One-Pot Synthesis of (5-Aminopyrazol-4-yl)-phosphonicAcid Derivatives from 1-Aryl-5-arylcarboxamidopyrazoles throughPyrazolo[4,3-c][1,5,2]-oxazaphosphinines

Abstract

1-Aryl-5-arylcarboxamidopyrazoles react with phosphorus(III) halides giving the new heterocyclic system: pyrazolo[4,3-c][1,5,2]oxazaphosphinine. Treatment of pyrazolo[4,3c] [1,5,2]oxazaphosphinines with nucleophilic or electrophilic reagents leads to a cleavage of the oxazaphosphinine ring yielding derivatives of (5-aminopyrazol-4-yl)phosphonic acid. R Ph i 1 a-d 2 3 a-d R = Br, δ P = 155 ppm 4 a,b R = Ph, δ P = 92 ppm 5 a,b R = 4-Me 2 N-C 6 H 4, δ P = 90 ppm Ar = a: Ph; b: 4-Cl-C 6 H 4 ; c: 3,4,5-(MeO) 3 C 6 H 2 ; d: 4-F-C 6 H 4 .