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 pho sphonate adducts (4a-c). On the other hand, the reactions of trisdialkylami nophosphines (3a,b) with 1a, 5-{[(1E)-(4-phenyl)methylene]amino}-1,3,4-thia diazole-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 di alkyl phosphonate adduct (7) and the dipolar product (8a) are obtained. Mor eover, triisopropyl phosphite (2c) reacts with 1b to give both the S-alkyl and the N-alkyl phosphonate adducts (9a,b), respectively. Mechanisms are pr oposed to explain the formation of the new products, and their structures w ere confirmed on the basis of elemental analysis and spectral studies. (C) 2001 John Wiley & Sons, Inc.