Di:phenyl-ether carboxylic acid derivs. prepn. - by oxidising methyl cpd. with di:chromate, used as plant protectant and polymer intermediates

摘要

Prepn. of a diphenyl ether mono- or di-carboxylic acid by oxidn. of the corresp. methyl cpd. at 50-350 degrees C and O2 partial pressure 0.1-100 atmos. g. is improved by oxidising a methyl cpd. (II) to an acid (I) with aq. alkali dichromate soln. at 150-350 degrees C and is not >100 bar. (R1 is H or Me; one of R2 and R3 is H and the other is Me, R4 is H or COOH; one of R5 and R6 is H and the other is COOH). (I) are intermediates for plant protectants or for polymers (US 2720507, GB-839404, BE-553897). They are obtd. without by-products (e.g. aldehydes) in high yields, without carboxylic acid solvents or heavy metal catalysts.