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.

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 γ-selective borylcupration into the trifluoromethyl-substituted allene, followed by copper(I)-ß-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.

Catalytic Enantioselective Synthesis of Allylic Boronates Bearing a Trisubstituted Alkenyl Fluoride and Related Derivatives.

The first catalytic method for diastereo- and enantioselective synthesis of allylic boronates bearing a Z-trisubstituted alkenyl fluoride is disclosed. Boryl substitution is performed with either a Z- or E-allyldifluoride and is catalyzed by bisphosphine/Cu complexes, affording products in up to 99 % yield with >98:2 Z/E selectivity and 99:1 enantiomeric ratio. A variety of subsequent modifications are feasible, and notable examples are diastereoselective additions to aldehydes/aldimines to access homoallylic alcohols/amines containing a fluorosubstituted stereogenic quaternary center.

A Copper(I)-Catalyzed Enantioselective γ-Boryl Substitution of Trifluoromethyl-Substituted Alkenes: Synthesis of Enantioenriched γ,γ-gem-Difluoroallylboronates.

The first catalytic enantioselective γ-boryl substitution of CF3 -substituted alkenes is reported. A series of CF3 -substituted alkenes was treated with a diboron reagent in the presence of a copper(I)/Josiphos catalyst to afford the corresponding optically active γ,γ-gem-difluoroallylboronates in high enantioselectivity. The thus obtained products could be readily converted into the corresponding difluoromethylene-containing homoallylic alcohols using highly stereospecific allylation reactions.

Copper(I)-Catalyzed Stereo- and Chemoselective Borylative Radical Cyclization of Alkyl Halides Bearing an Alkene Moiety.

The stereoselective borylative radical cyclization of alkyl halides containing an alkene moiety was developed using a copper(I)/diboron catalyst system. The optimized reaction conditions allowed us to control the chemoselectivity between the allylic substitution and the borylative radical cyclization. The borylation products were subsequently converted to highly functionalized organic compounds by derivatization of the newly formed C-B bond. This borylative radical cyclization offers a novel methodology for the stereoselective synthesis of various heterocyclic compounds.