Dynamic kinetic resolution of γ,γ-disubstituted indole 2-carboxaldehydes <i>via</i> NHC-Lewis acid cooperative catalysis for the synthesis of tetracyclic ε-lactones
作者:Kuruva Balanna、Soumen Barik、Sayan Shee、Rajesh G. Gonnade、Akkattu T. Biju
DOI:10.1039/d2sc03745a
日期:——
development of efficient and enantioselective routes to these target compounds. Described herein is the enantioselective synthesis of indole-fused ε-lactones by the N-heterocyclic carbene (NHC)-Lewis acid cooperative catalyzed dynamic kinetic resolution (DKR) of in situ generated γ,γ-disubstituted indole 2-carboxaldehydes. The Bi(OTf)3-catalyzed Friedel–Crafts reaction of indole-2-carboxaldehyde with 2-hydroxy
ε-内酯在各种生物活性化合物中普遍存在,激发了开发这些目标化合物的有效和对映选择性途径。本文描述的是通过原位生成的γ,γ-二取代吲哚2-甲醛的N-杂环卡宾(NHC)-路易斯酸协同催化动态动力学拆分(DKR)对吲哚稠合ε-内酯的对映选择性合成。 Bi(OTf) 3催化的吲哚-2-甲醛与2-羟基苯基对醌甲基化物的傅克反应生成γ,γ-二取代吲哚2-甲醛,在NHC和Bi(OTf) 3存在下生成γ,γ-二取代吲哚2-甲醛。以高达 93% 的产率和 >99 : 1 er 提供所需的四环 ε-内酯。此外,还对这种形式的[4+3]成环机制进行了初步研究。