Cu-Catalyzed Borylative and Silylative Transformations of Allenes: Use of β-Functionalized Allyl Copper Intermediates in Organic Synthesis

Abstract

Herein, copper-catalyzed borylative and silylative transformations of allenes using borylcopper or silylcopper as the active catalytic species are described. First, the synthesis and characterization of borylcopper and silylcopper complexes are briefly introduced. Next, the borylative transformations of allenes are summarized including hydro­boration, carboboration, and borylative allylation of carbonyl compounds. We next deal with the silylative transformations of allenes such as hydrosilylation, carbosilylation, and silylative allylation of carbonyl compounds.1 Introduction2 Synthesis of Borylcopper and Silylcopper Complexes3 Borylative Transformations4 Silylative Transformations5 Conclusions and Future Outlook

Copper–Hydride-Catalyzed Enantioselective Processes with Allenyl Boronates. Mechanistic Nuances, Scope, and Utility in Target-Oriented Synthesis

“…At the heart of the present studies are catalytic reactions that begin with the addition of a copper–boryl complex to an unsaturated hydrocarbon, generating an intermediate that then reacts in situ with an electrophile . Transformations involving allenes are particularly noteworthy (Scheme a) . A related set of reactions are promoted by a Cu–H complex .…”

Regio- and Stereoselective Synthesis of Multi-Alkylated Allylic Boronates through Three-Component Coupling Reactions between Allenes, Alkyl Halides, and a Diboron Reagent

“…The development of copper­(I)-catalyzed three-component coupling reactions between allenes, carbon electrophiles, and a boron source, namely, a carboboration of allenes, is an attractive research target due to the great utility of the borylation products and the interest in the regio- and stereodivergence of the borylation and carbo-functionalization reactions, which can provide access to a variety of alkenyl and allylic boronates (Figure A). − To date, most researchers have used the 2,1-borylcupration of mono- and gem -disubstituted allenes and developed the subsequent α-C–C bond formation for the preparation of linear alkenyl boronates I and γ-C–C bond formation for branched alkenyl boronates II (left arrow in Figure A and Figure B). In these reactions, an allylcopper­(I) species generated in situ via the regioselective 2,1-borylcupration of allenes is the key intermediate toward the alkenyl boronates.…”

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

“…Fluorine-containing organoboron compounds are attractive synthons that have great potential for the flexible assembly of an array of structurally diverse organofluorine compounds. , Recently, several groups have reported the selective syntheses of fluorine-containing organoboron compounds through transition metal-mediated C–F bond activation. , We previously reported the copper­(I)-catalyzed enantioselective borylation reactions of allyltrifluorides and allyldifluorides using bis­(pinacolato)­diboron . These reactions presumably proceed through the enantioselective borylcupration of alkenes followed by copper­(I)-β-fluoro elimination to give gem -difluoroallylboronates. , Based on our studies, we anticipated that 3-boryl-1,1- gem -difluorodienes could be efficiently synthesized by the borylation of 1-trifluoromethyl-substituted allenes through the regioselective borylcupration/copper­(I)-β-fluoro elimination sequence (Scheme b). ,, The products would be versatile intermediates to obtain potentially useful gem -difluoroalkenyl compounds, which are difficult to obtain by other methods, through cross-coupling reactions with aryl halides. In addition, a Diels–Alder reaction between the product and an electron-deficient alkene would allow the construction of complex structural motifs containing a difluoromethyl moiety (Scheme c).…”