Studies on organophosphorus compounds XXII The dimer of p-methoxyphenylthionophosphine sulfide as thiation reagent. a new route to O-substituted thioesters and dithioesters†

Simple alifatic and aromatic esters, such as ethyl, iso-propyl, and benzyl benzoates, benzyl butanoate, ethyl heptanoate, and ethyl 1- and 2-naphthoate, respectively, react with the dimer of p-methoxyphenylthiono-phosphine sulfide 1 in anhydrous xylene at 140°C to give the corresponding 0-substituted thioesters in nearly quantitative yields. Also simple alifatic and aromatic S-substituted thioesters, such as S-phenyl, S-benzyl and S-tert-butyl thiobenzoates, S-phenyl and S-benzyl thioacetates, and S-ethyl thiobutanoate, produced the corresponding dithioesters in nearly quantitative yields upon treatment with 1 in anhydrous toluene at 110°C. 13C NMR data for the carbonyl- and corresponding thiocarbonyl carbons, have been recorded and a linear relation between the chemical shifts of CS and CO is found: δ(CS) = 1.75·δ (CO) - 79.6 for 0-substituted thioesters and δ(CS) = 1.31.δ (CO) - 22.1 for dithioesters. An anomalous reaction has been observed: Thiobenzoic acid, S,S'-methylene ester 2 reacted with 1 to give 4,5-diphenyl-1-1,3-dithiol-2-thion 3.