Asymmetric Reactions Enabled By Organocatalysts And Combined Catalysts With Metal Complexes

In the21st century, organocatalysis has entered the prosperous era under the promotion of several researchers in organic chemistry. Recent decades has witnessed a growing number of organic chemists working on the organocatalysis. Nowadays, asymmetric organocatalysis has been one of the hottest research fields in homogeneous catalysis. Because chiral phosphoric acids derived from BINOL and SPINOL derivatives exhibited high catalytic activity and stereoselectivity, and therefore are particularly effective for a variety of types of reactions. As a result, chiral phosphoric acid catalysis has become an important research project in the field of asymmetric organocatalysis.Several chiral phosphoric acids could effectively activate unsaturated chemical bounds by hydrogen-bonding interaction (carbonyl compounds, imines, α,β-unsaturated compounds) to render important asymmetric reactions. Basically, the phosphoric acid activates the unsaturated chemical bounds by lowering LUMO and thereby facilitates the double bond C=X to be attacked by nucleophilic reagents. We herein report a chiral phosphoric acid catalyzed Friedel-Crafts alkylation reaction of terminal1,1-diarylalkenes bearing a directing group with indoles, delivering a broad range of synthetically useful enantioenriched indole derivatives containing acyclic all-carbon quaternary stereocenters in excellent yields and with high enantioselectivities. This reaction features a break-through in asymmetric Friedel—Crafts reactions by using terminal1,1-diaryalkenes as alkylating reagents, which avoids the generation of side products.The combined catalysis of organocatalysts and metal complexs is a highly efficient strategy for the creation of new catalytic process. This concept can not only create new transformations that either of individual catalyst systems is difficult to afford by sequential or cooperative catalysis, but also is able to build up structurally complicated molecule in a one-pot manner.[6,5,6]-carbotricyclic skeleton represents the core structure of naturally occuring taiwaniaquinoids. Herein, we have developed a highly stereoselective one-pot sequential cyclization reaction of (E)-4-(2-ethynylphenyl)-but-3-en-2-ones with maleimides sequentially catalyzed by a cinchona alkaloid-based primary amine and a gold complex, providing a facile approach to access the [6,5,6]-tricyclic skeleton in fairly good yield and with perfect enantioselectivities. Importantly, the combination of dienamine catalysis and enamine/gold cooperative catalysis would allow the design of new sequential reactions for efficient construction of structurally complicated polycyclic compounds.