Diastereo- and Atroposelective Synthesis of Bridged Biaryls Bearing an Eight-Membered Lactone through an Organocatalytic Cascade
摘要:
We present herein an unprecedented stereoselective synthesis of bridged biaryls with defined axial and central chirality from readily available starting materials. This N-heterocyclic carbene-catalyzed method proceeds through propargylic substitution of azolium enolates followed by two-directional cyclization, as supported by DFT calculation. A range of benzofuran/indole-derived bridged biaryls bearing an eight-membered lactone are accessed with uniformly high stereoselectivity (>98:2 dr, mostly >98% ee).
Rh-catalyzed direct synthesis of 2,2′-dihydroxybenzophenones and xanthones
作者:Maddali L. N. Rao、Boddu S. Ramakrishna
DOI:10.1039/c6ra18647e
日期:——
An efficient rhodium-catalyzed direct synthesis of 2,2′-dihydroxybenzophenones and xanthones was developed from functionalized salicylaldehydes. This approach provides an easy access to various functionalized 2,2′-dihydroxybenzophenone and xanthone core skeletons. This study also revealed the crucial role of the hydroxy group in the reductive homo-coupling process to generate 2,2′-dihydroxybenzophenones
A concise and efficient method was developed for the synthesis of chromeno[3,4- c ]chromene-6,7-dione using readily available bis(2-hydroxyphenyl)methanone and Meldrum's acid. The protocol displays a broad substrate scope and good functional group tolerance, including alkyl, alkoxyl, aryl and halogens. These π-extended scaffolds showed blue-green fluorescence with a large Stokes shift. The photophysical