关键词: 钌, 亚丙二烯基, 炔丙醇, 氧转移, 亚甲基烯酮, 烯酮

A ruthenium-catalyzed oxygenative transformation of terminal propargyl alcohols to metheyleneketenes via allenylidene intermediates has been developed for the synthesis of a variety of α,β-unsaturated carboxylic acid derivatives. Mechanistic study experiments disclosed that oxygen transfer from pyridine-N-oxide to ruthenium allenylidene generated from the reaction of the catalyst CpRuCl(PPh₃)₂/NaBPh₄ with terminal propargyl alcohol resulted in the formation of the reactive methyleneketene intermediate, which was trapped into nucleophilic addition reactions to afford the α,β-unsaturated product. This reaction offers an attractive complementary strategy to the traditional approach for the synthesis of this class of unsaturated compounds, but in a distinct mechanism, which provides a novel method for the transformation of propargylic alcohols. The metal allenylidene-to-methyleneketene transformation also represents a new mechanistic modality for metal allenylidene-mediated catalysis.

Key words: ruthenium, allenylidene, propargyl alcohol, oxygen-transfer, methyleneketene, ketene