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Catalytic, Transition-Metal-Free Semireduction of Propiolamide Derivatives: Scope and Mechanistic Investigation

R. Justin Grams, Christopher J. Garcia, Connor Szwetkowski and Webster L. Santos*

*Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061, United States, Email: santoswvt.edu

R. J. Grams, C. J. Garcia, C. Szwetkowski, W. L. Santos, Org. Lett., 2020, 22, 7013-7018.

DOI: 10.1021/acs.orglett.0c02567 (free Supporting Information)


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Abstract

A transition-metal-free semireduction of 3-substituted primary and secondary propiolamides with pinacolborane and catalytic potassium tert-butoxide provides 3-substituted acrylamide derivatives in very good yield with excellent E selectivity. Mechanistic studies suggest that an activated Lewis acid-base complex transfers a hydride to the α-carbon followed by rapid protonation in a trans fashion.

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proposed mechanism



Key Words

semireduction of alkynes, pinacolborane


ID: J54-Y2020