A catalytic enantioselective aza-Diels–Alder reaction of unactivated acyclic dienes with aryl-, alkenyl-, and alkyl-substituted imines is described. With 5–10 mol% loadings of a new Brønsted acid catalyst, the aza-Diels–Alder reaction of unactivated acyclic dienes proceeded to give the corresponding aza-Diels–Alder adducts in high yields (up to 98%) with excellent enantioselectivity (up to 98% ee). Preliminary DFT calculations suggest that the reaction proceeds through a chiral ion pair intermediate.

Catalyst-controlled switching of diastereoselectivity from high syn-selectivity (>98/2 dr, syn) to anti-selectivity (up to 96/4 dr, anti) of the asymmetric nitro-Michael reaction of furanones is described. Anti-diastereoselectivity of the nitro-Michael reaction is very rare. With 0.1–5 mol % loadings of an epi-quinine catalyst, the reaction of 5-substituted 2(3H)-furanones with nitroalkenes smoothly proceeded to give the anti-Michael adducts in good yields (up to 95%) with excellent diastereo- and enantioselectivities (up to 96/4 dr, anti; up to 99% ee). DFT calculations support a model that accounts the high anti-diastereoselectivity.

•Michael addition of furanones to β,β-disubstituted nitroalkenes proceeded smoothly.•Unusual high catalytic activity of epi-quinine derivatives was proved.•Method for the construction of chiral all-carbon quaternary centers was developed.•Diastereo- and enantioselectivities are almost perfect (>98:2 dr; 95–99% ee).Epi-quinine-catalyzed asymmetric nitro-Michael addition of furanones to β,β,-disubstituted nitroalkenes is described. The reaction proceeded smoothly with 1–5 mol % loadings of epi-quinine catalysts at room temperature, giving the corresponding Michael adducts in high yields (72–93%) with extremely high diastereo- and enantioselectivities (>98/2 dr, syn major; 95–99% ee). This reaction provides an effective and straightforward method for constructing all-carbon quaternary stereogenic centers adjacent to oxygen-containing quaternary stereogenic centers.

High catalytic activity of novel epi-quinine-derived 3,5-bis(CF3)benzamide in the asymmetric nitro-Michael reaction is described. With 0.1–5 mol % loadings of this catalyst, the addition of 5-substituted 2(3-H)-furanones to a wide range of nitroalkenes involving challenging substrates, β-alkylnitroalkenes, smoothly proceeded, giving the Michael adducts in high yields (>90%) with excellent diastereo- and enantioselectivity (>98:2 dr, syn major; 88–98% ee). DFT calculation was carried out to account for the high catalytic activity.

The 29Si NMR studies of chiral pentacoordinate silyl triflimides having a stereogenic center at silicon have revealed that a chiral silicon center is highly configurationally unstable. Such configurational instability has an enormously beneficial effect on the diastereo- and enantioselectivity of the catalytic asymmetric Diels–Alder reaction.

The synthesis and structures of silaoxazolinium salts 2 and their application to the catalytic Mukaiyama aldol reaction are described. The reaction of (N-amidomethyl)dimethylchlorosilane (1a) or (N-amidomethyl)bis(trimethylsilyl)chlorosilane (1b) with metal salts of weakly coordinating anions such as Na[TFPB] (TFPB = B[3,5-(CF3)2C6H3]4–) and Cs[CB11H12] (CB11H12– = carba-closo-dodecaborate) gave the corresponding five-membered-ring silaoxazolinium salts 2 in high yields (93–97%). The structures of a series of silaoxazolinium salts 2 were determined by X-ray crystal analysis as well as 29Si NMR spectra. It was proved that the silicon atoms of silaoxazolinium salts 2a,b are nearly completely free from the coordination of anions, and the geometries of the silicon centers are distorted tetrahedra. The 29Si chemical shifts of salts 2 appeared in the range +31 to +49 ppm, revealing the appreciable silylium cation character of the silicon. The silaoxazolinium salt of TFPB anion 2a exhibited effective catalytic activity for the Mukaiyama aldol reaction of low reactive unactivated ketones such as cyclohexanone and acetophenone, giving the corresponding aldol products in high yields. The catalytic activity is highly dependent on the nature of the counteranions and the substituents on the silicon. DFT calculations of silaoxazolinium cation have disclosed that positive charges of silaoxazolinium cations are mainly located at the silicon atoms, while the nitrogen atoms and oxygen atoms are negatively charged.

The 29Si NMR studies of chiral pentacoordinate silyl triflimides having a stereogenic center at silicon have revealed that a chiral silicon center is highly configurationally unstable. Such configurational instability has an enormously beneficial effect on the diastereo- and enantioselectivity of the catalytic asymmetric Diels–Alder reaction.