Synthesis of Alkylidenecyclopentenones and Dialkylidenecyclopentenones via the Coupling of Propargylic Alcohol and 2-Alkyne-1,4-diol Derivatives with Cyclopropylcarbene–Chromium Complexes
摘要:
The coupling of propargylic alcohols and their derivatives with cyclopropylcarbene-chromium complexes has been investigated. The coupling reaction leads to alkylidenecyclopentenones or alkoxyalkyl-cyclopentenones, depending on the leaving group ability of the propargyl substituent. A mechanism involving formation of a cyclopentadienone, followed by reduction and beta-elimination is proposed. Coupling of cyclopropylcarbene complexes with 2-alkyne-1,4-diol derivatives leads to dialkylidenecyclopentenone derivatives via a double elimination process. (C) 2000 Elsevier Science Ltd. All rights reserved.
Organocatalytic Asymmetric Synthesis of Propargylamines with Two Adjacent Stereocenters: Mannich-Type Reactions of In Situ Generated C-Alkynyl Imines with β-Keto Esters
作者:Taichi Kano、Taiga Yurino、Keiji Maruoka
DOI:10.1002/anie.201304963
日期:2013.10.25
Side by side: The title reaction is catalyzed by the chiral Brønsted acid (S)‐1, and affords hitherto less accessible chiral propargylamines, having twoadjacentstereocenters, in good to excellent diastereo‐ and enantioselectivities. Boc=tert‐butoxycarbonyl.
Benzannulation of Substituted 3-Alkoxycarbonylhex-3-en-5-ynoic Acids: A New Route to 4-Substituted 3,5-Dihydroxybenzoic Acids Derivatives
作者:Stefano Serra、Claudio Fuganti
DOI:10.1055/s-2002-34212
日期:——
A new regioselective pathway to 4-substituted 3,5-dihydroxybenzoic acids derivatives is described here. According to this procedure substituted propargylic aldehydes are converted into substituted 3-alkoxycarbonylhex-3-en-5-ynoic acids, which are in turn, treated with acetic anhydride in the presence of sodium acetate to give the substituted benzoic acids derivatives. The aromatic moiety constructed
Regioselective Reversal in the Cyclization of 2-Diazo-3,5-dioxo-6-ynoates (Ynones, Ynamide): Construction of γ-Pyrones and 3(2<i>H</i>)-Furanones Starting from Identical Materials
作者:Feng Wang、Shengle Lu、Bo Chen、Yali Zhou、Ying Yang、Guisheng Deng
DOI:10.1021/acs.orglett.6b02973
日期:2016.12.16
The AgSbF6-catalyzed cyclization of 2-diazo-3,5-dioxo-6-ynoates (ynones, ynamide) in alcoholic solvents affords γ-pyrones, whereas the AgOAc-catalyzed cyclization in 1,2-dichloroethane (DCE) produces 3(2H)-furanones. The cyclization reactions proceeded cleanly under mild reaction conditions, and the desired γ-pyrones or 3(2H)-furanones were obtained in excellent yield. It was observed for the first
N-Boc-aminals as easily accessible precursors for less accessible N-Boc-imines: facile synthesis of optically active propargylamine derivatives using Mannich-type reactions
We developed a facile and practical synthesis of N-Boc-aminals, which can be used as precursors for less accessible N-Boc-imines. Aminals were obtained via simple dehydration condensation reactions of t-butyl carbamate (BocNH2) and various aldehydes in acetic anhydride, followed by filtration and washing with hexane. The obtained N-Boc-alkynylaminals could be successfully applied in enantioselective
An Organocatalytic Cascade Approach toward Polysubstituted Quinolines and Chiral 1,4-Dihydroquinolines-Unanticipated Effect of N-Protecting Groups
作者:Xinshuai Zhang、Xixi Song、Hao Li、Shilei Zhang、Xiaobei Chen、Xinhong Yu、Wei Wang
DOI:10.1002/anie.201202161
日期:2012.7.16
of a divergent organocatalytic aza‐Michael/aldol cascade process towardquinolines and 1,4‐dihydroquinolines depends on the choice of the N‐protecting group (see scheme; TEA=triethylamine, TMS=trimethylsilyl). Use of an electron‐donating sulfonyl group results in an unanticipated aza‐Michael/aldol/aromatization cascade to give polysubstitutedquinolines (right). In contrast, chiral 1,4‐dihydroquinolines