5, ZSM-11, HY—a crystal structure of faujasite, HBEA Al-MCM-41, MCM-41 and HX.
In another embodiment of the invention, the catalyst comprises amorphous silica-alumina.
The present invention also relates to develop a process for the preparation of phenyl pyridines of the formula
from acetophenone and allyl alcohol over a zeolite catalyst.
DETAILED DESCRIPTION OF THE INVENTION
Aryl pyridine bases are obtained according to the process of this invention by reacting an aryl aldehyde and/or ketone with allylic alcohols (alkenyl alcohol or aldehyde) in presence of ammonia in gaseous phase in the presence of a catalyst, which is selected from varied Si :Al ratio in the range 2.5 to 140 or a catalyst with a particular Si/Al ratio modified with at least one metal compound selected from the group consisting of lanthanum compounds, lead compounds and cobalt compounds by impregnation or ion exchange methods. Among zeol
Kulkarni Shivanand Janardan
Nagabandi Srinivas
Raghavan Kondapuram Vijaya
Vippagunta Radha Rani
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