Electrochemical prodn. of benzaldehyde di:alkyl acetal - by oxidn. of toluene deriv. in alcohol soln., converted to corresp. benzaldehyde by acid hydrolysis

摘要

(A) Prodn. of opt. substd. benzaldehyde dialkylacetals comprises anodic oxidn. of a toluene deriv. (I) dissolved in an alkanol in presence of a conductivity salt (II). (R1 = H, (ar)alkyl, aryl, (ar)alkoxy or aryloxy; R2 and R3 = H, (ar)alkyl or aryl. Y = alkali metal or ammonium, opt. partly or completely substd. by alkyl or benzyl; A = SO2 or -P(O)(R6)-; R5 = OH, OY or is (ar)alkyl, aryl, (ar)alkoxy or aryloxy opt. substd. by alkyl and/or halo; R6 = (ar)alkoxy, aryloxy, OH or OY). Oxidation is at current density 0.1-50 A/dm2 and the by-prods. formed are recycled to the starting material opt. after treatment with catalytically-activated H2 (esp. that generated at the cathode). (B) Also new is prodn. of opt. substd. benzaldehydes (III) by hydrolysis of reaction mixts. contg. the acetals with >=1 equiv. of water in presence of acid or acidic ion exchanger catalyst. (III) are useful in perfumery. The corresp. acetals are now made simply with high selectivity and purity.