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Solid-phase Synthesis of [4.4] Spirocyclic Oximes
Published on: February 6, 2019
A facile access to polyfunctional oxygen-containing heterocycles via intramolecularly formed protic oxonium ylide
1Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, East China Normal University, Shanghai 200062 (China).
Abstract:
Based on the assumption that intramolecularly formed protic oxonium ylides could be trapped by electrophiles, transition-metal-catalyzed reactions of diazoesters bearing a primary hydroxy group with electron-deficient aldehydes and isatins were examined. Good to high chemo- and diastereoselectivities were achieved with reactions catalyzed by Cu(hfacac)2. The reactions were assumed to occur via tandem intramolecular protic oxonium ylide formation and subsequent aldol-type addition. They not only provided an efficient entry to 3-substituted 1,4-dioxan-2-one heterocycles with at least one quaternary carbon center but also provided experimental evidence for a stepwise pathway for the transition-metal-catalyzed intramolecular O-H insertion of diazo compounds.
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