Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Patent
1997-03-17
1999-02-16
Owens, Amelia
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
549289, 549285, C07D31108
Patent
active
058722653
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a new process for producing coumarin and substituted coumarins starting from substituted hexahydrocoumarins or from substituted dihydrocoumarins.
Coumarin compounds are widely used in the field of perfumes, flavoring agents, dyestuffs, and as intermediate products for agricultural and pharmaceutical products.
It has been known since the last century that coumarin can be prepared by condensing salicylaldehyde with ethanoic anhydride in the presence of sodium ethanoate (Perkin, J. Chem. Soc. 21, 53, 1868). Coumarin is currently produced industrially by using the Perkin reaction, modified appropriately to improve yields.
U.S. Pat. No. 2,204,008 describes a process for preparing coumarin in which the salicylaldehyde, the ethanoic anhydride, and the sodium ethanoate, in a ratio of 1:2:2 respectively, are heated to 150.degree. C. in the presence of salts of Co, Fe, Ni, Mn, Pt, and Pd; heating to 180.degree.-200.degree. C. is performed after a further addition of ethanoic anhydride and ethanoic acid. The yield obtained is 64.5%.
Austrian patents No. 272332 and 272333 describe a process for producing and purifying coumarin, again starting from salicylaldehyde and ethanoic anhydride. By appropriately varying the percentage of sodium ethanoate and raising the temperature to 210.degree. C., 80% yields are achieved.
All these procedures have the drawback that they use an expensive reagent, such as salicylaldehyde, and use ethanoic anhydride and sodium ethanoate, and therefore problems arise in the disposal or recovery of the ethanoic acid and of the sodium salt. Accordingly, new methods for preparing coumarin that do not use salicylaldehyde have been developed.
German patent No. 2 041 563 and U.S. Pat. No. 3,878,074, 3,859,311, 3,963,473, and 3,888,883 describe a new method for preparing coumarins starting from phenolic derivatives and vinylation thereof with acrylic derivatives. However, coumarin yields are not great (51%) and there are several by-products (Kirk-Othmer, vol. 7, page 200, 3rd ed.).
U.S. Pat. No. 3,998,851 describes a process for preparing coumarin compounds starting from o-hydroxycinnamic acid or esters thereof in the presence of metallic catalysts of Group VIII of the periodic table. In this case, too, very expensive reagents and very drastic operating conditions are used.
U.S. Pat. No. 3,891,678 describes a process for co-producing coumarin and dihydrocoumarin by dehydrogenating hexahydrocoumarin in the presence of metallic catalysts of Group VIII of the period system of elements. Co-production causes problems in the disposal of the less wanted product. There is also the need to provide means for separating and purifying the two products.
U.S. Pat. No. 3,856,819 describes the dehydrogenation of dihydrocoumarin in the presence of the same catalysts and in the presence of a flow of air. The maximum conversion that is achieved is 70%, and the catalyst undergoes a rapid deactivation process.
The recent Japanese patents JP 33153/89 and JP 197098/90 describe a process for obtaining dihydrocoumarin and coumarin by cyclization of esters of 3-(2-cyclohexanoyl)-propanoic acid or derivatives thereof and simultaneous dehydrogenation of the obtained hexahydrocoumarin, in the presence of metals such as Pt, Pd, Ru, and promoters such as barium sulfate, nickel oxide, and chromium salts.
This process has the problem of the co-production of coumarin and dihydrocoumarin and therefore of separating them to recover the products. In all the examples provided in the mentioned patents, the coumarin and the dihydrocoumarin are obtained in a molar ratio of approximately 1:1, and the production process must provide for an expensive step for separating the two products, which are marketed as pure substances. The use of refinements described in the various patents, such as feeding an inert gas or air to remove the hydrogen from the reaction environment (U.S. Pat. No. 3,856,819), executing of the reaction in vacuum (JP 277688/91), or using specifically designed catalysts (JP 494/92) is useless in
REFERENCES:
patent: 3523125 (1970-08-01), Theissen et al.
Alini Stefano
Cotarca Livius
Delogu Pietro
Coleman Henry D
Industrie Chimiche Caffaro S.P.A.
Owens Amelia
Sudol R. Neil
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