Allenyl ethers as precursors of .alpha.-methylene-.gamma.-butyrolactones and botryodiplodin derivatives

TLDR: In this paper, the authors showed that β-Bromopropargyl ethers can be isomerized with potassium tert-butoxide (KO-t-Bu) into the corresponding allenyl derivatives 3a-h, 13, 14, and 9d-h.

Abstract: β-Bromopropargyl ethers 2a-h, 11, and 12 or allyl propargyl ethers 8d-h are easily isomerized with potassium tert-butoxide (KO-t-Bu) into the corresponding allenyl derivatives 3a-h, 13, 14, and 9d-h. These compounds afford α-methylene-γ-butyrolactones 7a-h, 25, and 26 by application of the sequence halogenation/dehydrohalogenation/homolytic carbocyclization. Starting from methyl vinyl ketone 1i, similar transformations lead to botryodiplodin (27) or ethoxybotryodiplodin (28)