ArticleBase-mediated formal [3+2] cycloaddition of β,γ-alkenyl esters and p-TsN3 for the synthesis of pyrazoles

A novel 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-mediated formal cycloaddition of β,γ-alkenyl esters with p-tolylsulfonylazide (p-TsN3) for the synthesis of 3,5-disubstituted pyrazoles has been developed. The reaction proceeded through diazotization of β,γ-alkenyl esters sequential with thermodynamic cyclization. p-Tolylsulfonylazide played a role as a source of two-nitrogen synthons. The reaction employs readily available starting materials, tolerates a wide range of functional groups, and proceeds under mild conditions.

An efficient DBU-mediated formal [3+2] cycloaddition of β,γ-alkenyl esters with p-tolylsulfonylazide (p-TsN3) for the synthesis of 3,5-disubstituted pyrazoles has been developed.73