Nickel-catalyzed borylation of halides and pseudohalides with tetrahydroxydiboron [B2(OH)4]

3-Cyanoallyl boronates are versatile building blocks in the synthesis of polysubstituted thiophenes

We report the preparation of hitherto unprecedented 3-cyanoallyl boronates using condensation of the parent α-boryl aldehyde and nitriles. The resulting allyl boronates have been used to generate a wide range of borylated thiophenes, which represent a valuable class of heterocycles in modern drug discovery. Subsequent Suzuki-Miyaura cross-coupling enabled the synthesis of pharmaceutically important 3,5-disubstituted aminothiophenes. Moreover, late stage functionalization gave access to borylated bromothiophene and thieno[2,3-b]pyridines.

Convenient and General Zinc-Catalyzed Borylation of Aryl Diazonium Salts and Aryltriazenes under Mild Conditions

A convenient and general zinc‐catalyzed borylation of aryl diazonium salts and aryltriazenes has been developed. With bis‐ (pinacolato)diboron as the borylation reagent, aryldiazonium tetrafluoroborate salts and aryltriazenes were transformed into the corresponding arylboronates in moderate to excellent yields under mild conditions. As a convenient and practical methodology, no additional ligands, base, or any other additives are required here.

Well-defined nickel and palladium precatalysts for cross-coupling

Transition metal-catalysed cross-coupling is one of the most powerful synthetic methods and has led to vast improvements in the synthesis of pharmaceuticals, agrochemicals and precursors for materials chemistry. A major advance in cross-coupling over the past 20 years is the utilization of well-defined, bench-stable Pd and Ni precatalysts that do not require the addition of free ancillary ligand, which can hinder catalysis by occupying open coordination sites on the metal. The development of precatalysts has resulted in new reactions and expanded substrate scopes, enabling transformations under milder conditions and with lower catalyst loadings. This Review highlights recent advances in the development of Pd and Ni precatalysts for cross-coupling, and provides a critical comparison between the state of the art in Pd- and Ni-based systems.

Formal nucleophilic borylation and borylative cyclization of organic halides

Recent advances in borylations of organic halides, including both transition-metal-catalyzed and metal-free methods are summarized. Borylative cyclization is also discussed.

Crystal structure of 2-isopropyl-5,7'-dimethyl-1',3',3a',6',8a',8b'-hexa-hydro-spiro-[cyclo-hexane-1,6'-furo[3,4-d]imidazo[1,5-b]isoxazol]-8'(7'H)-one

Cyclo­addition reaction between a menthone-based chiral nitrone and 2,5-di­hydro­furan under microwave activation affords a enanti­opure cyclo­adduct in good yields and with high stereoselectivity

In the title compound, C₁₇H₂₈N₂O₃, the isoxazolidine ring adopts an envelope conformation with the O atom deviating from the mean plane of the other four ring atoms by 0.617 (1) Å. In the crystal, mol­ecules are linked via weak C—H⋯O hydrogen bonds, forming chains which extend along the b-axis direction.

Diboron(4) Compounds: From Structural Curiosity to Synthetic Workhorse

Although known for over 90 years, only in the past two decades has the chemistry of diboron(4) compounds been extensively explored. Many interesting structural features and reaction patterns have emerged, and more importantly, these compounds now feature prominently in both metal-catalyzed and metal-free methodologies for the formation of B-C bonds and other processes.

Efficient metal-free photochemical borylation of aryl halides under batch and continuous-flow conditions

A rapid, chemoselective and metal-free C-B bond-forming reaction of aryl iodides and bromides in aqueous solution at low temperatures was discovered. This reaction is amenable to batch and continuous-flow conditions and shows exceptional functional group tolerance and broad substrate scope regarding both the aryl halide and the borylating reagent. Initial mechanistic experiments indicated a photolytically generated aryl radical as the key intermediate.

Scalable, Metal- and Additive-Free, Photoinduced Borylation of Haloarenes and Quaternary Arylammonium Salts

We report herein a simple, metal- and additive-free, photoinduced borylation of haloarenes, including electron-rich fluoroarenes, as well as arylammonium salts directly to boronic acids. This borylation method has a broad scope and functional group tolerance. We show that it can be further extended to boronic esters and carried out on gram scale as well as under flow conditions.

Metal-free borylation of electron-rich aryl (pseudo)halides under continuous-flow photolytic conditions

A photochemical borylation of electron-rich aryl (pseudo)halides via a triplet aryl cation mechanism has been described.

A mild carbon-boron bond formation from diaryliodonium salts

The direct metal-free borylation of diaryliodonium salts with diboron reagents is now demonstrated to be a feasible process toward formation of aryl boronic esters without any additive or catalysts, and it can be extended to a two-step C-C coupling of both aryl groups of the initial diaryliodonium reagent.

Mono-Oxidation of Bidentate Bis-phosphines in Catalyst Activation: Kinetic and Mechanistic Studies of a Pd/Xantphos-Catalyzed C-H Functionalization

Kinetic, spectroscopic, crystallographic, and computational studies probing a Pd-catalyzed C-H arylation reaction reveal that mono-oxidation of the bis-phosphine ligand is critical for the formation of the active catalyst. The bis-phosphine mono-oxide is shown to be a hemilabile, bidentate ligand for palladium. Isolation of the oxidative addition adduct, with structural elucidation by X-ray analysis, showed that the mono-oxide was catalytically competent, giving the same reaction rate in the productive reaction as the Pd(II)/xantphos precursor. A dual role for the carboxylate base in both catalyst activation and reaction turnover was demonstrated, along with the inhibiting effect of excess phosphine ligand. The generality of the role of phosphine mono-oxide complexes in Pd-catalyzed coupling processes is discussed.

A modified procedure for the palladium catalyzed borylation/Suzuki-Miyaura cross-coupling of aryl and heteroaryl halides utilizing bis-boronic acid

A modified Pd-catalyzed method of forming aryl- and heteroarylboron species and a two-step, one-pot borylation/Suzuki-Miyaura cross coupling using the atom economical tetrahydroxydiboron (bis-boronic acid, BBA) is reported. By using ethylene glycol as an additive, the new method results in increased yields, lower BBA loading, faster reaction times, and a broader reaction scope, including previously problematic substrates such as heterocycles.

A practical and general ipso iodination of arylboronic acids using N-iodomorpholinium iodide (NIMI) as a novel iodinating agent: mild and regioselective synthesis of aryliodides

A mild and efficient protocol for the ipso-iodination of aryl boronic acids using N-iodomorpholinium iodide (NIMI) generated in situ from morpholine and molecular iodine as a novel iodinating agent has been developed.

Direct introduction of a naphthalene-1,8-diamino boryl [B(dan)] group by a Pd-catalysed selective boryl transfer reaction

Under Palladium-catalysed Miyaura-type reaction conditions, a non-symmetrical diboron reagent, B(pin)-B(dan), was found to selectively deliver the B(dan) moiety to aryl bromides and chlorides. This method represents a direct and efficient way to masked boronic acids and boron-differentiated di- and polyboron compounds.

A fluoride-driven ionic gate based on a 4-aminophenylboronic acid-functionalized asymmetric single nanochannel

Fluorine is one of the human body's required trace elements. Imbalanced fluoride levels severely affect the normal functioning of living organisms. In this article, an anion-regulated synthetic nanochannel is described. A fluoride-driven ionic gate was developed by immobilizing a fluoride-responsive functional molecule, 4-aminophenylboronic acid, onto a single conical polyimide nanochannel. When the ionic gate was in the presence of fluoride, the boron bound F-, and the hybridization of the boron center changed from sp2 to sp3. Thus, negatively charged monofluoride adduct (RB(OH)2F-), difluoride adduct (RB(OH)F2-), and trifluoride adduct (RBF3-) modified surfaces with different wettability would be formed successively by increasing the concentration of F-. On the basis of the variation of surface charge and wettability, the nanochannel can actualize reversible switching between the "off" state and the "on" state in the absence and presence of F-, respectively. As an anion-regulated synthetic nanochannel, this fluoride-driven ionic gate was characterized by measuring ionic current, which possesses high sensitivity, fine selectivity, and strong stability. Thus, this gate may show great promise for use in biosensors, water quality monitoring, and drug delivery.

Arylation and heteroarylation of thienylsulfonamides with organotrifluoroborates

A mild, practical protocol has been developed for the Suzuki cross-coupling of unprotected thienylsulfonamides from air- and bench-stable organotrifluoroborates in the absence of a protecting group on the sulfonamide nitrogen. The developed synthetic method can be applied to the preparation of various arylated and heteroarylated thienylsulfonamides under conditions that are tolerant of a broad range of functional groups.

Palladium-catalyzed hydroxylation of aryl and heteroaryl halides enabled by the use of a palladacycle precatalyst

A method for the hydroxylation of aryl and heteroaryl halides, promoted by a catalyst based on a biarylphosphine ligand tBuBrettPhos (L5) and its corresponding palladium precatalyst (1), is described. The reactions allow the cross-coupling of both potassium and cesium hydroxides with (hetero)aryl halides to afford a variety of phenols and hydroxylated heteroarenes in high to excellent yield.

Copper nanoparticle-catalyzed borylation of alkyl bromides with an organodiboron compound

Borylation of primary and secondary alkyl bromides with bis(pinacolato)diboron was carried out in the presence of commercially available copper nanoparticles as catalysts.

Ni(ii)–salt catalyzed activation of primary amine-sp3Cα–H and cyclization with 1,2-diketone to tetrasubstituted imidazoles

NiCl₂·6H₂O and Ni(OAc)₂·4H₂O were found as efficient catalysts for C–H activation of benzyl and aliphatic amines for an unprecedented multi C–N bond forming cyclization with 1,2-diketones under refluxing toluene to furnish highly substituted and polycyclic imidazoles.