An efficient N,N’-dioxide-scandium(III) complex catalytic system has been developed for the asymmetric dearomatization of β-naphthols through conjugateaddition to alkynones. A variety of Z-predominated β-naphthalenone compounds were obtained in moderate to high yields with excellent enantioselectivities (up to 98% ee). Moreover, a possible transition state was proposed to explain the origin of the
The asymmetric synthesis of γ-alkenyl butenolides was accomplished by conjugatedaddition of butenolides to alkynones. Both terminal alkynones and nonterminal alkynones were applicable to the N,N′-dioxide–scandium(III) catalytic system. The corresponding products were obtained in good to excellent yields (up to 99%) with high E/Z ratios and high enantioselectivities (up to 98% ee). The novel methods
Concise Assembly of Highly Substituted Furan-Fused 1,4-Thiazepines and Their Diels−Alder Reactions with Benzynes
作者:Hanfeng Ding、Yiping Zhang、Ming Bian、Weijun Yao、Cheng Ma
DOI:10.1021/jo702299m
日期:2008.1.1
A facile and highly efficient three-component reaction of thiazole or benzothiazole carbenes, disubstituted ketenes, and activated alkynes is disclosed. With this methodology, a polysubstituted ring system containing furo[2,3-c]thiazepine core can be constructed from simple and readily accessible starting materials in good yields. The scope and limitation of this transformation were investigated in detail by using various thiazole carbene, ketene, and alkyne components. Furthermore, the synthetic utilities of these unique polyheterocyclic compounds were demonstrated via their Diels-Alder reactions with benzynes to furnish thiazepine-fused 7-oxanorbornadiene derivatives in excellent yields.
A Ring-Expansion Methodology Involving Multicomponent Reactions: Highly Efficient Access to Polysubstituted Furan-Fused 1,4-Thiazepine Derivatives