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A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species
Published on: August 16, 2018
Cobalt-Catalyzed Regio- and Enantioselective Reductive Coupling of 1,3-Enynes with Imines
Kakoli Maji1, Sudipta Paul1, Biplab Maji1
1Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur 741246, India.
Abstract:
We report a cobalt-catalyzed asymmetric reductive coupling of 1,3-enynes with N-sulfonyl imines, affording chiral dienyl amines with excellent regio- and enantioselectivity. Using an Earth-abundant cobalt complex and a commercially available chiral diphosphine ligand, the method delivers up to 96% yield, up to >99% ee, and >20:1 regioselectivity. Water proved to be essential as an additive, enabling high yields with maintained stereocontrol. The reaction shows a broad scope, tolerating diverse aromatics and 1,3-enynes, and is effective for pharmaceutically relevant substrates, giving products with 99% ee. Mechanistic studies indicate a cobalt-mediated oxidative cyclization with water being critical for catalyst turnover.
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