A new type of imine α-anion derived from 3-methyl-4-phenyl-1,2,5-thiadiazole 1,1-dioxide.: Tautomerization and dimerization reactions

Proton abstraction from 3-methyl-4-phenyl-1,2,5-thiadiazole 1,l-dioxide (1b) in basic non-aqueous media generated a resonance-stabilized anion (1b(-)) that added to Ib producing a dimer, 3-phenyl-4-(4-phenyl-3-methylene-1,2,5-thiadiazolin-2-yl 1,1-dioxide)-4-methyl-1,2,5-thiadiazoline 1,1-dioxide (2). The anion and the dimer were also electrochemically generated by the cathodic reduction of Ib in acetonitrile solution. The neutralization of basic ethanolic solutions containing 1b(-) caused the precipitation of the tautomer of 1b, 3-phenyl-4-methylene- 1.2,5-thiadiazoline 1,1-dioxide (3). The anion 1b, and the new compounds 2 and 3 were characterized and identified by NMR, IR and UV-VIS spectroscopic techniques. Their voltammetric behavior was also investigated. Copyright (C) 2001 John Wiley & Sons, Ltd.