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Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions
Published on: July 17, 2020
Rhodium-Catalyzed Atroposelective Synthesis of Conformationally Stable C(sp2)-C(sp3) Atropisomers via C-H Activation
Xiaomei Wang1, Shunle Hu1, Yue Shi2
1Institute of Frontier Chemistry, School of Chemistry and Chemical Engineering, Shandong University, Qingdao 266237, China.
Abstract:
C(sp2)-C(sp3) axially chiral scaffolds represent an unusual class of atropisomeric systems. Given their low configurational stability, the asymmetric synthesis of C(sp2)-C(sp3) atropisomers remains dauntingly challenging. Reported herein is the enantioselective synthesis of isoquinolones bearing both a C(sp2)-C(sp3) axis and a proximal stereogenic center with a 5,6-ring linkage. This is realized via Rh(III)-catalyzed C-H activation of benzamides and [4 + 2] annulation with rationally designed 9-fluorenylacetylenes. The coupling system features mild, redox-neutral conditions and excellent enantioselectivity and diastereoselectivity. Migratory insertion into the alkyne has been established as both an enantio- and diastereodetermining step in the catalytic cycle.
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