A Facile Synthesis of 2H-Chromenes and 9-Functionalized Phenanthrenes through Reactions between α,β-Unsaturated Compounds and Arynes
作者:Tiexin Zhang、Xian Huang、and Luling Wu
DOI:10.1002/ejoc.201200042
日期:2012.6
Facile syntheses of 2H-chromenes or 9-functionalizedphenanthrenes under mild conditions in moderate to good yields have been developed. They each involve annulations of arynes with α,β-unsaturatedcompounds bearing different electron-withdrawing groups (EWGs). Depending on the natures of the different EWGs, the reactions proceed by different pathways: enals react with arynesthrough a tandem [2+2]
Facile access to 2,2-diaryl 2<i>H</i>-chromenes through a palladium-catalyzed cascade reaction of <i>ortho</i>-vinyl bromobenzenes with <i>N</i>-tosylhydrazones
作者:Heng Zhang、Yinghua Yu、Xueliang Huang
DOI:10.1039/d0ob00978d
日期:——
A palladium-catalyzed cascade reaction of ortho-vinyl bromobenzenes with N-tosylhydrazones has been developed, which provides a facile approach to 2,2-disubstituted 2H-chromenes. The migration of palladium from the aryl to vinyl position is crucial, as the in situ produced vinyl palladium intermediate could further react with diazocompounds to generate the reactive species for the sequential annulation
Rhodium(III)-Catalyzed Transannulation of Cyclopropenes with<i>N</i>-Phenoxyacetamides through CH Activation
作者:Hang Zhang、Kang Wang、Bo Wang、Heng Yi、Fangdong Hu、Changkun Li、Yan Zhang、Jianbo Wang
DOI:10.1002/anie.201408555
日期:2014.11.24
An efficient rhodium(III)‐catalyzed synthesis of 2H‐chromene from N‐phenoxyacetamides and cyclopropenes has been developed. The reaction represents the first example of using cyclopropenes as a three‐carbon unit in rhodium(III)‐catalyzed C(sp2)Hactivations.
From consideration of physical data and the mode of formation, structure VII is suggested for the 2,2-dimethylchromen dimer. Reaction of coumarin with phenylmagnesiumbromide gave 1,1-diphenyl-3(2-hydroxyphenyl)-prop-2-en-1-ol and 1,3-diphenyl-3(2-hydroxyphenyl)propan-1-one. On acid treatment these cyclized to 2,2-diphenylchromen and 2,4-diphenyl-4H-chromen respectively. These findings contradict the
Catalysis by β-Cyclodextrin Hydrate - Synthesis of 2,2-Disubstituted 2<i>H</i>
-Chromenes in Aqueous Medium
作者:Avishek Ghatak、Sagar Khan、Sanjay Bhar
DOI:10.1002/adsc.201500358
日期:2016.2.4
well as propargyl ethers with differently substituted phenols under ambient atmosphere in aqueous medium has been developed using β‐cyclodextrin hydrate as an efficient, recyclable and stable catalyst. This is the first report where β‐cyclodextrin hydrate acted as a catalyst for an organic transformation but β‐cyclodextrin alone failed.