One-Pot Synthesis of 3,4-Disubstituted Coumarins under Catalysis of Mn3O4 Nanoparticles
作者:Huayin Sun、Yonghui Zhang、Fengfeng Guo、Yizhe Yan、Changfeng Wan、Zhenggen Zha、Zhiyong Wang
DOI:10.1002/ejoc.201101578
日期:2012.1
The one-potsynthesis of 3,4-disubstitutedcoumarins from substituted 2-(hydroxymethyl)phenols with β-keto esters catalyzed by Mn3O4nanoparticles was developed. A series of 3,4-disubstitutedcoumarin derivatives were obtained in good yields.
transition‐metal and a Brønsted acid catalyst were shown to act synergistically to produce a transient oxonium ylide and ortho‐quinone methide, respectively, in two distinct cycles. These intermediates underwent subsequent coupling in a conjugate‐addition–hemiacetalization event in generally good yield with excellent diastereo‐ and enantioselectivity.
methides (o-QMs) from 2-hydroxybenzyl alcohols has been achieved for the synthesis of substituted benzopyrans in good yields. The developed reaction involves nucleophilic attack of o-QM to α-imino rhodium carbenoid to generate a carbonyl ylide followed by 6π-electrocyclization and isomerization. Furthermore, the utility of the methodology was demonstrated in the one-pot synthesis and construction of
Catalytic asymmetric [4+2] cycloaddition of 1-((2-aryl)vinyl)naphthalen-2-ols with <i>in situ</i> generated <i>ortho</i>-quinone methides for the synthesis of polysubstituted chromanes
An efficient asymmetric [4+2] cycloaddition of 1-((2-aryl)vinyl)naphthalen-2-ols and in situ generated ortho-quinone methides with chiral phosphoric acid as the catalyst was developed. This reaction enables the highly enantioselective synthesis of chiral polysubstituted chromanes bearingmultiple contiguous stereogeniccenters in excellent yields and stereoselectivities (up to 99% yield, >95 : 5 dr