Cross Coupling between sp3-Carbon and sp3-Carbon Using a Diborylmethane Derivative at Room Temperature

Enantio- and Diastereoselective Synthesis of Hydroxy Bis(boronates) via Cu-Catalyzed Tandem Borylation/1,2-Addition

Catalytic enantioselective synthesis of 1-hydroxy-2,3-bisboronate esters through multicomponent borylation/1,2-addition is reported. Catalyst and substrates are readily available, form both a C-B and C-C bond, and generate up to three contiguous stereocenters. The reaction is tolerant of aryl, vinyl, and alkyl aldehydes and ketones in up to 95% yield, >20:1 dr, and 99:1 er. Intramolecular additions to aldehydes and ketones result in stereodivergent processes. The hydroxy bis(boronate) ester products are amenable to site-selective chemical elaboration.

Enantio- and Diastereoselective 1,2-Additions to α-Ketoesters with Diborylmethane and Substituted 1,1-Diborylalkanes

The catalytic enantioselective synthesis of boronate-substituted tertiary alcohols through additions of diborylmethane and substituted 1,1-diborylalkanes to α-ketoesters is reported. The reactions are catalyzed by readily available chiral phosphine/copper(I) complexes and produce β-hydroxyboronates containing up to two contiguous stereogenic centers in up to 99:1 e.r. and greater than 20:1 d.r. The utility of the organoboron products is demonstrated through several chemoselective functionalizations. Evidence indicates the reactions occur via an enantioenriched α-boryl-copper-alkyl intermediate.

Catalytic SN2'- and Enantioselective Allylic Substitution with a Diborylmethane Reagent and Application in Synthesis

A catalytic method for the site- and enantioselective addition of commercially available di-B(pin)-methane to allylic phosphates is introduced (pin=pinacolato). Transformations may be facilitated by an NHC-Cu complex (NHC=N-heterocyclic carbene) and products obtained in 63-95 % yield, 88:12 to >98:2 S(N)2'/S(N)2 selectivity, and 85:15-99:1 enantiomeric ratio. The utility of the approach, entailing the involvement of different catalytic cross-coupling processes, is highlighted by its application to the formal synthesis of the cytotoxic natural product rhopaloic acid A.

Synthesis of 1,1-diboronate esters by cobalt-catalyzed sequential hydroboration of terminal alkynes

Co-catalyzed sequential hydroborations of alkyl and aryl alkynes with pinacolborane produce 1,1-diboronate esters with high selectivity and yields.

Copper-catalyzed cross-coupling reactions of epoxides with gem-diborylmethane: access to γ-hydroxyl boronic esters

Herein, we describe a novel copper-catalyzed epoxide opening reaction with gem-diborylmethane.

Pd-catalyzed cross-coupling of 1,1-diborylalkanes with aryl triflates

The Pd-catalyzed synthesis of benzylboronic esters through coupling of aryl triflates with 1,1-diborylalkane under ambient conditions is described.

Chemoselective catalytic reduction of conjugated α,β-unsaturated ketones to saturated ketones via a hydroboration/protodeboronation strategy

A novel copper-catalyzed chemoselective reduction of a carbon–carbon double or triple bond to a carbon–carbon single bond on α,β-unsaturated ketones is developed, this reaction proceeds under hydrogen gas or stoichiometric metal hydride free conditions.

Unsymmetrical 1,1-diborated multisubstituted sp(3)-carbons formed via a metal-free concerted-asynchronous mechanism

We have experimentally proved the unsymmetrical 1,1-diboration of diazo compounds, formed in situ from aldehydes and cyclic and non-cyclic ketones, in the absence of any transition metal complex. The heterolytic cleavage of the mixed diboron reagent, Bpin-Bdan, and the formation of two geminal C-Bpin and C-Bdan bonds has been rationalised based on DFT calculations to occur via a concerted-asynchronous mechanism. Diastereoselection is attained on substituted cyclohexanones and DFT studies provide understanding on the origin of the selectivity. The alkoxide-assisted selective deborylation of Bpin from multisubstituted sp(3)-carbon and generation of a Bdan stabilized carbanion, easily conducts a selective protodeboronation sequence.

Boron-selective reactions as powerful tools for modular synthesis of diverse complex molecules

In the context of modular and rapid construction of molecular diversity and complexity for applications in organic synthesis, biomedical and materials sciences, a generally useful strategy has emerged based on boron-selective chemical transformations. In the last decade, these types of reactions have evolved from proof-of-concept to some advanced applications in the efficient preparation of complex natural products and even automated precise manufacturing on the molecular level. These advances have shown the great potential of boron-selective reactions in simplifying synthetic design and experimental operations, and should inspire new developments in related chemical and technological areas. This tutorial review will highlight the original contributions and representative advances in this emerging field.

FeCl2-catalyzed hydroboration of aryl alkenes with bis(pinacolato)diboron

Alkylboronates were synthesized by a ligand-free ferrous chloride catalyzed anti-Markovnikov hydroboration of un-activated aryl alkenes with bis(pinacolato)diboron.

Catalyst-controlled reverse selectivity in C–C bond formation: NHC-Cu-catalyzed α-selective allylic alkylation with organolithium reagents

An efficient and highly α-selective copper-catalyzed allylic alkylation of allylic halides with organolithium reagents is presented.

Exhibition of the Brønsted acid–base character of a Schiff base in palladium(ii) complex formation: lithium complexation, fluxional properties and catalysis of Suzuki reactions in water

The Brønsted acid–base character of bis(iminopyrrolylmethyl)amine was shown through the X-ray structures of palladium complexes. The bischelated palladium complex is fluxional as studied by the VT ¹H NMR method and effectively catalyzes Suzuki reactions in water.

Nonracemic allylic boronates through enantiotopic-group-selective cross-coupling of geminal bis(boronates) and vinyl halides

Under the influence of a chiral palladium catalyst, 1,1-bis(pinacolboronate) esters undergo asymmetric cross-coupling with bromoalkenes to generate nonracemic allyl boronates with high levels of enantioselectivity. The so-formed allyl boronates may be oxidized with hydrogen peroxide to provide secondary allylic alcohols or with nitrosobenzene to furnish nonracemic tertiary allylic alcohols. Mechanistic experiments suggest the operation of a pathway involving outer-sphere stereoinvertive transmetalation.

Simple access to elusive α-boryl carbanions and their alkylation: an umpolung construction for organic synthesis

The reaction of 1,1-bis(pinacolboronate) esters with alkyl halides can be effected by metal alkoxides and provides a strategy for the construction of organoboronate compounds. The reaction is found to occur by alkoxide-induced deborylation and generation of a boron-stabilized carbanion.

A catalytic enantiotopic-group-selective Suzuki reaction for the construction of chiral organoboronates

Catalytic enantiotopic-group-selective cross-couplings of achiral geminal bis(pinacolboronates) provide a route for the construction of nonracemic chiral organoboronates. In the presence of a chiral monodentate taddol-derived phosphoramidite ligand, these reactions occur with high levels of asymmetric induction. Mechanistic experiments with chiral (10)B-enriched geminal bis(boronates) suggest that the reaction occurs by a stereochemistry-determining transmetalation that occurs with inversion of configuration at carbon.

Formal carbon insertion of N-tosylhydrazone into B-B and B-Si bonds: gem-diborylation and gem-silylborylation of sp3 carbon

A convenient method is developed to synthesize 1,1-diboronates from the corresponding N-tosylhydrazones. This method is also applicable to synthesize 1-silyl-1-boron compounds. Meanwhile, derivatization and consecutive Pd-catalyzed cross-coupling reactions with 1,1-boronates were explored, demonstrating the synthetic potential of 1,1-diboronates.

One-pot synthesis of symmetrical and unsymmetrical diarylmethanes via diborylmethane

A one-pot synthesis of diarylmethanes from air-stable diborylmethane via the Suzuki-Miyaura cross-coupling reaction is described. The present approach realizes the synthesis of various symmetrical and unsymmetrical diarylmethanes in good to excellent yields.