Olefination of α,α′-Divinyl Ketones through Catalytic Meyer−Schuster Rearrangement

The direct olefination of 1,4-dien-3-ones remains a synthetic challenge. A two-step protocol, employing acetylide addition followed by catalytic Meyer−Schuster rearrangement has been developed for the olefination of 1,4-pentadien-3-ones to afford [3]dendralenes. Many of the traditional methods for the Meyer−Schuster rearrangement of alkynyl carbinols are not suitable with these highly unsaturated substrates because of their acid sensitivity. Unexpected reactivity during attempted rearrangement, including Nazarov-type electrocyclizations, is presented, along with conditions to promote the Meyer−Schuster rearrangement of ethoxyacetylene adducts using catalytic VO(acac)2.