Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2000-03-30
2001-11-20
Reamer, James H (Department: 1614)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
Reexamination Certificate
active
06320082
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an improved process for the preparation of acyl naphthyl ethers from naphthyl ethers. Acyl naphthyl ethers are important intermediates in the preparation of drugs, pharmaceuticals and polyesters. More particularly, this invention relates to an improved process for the preparation of acyl napthly ethers from naphthyl ethers using C2-C5 acid anhydrides as acylating agents employing zeolite beta as synthesised, microcrystalline or microcrystalline modified zeolite beta.
This invention particularly relates to an ecofriendly process for acylation of naphthyl ethers using acid anhydrides as acylating agents and zeolite beta as catalyst dispensing with the use of stoichiometric amounts of corrosive, toxic aluminum chloride and hydrogen fluoride as Friedel-Crafts reagents. The acylated products are important intermediates for the preparation of drugs and pharmaceuticals and of monomers for polyesters. For example, 6-acetyl-2-methoxynaphthalene or 6-propionyl-2-methoxy naphthalene are intermediates for naproxen, a non-steroidal anti-inflammatory, analgesic, anti-pyretic drug.
BACKGROUND OF THE INVENTION
Reference may be made to U.S. Pat. Nos. 3,803,245 and 3,994,968 wherein acylation of 2-methoxynaphthalene is carried by aluminum chloride in nitrobenzene. The inherent disadvantages in the use of conventional Lewis acid metal chlorides for Friedel-Crafts acylation are that they are non-regenerable and require more than stoichiometric amounts because of strong complexation with the carbonyl product formed. Work-up to decompose the resultant intermediate complex by hydrolysis results in the generation of a large amount of waste product and employment of lengthy, cumbersome and expensive separation process. Reference may be made to U.S. Pat. Nos. 4,593,125 and 4,670,603 wherein naphthyl ethers are acylated with carboxylic acids, carboxylic acid halide or anhydrides in anhydrous hydrofluoric acid. The drawbacks are that hydrofluoric acid is extremely toxic, corrosive, and thus warrants maintenance of stringent safety conditions and requires expensive equipment in order to work with hydrofluoric acid. Further the use of hydrofluoric acid as a solvent, generates large amounts of salts as effluents upon neutralization.
Reference may be made to a publication by Prins et al., Studies in Surface Science and Catalysis, 94, 397, 1995 wherein naphthyl ether in sulfolane solvent is acylated with acetic anhydride using zeolite H
30
-beta obtained through various options. The drawback is that the selectivity towards 6acetyl-2-methoxynaphthalene, a desired regiomer, is poor.
Reference may be made to a publication by Choudary et al., Applied Catalysis A; 171, 159, 1998 wherein aromatic ethers are acylated with acid anhydrides in the presence of metal ion exchanged clays with moderate to good yields. The drawback is that the selectivity towards 6-acetyl-2-methoxynaphthalene is very poor.
Reference may be made to a publication by Holderich et al., Journal of Catalysis, 185, 408, 1999 wherein H
30
-beta zeolite with varying acidic sites obtained through acid treatment was used to effect acylation of naphthyl ether with acetic anhydride in sulfolane solvent. The drawbacks are the yields and selectivities are moderate.
Reference may be made to a U.S. Pat. No. 5,277,529 wherein the acylation of naphthyl ethers with carboxylic acids, anhydrides or chlorides was carried out both in liquid phase and vapour phase employing H
30
beta zeolite. The drawback is that the yields are poor (9-35%).
OBJECTS OF THE INVENTION
The main object of the present invention is to provide an improved process for the preparation of acyl naphthyl ethers by reacting naphthyl ethers with acid anhydrides aas an acylating agent in the presence of a zeolite beta catalyst which obviates the drawbacks as detailed above.
It is another object of the invention to provide an ecofriendly process for the acylation of naphthyl ethers.
It is another object of the invention to dispense with the use of corrosive and stoichiometric quantities of aluminium chloride and HF.
It is a further object of the invention to provide for the use of zeolite beta synthesised, microcrystalline or microcrystalline modified zeolite beta as catalysts for the acylation of naphthyl ethers.
It is another object of the invention to provide a process for the preparation of acyl naphthyl ethers wherein the selectivity and the yields are good and the work up procedure is simple.
It is another object of the invention to provide a process for the preparation of acyl naphthyl ethers without any disposal problem and wherein the catalyst can be used for several cycles with consistent activity.
It is another object of the invention to provide a process for the preparation of acyl naphthyl ethers, which is economical.
Still another object of the present invention is to use of C2-C5 acid anhydrides selected from acetic anhydride to valeric anhydride as acylating agents.
SUMMARY OF INVENTION
Accordingly, the present invention provides a process for the preparation of acyl naphthyl ethers useful as important intermediates for drugs and pharmaceuticals and polyesters, said process comprising reacting a naphthyl ether with a C2-C5 acid anhydrides as an acylating agent in the presence of zeolite beta catalyst with Si/Al ratio of 4 to 100, in nitrobenzene as solvent at a temperature in the range of 80-180° C. for a period of 2-24 h, and recovering the acylated naphthyl ethers by conventional methods.
In an embodiment of the invention, the zeolite beta catalyst is selected from a synthesised, microcrystalline, or microcrystalline modified zeolite beta.
In another embodiment of the invention the Si/Al ratio of the zeolite beta as synthesised, microcrystalline or microcrystalline modified zeolite beta is preferably 4 to 20.
In a further embodiment of the invention the particle size of microcrystalline zeolite beta is 1 &mgr;m to 10 &mgr;m.
In another embodiment of the invention, the quantity of the catalyst is 1 to 30% by weight with respect to the substrate.
In still another embodiment of the invention C2-C5 acid anhydrides selected from acetic anhydride to valeric anhydride are used as acylating agents.
In still another embodiment of the invention the reaction is effected at a temperature in the range of 80 to 180° C. for 2-24 hrs.
Yet another object of the present invention is the ratio of naphthyl ether and acylating agent is 1:1 to 1:5.
In another embodiment of the invention, the quantity of the catalyst used is 5 to 30% by weight with respect to the substrate.
REFERENCES:
patent: 5138098 (1992-08-01), Hagen et al.
patent: 5227529 (1993-07-01), Neuber et al.
patent: 5817878 (1998-10-01), Spagnol et al.
patent: 5962743 (1999-10-01), Gruber et al.
patent: 6121496 (2000-09-01), Gilbert et al.
patent: 9635656 (1996-11-01), None
patent: 9748665 (1997-12-01), None
English Abstract Of WO 97/48665 Dated Dec. 24, 1997.
English Abstract Of WO 96/35656 Dated Nov. 14, 1996.
Kim, S.D. et al. “The Regioselective Acylation of 2-Methoxynaphthalene to . . . ” J. Mol. Catal. A:Chem (2000), 152 pp. 33-45.
Choudary Boyapati Manoranjan
Kantam Mannepalli Lakshmi
Raghavan Kondapuram Vijaya
Ranganath Kalluri Venkata Sri
Sateesh Mutyala
Council of Scientific and Industrial Research
Ladas & Parry
Reamer James H
LandOfFree
Process for acylation of naphthyl ethers does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for acylation of naphthyl ethers, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for acylation of naphthyl ethers will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2613375