Dimeric Manganese‐Catalyzed Hydroarylation and Hydroalkenylation of Unsaturated Amides

An unprecedented Mn(I)‐catalyzed selective hydroarylation and hydroalkenylation of unsaturated amides with commercially available organic boronic acids is reported. Alkenyl boronic acids have been successfully employed for the first time in Mn(I)‐catalyzed carbon–carbon bond formation. A wide array of β‐alkenylated amide products can be obtained in moderate to good yields, which offers practical access to five‐ and six‐membered lactams. This protocol has predictable regio‐ and chemoselectivity, excellent functional group compatibility and ease of operation in air, representing a significant step‐forward towards manganese‐catalyzed C?C coupling.     

Rh(I)-catalyzed asymmetric synthesis of 3-substituted isoindolinones through CO gas-free aminocarbonylation

A highly efficient and accessible synthesis of chiral 3-substituted isoindolinone frameworks is described. The synthesis involved the Rh(I)-catalyzed asymmetric arylation of boronic acids to 2-halobenzaldimines and the subsequent Rh(I)-catalyzed intramolecular aminocarbonylation of the resulting 2-halobenzylamines using an aldehyde as the carbonyl source. The method tolerates a variety of functional groups, yielding isoindolinone derivatives in moderate to high yields with high ee-values. In addition, two Rh(I)-catalyzed transformations could be efficiently accomplished in a one-pot sequence to give chiral isoindolinones by the simple addition of a ligand and an aldehyde after the Rh(I)-catalyzed asymmetric arylation.     

Tunable carbon-carbon and carbon-sulfur cross-coupling of boronic acids with 3,4-dihydropyrimidine-2-thiones

Direct microwave-assisted Pd(0)-catalyzed/Cu(I)-mediated carbon-carbon cross-coupling of 3,4-dihydropyrimidine-2-thiones and boronic acids under Liebeskind-Srogl conditions leads to 2-aryl-1,4-dihydropyrimidines in moderate to high yield. In contrast, Cu(II)-mediated reaction of the same substrates leads to carbon-sulfur cross-coupling. [reaction: see text]     

A Lewis Base Catalysis Approach for the Photoredox Activation of Boronic Acids and Esters

We report herein the use of a dual catalytic system comprising a Lewis base catalyst such as quinuclidin‐3‐ol or 4‐dimethylaminopyridine and a photoredox catalyst to generate carbon radicals from either boronic acids or esters. This system enabled a wide range of alkyl boronic esters and aryl or alkyl boronic acids to react with electron‐deficient olefins via radical addition to efficiently form C−C coupled products in a redox‐neutral fashion. The Lewis base catalyst was shown to form a redox‐active complex with either the boronic esters or the trimeric form of the boronic acids (boroxines) in solution.     

Mizoroki-Heck type reaction of organoboron reagents with alkenes and alkynes. A Pd(II)-catalyzed pathway with Cu(OAc)2 as an oxidant

[reaction: see text]. In contrast to the Pd(0)-catalyzed mechanism by Uemura, Mizoroki-Heck type reaction of boronic acids is found to proceed under a Pd(II)-mediated pathway using a catalytic amount of Pd(OAc)2 in the presence of Cu(OAc)2 as an oxidant. Treatment of a variety of alkenes with boronic acids, boronates, and sodium tetraphenylborate furnishes beta-arylated and alkenylated products in good to excellent yields. The reactions with norbornene, norbornadiene, and diphenylacetylene are also performed to give 1:2 or 2:1 coupling products.     

Allylpalladium umpolung in the three-component coupling synthesis of homoallylic amines

[Structure: see text] Homoallylic amines and alpha-amino esters were prepared via a Pd(II)-catalyzed coupling of boronic acids and 1,2-nonadiene with ethyl iminoacetate or aliphatic, aromatic, and heteroaromatic imines. The allylpalladium umpolung was induced by a Pd(OAc)2 catalyst with commercial phosphine ligands.     

Chan-Lam-type S-arylation of thiols with boronic acids at room temperature

In this work, an efficient CuSO(4)-catalyzed S-arylation of thiols with aryl and heteroaryl boronic acids at room temperature is established. This catalytic system can tolerate a wide variety of thiols and arylboronic acids in the presence of only 5 mol % of CuSO(4) as the catalyst and inexpensive 1,10-phen·H(2)O as the ligand. Moreover, this catalytic system used environment-friendly solvent (EtOH) and oxidant (oxygen).     

Silver catalyzed C–C and C–S coupling of aryl halides and thiols with boronic acids

An efficient Ag(I) catalyzed carbon–carbon and carbon–sulfur bond formation reaction of aryl halides and thiols with boronic acids has been demonstrated. Using this protocol, substrates with a wide range of functional group including electron-rich, and electron deficient substituents have been explored. These reactions are particularly useful to prepare symmetrical and unsymmetrical biphenyls and thioethers. These products were isolated in high yield.     

N-vinylpyridinium and -ammonium tetrafluoroborate salts: new electrophilic coupling partners for Pd(0)-catalyzed Suzuki cross-coupling reactions

N-Vinylpyridinium and -trialkylammonium tetrafluoroborate salts represent a new class of electrophilic coupling partner for Pd(0)-catalyzed Suzuki cross-coupling reactions and give very good to excellent yields of products with a wide range of boronic acids. The salts are easily prepared from activated acetylenes and pyridinium or trialkylammonium tetrafluoroborates to form crystalline, air-stable, and nonhygroscopic crystals. [reaction: see text].     

PdCl2(dppf)-catalyzed in situ coupling of 2-hydroxypyridines with aryl boronic acids mediated by PyBroP and the one-pot chemo- and regioselective construction of two distinct aryl-aryl bonds

We present a PdCl(2)(dppf)-catalyzed synthesis of 2-arylated pyridine derivatives via the in situ coupling of 2-OH pyridines and boronic acids mediated by PyBroP. In addition, the highly chemo- and regioselective construction of two different aryl-aryl bonds via a one-pot operation has also been demonstrated by the orthogonal use of this method with the Ni-catalyzed Suzuki-Miyaura coupling of phenols.     

The first synthesis of pyrido[2,1-a]phthalazinium system and its three thieno-fused analogues

Substituted biaryl compounds 9, 14–16 were synthesized through Pd(0)-catalyzed cross coupling reactions between boronic acids or tin derivatives and aryl halides. N-Amination, and subsequent ring closure resulted in the new angularly-fused pyrido[1,2-b]pyridazinium systems 1–4 . The use of silver oxide as a cocatalyst in the couplings of tin derivatives was essential in order to obtain rapid reaction and better yields. Structures were determined by ¹H nmr and ¹³C nmr spectra.     

Copper(I) 3-Methylsalicylate Mediates the Chan–Lam N-Arylation of Heterocycles

Copper(I) 3-methylsalicylate (CuMeSal) mediates N-arylation reactions between aryl boronic acids and aromatic heterocycles (Chan–Lam coupling) under moderate reaction conditions (K₂CO₃, methanol, 65 °C, in air, 3–5 h). Both electron-rich and electron-deficient aryl boronic acids and a diverse set of N-heterocycles were allowed to react and gave N-arylation products in reasonable yields, which demonstrate the utility of this catalyst.     

N-amidation by copper-mediated cross-coupling of organostannanes or boronic acids with o-acetyl hydroxamic acids

A general nonoxidative N-amidation of organostannanes and boronic acids has been developed. Under nonbasic conditions a wide variety of aryl, alkenyl, and heteroaryl organostannanes and boronic acids couple efficiently with O-acetyl hydroxamic acids in the presence of Cu(I) sources.     

Cp*RhIII-Catalyzed Sterically Controlled C(sp3)−H Selective Mono- and Diarylation of 8-Methylquinolines with Organoborons**

Herein, the Rh^III-catalyzed selective monoarylation and diarylation (symmetrical and unsymmetrical) of 8-methylquinolines with organoboron reagents are disclosed. The selective monoarylation of primary C(sp³)−H bonds is achieved by using 7-substituted 8-methylquinolines or by changing the quantity of the aryl boronic acids. The method is also applicable for the arylation of 2-ethylpyridines, and the heteroarylation with thiophene-2-ylboronic acids. Symmetrical and unsymmetrical diarylation of 8-methylquinolines have been carried out in one-pot and sequential manner, respectively. Late-stage monoarylation of oxime derivatives and gram-scale synthesis of monoarylated products has also been carried out. A mechanistic study revealed that the current reaction is first order with respect to both reactants and a five-membered rhodacycle intermediate may be involved in the catalytic cycle.     

Microwave-enhanced rhodium-catalyzed conjugate-addition of aryl boronic acids to unprotected maleimides

Various boronic acids were treated with a rhodium (I) catalyst enabling their 1,4-conjugate addition to unprotected maleimide. The scope of the reaction was explored to include both electron-rich and electron poor boronic acids. These reactions were also performed in the microwave resulting in reduced reaction times and improved efficiencies. Additionally, substrates that were recalcitrant under conventional conditions were successfully reacted under microwave conditions. The reaction worked satisfactorily with boronic acids having a free OH or NH group.     

Palladium-catalyzed allylic cross-coupling reactions of primary and secondary homoallylic electrophiles

The Pd(0)-catalyzed allylic cross-coupling of homoallylic tosylate substrates using boronic acids and pinacol esters is reported. The reaction uses 2-(4,5-dihydro-2-oxazolyl)quinoline (quinox) as a ligand and is performed at ambient temperature. The scope of the reaction is broad in terms of both the boronate transmetalating reagent and the substrate and includes secondary tosylates. Mechanistic studies support an alkene-mediated S(N)2-type stereoinvertive oxidative addition of unactivated primary and secondary alkyl tosylates.     

Benzylic substitution of gramines with boronic acids and rhodium or iridium catalysts

Gramine-MeI salts were useful starting materials for the synthesis of 3-benzyl- and 3-allylindoles by the 1,4-addition of boronic acids to the C=C-C=N linkages generated in situ under Rh(I)-catalysis. On the other hand, under Ir(I) catalysis, the reaction of gramines with indoles was used to produce nonsymmetrical diindolylmethanes. [reaction: see text]     

N-substituted imines by the copper-catalyzed N-imination of boronic acids and organostannanes with O-acyl ketoximes

Catalytic quantities of copper(I) or copper(II) sources catalyze the N-imination of boronic acids and organostannanes through reaction with oxime O-carboxylates under nonbasic conditions. This method tolerates various functional groups and takes place efficiently using aryl, heteroaryl, and alkenyl boronic acids and stannanes.     

Palladium-catalyzed tandem cyclization/Suzuki coupling of 1,6-enynes: reaction scope and mechanism

A palldium(0)-catalyzed tandem cyclization/Suzuki coupling reaction of various 1,6-enyne substrates was developed. This Pd-catalyzed enyne cyclization reaction represents a new process for the synthesis of stereodefined alpha-arylmethylene-gamma-butyrolactones, lactams, multifunctional tetrahydrofurans, pyrrolidines, and cyclopentanes. The mechanism of the reaction was studied by the employment of different enyne isomers and boronic acids; a pi-allyl palladium intermediate was suggested to explain the formation of the cyclic products. The stereochemistry of this reaction can be well explained by a chairlike transition state.     

乙二醇中钯催化无配体的室温Suzuki反应

报道了一种在室温下醋酸钯催化乙二醇中无外加配体的Suzuki反应体系.以K3PO4·7H2O为碱,在该体系中可高效进行芳基溴代物和芳基硼酸的Suzuki交叉偶联反应,具有反应条件温和、无需惰性气体保护等特点.在n(ArBr)=0.5mmol,n(ArB(OH)2)=0.75mmol,x(Pd(OAc)2)=0.5mol%,n(K3PO4·7H2O)=1.0mmol,v(乙二醇)=2ml的优化条件下,4-溴苯甲醚和苯硼酸反应20min,分离收率即达95%.