Bis(pinacolato)diborane Promoted Selective Transfer Hydrogenation of Alkynes to Prepare Alkanes

Abstract

We report a transition-metal-free and bis(pinacolato)diborane (B₂Pin₂)-promoted transfer hydrogenation of various alkynes to alkanes in high yields with methanol as hydrogen source under mild reaction conditions. Control experimental results revealed that bis(pinacolato)diborane and methanol played important roles for the transfer hydrogenation of alkynes to alkanes. It is shown that in situ generated borane was the key reductant for the activated alkynes whereas bis(pinacolato)diborane served as strong Lewis acid reagents for diarylacetylenes. More importantly, these transfer hydrogenations could be applied into modifying natural products and a CF₃-substituted alkyl group could be easily introduced into complex molecules. The present method highlights mild reaction conditions, broad substrate scope of alkynes, transition-metal free transfer hydrogenation, and gram scalable preparations without column chromatography.

Keywords

Reduction / Bis(pinacolato)diborane / Hydrogen source / Transfer hydrogenation / Alkyne / Alkane / Hydrogen transfer / Selectivity

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