Hydrosilylation and Mukaiyama aldol-type reaction of quinolines and hydrosilylation of imines catalyzed by a mesoionic carbene-stabilized borenium ion.

Aldimines and ketimines containing electron-donating and electron-withdrawing groups can be hydrosilylated with borenium catalysts at as low as 1 mol% catalyst loading at room temperature, providing the corresponding secondary amines in excellent yields. Reactions with 2-phenylquinoline gave the 1,4-hydrosilylquinoline product selectively which can be further functionalized in a one-pot synthesis to give unique γ-amino alcohol derivatives. Control experiments suggest that the borenium ion catalyzes both the hydrosilylation and subsequent addition to the aldehyde.

Synthesis of Chiral -Heterocyclic Allylboronates via the Enantioselective Borylative Dearomatization of Pyrroles.

The first enantioselective synthesis of five-membered -heterocyclic allylboronates has been accomplished by a C-B bond-forming dearomatization of pyrroles using a copper(I) catalyst. This reaction involves the regio- and enantioselective addition of a borylcopper(I) species to pyrrole-2-carboxylates, followed by the diastereoselective protonation of the resulting copper(I) enolate to afford pyrrolidine-type allylboronates. The products are highly attractive reagents for the rapid construction of pyrrolidine derivatives that bear five consecutive stereocenters via subsequent allylboration/oxidation processes.

Copper(i)-catalysed stereoselective debromoborylation of aliphatic 1,1-dibromo-1-alkenes with bis(pinacolato)diboron.

A stereoselective debromoborylation of aliphatic 1,1-dibromo-1-alkenes to prepare (Z)-1-bromo-1-alkenylboronate esters using copper(i) catalysts was developed. The debromoborylation of various aliphatic 1,1-dibromo-1-alkenes in the presence of a copper(i) catalyst and bis(pinacolato)diboron proceeded smoothly to produce (Z)-1-bromo-1-alkenylboronate esters in good yields with only Z geometry.

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 CF -substituted alkenes is reported. A series of CF -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.

Stereodivergent hydrodefluorination of gem-difluoroalkenes: selective synthesis of (Z)- and (E)-monofluoroalkenes.

We have developed a novel approach for the stereodivergent hydrodefluorination of gem-difluoroalkenes using copper(i) catalysts to obtain stereodefined monofluoroalkenes. Both (Z)- and (E)-terminal monofluoroalkenes were obtained by the hydrodefluorination of gem-difluoroalkenes in the presence of copper(i) catalysts and diboron or hydrosilane, respectively, with high stereoselectivity. DFT calculations were conducted to elucidate the stereoselectivity.