Vinylboronic Acids Research Articles

A general, simple catalyst for enantiospecific cross couplings of benzylic ammonium triflates and boronic acids: no phosphine ligand required

Highly improved conditions for the enantiospecific cross coupling of benzylic ammonium triflates with boronic acids are reported. This method relies on the use of Ni(cod)2 without ancillary phosphine or N-heterocyclic carbene ligands as catalyst. These conditions enable the coupling of new classes of boronic acids and benzylic ammonium triflates. In particular, both heteroaromatic and vinyl boronic acids are well tolerated as coupling partners. In addition, these conditions enable the use of ammonium triflates with a variety of substituents at the benzylic stereocenter. Further, naphthyl-substitution is not required on the benzylic ammonium triflate; ammonium triflates with simple aromatic substituents also undergo this coupling. Good to high yields and levels of stereochemical fidelity are observed. This new catalyst system greatly expands the utility of enantiospecific cross couplings of these amine-derived substrates for the preparation of highly enantioenriched products.

ChemInform Abstract: Palladium‐Catalyzed Suzuki—Miyaura Cross‐Coupling of α‐Halomethyl Oxime Ethers and Site‐Selective Cross‐Coupling of Dihalo Derivatives.

AbstractThe Pd‐catalyzed cross‐coupling reaction of chloromethyl oxime ethers with a wide range of aryl‐, heteroaryl‐, and vinylboronic acids proceeds with good yields.

Copper-catalyzed trifluoromethylthiolation of aryl and vinyl boronic acids with a shelf-stable electrophilic trifluoromethylthiolating reagent

A new high yielding method for the preparation of a shelf-stable electrophilic trifluoromethylthiolating reagent, N-(trifluoromethylthio)phthalimide, is described. Reaction of this reagent with a variety of aryl and vinyl boronic acids in the presence of a copper catalyst generated the trifluoromethylthiolated arenes and alkenes in good to excellent yields.

Mn(II)/O2-promoted oxidative annulation of vinyl isocyanides with boronic acids: synthesis of multi-substituted isoquinolines.

An efficient manganese(II)/O2-promoted oxidative radical cascade reaction was developed for the modular synthesis of multi-substituted isoquinolines from easily accessible vinyl isocyanides and boronic acids.

ChemInform Abstract: Ligand‐Dependent Site‐Selective Suzuki Cross‐Coupling of 3,5‐Dichloropyridazines.

General methods for the highly site-selective Suzuki monocoupling of 3,5-dichloropyridazines have been discovered. By changing the ligand employed, the preferred coupling site can be switched from the 3-position to the 5-position, typically considered the less reactive C–X bond. These conditions are applicable to the coupling of a wide variety of aryl-, heteroaryl-, and vinylboronic acids with high selectivities, thus enabling the rapid construction of diverse arrays of diarylpyradazines in a modular fashion.

Synthesis of trans-2-(Trifluoromethyl)cyclopropanes via Suzuki Reactions with an N-Methyliminodiacetic Acid Boronate

trans-2-(Trifluoromethyl)cyclopropylboronic acid N-methyliminodiacetic acid (MIDA) ester 5 was synthesized as a pure diastereomer from vinylboronic acid MIDA ester and (trifluoromethyl)diazomethane in a single step. An X-ray study confirmed the trans-stereochemistry around the cyclopropyl ring. Use of 5 in Suzuki reactions, with a variety of aryl or heteroaryl coupling partners, provided trans-2-(trifluoromethyl)cyclopropyl products in moderate to excellent yields (17-90%).

Palladium‐Catalyzed Suzuki–Miyaura Cross‐Coupling of α‐Halomethyl Oxime Ethers and Site‐Selective Cross‐Coupling of Dihalo Derivatives

AbstractThe cross‐coupling reaction of chloro‐ and bromomethyl oxime ethers with a wide range of aryl‐, heteroaryl‐ and vinylboronic acids in the presence of catalytic palladium complexes with different phosphines has been carried out with good yields (60–98%, 40 examples). Regioselective cross‐coupling reactions differentiating between an alkyl or aryl position are achieved from dihalo oxime ethers containing Csp2‐ and Csp3‐halogen bonds using mono‐ or dicoordinated palladium catalysts such as Pd(dba)2/P(o‐tolyl)3 or Pd(PPh3)4. The selective orthogonal functionalization of dihalo oxime ethers is also described. Site‐selective transformations allow the introduction of the biaryl motif into dihalo oxime ethers preserving the highly activated alkyl halide moiety vicinal to the oxime group for further transformations. In this context, Z‐ and E‐oxime ethers could be considered as synthetic equivalents of ketones in palladium‐catalyzed Suzuki reactions.magnified image

Ligand-Dependent Site-Selective Suzuki Cross-Coupling of 3,5-Dichloropyridazines

General methods for the highly site-selective Suzuki monocoupling of 3,5-dichloropyridazines have been discovered. By changing the ligand employed, the preferred coupling site can be switched from the 3-position to the 5-position, typically considered the less reactive C-X bond. These conditions are applicable to the coupling of a wide variety of aryl-, heteroaryl-, and vinylboronic acids with high selectivities, thus enabling the rapid construction of diverse arrays of diarylpyradazines in a modular fashion.

Synthesis of 5-substituted 3-mercapto-1,2,4-triazoles via Suzuki–Miyaura reaction

Abstract 3-Bromo- and 3-iodo-N,S-dibenzyl-5-mercapto-1,2,4-triazoles were prepared and demonstrated as versatile building blocks for Suzuki–Miyaura cross-coupling with aryl, heteroaryl, and vinyl boronic acid derivatives. Deprotection of the resulting coupling products provided 5-substituted-3-mercapto-1,2,4-triazoles in good overall yields. This represents a novel and convenient approach for the introduction of a 3-mercapto-1,2,4-triazole substructure into target compounds.

ChemInform Abstract: Copper‐Catalyzed Trifluoromethylation of Aryl‐ and Vinylboronic Acids with Generation of CF3‐Radicals.

AbstractThe title reaction uses less expensive and stable Langlois reagent, CF3SO2Na, as the CF3 source and relies both on transition metal catalysis and selective radical reactions.

Copper-Catalyzed Trifluoromethylation of Aryl- and Vinylboronic Acids

Key words boron - copper - Langlois reagent - trifluoromethylation

ChemInform Abstract: Preparation and Rearrangement of N‐Vinyl Nitrones: Synthesis of Spiroisoxazolines and Fluorene‐Tethered Isoxazoles.

AbstractThe thermal rearrangement of fluorenone N‐vinyl nitrones (IIIc)‐(IIIf) gives rise to spiroisoxazolines such as (VIII) and (IX).

Thiadiazoloquinoxaline-Based Narrow Energy Gap Molecules for Small Molecule Solar Cell Applications

Polymer bulk heterojunction (BHJ) solar cells consisting of the photoactive layer containing the interpenetrating network of electron donating polymer and electron accepting PC71BM has been proved to be quite effective in converting the solar energy into electrical energy. After many efforts, the power conversion efficiency (PCE) of the polymer solar cells (PSCs) was improved up to 9.2%. Unfortunately, the PCEs of the PSCs were found to be highly affected by the synthetic characteristics of the donor polymers. At present, the poor reproducibility of the synthetic polymer characteristics such as purity, molecular weight, regioregularity and polydispersity of each batch of the polymerization limits the commercial application of PSCs. On the other hand, small molecule organic solar cells (SMOSCs) fabricated from the photoactive layer containing organic small molecule as an electron donor and PC71BM as an electron acceptor also showed promising performances in terms of PCE. The PCE of the solution-processed SMOSCs was reached up to 7%. and that for the vacuum-processed tandem SMOSCs was improved up to 10.7%. The overall PCE of SMOSCs is quite close to the maximum PCE obtained from the PSCs. This inspires us to develop new low band gap small molecules for SMOSCs application. It is well known that the PCE of solar cell devices is strongly dependent on the light harvesting ability of the photoactive layer. To improve the light harvesting ability of the active layer, it is essential to utilize the donor molecules which can absorb the sun light from 300 nm to 1000 nm, along with that the absorption band of donor molecules should be located at the maximum solar flux region (500 nm to 800 nm) of the solar spectra. In our attempt to prepare narrow energy gap small molecules, we were interested in utilizing thiadiazoloquinoxaline units, because certain polymers containing thiadiazoloquinoxaline units have been known to show their absorption band from 300 nm to 1200 nm. In this study, we prepared two new thiadiazoloquinoxaline-based low band gap small molecules, TDQ-SM1 and TDQ-SM2, shown in Scheme 1 and studied their optical, electrical and photovoltaic properties. In this study, to recognize the influence of the substituent bonded to the quinoxaline ring of the thiadiazoloquinoxaline unit, isobutyl and thiophene substituted thiadiazoloquinoxaline compounds 1 and 2 were coupled with commercially available trans-2-(4-pentylphenyl)vinylboronic acid pinacol

An Electrophilic Hypervalent Iodine Reagent for Trifluoromethylthiolation

Sulfur and friends: A new electrophilic hypervalent iodine reagent 1 has been developed for direct trifluoromethylthiolation. A variety of nucleophiles, including β-ketoesters, aldehydes, amides, aryl or vinyl boronic acids, and alkynes, reacted with 1 under mild conditions to give the corresponding trifluoromethylthiolated compounds in good to excellent yields.

Pd-catalyzed Suzuki coupling reaction of chloroalkylidene-β-lactones with LB-Phos as the ligand

In this paper, LB-Phos·HBF(4) salt has been applied for the Pd-catalysed Suzuki coupling reactions of optically active (Z)-α-choroalkylidene-β-lactones. Aryl, vinyl, alkyl and heteroaromatic boronic acids may be coupled with optically active β-lactones affording corresponding optically active products highly selectively and efficiently.

Copper-catalyzed trifluoromethylation of aryl- and vinylboronic acids with generation of CF3-radicals

The selective trifluoromethylation of aryl- and vinylboronic acids proceeds smoothly with CF3SO2Na (Langlois reagent) in the presence of copper catalysts and t-BuOOH. Therefore, the method relies both on transition metal catalysis and selective radical reactions. Advantageously, the protocol can be performed at room temperature under an air atmosphere and avoids the issue of poor regioselectivity.

A General Method for the Enantioselective Synthesis of α-Chiral Heterocycles

The enantioselective formation of stereocenters proximal to unprotected heterocycles has been accomplished. Thus, vinyl boronic acids are added to heterocycle-appended enones via a modified-BINOL catalyst. Catalyst design was key to enable a general reaction. High yields and useful er's are observed for a host of common heteroaryls.

ChemInform Abstract: Optimized Conditions for Styrene Syntheses Using Suzuki—Miyaura Couplings and Catalyst‐Ligand‐Base Pre‐Mixes.

AbstractPre‐mixes of catalyst, ligand and base are used for the Suzuki—Miyaura coupling of 2‐bromo‐benzylamines (I) with vinylboronic acids (II).

Preparation and Rearrangement of N-Vinyl Nitrones: Synthesis of Spiroisoxazolines and Fluorene-Tethered Isoxazoles

N-Vinyl nitrones derived from fluorenone have been prepared via a copper-mediated coupling between fluorenone oxime and vinyl boronic acids. These compounds undergo subsequent rearrangement and addition reactions that are distinct from the traditional [3 + 2] cycloaddition reactivity of nitrones. Thermal rearrangements of fluorenone N-vinyl nitrones give spiroisoxazolines, while treatment with alkynes provides fluorene-tethered isoxazoles. The scope and limitations of the preparation of fluorenone N-vinyl nitrones and their subsequent rearrangement and addition reactions are discussed.

Catalyst-controlled regioselectivity in the synthesis of branched conjugated dienes via aerobic oxidative Heck reactions.

Pd-catalyzed aerobic oxidative coupling of vinylboronic acids and electronically unbiased alkyl olefins provides regioselective access to 1,3-disubstituted conjugated dienes. Catalyst-controlled regioselectivity is achieved by using 2,9-dimethylphenanthroline as a ligand. The observed regioselectivity is opposite to that observed from a traditional (nonoxidative) Heck reaction between a vinyl bromide and an alkene. DFT computational studies reveal that steric effects of the 2,9-dimethylphenanthroline ligand promote C-C bond formation at the internal position of the alkene.