GB453482A - Improvements in or relating to the production of vanillin and like alkoxy-hydroxy-benzaldehydes - Google Patents

Abstract

Vanillin and like alkoxy-hydroxy-benzaldehydes are prepared by oxidizing a 4-hydroxy-3-alkoxy phenyl glycollic acid having the general formula <FORM:0453482/IV/1> (where R represents an alkyl group) to the corresponding 4 - hydroxy - 3 - alkoxy - benzaldehyde by heating in an aqueous solution of caustic alkali with an aryl nitro compound in which the aryl group does not contain any negative substituent. The glycollic acid may be produced by hydrolysis of the corresponding trichlorocarbinol compound, and the oxidation may be performed either simultaneously or successively. The preferred oxidizing agent is nitrobenzene, but other agents which may be used are nitrotoluene, dinitrobenzene and their homologues. The preferred temperatures are from 110 to 170 DEG C. In examples: (1) trichloromethylguaiacyl carbinol is oxidized in caustic soda solution with nitrobenzene at 150 DEG C. for two hours. The product is extracted with benzene, acidified with hydrochloric acid, and the vanillin extracted with ether; (2) as in example (1) except that the caustic soda solution is less concentrated; (3) as in example (1) except that meta-dinitrobenzene is used as the oxidizing agent; (4) trichloromethylguaethyl carbinol is treated as in example (1) to yield ethavan (3-ethoxy-4-hydroxy-benzaldehyde); (5) as in example (4) except that the heating was at a lower temperature for a longer period; (6) as in example (4) except that the heating was at a higher temperature for a shorter period; (7) as in example (4) except that the oxidizing agent is meta - nitro toluene; (8) trichloromethylguaethyl carbinol is hydrolyzed in caustic soda solution to the guaethyl glycollic acid which is isolated and then separately oxidized by nitrobenzene to 3-ethoxy-4-hydroxybenzaldehyde. The trichlorocarbinol compound may be produced by condensation of chloral or chloral hydrate with a 2-alkoxy phenol.