Reaction rate differences between organotrifluoroborates and boronic acids in BINOL-catalyzed conjugate addition to enones

Chiral Binaphthol-Catalyzed Enantioselective Conjugate Addition of Alkenyl and Arylboronic Acids to α,β-Unsaturated Cyclic N-Sulfonyl Ketimines

The chiral binaphthol-catalyzed enantioselective conjugate addition of alkenylboronic acids and heteroarylboronic acids to cyclic N-sulfonyl ketimines is reported, providing the 1,4-addition products in high yields and moderate to excellent enantioselectivities (up to >99% ee). This mild, scalable catalytic system exhibits high efficiency and broad substrate scopes. Additionally, arylboronic acids were viable nucleophiles under more forcing conditions.

Regio- and enantioselective synthesis of acyclic quaternary carbons via organocatalytic addition of organoborates to (Z)-Enediketones

The chemical synthesis of molecules with closely packed atoms having their bond coordination saturated is a challenge to synthetic chemists, especially when three-dimensional control is required. The organocatalyzed asymmetric synthesis of acyclic alkenylated, alkynylated and heteroarylated quaternary carbon stereocenters via 1,4-conjugate addition is here catalyzed by 3,3´-bisperfluorotoluyl-BINOL. The highly useful products (31 examples) are produced in up to 99% yield and 97:3 er using enediketone substrates and potassium trifluoroorganoborate nucleophiles. In addition, mechanistic experiments show that the (Z)-isomer is the reactive form, ketone rotation at the site of bond formation is needed for enantioselectivity, and quaternary carbon formation is favored over tertiary. Density functional theory-based calculations show that reactivity and selectivity depend on a key n→π* donation by the unbound ketone's oxygen lone pair to the boronate-coordinated ketone in a 5-exo-trig cyclic ouroboros transition state. Transformations of the conjugate addition products to key quaternary carbon-bearing synthetic building blocks proceed in good yield.

Highly Enantioselective Chiral Diol-Catalyzed Conjugate Addition of Boronic Acids to α,β-Unsaturated Trifluoromethyl Ketones

The (R)-3,3'-(3,5-(CF3)2-C6H3)2-BINOL-catalyzed enantioselective conjugate addition of organic boronic acids to α,β-unsaturated 1,1,1-trifluoromethyl ketones affords corresponding addition products bearing a stereogenic center at the β-position in moderate to high yields and excellent enantioselectivities (up to 99% ee), without any 1,2-addition product formation. Moreover, this catalytic protocol features mild reaction conditions, a broad substrate scope, suitability for alkenylboronic acids and (hetero)arylboronic acids, and easy scale-up.

Enantioselective Synthesis of Chiral Organosilicon Compounds by Organocatalytic Asymmetric Conjugate Addition of Boronic Acids to β-Silyl-α,β-Unsaturated Ketones

Herein, we report (R)-3,3'-(3,5-(CF₃)₂-C₆H₃)₂-BINOL-catalyzed enantioselective conjugate addition of organic boronic acids to β-silyl-α,β-unsaturated ketones, furnishing moderate to excellent yields of the corresponding β-silyl carbonyl compounds with stereogenic centers in excellent enantioselectivities (up to 98% ee). Moreover, the catalytic system features mild reaction conditions, high efficiency, broad substrate scope, and easy scale-up.

Enantioselective Conjugate Addition of Boronic Acids to α,β-Unsaturated 2-Acyl Imidazoles Catalyzed by Chiral Diols

Herein, we report the enantioselective conjugate addition of organic boronic acids to α,β-unsaturated 2-acyl imidazoles using (R)-3,3'-I₂-BINOL as the catalyst. The catalytic system shows high efficiency and tolerance to alkenylboronic acids and heteroarylboronic acids. The corresponding Michael addition products were obtained in moderate to excellent yields and with moderate to excellent enantioselectivities (up to 97% ee). A gram-scale reaction was also conducted, and the desired product was obtained in high yield with no erosion in enantioselectivity. Finally, the synthetic utility of the methodology was demonstrated by transforming the 2-acyl imidazole moiety to the corresponding aldehyde, carboxylic acid, ester, and amide derivatives.

Chiral dihydroxytetraphenylene-catalyzed enantioselective conjugate addition of boronic acids to β-enaminones

An efficient (S)-2,15-Cl2-DHTP-catalyzed enantioselective conjugate addition of organic boronic acids to β-enaminones has been developed.