Organophosphorus compounds. XVIII. Synthesis of 2-Phenyl-2,3-dihydro-1H-1,2-benzazaphosphole 2-sulfide by pyrolysis of (2-Aminobenzyl)phenyldithiophosphinic acid

Abstract

Reaction of 2-phthalimidobenzyl bromide (12b) with the dialkyl phenylphosphonites (13a-c) afforded the corresponding alkyl phosphinates (14a-c) which upon hydrazinolysis yielded the respective (2-aminobenzy1)phenylphosphinates (16a-c). Reduction of the phosphinates (16a) or (16b) with lithium aluminium hydride gave (2-aminobenzyl)phenylphosphine (15), characterized by its conversion into crystalline 2,3-diphenyl-1,2,3,4-tetrahydro-1,3-benzazaphosphori(n1e8 ). (2-Aminobenzyl) phenylphosphine (15) was heated with sulfur in benzene under reflux for 30 min to give 80% of (2-aminobenzyl)phenyldithiophosphinic acid (20) which when heated between 100-200° in vacuum underwent elimination of hydrogen sulfide to yield 2-phenyl-2,3-dihydro-1H-l,2-benzazaphosphole 2-sulfide (22a). Several other new phosphorus compounds are described. An attempt to prepare a 1H-1,2-benzazaphosphole derivative by photolysis of methyl benzylphosphonic azide (7) was unsuccessful.