Salicylaldehyde prodn. - by ozonisation of o-propenyl-phenol, followed by redn. of the ozonisation prod.

摘要

Process for prodn. of salicylaldehyde (I) comprises ozonisation of o-propenylphenol (II), followed by redn. of the prod. (II) is obtd. by reaction of allyl chloride with phenol, followed by Claisen rearrangement of the phenyl allyl ether obtd., and isomerisation; ozonisation is carried out pref. at -30 to -60 deg.C, in protic solvent (alcohols, acids) to give the aldehyde and the hydroperoxy-acetal of acetaldehyde, or in non-protic solvents to give ozonides; these intermediates are then reduced, pref. with Me2S. USE/ADVANTAGE - Provides a simple process for the prodn. of (I) in good yield; prior-art processes give low yields of (I) and large amts. of environmentally harmful by-prods. In an example, a stream of oxygen (200 l/hr.) contg. ozone (28 g/hr.) was passed into a soln. of 134g (1 mol.) (II) in 1370 ml methanol at -60 deg.C, for 100 mins.; 110 ml Me2S was then added, and the mixt. was refluxed for 1 hr. until the peroxide content was reduced to 0.035 mol., after which it was worked up by distn. to give Me2S, methanol and 181g of a fraction contg. 68% (I) and DMSO; this fraction was mixed with 200 ml toluene and extd. with 4 x 100 ml water to remove the DMSO, then redistilled to give 109g (I) (89.3% yield).