Shoba VM, Takacs JM. Remarkably Facile Borane-Promoted, Rhodium-Catalyzed Asymmetric Hydrogenation of Tri- and Tetrasubstituted Alkenes.
J Am Chem Soc 2017;
139:5740-5743. [PMID:
28394591 PMCID:
PMC5408738 DOI:
10.1021/jacs.7b02581]
[Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
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Oxime-directed
catalytic asymmetric hydroboration is diverted to
catalytic asymmetric hydrogenation (CAH) upon the addition of a proton
source, such as MeOH, or by running the reaction under a hydrogen
atmosphere. A borane (e.g., pinacolborane) is required to promote
CAH. Tri- and tetrasubstituted alkenes, including the challenging
all-alkyl tetrasubstituted alkenes, undergo CAH with enantiomer ratios
(er) as high as 99:1. The mild reaction conditions, i.e., ambient
temperature, moderate reaction times, and the need for only a slight
excess of H2, contrast those used in most state-of-the-art
catalysts for related substrates.
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