Synthesis of cycloalkanone-fused cyclopropanes by Au(I)-catalyzed oxidative ene-yne cyclizations
摘要:
Au(I)-catalyzed oxidative cyclizations that successfully convert 1,5-ene-ynes and a 1,6-ene-yne to the corresponding cycloalkanone-fused cyclopropanes are described. This Au(I)-catalyzed oxidative cyclization can be effectively applied to various substrates and is an alternative to the previously used intramolecular cyclopropanation that required potentially explosive diazo compound. (C) 2014 Elsevier Ltd. All rights reserved.
描述了基于环己-1,4-二烯的气态碘化氢替代品的设计和克级合成。通过用中等强度的布朗斯台德酸引发,碘化氢从替代物转移到 CC 多重键上,例如炔烃和丙二烯,而没有游离碘化氢的参与。代用品碎片化为甲苯和乙烯,易挥发废物。这种氢碘化反应避免了对碘化氢或氢碘酸的不稳定处理。通过这种方式,可以以立体控制的方式访问范围广泛的以前未知或难以制备的乙烯基碘。
analysis, and the outcome of the enantioselectivities is explained well by our proposed models A and B. The products possess great potential for natural product synthesis because (1) many different chemistries of cyclopropane, ketone, and sulfone are available, and (2) the products are generally highly crystalline, facilitating the supplies of enantiomerically pure synthetic intermediates.
这项工作描述了对 α-重氮-β-酮砜的分子内环丙烷化的高度对映选择性不对称催化的发展。我们发现,当 α-重氮-β-酮基甲基砜与新制备的配体 2e 一起使用时,α-重氮-β-酮基砜的催化不对称分子内反应通常以高对映选择性进行。产品的绝对构型已通过 X 射线晶体学分析确定,我们提出的模型 A 和 B 很好地解释了对映选择性的结果。这些产品具有天然产物合成的巨大潜力,因为 (1) 环丙烷的许多不同化学性质、酮、砜都有,(2)产物一般是高度结晶的,
Metal-Free Transfer Hydrobromination of C–C Triple Bonds
作者:Weiqiang Chen、Martin Oestreich
DOI:10.1021/acs.orglett.9b01431
日期:2019.6.21
A transfer hydrobromination of C–C triplebonds inititated by Brønsted acids is reported. Hydrogen bromide is released stepwise from a bench-stable cyclohexa-1,4-diene-based surrogate, generating biphenyl and ethylene as waste. A range of vinyl bromides was prepared from terminal and internal, mainly acceptor-substituted alkynes with good functional-group tolerance.
An aldehyde with a cyclohexa‐2,5‐dienyl group in the α‐position is introduced as a storable surrogate of highly reactive acetaldehyde. The cyclohexa‐2,5‐dienyl unit is compatible with an enantioselective Michael addition to nitroalkenes promoted by a Hayashi–Jørgensen catalyst and can be removed by a boron Lewis acid mediated C−C bond cleavage. The robust two‐step sequence does not require a large