Hongjun Liu, Dasheng Leow, Kuo-Wei Huang and Choon-Hong Tan
Journal of the American Chemical Society, 2009, 131, 7212–7213. (Highlighted in Synfacts, 2009, 7, 0794-0794; contributors: Benjamin List, Steffen Müller)
Abstract: We report that chiral bicyclic guanidine 1 is found to catalyze the isomerization of alkynes to chiral allenes with high enantioselectivities. This Brønsted base catalyzed 1,3-proton shift reaction, an efficient and atom economical reaction, proceeds through deprotonation and protonation sequences. The axial chirality of the allenes is efficiently transferred to functionalized butenolides and cycloaddition products. We also successfully demonstrate the stereospecific synthesis of butenolide through allenoate cyclization with a catalytic cationic Au(I) complex.
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