The Reaction of Phosphorus Decasulfide with some Hydrazides and their Hydrazones: New Route for Construction of Four‐membered, Five‐membered, and Six‐membered Phosphorus Heterocycles

Reaction of some selected benzoic acid hydrazides 1a – c with phosphorus decasulfide P 4 S 10 in dry pyridine afforded some novel pyridine solvate of 1,3,4,2‐thiadiazaphospholes 2a – c . Similarly, treatment of their corresponding hydrazones 3a – c toward phosphorus decasulfide under the same reaction conditions gave the corresponding thio ‐analog 4 and 1,3,2‐benzoxazaphosphinine and benzodiazaphosphinine pyridine solvates 5a,b , respectively. Treatment of (thio)semicarbazides and their corresponding (thio)semicarbazones with phosphorus decasulfide in dry pyridine yielded the novel 1,2,4,3‐triazaphospholidines 6a,b , and 1,3,2‐diazaphosphetidines 8a,b , respectively. Moreover, cyclization of (thio)carbohydrazides and their mono‐ (thio)carbohydrazones with phosphorus decasulfide produced 1,2,4,3‐triazaphospholidines 9a,b and 11a,b , respectively. The structures of these products were confirmed from analytical and spectral data.