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Solid-phase Synthesis of [4.4] Spirocyclic Oximes
Published on: February 6, 2019
Diversity-Oriented Synthesis of Spirocyclopentadiene Oxindoles and 2-Acyl Cyclopenta[b]indoles via Intramolecular
Yu-Hsuan Chen1, Ru-Yin Yu1, Wey-Chyng Jeng1
1Department of Chemistry, National Taiwan Normal University, 88, Sec. 4, Ting-Chow Road, Taipei 11677, Taiwan, R.O.C.
Abstract:
Herein, we report an efficient strategy for the diversity-oriented synthesis of spirocyclopentadiene oxindoles and 2-acyl cyclopenta[b]indoles. A phospha-1,6-addition of PBu3 to α,β,γ,δ-unsaturated oxindoles provides phosphorus zwitterions as key intermediates and a branching point for the synthesis of these diverse cyclic products. Notably, spiro compounds are formed via a unique δ-C-acylation/Wittig reaction sequence, while the proton transfer/Wittig/β-acylation reactions afforded 2-acyl cyclopenta[b]indoles. Significantly, this study discloses the first report of a direct β-acylation reaction of an α,β-unsaturated ester bearing an endocyclic double bond.
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