Intramolecular cyclization of N-hetarylphosphinimidic isocyanates in the synthesis of 1,7-dihydro-4H-imidazo[4,5-d][1,3,2]diazaphosphinin-4-one (2-phosphapurine)
N-(4-imidazolyl)phosphinimidic isocyanates obtained by the reaction of the corresponding chlorophosphine N-hetarylimide with alkali metal cyanates can undergo intramolecular heterocyclization to yield previously unknown phosphapurine derivatives containing an endocyclic PN double bond. This radically novel approach to building the 2-phosphapurine system shows promise for the synthesis of related phosphorus-containing