Prepn. of alpha-hydroxy-methyl-aryl-ketal(s) - by electrochemical oxidation of an aryl-methyl ketone with an alkanol in the presence of a small amt. of water

摘要

The prepn. of alpha-hydroxymethyl arylketals of formula (I) comprises electrochemical oxidation of an arylmethylketone of formula (II) with an alkanol of formula R2OH (III) in the presence of an auxiliary electrode and 0-5 wt.% water R1 = H, 1-20C alkyl, 2-20C alkenyl, 2-20C alkynyl, 2-20C alkoxyalkyl, 4-20C alkenyloxyalkyl, 3-12C cycloalkyl or 4-20C cycloalkylalkyl, R2 = 1-8C alkyl; R3-R7 = each H, 1-8C alkyl, 1-8C alkoxy, 2-8C alkenyl, 3-8C alkenyloxy, 2-8C alkynyl, 3-8C alkynyloxy, halogen, CN, Ph, PhO, halophenyl, halophenoxy, carboxy, 2-8C alkoxycarbonyl, 3-8C alkenyloxycarbonyl, 3-8C alkynyloxycarbonyl; or R3 and R4 or R4 and R5 together form -(CH2)-n or -(CH=CH)-m opt. substd. mono- or di- substd. by 1-8C alkyl, 1-8C alkoxy and/or halogen n = 1-10 m = 1-3. USE/ADVANTAGE - (I) are intermediates in the prepn. of hydroxyphenones and can therefore be used in the prepn. of plant protecting agents photoinitiators and pharmaceuticals. The process overcomes the disadvantages (e.g. poor yields, multi-stage reactions, rearrangement instead of substitution, long reaction times) associated with previous processes.