Copper(I)-Catalyzed Boryl Substitution of 1-Trifluoromethyl Allenes for the Synthesis of 3-Boryl-Substituted 1,1-gem-Difluorodienes

A method to synthesize 3-boryl-1,1-gem-difluorodienes via the copper(I)-catalyzed boryl substitution of trifluoromethyl-substituted allenes was developed. The borylated compounds were obtained up to 91% yield with excellent selectivity. We proposed that the reaction proceeded via gamma-selective borylcupration into the trifluoromethyl-substituted alien; followed by copper(I)-beta-fluoro elimination. Subsequent transformations of the borylation product by Suzuki-Miyaura cross-coupling or Diels-Alder reaction provided various compounds bearing a difluoro moiety, which are difficult to synthesize by existing methods

A Copper(I)-Catalyzed Radical-Relay Reaction Enabling the Intermolecular 1,2-Alkylborylation of Unactivated Olefins

The first catalytic intermolecular 1,2-alkylborylation reaction via a radical-relay mechanism between unactivated olefins, bis(pinacolato)diboron, and an alkyl electrophile is reported. Successful implementation of this method requires that the competing boryl substitution of the alkyl electrophile is retarded to facilitate the radical relay. This challenge was overcome using electronically or sterically demanding alkyl electrophiles, which results in the simultaneous and highly regioselective introduction of a gem-difluoro, monofluoro, tertiary, or secondary alkyl group and a boryl group across the C=C double bond

Cu(I)-Catalyzed Enantioselective gamma-Boryl Substitution of Trifluoromethyl- and Silyl-Substituted Alkenes

Asymmetric gamma-boryl substitution of trifluoromethyl- and silyl-substituted alkenes has been investigated. A variety of substrates were reacted with bis(pinacolato)diboron in the presence of a copper(I) salt and optically active C-1 symmetric QuinoxP*-type bisphosphine ligand as the catalyst. The optically active silyl-substituted gem-difluoroallylboronates products bearing a stereogenic C-B bond, which have never been synthesized before, were obtained in good yield with high enantioselectivity (up to 83% and up to 86% ee, respectively). The resulting allylboron compounds undergo a stereoselective allylboration with a range of aldehydes to afford chiral silyl- and difluoromethylene-containing homoallylic alcohols without significant loss in their enantiomeric purity. The resulting silyl groups in the derivatives can serve as cross-coupling sites, allowing further transformation into structurally complex fluorinated chiral molecules