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Base-mediated formal [3+2] cycloaddition of β,γ-alkenyl esters and p-TsN3 for the synthesis of pyrazoles
- Zhao, Mi-Na, Zhang, Mei-Na, Ren, Zhi-Hui, Wang, Yao-Yu, Guan, Zheng-Hui
- Science bulletin 2017 v.62 pp. 493-496
- esters, pyrazoles, thermodynamics
- 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.