Highly enantioselective syntheses of homopropargylic alcohols and dihydrofurans catalyzed by a bis(oxazolinyl)pyridine-scandium triflate complex.

Lewis acid promoted reactions of allylsilanes and allenylsilanes provide access to important building blocks for natural product synthesis.1 For example, trimethylsilylallenes function as propargylic anion equivalents in aldehyde addition reactions (eq 1, Path A).2 If the silicon center is sterically congested, the normal addition pathway is suppressed and functionalized dihydrofurans are produced (eq 1, Path B).3 Although both transformations may be promoted by stoichiometric amounts of titanium tetrachloride, enantioselective reactions of allenylsilanes have not been reported.4 In this Communication, we describe highly enantioselective scandium triflate catalyzed addition and annulation reactions of allenylsilanes with ethyl glyoxylate.