REACTIONS OF PHOSPHORUS MONOTHIO ACIDS WITH ALIPHATIC DIAZO COMPOUNDS

Abstract

Reactions of phosphorus monothio acids with diazomethane, diazoacetone, diphenyldiazomethane, and diazofluorene have been studied. The ratio of the yields of the S- and O-derivatives Q_S/Q_O has been found to be dependent on three factors: i) the nature of substituents at phosphorus - with electron-donor substituents raising the O-derivative yield and the quantity log (Q_S/Q_O) varying as εσ of the substituents; (ii) stability of alkyldiazonium and carbocation - with Q_O increasing with the carbocation stability; and (iii) polarity of the medium - the O-derivative yield rises with dielectric permeability of the medium and Q_S/Q_O has been found to be a linear function of 1/D. The most probable mechanism has been established as proton transfer from the acid to the diazocompound followed be formation of the S-derivative and the O-derivative. The former results from an S_N2 reaction of the alkyldiazonium cation with the thiol-thione anion within the ion pair. The O-derivative arises from the thiol-thion anion and the carbocation; the latter resulting from decomposition of the alkyldiazonium cation within the ion pair.