Phosphine-catalyzed dearomative (3 + 2) annulation of 2-nitrobenzofurans and nitrobenzothiophenes with allenoates
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Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions
Published on: July 17, 2020
Jian-Qiang Zhao1, Lei Yang, Yong You
1Institute for Advanced Study, Chengdu University, Chengdu 610106, China. zhaojianqiang@cdu.edu.cn.
Abstract:
An efficient Ph2PMe-catalyzed dearomative (3 + 2) annulation of 2-nitrobenzofurans, 2-nitrobenzothiophenes, and 3-nitrobenzothiophenes with allenoates has been developed. With the developed protocol, a series of structurally important cyclopenta[b]benzofurans and cyclopenta[b]benzothiophenes were obtained in good to excellent yields (up to 98%) under mild conditions. In addition, preparative-scale experiments and transformations were conducted to exemplify the synthetic utility. The asymmetric version of this dearomative (3 + 2) annulation reaction was tentatively investigated by using chiral phosphine catalysts.
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