E-Selective partial transfer hydrogenation of internal acetylenes enabled by water-promoted Fe(CO)5 catalysis

Abstract

Hydrogen transfer via water splitting with an iron catalyst presents challenging opportunities. In this note, we have introduced a novel approach for the transfer hydrogenation of internal acetylenes, yielding highly chemo- and stereo-selective E-stilbenes using an earth-abundant iron-catalyst and water as a green hydrogen source. The established protocol showed a broad applicability towards various directing acetylenes, while maintaining high tolerance for functional groups. The method avoids the common issue of isomerization and over-reduction to alkanes. Interestingly, the method is cost-effective for the synthesis of deuterated substrates too. The iron-hydride formed as an intermediate is responsible for the semi-hydrogenation of alkynes, and it is validated through DFT calculations.