A visible-light-driven radical silylative cyclization of aza-1,6-dienes featuring an acrylonitrile or acrylate moiety and an electron-neutral olefin was developed, which allows for stereoselective synthesis of densely functionalized piperidines in a highly atom-economical manner. Depending on the substitution pattern of the electron-neutral olefin, poor-to-excellent diastereoselectivity was observed. It was suggested that the 6-exo-trig cyclization was initiated by a chemoselective addition of silyl radical toward electron-deficient olefin and the geometry of the remaining olefin is closely associated with the cis-stereoselectivity. DFT calculations supported that a transition state with a cyano group locating at the axial position of the forming piperidine ring might be involved, in which either the increase of 1,3-diaxial repulsion or the lack of hydrogen bonding interaction will diminish diastereoselectivity.

A visible light-promoted hydrosilylation of alkynes has been explored and achieved using 1 mol % organic dye Eosin Y as the photocatalyst and a catalytic amount of thiol as the radical quencher. The corresponding alkenylsilanes were provided with high regio- and stereoselectivites in the reactions of various terminal and internal alkynes. The experimental evidence shows that the reaction is preferentially initiated by a single electron transfer process, and a photoredox pathway is suggested.

A visible light-driven radical hydrosilylation of electron-neutral and -rich alkenes has been investigated on the basis of a newly developed catalytic reaction system composed of eosin Y, thiol, and base additives. A variety of linear and cyclic alkenes with different substitution patterns were found to undergo such metal-free hydrosilylation with tertiary and secondary hydrosilanes in a chemo-, regio-, and stereoselective manner. Comparison of the reactivity of diene compounds and late-stage hydrosilylation of steroid drugs were also explored. Deuterium labeling experiments reveal that a stepwise formation of C-Si and C-H bonds with a trans stereochemistry is preferred, in which the thiol may behave as a hydrogen atom transfer agent.

A gram-scale organocatalytic enantioselective Michael addition of α-nitrocyclohexanone to acrolein has been developed, and it was successfully applied to a concise two-step synthesis of (1S)-azaspiro[4.5]decan-6-one, a useful chiral building block for the synthesis of a variety of natural alkaloids.

The Bronsted acid-promoted dimerization of o-alkynylbenzaldehydes has been discovered and studied in the presence of 45% aq. HBF4 in acetic acid. The developed cascade methodology provides a convenient one-step synthesis of symmetrical 2,3,6,7-dibenzo-9-oxabicyclo[3.3.1]nona-2,6-diene (Kagan's ether) analogues bearing various functionalities.

AbstractDimerization of o‐alkynylbenzaldehydes towards Kagan′s ether analogues proceeds smoothly in the presence of aqueous HBF4 in acetic acid.

A target-oriented highly enantioselective multifunctional organocatalytic approach has been developed to construct the bicycle-[3.3.1]nona-2,6-dien-9-one core of (−)-huperzine A for the first time, with up to 95% ee in the gram-scale procedure. The newly established methodology is also eligible to synthesize a variety of bicyclo[3.3.1]nona-2,6-dien-9-ones in high enantiopurities, and thus is useful for the future development of novel huperzine A analogs with medicinal interests.

A Pd-catalyzed coupling reaction of ArBr/ArCl/ArOTf with sodium thiosulfate takes place in presence of Cs2CO3 at 80°C. The reaction mixture is directly treated with Zn/HCl to afford aryl thiols in good to excellent yields.