Reactions of phosphite esters and trisdialkylaminophosphines with 5-substituted 1,3,4-thiadiazol derivatives

5-{[(1E)-(4-methoxyphenyl)methylene] amino}-1,3,4-thiadiazole-2-thiol (1a), reacts with tri-alkyl phosphites (2a-c) to give the respective dialkyl phosphonate adducts (4a-c). On the other hand, the reactions of trisdialkylaminophosphines (3a,b) with 1a, 5-{[(1E)-(4-phenyl)methylene]amino}-1,3,4-thiadiazole-2-thiol (1b) yield the corresponding open dipolar structures 6a-c. In the case of the reaction of triethyl phosphite (2a) with 1b, both the dialkyl phosphonate adduct (7) and the dipolar product (8a) are obtained. Moreover, triisopropyl phosphite (2c) reacts with 1b to give both the S-alkyl and the N-alkyl phosphonate adducts (9a,b), respectively. Mechanisms are proposed to explain the formation of the new products, and their structures were confirmed on the basis of elemental analysis and spectral studies. (C) 2001 John Wiley & Sons, Inc.