Alpha-hydroxy-methyl-ketal(s) and acetal(s) prepn. - by electrochemical oxidn. of carbonyl cpd. with an alkanol in presence of small amt. of water

摘要

The prepn. of alpha-hydroxymethyl acetals and alpha-hydroxy methyl ketals of formula (I) comprises electrochemical oxidn. of a carbonyl cpd. of formula (II) with an alkanol of formula (III) in the presence of an auxiliary electrode and 0.1-5 wt.% water. In the formulae, R1-R3 = each H, 1-20C alkyl, 2-20C alkenyl, 2-20C alkynyl, 3-12C cycloalkyl, 4-20C cycloalkylalkyl, 1-20C hydroxyalkyl, opt. 1-8C allyl-, 1-8C alkoxy-, halo-, 1-4C haloalkyl-, 1-4C haloalkoxy-, Ph-, PhO-, halophenyl-, halophenoxy-, carboxy-, 2-8C alkoxycarbonyl- or CN- substd. aryl or 7-20C arylalkyl; or R1 and R2 or R2 and R3 together form -(CH2)-n -(CH=CH)-m opt. mono- or di-substd. by 1-8C alkyl; 1-8C alkoxy and/or halogen; n = 1-10; m = 1-3; R4 = 1-8C alkyl. Cpds. of formula (Ia) are new, where R5 and R6 = each H, 1-20C alkyl, 1-20C hydroxyalkyl, 2-20C alkoxyalkyl, 2-20C alkenyl, 3-20C hydroxyalkenyl, 4-20C alkoxyalkenyl opt. mono- or di- 1-8C alkyl-, 1-8C alkoxy- or halo-substd. aryl or aryloxy; R2 = H or R6 and R7 together form -(CH2)-n or -(CH=CH)-m, opt. mono- or di-substd. by 1-8C alkyl, 1-8C alkoxy, and/or halogen; provided that R5 is not Ph is R6 or R7 and R4 = Me. USE/ADVANTAGE - (Ia) are intermediates in the prodn. of perfumes and plant protecting agents. The process overcomes disadvantages (e.g. low yields) associated with previous processes.