Upgrading biomass-derived glycerol into terminal olefins via molybdenum-catalyzed carbon-chain extension

Abstract

The upgrading of glycerol predominantly focuses on synthesizing low-carbon molecules containing three or fewer carbon atoms through chemical bond cleavage, while research on generating long-chain chemicals through carbon–carbon bond formation is relatively scarce. Herein, a novel molybdenum-catalyzed process for carbon chain extension of glycerol has been developed to produce 1,5-hexadiene, a terminal olefin. The molybdenum catalyst complexed with 8-hydroxyquinoline (Mo-8-HQ) achieved a 52% yield of 1,5-hexadiene when using triphenylphosphine as the reductant. Systematic experiments and theoretical calculations revealed that the reaction pathway comprised two Mo^VI–Mo^IV catalytic cycles, wherein glycerol initially underwent deoxydehydration to yield allyl alcohol as a crucial intermediate. Subsequently, the deoxygenation reaction proceeded to generate allyl radicals, which underwent C(sp³)–C(sp³) homo-coupling to form the diene product. This work significantly expands the realm of glycerol utilization and opens up novel avenues for the production of multifunctionalized chemicals with long carbon chains from renewable feedstocks.