Base-mediated formal [3+2] cycloaddition of β,γ-alkenyl esters and p-TsN3 for the synthesis of pyrazoles
Mi-Na Zhao1, Mei-Na Zhang1, Zhi-Hui Ren1
1Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, Department of Chemistry & Materials Science, Northwest University, Xi'an 710127, China.
Abstract:
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.
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