Cu-catalyzed regioselective diborylation of 1,3-enynes for the efficient synthesis of 1,4-diborylated allenes

Borylation of 1,3-enynes with bis(boronate)compounds often ends up with the formation of hydroborylated products,leaving the diborylation of 1,3-enynes for the formation of 1,4-diborylated allenes to be challenging.Herein,a copper-catalyzed chemo-,regio-,and stereo-selective diborylation of 1,3-enynes for the efficient construction of 1,4-diborylated allenes under base-free conditions was reported.A wide range of 1,3-enynes bearing various functional groups can participant in the reaction and afforded the corresponding 1,4-diborylated allenes in good to excellent yields,which was enabled by the protocol of Bpin to BF3K conversion.the borylcopper species was supposed to selectively attack the C-C triple bond of the 1,3-enynes.

Cobalt-catalyzed deoxygenative borylation of diaryl ketones

Geminal diboronates and diarylmethyl boronates are versatile building blocks in synthetic chemistry.We here reported a highly efficient approach for the synthesis of gem-bisborylalkanes and diarylmethyl boronates via cobalt-catalyzed deoxygenative borylation of diaryl ketones.This borylation protocol is compatible with a broad range of functionalized aryl groups,providing access to a wide array of boronic esters.The resulting boronic esters can be further transformed to various cross-coupling products and TPEs that represent important structural motifs in organic chemistry and materials science.

Electrochemical borylation of nitroarenes

A simple electrochemically mediated method for the conversion of nitroarenes to aryl boronic esters is presented.Electrochemical borylation of a diverse range of nitroarenes,including the late-stage borylation of bioactive molecules,is furnished at room temperature under simple conditions,thereby demonstrating the broad utility and functional-group tolerance of this protocol.This transformation provides a convenient and practical access to aryl boronic esters from widely available nitroarenes,which would significantly streamline the synthetic process of diverse functionalized arenes.

Heterogeneous photocatalytic borylation of aryl iodides mediated by isoreticular 2D covalent organic frameworks

Metal-free heterogeneous photocatalysts provide an environmental-friendly and cost-efficient avenue for green organic synthesis.Covalent organic frameworks(COFs)as heterogeneous photocatalysts showcase promising potential in the field of photocatalytic organic reactions due to their high porosity,insolubility and tailor-made functions.However,thus far,COF-based catalysts only mediated a few types of reactions.Herein,we developed a series of isoreticular nitrogen-rich covalent organic frameworks(N-COFs)with comparable porous structures as photocatalysts which effectively mediated the borylation of aryl iodides with broad substrate scope.Remarkably,6N-COF exhibits excellent photocatalytic efficiency and superior recyclability.It suggests a new pathway to construct efficient heterogeneous photocatalysts for the borylation of aryl halides.

Control of meta-selectivity in the Ir-catalyzed aromatic C-H borylation directed by hydrogen bond interaction:A combined computational and experimental study

The origin of regioselectivity in meta-selective C-H borylation of benzamides directed by hydrogen bond interaction between ligand and substrate is elucidated through combined computational and experimental studies.We discover that a non-directed pathway,in which the urea moiety in ligand recognizes the O atom in Bpin instead of substrate,competes with the directed pathway and erodes the meta-selectivity.The non-directed pathway is sensitive to steric repulsion between Bpin and urea,and thus can be impeded by introducing a bulky substituent into the urea moiety.Accordingly,we optimize the ligand and improve the meta-selectivity in the Ir-catalyzed C-H borylation of some previously reported unsuccessful arenes.

Synergistic Pd/Cu-catalyzed regio-and stereoselective cascade Heck cyclization/borylation/cross-coupling

A cooperative Pd/Cu-catalyzed three-component cross-coupling reaction of alkynes,B_(2)Pin_(2) and alkene-tethered aryl halides is reported.This reaction proceeds under mild conditions and shows broad sub-strate scope,providing a variety of heterocycles containing tetrasubstituted alkenylboronate moieties in synthetically useful yields with excellent chemoselectivity and regioselectivity.This transformation fea-tures the catalytic generation ofβ-borylalkenylcopper intermediates and their use in Pd-catalyzed Heck cyclization/cross-couplings.An enantioselective cascade cyclization/cross-coupling process has also been developed for the synthesis of enantiomerically enriched oxindole bearing a tetrasubstituted alkenyl-boronate moiety.

Protecting-group-free ortho-C–H borylation of anilines enabled by mesoionic carbene-Ir complex

We describe an iridium-catalyzed ortho-selective C–H borylation of unprotected anilines.The employing strongσ-donating cyclometalated mesoionic carbene as C^C bidentate ligand is crucial for the high ortho-selectivity.Computational studies support outer-sphere X–H⋅⋅⋅O_(boryl) hydrogen bond interactions,which are strengthened by bidentate C^C ligand introduction.The method shows broad substrate scope and high functional group tolerance.

Atomically Precise Metal Nanoclusters as Single Electron Transferers for Hydroborylation

The emergence of metal nanoclusters with atomically precise compositions and structures provides an opportunity for in-depth investigation of catalysis mechanisms and structure−property correlations at the nanoscale.However,a serious problem for metal nanocluster catalysts is that the ligands inhibit the catalytic activity through deactivating the surface of the nanoclusters.Here,we introduce a novel catalytic mode for metal nanoclusters,in which the nanoclusters initiate the catalysis via single electron transfer(SET)without destroying the integrity of nanoclusters,providing a solution for the contradiction between activity and stability of metal nanoclusters.We illustrated that the novel activation mode featured low catalyst loading(0.01 mol%),high TOF,mild reaction conditions,and easy recycling of catalyst in alkyne hydroborylation,which often suffered from poor selectivity,low functional group tolerance,etc.Furthermore,the catalyst[Au_(1)Cu_(14)(TBBT)_(12)(PPh_(3))_(6)]^(+)(TBBTH:p-tert-butylthiophenol)can be applied in highly efficient tandem processes such as hydroborylation−deuteration and hydroborylation−isomerization,demonstrating the utility of the introduced activation mode for metal nanoclusters.

Transition Metal Catalyzed Direct Oxidative Borylation of C--H Bonds

Organoboron is well-developed and broadly utilized organometallic reagents in organic synthesis due to its extraordinary performances in transition-metal catalyzed C-C and C-X bonds construction. Catalytic C--H borylation and further transformations catalyzed by transition metal catalysts in the absence of oxidants were well studied in decades. However, as known, transition metal catalyzed oxidative C-H borylations were not reviewed up to date. In this article the oxidative borylation of C（sp2）-H and C（sp3）-H bonds were summarized and their mechanisms were also accounted.

Base-catalyzed diborylation of alkynes: synthesis and applications of cis-1,2-bis(boryl)alkenes

An efficient, transition-metal free, and practical approach to cis-bis(boryl)alkenes from various alkynes was disclosed in the presence of a catalytic amount of K_2CO_3 under mild conditions. Meanwhile, tetrasubstituted alkenes and phenanthrene derivatives were readily constructed from the target diborylalkenes via Suzuki-Miyaura cross coupling.

Iron-Catalysed C(sp^(2))-H Borylation with Expanded Functional Group Tolerance

Arene C(sp^(2))-H bond borylation offers direct and efficient access to aryl boronic esters.Using in situ catalyst activation and photoirradiation,the iron-catalysed C(sp^(2))-H borylation reaction of carboarenes,pyrroles,and indoles has been developed using only bench-stable pre-catalysts and reagents.Good functional group tolerance was observed including those not reported using previous methods(ArNH_(2),ArOH,ArSiR_(3),ArP(O)(O)_(2),ArC(O)NR_(2)).Mechanistic studies revealed iron-catalysed reductive deoxygenation,C—F protodefluorination,and a demethylation of aryl methyl ethers by C—O sigma bond hydroboration.

Electrochemical Radical Borylation of Aryl Iodides

Herein,we report the first electrochemical strategy for the borylation of aryl iodides via a radical pathway using current as a driving force.A mild reaction condition allows an assorted range of readily available aryl iodides to be proficiently converted into synthetically valuable arylboronic esters under transition metal catalyst-free conditions.Moreover,this method also shows good functional group tolerance.Initial control mechanistic experiments reveal the formation of aryl radical as a key intermediate and the current plays an important role in the generation of radical intermediate.

Electrochemically promoted decarboxylative borylation of alkyl N-hydroxyphthalimide esters

An electrochemically promoted decarboxylative borylation reaction is reported. The reaction proceeds under mild conditions in an undivided cell without use of transition metal-or photo-catalysts. The key feature of the reaction is the compatibility of diboron reagents with the electrochemical conditions. This reaction exhibits broad substrate scope, good functional group tolerability, and easy scalability.

Access to chiral homoallylic vicinal diols from carbonyl allylation of aldehydes with allyl ethers via palladium-catalyzed allylic C-H borylation

Chiral homoallylic vicinal diols are found in many bioactive compounds and are among the most versatile functional groups in organic chemistry. Here, we describe an asymmetric carbonyl allylation of aldehydes with allyl ethers proceeding via allylic C-H borylation enabled by palladium and chiral phosphoric acid sequential catalysis, providing facile access to homoallylic vicinal anti-diols in high yields and with excellent stereoselectivity. This protocol enables the total synthesis of aigialomycin D to be finished within 7 steps.

Access to Stereodefined Multifunctionalizedβ,γ-Unsaturated Ketones via Chemo,Regio-and Diastereoselective Copper-Catalyzed Diborylation of Cross-Conjugated Enynones

Main observation and conclusion Stereodefinedβ,γ-unsaturated carbony|compounds are important yet synthetically challenging units in natural products and drugs.Disclosed herein is a mild,rapid copper-catalyzed diborylation reaction of cross-conjugated enynones as a step-economic and modular approach to stereodefined multifunctionalizedβ,γ-unsaturated ketones by fine control of chemo-,regio-,Z/E and diastereoselectivity.The substrate scope was examined and a possible catalytic cycle was proposed to explain the multifaceted selectivity.

Metal-free directed C-H borylation of 2-(N-methylanilino)-5-fluoropyridines and 2-benzyl-5-fluoropyridines

A novel method for metal-free C-H borylation of 2-(N-methylanilino)-5-fluoropyridines and 2-benzyl-5-fluoropyridines has been reported. The 5-fluoropyridine directed borylation reaction exhibited high efficiency and site exclusivity. The useful protocol could be executed on a gram-scale easily and the borylated products showed good derivatization applications. Moreover, the practicality of the strategy was expanded by the fact that the directing group could be removed in an acceptable yield.

Iron-Catalyzed Borylation and Silylation of Unactivated Tertiary,Secondary,and Primary Alkyl Chlorides

Herein,we describe an iron-catalyzed borylation and silylation of unactivated alkyl chlorides,delivering the tertiary,secondary,and primary alkylboronic esters,and secondary,primary alkylsilanes with high efficiency.This protocol exhibits broad substrate scope and good functional group compatibility,allowing the efficient late-stage borylation of biorelevant compounds,thus offering an excellent platform in drug discovery and development.Preliminary mechanistic studies suggest that an alkyl radical was involved in this catalytic system.

Synthesis,Structures,and Chiroptical Properties of NBN-Doped Helicenes with Boron Atoms in the Inner Rims

The precise synthesis of helicenes with topologically defined length and specific heteroatomic perturbation in the screw-like conjugated skeletons plays an emerging role in the manipulation of chiral materials.Facile,selective,and programmable routes to helicenes or heterohelicenes are highly desirable yet challenging for structure-chiroptical property relationship studies.Herein,we report the synthesis and characterization of NBN-doped helicenes with boron atoms in the inner rims,enabled by the highly regioselective one-pot borylation of rationally designed precursors with,namely,fold-in or pan-out manner.The incorporation of nonbonded boron and nitrogen atoms resulted in narrow-band emission and improved optical properties for the single-stranded carbon helix.In addition,numbers and arrangement modes of fused six-membered rings have distinct effects on configurational stability and chiroptical properties,revealing that BN-[6]H with strong circular dichroism is a promising candidate for chiral sensors.The combination of experimental and theoretical studies on these helical structures might provide insights into the design of helically chiral small-molecule-based sensors or emitters.

Chlorine Atom Transfer of Unactivated Alkyl Chlorides Enabled by Zirconocene and Photoredox Catalysis

Alkyl chlorides are robust precursors to carbon radicals;however,their relative inertness has hampered their practical use.Although modern photochemical strategies have greatly enhanced the utility of alkyl chlorides as radical precursors,these methods often depend on strongly reducing conditions leading to unproductive side reactions.Here,we report a catalytic radical generation from 1°,2°,and 3°unactivated alkyl chlorides with zirconocene and photoredox catalysis,which enables both hydrogenation and borylation on a range of structurally complex molecules.This mild zirconocene-catalyzed protocol shows that zirconium can render the C−Cl bond cleavage more exergonic and can lower the activation energy of the transition state,amplifying the ability of metallocenes toward halogen atom transfer.

An Olefinic 1,2-α-Boryl Migration Enables 1,2-Bis(boronic esters)via Radical-Polar Crossover Reaction

A radical-induced 1,2-α-boryl migration through radical polar crossover reactions has been described.In this work,in situ formed vinyldiboron“ate”complexes from alkenyl Grignard reagent and diborylalkanes react with commercial radical precursors under light initiation.This three-component process enables diborylation of alkene.This protocol features high atom economy,a broad substrate scope as well as good functional group toleration with mild conditions.