A NEW-TYPE OF HIGHLY POLAR 1,3-DIPOLES - SYNTHESIS AND CHEMISTRY OF THIOCARBONYL-STABILIZED PYRAZOLIDIN-AZOMETHINEIMINES

3-Thioxopyrazolidine-azomethineimines (2) are synthesized from their 3 -oxo analogues (1) and Lawesson's reagent (LR). The electron structure s of 1 and 2 resemble those of polymethines, dipole moments of 2 are e ven higher than those of 1; further physical organic data are discusse d. With NaBH4 2 gives 3-thioxopyrazolidines (8). These are S-mono- (10 ) and (N-1), S-bisalkylated (11). S-Alkylation of 2 affords pyrazolini um salts (7). 1,3-Dipolar cycloaddition of enamines to 2 results in [p i4s +pi2s] products (12, 13), HOMO/LUMO energies of 1 and 2 are given. Models of gamma-thiolactams (17, 19), mimicing antibiotics, are gaine d via 1,3-dipolar cycloadducts of 1 with LR.