Metal-free synthesis of aryl esters by coupling aryl carboxylic acids and aryl boronic acids

A facile synthesis of aryl esters is developed by coupling aryl carboxylic acids and aryl boronic acids in the presence of PhI(OAc)₂ and carbonyl diimidazole. A wide range of functional groups were tolerant to the metal-free reaction condition that led to the desired products in good yields.     

CuI-catalyzed direct synthesis of diaryl thioethers from aryl boronic acids and arylsulfonyl chlorides

A CuI-catalyzed direct coupling of aryl boronic acids with arylsulfonyl chlorides for the preparation of diaryl thioethers was developed. The reaction is initiated by a PPh₃ reduction of the arylsulfonyl chloride, followed by a CuI-catalyzed C–S coupling with an aryl boronic acid. Various arylsulfonyl chlorides can directly serve as a sulfur source in this mild and efficient reaction giving the desired products in moderate to good yields. Moreover, this practical method has also been applied to the thioetherification of aryl iodides and acetylacetones.     

A mild and efficient copper-catalyzed N-arylation of unprotected sulfonimidamides using boronic acids

An efficient and low cost copper catalyzed system for N-arylation of sulfonimidamides has been developed. The reaction proceeds at room temperature under base free conditions. Various N-aryl, N-heteroaryl, and N-cyclopropyl sulfonimidamides were obtained in good to excellent yields.     

One-pot synthesis of bromodifluoroacetimidoyl halides and its Suzuki coupling reactions with aryl boronic acids

N-aryl bromodifluoroacetimidoyl halides were prepared by the reaction of bromodifluoroacetic acid, triphenyl phosphine, p-arylaniline and triethylamine in tetrachloromethane in good yields. Palladium-catalyzed cross-coupling reaction of N-aryl bromodifluoroimidoyl iodide with arylboronic acids was realized to afford bromodifuoromethyl ketimine in good yields.     

Palladium-catalyzed carbonylative coupling of pyridine halides with aryl boronic acids

The carbonylative Suzuki cross-coupling of a variety of mono-iodopyridines and bromopyridines (1a,b, 3a-c, 5) catalyzed by palladium-phosphane systems has been studied to prepare benzoylpyridine derivatives (2, 4, 6). The selectivity and the rate of the reaction are highly dependent on the reaction conditions, i.e. nature of the palladium catalyst precursor, solvent, temperature and CO pressure. The main side-products arise from direct, non-carbonylative cross-coupling. Under optimized conditions, benzoylpyridines are recovered in high yields (80-95%). The order of reactivity decreases from iodo- to bromopyridines and from 2-, 4- to 3-substituted halopyridines. The reactivity of dihalopyridines has been investigated; 2,6-dibromopyridine (7) and 3,5-dibromopyridine (11) are selectively transformed into either the corresponding benzoyl-phenylpyridine (8, 12) or the corresponding dibenzoylpyridine (9, 13). Dissymmetric 2,5-dihalopyridines (15a,b) are transformed into 2-benzoyl-5-bromopyridine (16) or 2,5-dibenzoylpyridine (17) in high yields.     

Palladium-catalyzed, copper(I)-mediated coupling of boronic acids and benzylthiocyanate. A cyanide-free cyanation of boronic acids

A new method for the synthesis of nitriles is described. As a complement to the classic cyanation of aryl halides using cyanide sources and a transition metal catalyst, the palladium-catalyzed cross-coupling of thiocyanates with boronic acids in the presence of copper(I) thiophene-2-carboxylate (CuTC) affords nitriles in good to excellent yields.     

A mild and efficient new synthesis of aryl sulfones from boronic acids and sulfinic acid salts

A new efficient and mild preparation of sulfones from boronic acids and sulfinic acid salts is reported. The cross-coupling reaction mediated by cupric acetate gives access to a variety of sulfones in excellent yield.     

A highly efficient microwave-assisted suzuki coupling reaction of aryl perfluorooctylsulfonates with boronic acids

[reaction: see text] A new strategy to improve the efficiency of Suzuki coupling reactions is introduced by combining fast microwave reaction with easy fluorous separation. Aryl perfluorooctylsulfonates derived from the corresponding phenols are coupled with aryl boronic acids to form biaryls under general microwave conditions. Both intermediates and products are purified by solid-phase extraction over FluoroFlash silica gel. Application of this tagging strategy to multistep synthesis of biaryl-substituted hydantoin is also described.     

Mild and rapid hydroxylation of aryl/heteroaryl boronic acids and boronate esters with N-oxides

Aryl and heteroaryl boronic acids and boronate esters are rapidly, often within minutes, transformed into the corresponding phenols by N-oxides in an open flask at ambient temperature. This transformation has broad compatibility with a variety of functional groups.     

A general synthesis of diarylketones by means of a three-component cross-coupling of aryl and heteroaryl bromides, carbon monoxide, and boronic acids

Pd(OAc)2/di-1-adamantyl-n-butylphosphine (cataCXium A) is highly active in the three-component Suzuki carbonylation and represents the most general catalyst system reported up to now. A broad range of aryl/heteroaryl bromides and aryl boronic acids can be coupled to the corresponding diarylketones at low catalyst loadings.     

Highly effective copper-catalyzed decarboxylative coupling of aryl halides with alkynyl carboxylic acids

We have developed a highly effective copper-catalyzed decarboxylative coupling of alkynylcarboxylic acids with various aryl and alkyl halides at 2 mol% loading of copper. This method is simple, economical and practical for the synthesis of disubstituted alkyne compounds.     

A practical electromediated ipso-hydroxylation of aryl and alkyl boronic acids under an air atmosphere

An efficient electromediated aerobic ipso-hydroxylation reaction of aryl and alkyl boronic acids has been developed. Furthermore, mechanistic insight into the role of superoxide anions in this reaction has also been provided based on electrochemical studies and experimental results.     

Palladium-catalyzed carbonylative coupling of benzyl chlorides with aryl boronic acids in aqueous media

A novel chemoselective protocol for the carbonylative Suzuki coupling of benzyl chlorides with aryl boronic acids at low pressure of carbon monoxide has been developed. Applying a commercially available palladium acetate/PCy₃ catalyst system in the presence of potassium phosphate as the base and water as the solvent the coupling reactions proceeded smoothly. To demonstrate the general applicability 12 different α-arylated acetophenones have been synthesized in moderate to good yields (41-78%) under mild conditions.     

Lewis acid-catalyzed, copper(II)-mediated synthesis of heteroaryl thioethers under base-free conditions

A Lewis acid (Ag(I), Ni(II), or Fe(II)) catalyzed, Cu(II)-mediated thiolation reaction between heteroarenes and thiols was achieved with good yield under base-free conditions. DMSO could serve as an effective methylthiolation reagent for the synthesis of heterocyclic methyl thioethers.     

Solid-phase synthesis of aryl, heteroaryl, and sterically hindered alkyl amines using the Curtius rearrangement

An efficient method for the solid-phase synthesis of aryl amines, heteroaryl amines, and sterically hindered alkyl amines has been developed. The key step in this process was the formation of resin-bound carbamates (B) by the Curtius rearrangement of aryl carboxylic acids with Wang resin providing the trapping hydroxyl group. N-Alkylation reactions of B gave secondary amines in good yield. Some biaryl amines, which are found widely in biologically active substances, were also prepared by the Suzuki reaction of resin-bound carbamates of 2-iodoaniline (16) or 3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)aniline (21). The developed methods can be applied to the preparation of libraries containing aryl, heteroaryl, and sterically hindered alkyl amine structures as the pharmacophores.     

The palladium-catalyzed cross-coupling reactions of trifluoroethyl iodide with aryl and heteroaryl boronic acid esters

The cross-coupling reactions of 1,1,1-trifluoro-2-iodoethane with aryl and heteroaryl boronic acid esters have been successfully achieved. The new protocol allows for a convenient introduction of trifluoroethyl groups into a variety of aryl and heteroaryl moieties under mild conditions.     

Direct synthesis of diaryl sulfides by copper-catalyzed coupling of aryl halides with aminothiourea

An efficient and simple protocol of copper-catalyzed C-S bond formation between aryl halides and inexpensive and commercially available aminothiourea is reported.A variety of symmetrical diaryl sulfides can be synthesized in good to excellent yields up to 94%with the advantage of avoiding foul-smelling thiols.