Deprotonation of 2-Substituted Pyrazole 1-Oxides.

Abstract

H-3 and H-5 are more acidic in 2-benzylpyrazole 1-oxide than in the parent 1-benzylpyrazole. Deprotonation, followed by addn. of di-Me disulfide, proceeds with low mono- and regioselectivity to give a mixt. of 3-(methylthio)-, 5-(methylthio)- and 3,5-bis(methylthio)-substituted products. With chloroform as the electrophile, addn. takes place exclusively at the 5-position. The extensive deoxygenation taking place during these reactions is effected by hydrogen formed during the deprotonation. [on SciFinder(R)]