NOVELTY - Preparing a polyunsaturated ester or thioester, comprises (1) combining, in a first vessel, a carboxylic acid or thioacid in the presence of a phosphine and an azodicarboxylate compound under conditions that deprotonate all of the carboxylic acid or thioacid in it, (2) combining, in a second vessel, a polyunsaturated alcohol and at least one antioxidant, and (3) mixing the contents of the first and second vessels to form the polyunsaturated ester or thioester.    USE - The process is useful for preparing a polyunsaturated ester or thioester, which is useful for preparing polyunsaturated thiol and polyunsaturated ketone (all claimed) that is useful in pharmaceuticals.    ADVANTAGE - The process is capable of preparing the polyunsaturated ester or thioester with high purity and yield in an environmentally friendly manner.    DETAILED DESCRIPTION - Preparing a polyunsaturated ester or thioester, comprises (1) combining, in a first vessel, a carboxylic acid or thioacid in the presence of a phosphine and an azodicarboxylate compound under conditions that deprotonate all of the carboxylic acid or thioacid in it, (2) combining, in a second vessel, a polyunsaturated alcohol and at least one antioxidant, and (3) mixing the contents of the first and second vessels to form the polyunsaturated ester or thioester. INDEPENDENT CLAIMS are included for:    (1) preparing an polyunsaturated thiol, comprising (1a) combining, in a first vessel, a polyunsaturated thioacid in the presence of a phosphine and an azodicarboxylate compound under conditions that deprotonate all of the thioacid, (2a) combining, in a second vessel, a polyunsaturated alcohol and at least one antioxidant, (3a) mixing the contents of the first and second vessels to form the polyunsaturated thioester, and (4) adding the antioxidant to the polyunsaturated thioester of step (3a), and reducing the thioester from the step (3a) under conditions sufficient to make a polyunsaturated thiol; and    (2) preparing an polyunsaturated ketone compound, comprising the steps (1a)-(4a) as per above se, where the polyunsaturated alcohol is of formula (R-OH) (I), and the polyunsaturated thiol is of formula (R-SH) (II), and reacting the polyunsaturated thiol with carbonyl compounds of formula ((LG)R3COX) (III), optionally in the presence of further added antioxidant, to form a polyunsaturated ketone compound of formula (R2-CO-X) (IV).    R = 9-23C-polyunsaturated hydrocarbyl;    LG = leaving group;    X = electron withdrawing group;    R3 = 1-3C-alkylene group carrying a leaving group; and    R2 = 10-24C-polyunsaturated hydrocarbyl interrupted beta , gamma or delta position from the ketone group by S.