3+2] Cycloaddition reactions of β-diazo-α,α-difluoromethylphosphonates with α,β-unsaturated esters

Abstract

(β-diazo-α,α-difluoroethyl)phosphonates as an analog of difluoro diazoethane has been designed as a powerful tool for the assembly of α,α-difluorinated phosphonate-containing molecules. Here, we report a [3+2] dipolar cycloaddition reaction of in situ generated (β-diazo-α,α-difluoroethyl)phosphonates and α,β-unsaturated esters. This mild protocol delivers a diverse array of (β-amino-α,α-difluoroethyl)phosphonates and simple unsaturated esters into highly valuable difluoromethylene phosphonate-containing pyrazoline carboxylates with good chemical yields. Furthermore, the utility of this method has been demonstrated by the large-scale synthesis.