Co-oligomerization of butadiene and carbon dioxide catalysed by tertiary phosphine–palladium complexes

Abstract

Tertiary phosphine–palladium complexes catalyse the co-oligomerization reaction of butadiene and carbon dioxide under mild conditions of temperature and pressure (70 °C, 100 atm) to yield (E)-2-ethylidenehept-6-en-5-olide (2) and octadienyl esters of (E)-2-ethylidenehepta-4,6-dienoic acid (3b, c) and of 2-vinylhepta-4,6-dienoic acid (4b, c). At higher temperature (90 °C) esters (3b, c) yield octa-1,3,7-triene and (E)-2-ethylidenehepta-4,6-dienoic acid through an oxidative addition of the allyl carbon–oxygen bond to a palladium(0) species. Subsequent reactions of the carboxylic acid in the presence of [PdLn](L = tertiary phosphine) complexes yield (E)-2-ethylidenehept-5-en-4-olide (1) and 2-ethylhepta-2,4-dien-4-olide (5).