oxa-[4+2] cycloaddition reaction promoted by a thioxanthylium photoredox catalyst under irradiation with green light has been developed. The reaction of ortho-quinone methides with styrenes smoothly affords the desired cycloadducts. Especially styrenes bearing electron-donating groups are efficiently transformed in this reaction. This method represents a sustainable way to carry out oxa-[4+2] cycloaddition
Synthesis of Difluorinated Heterocyclics through Metal-Free [8+1] and [4+1] Cycloaddition of Difluorocarbene
作者:Yimin Jia、Yuan Yuan、Jinfeng Huang、Zhong-Xing Jiang、Zhigang Yang
DOI:10.1021/acs.orglett.1c00577
日期:2021.4.2
With Ph3P+CF2COO– or TMSCF2Br as the difluorocarbene sources, a facile metal-free cycloaddition between heteroconjugated alkenes and difluorocarbene was developed for the highly convergent synthesis of novel difluorinated heterocyclics, including gem-difluorinated azetidines and 2,3-dihydrobenzofurans. The cycloaddition features high reactivity and regioselectivity, as well as good tolerance of various
Formal Asymmetric Catalytic Thiolation with a Bifunctional Catalyst at a Water-Oil Interface: Synthesis of Benzyl Thiols
作者:Wengang Guo、Bo Wu、Xin Zhou、Ping Chen、Xu Wang、Yong-Gui Zhou、Yan Liu、Can Li
DOI:10.1002/anie.201409894
日期:2015.4.7
The transformation proceeds with high yield (up to 99 %) and stereoselectivity (up to 97:3 e.r.) using water as solvent under mild conditions. The catalyst system provides a new strategy for the synthesis of optically active benzyl mercaptans. Control experiments suggested that o‐QMs are generated by the tertiary amine moiety of the squaramide organocatalyst and that the water–oil biphase is crucial
Asymmetric Synthesis of Triarylmethanes by Rhodium-Catalyzed Enantioselective Arylation of Diarylmethylamines with Arylboroxines
作者:Yinhua Huang、Tamio Hayashi
DOI:10.1021/jacs.5b03277
日期:2015.6.24
where Ar(1) is substituted with a 2-hydroxy group, with arylboroxines (Ar(3)BO)3 in the presence of a chiral diene-rhodium catalyst gave high yields of chiral triarylmethanes (Ar(1)Ar(2)CH*Ar(3)) with high enantioselectivity (up to 97% ee). The reaction is assumed to proceed through o-quinone methide intermediates which undergo Rh-catalyzed asymmetric 1,4-addition of the arylboron reagents.
N-Heterocyclic Carbene Catalyzed [4+3] Annulation of Enals and<i>o</i>-Quinone Methides: Highly Enantioselective Synthesis of Benzo-ε-Lactones
作者:Hui Lv、Wen-Qiang Jia、Li-Hui Sun、Song Ye
DOI:10.1002/anie.201303903
日期:2013.8.12
Enantioselectivity through H bonding: An unprecedented [4+3] annulation of enals with o‐quinone methides catalyzed by N‐heterocyclic carbenes (NHCs) to give benzo‐ε‐lactones is described. High to excellent enantioselectivity was achieved by using a chiral triazolium NHC having a free OH group, which participates in a hydrogen‐bonding interaction with the substrate.