Synthesis of (3-tert-Butylpyrazolo[5,1-c][1,2,4]triazin-4-yl)phosphine Oxides

Abstract

Aromatic 7-R1-8-R2-3-tert-butylpyrazolo[5,1-c][1,2,4]triazines (R1 = H, Br; R2 = H, Me, Br) reacted with lithium diphenyl- and methyl(phenyl)phosphides in THF at lower temperature to give nucleophilic addition products to the C4 atom. Further oxidation with atmospheric oxygen or N-bromosuccinimide afforded previously unknown (3-tert-butylpyrazolo[5,1-c][1,2,4]triazin-4-yl)phosphine oxides and 2,2-dibromoacetamide as a by-product. The structure of the isolated compounds was confirmed by IR, 1H, 13C, and 31P NMR, and mass spectra and X-ray analysis.