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Solid-phase Synthesis of [4.4] Spirocyclic Oximes
Published on: February 6, 2019
[4+1] cyclization of α-diazo esters and mesoionic N-heterocyclic olefins
Qiuming Liang1,2, Yimin Zeng1, Pedro A Mendez Ocampo1
1Davenport Chemical Research Laboratories Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, M5S 3H6, Canada. d.song@utoronto.ca.
Abstract:
Prompted by the recent stepwise mechanistic proposal for the Huisgen [3+2] cycloaddition reaction between enamine and α-diazo ester, where the nucleophilic addition of the enamine carbon onto the terminal nitrogen of diazo ester is crucial, we examined the possible use of N-heterocyclic olefins (NHOs) as highly electron-rich dipolarophiles in these reactions. The mesoionic NHOs derived from 1,2,3-triazoles undergo fast [4+1] cycloaddition to give 3-(triazolium-4-yl)-(3H)-pyrazol-4-olates at room temperature. The reaction mechanism has been explored through experimental and DFT computational studies.
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