Cobalt-Catalyzed Selective Hydroboration of 1,3-Enynes with HBpin toward 1,3-Dienylboronate Esters.

An efficient cobalt-catalyzed selective hydroboration of 1,3-enynes with HBpin toward 1,3-dienylboronate esters is disclosed. With a commercially available catalytic system of Co(acac) and dppf, the hydroboration reactions proceeded well to afford a wide range of 1,3-dienylborates in moderate to high yields. This protocol features a cheap base-metal catalytic system, broad substrate scope, excellent selectivity, easy gram-scale preparation, and good functional group tolerance and provides access to synthetically valuable 1,3-dienylborates.

Mixed-Valence BN-Doped Corannulene Trimer Radical Cations.

Mixed-valence (MV) dimers have been extensively investigated, however, the structure and properties of purely organic MV trimers based on open-shell polycyclic aromatic hydrocarbons remain elusive. Herein, unprecedented MV BN-doped corannulene radical cations [BN-Cor1] ⋅⋅  ⋅ 2[BAryl ] and [BN-Cor2] ⋅⋅  ⋅ 2[BAryl ] were synthesized via chemical oxidation, and their structures were unambiguously confirmed by single-crystal X-ray diffraction. These uncommon radical cations consist of three corannulene cores and two [BAryl ] anions, and three corannulene motifs [BN-Cor1] ⋅⋅ and [BN-Cor2] ⋅⋅ in the unit cell exhibit a trimer structure with a slipped π-stacking configuration.

Cobalt-Catalyzed Asymmetric Remote Borylation of Alkyl Halides.

Enantioselective functionalization of racemic alkyl halides is an efficient strategy to assemble complex chiral molecules, but remains one of the biggest challenges in organic chemistry. The distant and selective activation of unreactive C-H bonds in alkyl halides has received growing interest as it enables rapid generation of molecular complexity from simple building blocks. Here, we reported a cobalt-catalyzed remote borylation of alkyl (pseudo)halides (alkyl-X, X=I, Br, Cl, OTs) with pinacolborane (HBpin) and presented a robust approach for the generation of valuable chiral secondary organoboronates from racemic alkyl halides.

Transition-Metal Free C-C Bond Cross-Coupling of Aryl Ethers with Diarylmethanes.

We describe a general and efficient transition-metal free C-C bond cross-coupling of (hetero)aryl ethers and diarylmethanes via C(sp)-O bond cleavage. The coupling reactions mediated by KHMDS proceeded well with high efficiency, broad substrate scope, and good functional group tolerance. The robustness and practicability of this protocol also have been demonstrated by easy gram-scale preparation and diversified product derivatization.

Catalyst-free C(sp)-H functionalization of methyl azaarenes with heteroaromatic trifluoromethyl ketone hydrates: "all-water" synthesis of α-trifluoromethyl tertiary alcohols.

An efficient catalyst-free C(sp)-H bond functionalization of methyl azaarenes with heteroaromatic trifluoromethyl ketone hydrates in neat water has been developed for the synthesis of α-trifluoromethyl tertiary alcohols bearing N-heteroaromatics. This method not only features excellent efficiency, broad substrate scope, catalyst-free conditions, and easy gram-scale preparation but also represents a new and rare example of "all-water" synthesis of trifluoromethylated molecules.

Rhodium-Catalyzed Remote Borylation of Alkynes and Vinylboronates.

Remote functionalization involving a fascinating chain-walking process has emerged as a powerful strategy for the rapid access to value-added functional molecules from readily available feedstocks. However, the scope of current methods is predominantly limited to mono- and di-substituted alkenes. The remote functionalization of multi- and heteroatom-substituted alkenes is challenging, and the use of alkynes in the chain walking is unexplored.

Asymmetric Oxidative Lactonization of Enynyl Boronates.

Oxidation of C-B bonds is extensively used in organic synthesis, materials science, and chemically biology. However, these oxidations are usually limited to the oxidation of C(sp )-B and C(sp )-B bonds. The C(sp)-B bond oxidation is rarely developed.

Enantioselective Cobalt-Catalyzed Hydroboration of Ketone-Derived Silyl Enol Ethers.

Catalytic asymmetric hydroboration of alkenes is a powerful tool for the synthesis of natural products, agrochemicals, and pharmaceuticals via the versatile transformations of chiral alkyl boronic esters. However, the scope of available alkenes is limited to styrenes, activated alkenes, and compounds with directing groups. The catalytic enantioselective hydroboration of heteroatom-substituted alkenes is rarely explored and those catalyzed by earth-abundant metals are yet to be reported.

Palladium-Catalyzed Suzuki-Miyaura Cross-Coupling of Oxygen-Substituted Allylboronates with Aryl/Vinyl (Pseudo)Halides.

An efficient palladium-catalyzed Suzuki-Miyaura cross-coupling reaction of oxygen atom-substituted allylboronates with aryl/vinyl bromides, iodides, and triflates has been developed. The present coupling reactions proceeded smoothly to provide a variety of allylic siloxanes with high efficiency and excellent regioselectivity. This protocol features broad substrate scope, excellent functional group tolerance, and easy gram-scale preparation, and offers an alternative approach for the synthesis of allylic alcohols and their derivatives.

Rh-Catalyzed Coupling of Aldehydes with Allylboronates Enables Facile Access to Ketones.

We present herein a novel strategy for the preparation of ketones from aldehydes and allylic boronic esters. This reaction involves the allylation of aldehydes with allylic boronic esters and the Rh-catalyzed chain-walking of homoallylic alcohols. The key to this successful development is the protodeboronation of alkenyl borylether intermediate via a tetravalent borate anion species in the presence of KHF and MeOH.

Ligand-controlled cobalt-catalyzed remote hydroboration and alkene isomerization of allylic siloxanes.

The Co-catalyzed remote hydroboration and alkene isomerization of allylic siloxanes were realized by a ligand-controlled strategy. The remote hydroboration with dcype provided borylethers, while xantphos favored the formation of silyl enol ethers.

Rhodium-Catalyzed β-Dehydroborylation of Silyl Enol Ethers: Access to Highly Functionalized Enolates.

An efficient rhodium-catalyzed β-dehydroborylation of aldehyde-derived silyl enol ethers (SEEs) with bis(pinacolato)diboron (Bpin) is disclosed. The borylation reactions proceeded well with alkyl- and aryl-substituted SEEs, affording a wide array of valuable functionalized β-boryl silyl enolates with high efficiency and excellent stereoselectivity. Moreover, the borylated products, through versatile carbon-boron bond transformations, were readily converted into diverse synthetically useful molecules, including α-hydroxy ketones, functionalized SEEs, and -difunctionalized aldehydes.

Phosphination of Phenol Derivatives and Applications to Divergent Synthesis of Phosphine Ligands.

We describe a general and efficient protocol for the synthesis of organophosphine compounds from phenols and phosphines (RPH) via a metal-free C-O bond cleavage and C-P bond formation process. This approach exhibits broad substrate scope and excellent functional group tolerance. The synthetic utilities of this protocol were demonstrated by the synthesis of chiral ligands via the various transformations of cyano groups and their applications in asymmetric catalysis.

Cobalt-Catalyzed Remote Hydroboration of Alkenyl Amines.

We here present a generally applicable cobalt-catalyzed remote hydroboration of alkenyl amines, providing a practical strategy for the preparation of borylamines and aminoalcohols. This method shows broad substrate scope and good functional group tolerance, tolerating a series of alkenyl amines, including alkyl-alkyl amines, alkyl-aryl amines, aryl-aryl amines, and amides. Of note, this protocol is also compatible with a variety of natural products and drug derivatives.

A mild and practical method for deprotection of aryl methyl/benzyl/allyl ethers with HPPh and BuOK.

A general method for the demethylation, debenzylation, and deallylation of aryl ethers using HPPh and BuOK is reported. The reaction features mild and metal-free reaction conditions, broad substrate scope, good functional group compatibility, and high chemical selectivity towards aryl ethers over aliphatic structures. Notably, this approach is competent to selectively deprotect the allyl or benzyl group, making it a general and practical method in organic synthesis.

Enantioselective Rh-Catalyzed Hydroboration of Silyl Enol Ethers.

The asymmetric hydroboration of alkenes has proven to be among the most powerful methods for the synthesis of chiral boron compounds. This protocol is well suitable for activated alkenes such as vinylarenes and alkenes bearing directing groups. However, the catalytic enantioselective hydroboration of O-substituted alkenes has remained unprecedented.

Benzannulation of isobenzopyryliums with electron-rich alkynes: a modular access to β-functionalized naphthalenes.

Described here is a modular strategy for the rapid synthesis of β-functionalized electron-rich naphthalenes, a family of valuable molecules lacking general access previously. Our approach employs an intermolecular benzannulation of generated isobenzopyrylium ions with various electron-rich alkynes, which were not well utilized for this type of reaction before. These reactions not only feature a broad scope, complete regioselectivity, and mild conditions, but also exhibit unusual product divergence depending on the substrate substitution pattern.

Rhodium-Catalyzed Deoxygenation and Borylation of Ketones: A Combined Experimental and Theoretical Investigation.

The rhodium-catalyzed deoxygenation and borylation of ketones with Bpin have been developed, leading to efficient formation of alkenes, vinylboronates, and vinyldiboronates. These reactions feature mild reaction conditions, a broad substrate scope, and excellent functional-group compatibility. Mechanistic studies support that the ketones initially undergo a Rh-catalyzed deoxygenation to give alkenes via boron enolate intermediates, and the subsequent Rh-catalyzed dehydrogenative borylation of alkenes leads to the formation of vinylboronates and diboration products, which is also supported by density functional theory calculations.

An efficient [3+2] annulation for the asymmetric synthesis of densely-functionalized pyrrolidinones and γ-butenolides.

Disclosed here is a new [3+2] annulation of siloxy alkynes that provides robust access to highly enantioenriched, densely-substituted pyrrolidinones and γ-butenolides, whose direct synthesis remains challenging. This process also represents a rare asymmetric synthesis of enantrioenriched molecules from siloxy alkynes.

Rational Design and Bulk Synthesis of Water-Containing Supramolecular Polymers.

The utilization of structural water in chemical self-assembly has not only effectively eliminated the negative influences of solvents from solutions or gels but has also provided new insight into the fabrication of new materials in bulk. However, up to now, supramolecular polymerization triggered by structural water has been dominated more by serendipity than rational design. After carefully analyzing the chemical structures of artificial monomers and gaining a deep understanding of the water-triggered assembly process, we report herein the bulk formation of polymeric materials from water and low-molecular weight monomers by rational design instead of serendipity.

Divergent and Stereoselective Synthesis of Tetraarylethylenes from Vinylboronates.

The synthesis of a new tetraborylethylene (TBE) is reported, and its application in the preparation of [4+0]-tetraarylethenes (TAEs) is elucidated. TAEs have widespread applications in material science and supramolecular chemistry due to their aggregation-induced emission (AIE) properties. The divergent and stereoselective synthesis of [3+1]-, [2+2]-, and [2+1+1]-TAEs via multiple couplings of vinylboronates with aryl bromides is demonstrated.

Lewis acid-promoted site-selective cyanation of phenols.

An efficient Lewis acid-promoted site-selective electrophilic cyanation of 3-substituted and 3,4-disubstituted phenols has been developed. The cyanation reactions using MeSCN as the cyanating reagent proceeded efficiently to afford a wide range of 2-hydroxybenzonitriles with high efficiency and excellent regioselectivity. This protocol could provide a practical method for the synthesis and modification of biologically active molecules.

Lewis Acid Mediated Electrophilic Cyanation of 2,2'-Biphenols.

A Lewis acid mediated electrophilic cyanation of 2,2'-biphenols with a trifluoromethanesulfonyl (Tf) protecting group is reported. The cyanation reactions with less toxic, commercially available MeSCN as a cyanating reagent afforded a range of 3-cyan-2,2'-biphenols in moderate to high yields. The use of trifluoromethanesulfonyl (Tf) as a protecting group is crucial to the success of this transformation.

Thermo/Anion Dual-Responsive Supramolecular Organoplatinum-Crown Ether Complex.

Stimuli-responsive complexes have attracted significant interest in supramolecular chemistry and material science. In this study, a new organoplatinum-crown supramolecular complex has been successfully constructed via the coordination of benzo-21-crown-7 () units and -Pt(PEt)(OTf). The resulting complex displays intriguing lower critical solution temperature (LCST) and anion-sensitive deassembly behavior.