Rhodium‐Catalyzed Atroposelective Access to Axially Chiral Olefins via C−H Bond Activation and Directing Group Migration

• Published in: Angewandte Chemie International Edition Vol. 61; no. 1; pp. e202111860 - n/a
• Main Authors: Mi, Ruijie, Chen, Haohua, Zhou, Xukai, Li, Nan, Ji, Danqing, Wang, Fen, Lan, Yu, Li, Xingwei
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 03-01-2022
• Edition: International ed. in English
• Subjects: Alkenes; Alkynes; Aromatic compounds; axially chiral alkenes; Coupling; C−H activation; directing group migration; Enantiomers; Indoles; Nitrogen; Oxidation; Regioselectivity; Rhodium; Substrates; C−H activation; axially chiral alkenes; directing group migration; alkynes; rhodium
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202111860

Axially chiral open‐chain olefins represent an underexplored class of chiral platform. In this report, two classes of tetrasubstituted axially chiral acyclic olefins have been accessed in excellent enantioselectivity and regioselectivity via C−H activation of (hetero)arenes assisted by a migratable directing group en route to coupling with sterically hindered alkynes. The coupling of indoles bearing an N‐aminocarbonyl directing group afforded C–N axially chiral acrylamides with the assistance of a racemic zinc carboxylate additive. DFT studies suggest a β‐nitrogen elimination–reinsertion pathway for the directing group migration. Meanwhile, the employment of N‐phenoxycarboxamide delivered C−C axially chiral enamides via migration of the oxidizing directing group. Experiments suggest that in both cases the (hetero)arene substrate adopts a well‐defined orientation during the C−H activation, which in turn determines the disposition of the alkyne in migratory insertion. Synthetic applications of representative chiral olefins are demonstrated.
Two classes of tetrasubstituted axially chiral olefins have been accessed in excellent enantioselectivity via RhIII‐catalyzed asymmetric C−H activation assisted by a migratable directing group.