Tetrahydrobenzochromene Synthesis Enabled by a Deconjugative Alkylation/Tsuji-Saegusa-Ito Oxidation on Knoevenagel Adducts

Visible-Light-Mediated Tandem Difluoromethylation/Cyclization of Alkenyl Aldehydes toward CF2H-Substituted Chroman-4-one Derivatives

An efficient and facile visible-light-mediated tandem difluoromethylation/cyclization of alkenyl aldehydes, with easily accessible and air-stable [Ph₃PCF₂H]⁺Br^- as the difluoromethylation reagent, has been established. A range of CF₂H-substituted chroman-4-one skeletons and their derivatives, such as 2,3-dihydroquinolin-4(1H)-ones, chroman, 3,4-dihydronaphthalen-1(2H)-one, 2,3-dihydrobenzofuran, and 2,3-dihydro-1H-inden-1-one, are efficiently produced in moderate to good yields with excellent chemoselectivity under mild reaction conditions.

Catalytic Asymmetric Cyanoalkylation of Electron-Deficient Olefins with Potassium Cyanide and Alkyl Halides

The stereoselective cyanoalkylation of electron-deficient olefins with potassium cyanide and alkyl halides was developed based on the utilization of modular chiral 1,2,3-triazolium salts featuring a hydrogen bond-donor ability as catalysts. The reaction involving multiple carbon-carbon bond formations proceeds via the enantioselective conjugate addition of a cyanide ion and the consecutive catalyst-controlled diastereoselective alkylation of intermediary chiral triazolium enolates. Control experiments revealed that the use of a properly tuned chiral triazolium ion as a catalyst and the presence of the cyano functionality in the intermediary enolate are of crucial importance for achieving high levels of acyclic absolute and relative stereocontrol.