Asymmetric Lewis acid organocatalysis of the Diels–Alder reaction by a silylated C–H acid

Silicon marries a chiral counterion Acid is among the oldest and most versatile of chemical catalysts, but its symmetrical protons can't guide reactions to favor a product over its mirror image. Chemists have resolved this shortcoming through the use of chiral conjugate bases. While the proton activates the substrate, the nearby counterion asymmetrically biases the space around it. Gatzenmeier et al. extend this approach to Lewis acid catalysis by silyl cations, which can activate a variety of substrates in complementary fashion to protons (see the Perspective by Dumoulin and Masson). By pairing these silyl groups with chiral carbon-based anions, they achieve highly enantioselective catalysis of Diels-Alder reactions. Science , this issue p. 949 ; see also p. 918