Fe‐catalyzed hydrohalogenative cyclization of cyclohexadienone‐containing enynes

Abstract

A Fe‐catalyzed hydrohalogenative cyclization of cyclohexadienone‐containing 1,n‐enynes to give three different types of compounds is discussed. 1,6‐enynes with a stoichiometric amount of FeX3 provided cis‐hydrobenzofurans with moderate stereoselectivity, whereas the reaction with TMSX (X = Cl, Br) as the halide source in the presence of Fe catalyst improved the stereoselectivity of halide addition highly. The alkyl vs aryl shows difference that the reaction of 1,6‐enynes bearing an alkylethynyl group gave meta alkenated phenols (2 examples) whereas a similar reaction of 1,6‐enynes with an arylethynyl group delivered only cis‐hydrobenzofurans (12 examples). 1,7‐enynes afforded tricyclic products (4 examples). The different reactivity of 1,6‐ and 1,7‐enynes is probably influenced by the formation of a six‐membered chair‐like intermediate in 1,6‐enynes.

Highly effective and selective FeBr3-promoted deuterium bromination/cyclization of 1,n-enynes

“…The decreased deuteration rate is likely due to the generation of H + during the arylation of 6 , which could result in the exchange of D + from D 2 O. Based on the above results and previous reports on cyclization of enynes as well as FeX 3 -promoted reactions, 17 a possible pathway is illustrated as shown in Scheme 2C. Iron ion active species C and C′ first form under the standard conditions, and then generate the carbonium cation D with 1a .…”

Progress in the Synthesis of Hydrobenzofurans from O-Cyclohexadienone-tethered 1,6-Enynes

“…2017 年 Ogoshi 等 [50] 首次实现 了 Ni(0)催化的环己二烯酮型 1,6 同样作为廉价且环境友好的金属铁, 其催化的 1,6-烯炔的环化反应也得到了广泛的关注 [52] . 2019 年, 郑建 鸿课题组 [53] 首次报道了 FeCl [54] , 但直到最近几年才有几 篇可见光催化 O-环己二烯酮型 1,6-烯炔自由基环化反 应的报道, Lam [55a] 、Volla [55b] 、徐燕丽 [55c] 等小组分别报 道了基于可见光催化 O-环己二烯酮型 1,6-烯炔自由基 环化反应的研究, Sahoo 小组 [56]…”