Synthesis of Substituted 2,3-Dihydro-1,3,4,2-Thiadiazaphospholes

Reactions of phosphorus trichloride (PCl3), thiophosphoryl trichloride (PSCl3) and tris(dialkylamino)phosphine (P(NR2)3) with substituted thiohydrazides (1a-1) under a variety of conditions led to thirty one substituted 2,3-dihydro-1,3,4,2-thiadiazaphospholes (2a-1, 3a-c, 4a-1). The side-reactions leading to 4h and 5 also are discussed. The elimination of HCl from 2-chloro-5-methylthio-2,3-dihydro-1,3,4,2-thiadiazaphosphole (2b) by 1,8-diazabicyclo-[5,4,0]-undec-7-ene (“DBU”) gave rise to 5-methylthio-1,3,4,2-thiadiazaphosphole dimer (6). The Staudinger reaction and sulfuration of 2-diethylamino-3-N-phenyl-5-methylthio-2,3-dihydro-1,3,4,2-thiadiazaphosphole (4a) with Me3SiN3 and S8 result in the formation of 2-(trimethylsilyl)imino-(7) and 2-thiono-(8) substituted counterparts respectively. The structures of the above products were confirmed by elemental analysis, IR, MS, and 1H-NMR, 13C-NMR and 31P-NMR.