Enantioenriched α-Trifluoromethyl Allylboranes via B–H Bond Insertion with Vinyl Triftosylhydrazones^†

Abstract

Asymmetric B–H bond insertion reactions of carbenes represent the most straightforward route to access organoboron compounds. We herein present a chiral dirhodium-catalyzed B−H bond insertion reaction of vinylcarbenes that enables direct access to enantioenriched α-trifluoromethyl allylboranes from readily accessible amine-borane adducts and triftosylhydrazones. This operationally simple protocol exhibits broad substrate scope and functional group tolerance, delivering optically active α-trifluoromethyl allylboranes with good to high yields and enantioselectivities. Additionally, we showcase the utility of this method through two functional group transformations. Combined experimental and computational studies provide insights into the origin of enantioselectivity in the B–H bond insertion process.

Keywords

Asymmetric B−H insertion / Chiral α-trifluoromethyl allylboranes / Vinylcarbenes / Triftosylhydrazone / Rhodium catalysis / Carbenes / Allylboranes / Density functional calculations

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