Copper-Catalyzed Regio-, Diastereo-, and Enantioselective Allylic Alkylation with 1,1-Diborylalkanes.

We report a copper-catalyzed regio-, diastereo-, and enantioselective allylic alkylation of allyl bromides using 1,1-diborylalkanes as prochiral nucleophiles. This methodology employs copper(I) bromide as a catalyst, an ()-BINOL-derived phosphoramidite as a ligand, and lithium benzoate as a crucial additive. The reaction affords enantioenriched homoallylic boronic esters possessing vicinal stereocenters in good yields and high diastereo- and enantioselectivity.

Axially chiral α-boryl-homoallenyl boronic esters as versatile toolbox for accessing centrally and axially chiral molecules.

Axially chiral allenes bearing organoboron groups are highly sought-after building blocks in organic synthesis due to their potential for generating a wide range of axially and centrally chiral molecules. However, the existing methods for preparing axially chiral allenes containing boron group are primarily limited to the synthesis of allenyl boronic esters, and strategies for accessing axially chiral homoallenyl boronic esters are still scarce. Here, we report the general method for synthesizing axially chiral α-boryl-homoallenyl boronic esters through a highly regio- and stereoselective copper-mediated S2'-addition of newly prepared (diborylalkyl)copper species to chiral propargyl electrophiles.

Diverse Synthesis of (Thio)ethers and (Thio)esters Using Halodiborylmethane as a Transformable C Building Block.

The development of effective strategies to forge C-O and C-S bonds in diverse chemical spaces is of considerable interest in synthetic organic chemistry. Herein we report a versatile approach for the modular synthesis of structurally diverse (thio)ethers and (thio)esters via homologative coupling of α-halodiborylmethane followed by transformation of the introduced diborylmethyl group. This method accommodates a wide array of oxygen- and sulfur-containing molecules, including biologically active compounds.

Anion-Mediated, Stereospecific Synthesis of Secondary and Tertiary Cyclopropylboronates from Chiral Epoxides and -Diborylalkanes.

We report a transition-metal-free deborylative cyclization approach to synthesize enantioenriched secondary and tertiary cyclopropylboronates using γ-phosphate-containing -diborylalkanes derived from chiral epoxides and -diborylalkanes. Our method enables the synthesis of a broad range of enantioenriched secondary and tertiary cyclopropylboronates in good yields with excellent stereospecificity. We demonstrate the versatility of our approach by performing a gram-scale reaction.

Iridium-Catalyzed Chemo-, Diastereo-, and Enantioselective Allyl-Allyl Coupling: Accessing All Four Stereoisomers of (E)-1-Boryl-Substituted 1,5-Dienes by Chirality Pairing.

Here, we report a highly chemo-, diastereo-, and enantioselective allyl-allyl coupling between branched allyl alcohols and α-silyl-substituted allylboronate esters, catalyzed by a chiral iridium complex. The α-silyl-substituted allylboronate esters can be chemoselectively coupled with allyl electrophiles, affording a diverse set of enantioenriched (E)-1-boryl-substituted 1,5-dienes in good yields, with excellent stereoselectivity. By permuting the chiral iridium catalysts and the substrates, we efficiently and selectively obtained all four stereoisomers bearing two consecutive chiral centers.

Stereoselective Access to Tetra- and Tri-Substituted Fluoro- and Chloro-Borylalkenes via Boron-Wittig Reaction.

Reported herein is the efficient synthesis of tetra- and tri-substituted (Z)-fluoro- and (Z)-chloro-borylalkenes by the Boron-Wittig reaction of ketones and aldehydes with bench-top stable halo-diborylmethanes. The substrate scope is broad and the Boron-Wittig reaction proceeds from a diverse range of ketones and aldehydes including biologically relevant molecules with fluoro- or chloro-diborylmethanes, providing tetra- and tri-substituted (Z)-fluoro- and (Z)-chloro-borylalkenes in good yields with high stereoselectivity. The utilities of the obtained (Z)-fluoro- and (Z)-chloro-borylalkenes are highlighted by further modifications to afford fluoroalkene derivatives or all-carbon substituted alkene.

Diborylmethyl Group as a Transformable Building Block for the Diversification of Nitrogen-Containing Molecules.

The development of new approaches to installing diverse carbon fragments to a nitrogen atom has attracted considerable attention in chemical science. While numerous strategies have been devised to forge C(sp )-N bonds, one conceptually powerful and straightforward approach is to insert a transformable sp -carbon unit onto a nitrogen atom for modular diversification. Here we describe the successful synthesis of halo-diborylmethanes and their applications to the preparation of nitrogen-substituted diborylmethanes through their homologative coupling with a variety of nitrogen nucleophiles including biologically relevant molecules.

Defluorinative C-C Bond-Forming Reaction of Trifluoromethyl Alkenes with -(Diborylalkyl)lithiums.

We report the transition-metal-free defluorinative C-C bond-forming reaction of trifluoromethyl alkenes with -(diborylalkyl)lithiums. This synthetic strategy provides access to a variety of 4,4-difluoro homoallylic diboronate esters, which serve as versatile intermediates in the efficient preparation of valuable -difluoroalkene derivatives. Further synthetic modifications are conducted to demonstrate the synthetic utility of the obtained 4,4-difluoro homoallylic diboronate esters.

Catalytic Chemo- and Enantioselective Transformations of -Diborylalkanes and (Diborylmethyl)metallic Species.

Chemo- and stereoselective transformations of polyborylalkanes are powerful and efficient methods to access optically active molecules with greater complexity and diversity through programmed synthetic design. Among the various polyborylalkanes, -diborylalkanes have attracted much attention in organic chemistry as versatile synthetic handles. The notable advantage of -diborylalkanes lies in their ability to generate two key intermediates, α-borylalkyl anions and (-diborylalkyl) anions.

Advances in transition metal-free deborylative transformations of -diborylalkanes.

Carbanions serve as key intermediates in a variety of chemical transformations. Particularly, α-borylcarbanions have received considerable attention in recent years because of their peculiar properties, including the ability of boron atom resonance to stabilise the adjacent negatively charged carbon atom. This feature article summarises recent progress in the synthetic utilisation of α-borylcarbanions, including carbon-carbon bond formation with alkyl halides, alkenes, N-heteroarenes, and carbonyls.

Copper-Catalyzed Enantiotopic-Group-Selective Allylation of -Diborylalkanes.

We report a copper-catalyzed enatiotopic-group-selective allylation of -diborylalkanes with allyl bromides. The combination of copper(I) bromide and H-BINOL derived phosphoramidite ligand proved to be the most effective catalytic system to provide various enantioenriched homoallylic boronate esters, containing a boron-substituted stereogenic center that is solely derived from -diborylalkanes, in good yields with high enantiomeric ratios under mild conditions. Experimental and theoretical studies have been conducted to elucidate the reaction mechanism, revealing how the enatiotopic-group-selective transmetalation of -diborylalkanes with chiral copper complex occurs to generate chiral α-borylalkyl-copper species for the first time.

Cobalt-Catalyzed Defluorosilylation of Aryl Fluorides via Grignard Reagent Formation.

Transition-metal-catalyzed transformations of the carbon-fluorine bond not only tackle an interesting problem of challenging bond activation but also offer new synthetic strategies where the relatively inert C-F bond is converted to versatile functional groups. Herein we report a practical cobalt-catalyzed silylation of aryl fluorides that uses a cheap electrophilic silicon source with magnesium. This method is compatible with various silicon sources and can be operated under aerobic conditions.

ZnMe-Mediated, Direct Alkylation of Electron-Deficient N-Heteroarenes with 1,1-Diborylalkanes: Scope and Mechanism.

The regioselective, direct alkylation of electron-deficient N-heteroarenes is, in principle, a powerful and efficient way of accessing alkylated N-heteroarenes that are important core structures of many biologically active compounds and pharmaceutical agents. Herein, we report a ZnMe-promoted, direct C2- or C4-selective primary and secondary alkylation of pyridines and quinolines using 1,1-diborylalkanes as alkylation sources. While substituted pyridines and quinolines exclusively afford C2-alkylated products, simple pyridine delivers C4-alkylated pyridine with excellent regioselectivity.

Facile Synthesis of α-Boryl-Substituted Allylboronate Esters Using Stable Bis[(pinacolato)boryl]methylzinc Reagents.

Reported herein is the utilization of bis[(pinacolato)boryl]methylzinc halides, whose structures are characterized via single-crystal X-ray analysis, as solid storable reagents for copper-catalyzed coupling with vinyliodonum salts. The reaction proceeds under mild conditions and shows broad scope with respect to vinyliodonium salts, affording various α-boryl-substituted allylboronate esters in good yields. Synthetic applications of the obtained products are also demonstrated.

Palladium-Catalyzed Chemoselective Negishi Cross-Coupling of Bis[(pinacolato)boryl]methylzinc Halides with Aryl (Pseudo)Halides.

We describe a palladium-catalyzed chemoselective Negishi cross-coupling of a bis[(pinacolato)boryl]methylzinc halide with aryl (pseudo)halides. This reaction affords an array of benzylic 1,1-diboronate esters, which can serve as useful synthetic handles for further transformations. The developed coupling reaction is compatible with various functional groups and can be easily scaled up.

Generation and Application of (Diborylmethyl)zinc(II) Species: Access to Enantioenriched gem-Diborylalkanes by an Asymmetric Allylic Substitution.

We report the successful generation of (diborylmethyl)zinc(II) species by transmetallation beteween isolable (diborylmethyl)lithium and zinc(II) halide (X=Br, Cl) and their application in the synthesis of enantioenriched gem-diborylalkanes bearing a stereogenic center at the β-position of the diboryl groups by an asymmetric allylic substitution reaction. The reaction has a broad substrate scope, and various enantioenriched gem-diborylalkanes can be obtained in good yields with excellent enantioselectivity. Further elaboration of the enantioenriched gem-diborylalkanes provides access to a diverse set of valuable chiral building blocks.

Confined Nucleation and Growth of PdO Nanocrystals in a Seed-Free Solution inside Hollow Nanoreactor.

This paper reports a novel and adaptable hollow nanoreactor system containing a solution of cucurbituril (CB) inside a silica nanoparticle (CB@h-SiO) which enables the nucleation and formation of nanocrystals (NCs) to be confined at the seed-free interior solution inside the cavity. The above nanospace confinement strategy restricted the volume of medium available for NC formation to the solution inside the cavity to a few tens of nanometers in size and allowed homogeneous NC nucleation to be examined. Harboring of CB@h-SiO in a Pd complex solution confined the nucleation and formation of PdO NCs to the well-isolated nanosized cavity protected by the silica nanoshell, allowing the convoluted formation of clustered PdO NCs to be thoroughly examined.

Chemo- and Stereoselective Crotylation of Aldehydes and Cyclic Aldimines with Allylic gem-Diboronate Ester.

We report a highly chemo- and stereoselective crotylation of aldehydes and cyclic aldimines with allylic-gem-diboronate ester as a new type of organoboron reagent. The allylic-gem-diboronate ester undergoes the crotylation with aldehydes and cyclic aldimines in excellent stereoselectivity, forming anti-5,6-disubstituted oxaborinin-2-ols or (E)-δ-boryl-anti-homoallylic amines in high efficiency. The reaction shows a wide range of substrate scope and excellent functional group tolerance.

Diastereo- and Enantioselective Synthesis of β-Aminoboronate Esters by Copper(I)-Catalyzed 1,2-Addition of 1,1-Bis[(pinacolato)boryl]alkanes to Imines.

Reported herein is an efficient copper(I)-catalytic system for the diastereo- and enantioselective 1,2-addition of 1,1-bis[(pinacolato)boryl]alkanes to protected imines to afford synthetically valuable enantioenriched β-aminoboron compounds bearing contiguous stereogenic centers. The reaction exhibits a broad scope with respect to protected imines and 1,1-bis[(pinacolato)boryl]alkanes, thus providing β-aminoboronate esters with excellent diastereo- and enantioselectivity. The synthetic utility of the obtained β-aminoboronate ester was also demonstrated.

Base-promoted, deborylative secondary alkylation of N-heteroaromatic N-oxides with internal gem-bis[(pinacolato)boryl]alkanes: a facile derivatization of 2,2'-bipyridyl analogues.

A base-promoted, secondary alkylation of N-heteroaromatic N-oxides using internal gem-bis[(pinacolato)boryl]alkanes as alkylation reagents is reported. The reaction exhibits a broad scope, providing deoxygenated secondary alkylated N-heteroaromatic compounds with high efficiency. The usefulness of the developed protocol is evidenced by the sequential direct alkylation of 2,2'-bipyridine-N-oxide.

Spontaneous Pt Deposition on Defective Surfaces of InO Nanocrystals Confined within Cavities of Hollow Silica Nanoshells: Pt Catalyst-Modified ITO Electrode with Enhanced ECL Performance.

Although the deposition of metallic domains on a preformed semiconductor nanocrystal provides an effective pathway to access diverse hybrid nanocrystals with synergistic metal/semiconductor heterojunction interface, those reactions that take place on the surface of semiconductor nanoscrystals have not been investigated thoroughly, because of the impediments caused by the surface-capping organic surfactants. By exploiting the interfacial reactions occurring between the solution and nanoparticles confined with the cavities of hollow nanoparticles, we propose a novel nanospace-confined strategy for assessing the innate reactivity of surfaces of inorganic semiconductor nanoparticles. This strategy was adopted to investigate the newly discovered process of spontaneous Pt deposition on InO nanocrystals.

Chemoselective Coupling of 1,1-Bis[(pinacolato)boryl]alkanes for the Transition-Metal-Free Borylation of Aryl and Vinyl Halides: A Combined Experimental and Theoretical Investigation.

A new transition-metal-free borylation of aryl and vinyl halides using 1,1-bis[(pinacolato)boryl]alkanes as boron sources is described. In this transformation one of the boron groups from 1,1-bis[(pinacolato)boryl]alkanes is selectively transferred to aryl and vinyl halides in the presence of sodium tert-butoxide as the only activator to form organoboronate esters. Under the developed borylation conditions, a broad range of organohalides are borylated with excellent chemoselectivity and functional group compatibility, thus offering a rare example of a transition-metal-free borylation protocol.

Transition-Metal-Free Regioselective Alkylation of Pyridine N-Oxides Using 1,1-Diborylalkanes as Alkylating Reagents.

Reported herein is an unprecedented base-promoted deborylative alkylation of pyridine N-oxides using 1,1-diborylalkanes as alkyl sources. The reaction proceeds efficiently for a wide range of pyridine N-oxides and 1,1-diborylalkanes with excellent regioselectivity. The utility of the developed method is demonstrated by the sequential C-H arylation and methylation of pyridine N-oxides.

Copper-Catalyzed Diastereoselective Addition of Diborylmethane to N-tert-Butanesulfinyl Aldimines: Synthesis of β-Aminoboronates.

We have developed a highly chemo- and diastereoselective alkylation of N-tert-butanesulfinyl aldimines with diborylmethane. Whereas the addition of diborylmethane under metal-free conditions shows poor diastereoselectivity, the use of a copper catalyst and a bidentate phosphine ligand significantly enhances the diastereoselectivity, providing chiral β-aminoboronates in good yields. On the basis of the stereochemical outcome, we propose that the reaction likely proceeds via a boron-chelating six-membered chairlike transition state.