On the preparation of 2-benzopyrylium-4-oxide and its cycloaddition properties
作者:Peter G. Sammes、Richard J. Whitby
DOI:10.1039/c39840000702
日期:——
Treatment of 1-acetoxy-1H-2-benzopyran-4-one with either base or heat generates the parent 2-benzopyrylium-4-oxide system which gives intermolecular cycloadducts with a variety of dipolarophiles, including olefins.
用碱或热处理1-乙酰氧基-1 H -2-苯并吡喃-4-酮产生母体2-苯并吡啶-4-氧化物体系,该体系产生分子间环加合物与多种双极性亲核试剂,包括烯烃。
Enantioselective 1,3-Dipolar (5+3) Cycloadditions of Oxidopyrylium Ylides and Vinylcyclopropanes toward 9-Oxabicyclononanes
作者:Yanfeng Gao、Yuanhao Mao、Zhiwei Miao
DOI:10.1021/acs.orglett.2c01037
日期:2022.4.29
We have developed an efficient and mild enantioselective palladium-catalyzed (5+3) cycloaddition of vinylcyclopropanes and oxidopyryliumylides generated in situ from benzopyranones, in the presence of a chiral PHOX ligand. These reactions afford various highly functionalized bridged oxa-[3.3.1]carbocycles with three stereogenic centers that are challenging to synthesize, in moderate to good yields
Silver-Catalyzed Tandem Cycloisomerization/[5 + 2] Cycloaddition of 3-Cyclopropylideneprop-2-en-1-ones with Oxidopyrylium Ylides to Form Bibridged Benzocycloheptanones
cycloisomerization/[5 + 2] cycloaddition reactions between readily accessible cyclopropyl-tethered allenyl ketones and benzopyranone-derived oxidopyrylium ylides. The reactions proceed via a cyclobutene-fused furan intermediate generated in situ by a cycloisomerization/1,2-carbene transfer/ring-expansion cascade. This method, which features an unprecedented formal [5 + 2] cycloaddition, delivers good to