Palladium-catalyzed cross-coupling of cyclopropanols with aryl halides under mild conditions

Intra- and intermolecular palladium-catalyzed cross-coupling of cyclopropanols with aryl halides can be achieved in good yields under mild conditions.     

Palladium-catalyzed denitrogenative cross-coupling of aryl halides with arylhydrazines under mild reaction conditions

Transition Metal Chemistry - A greener approach for the synthesis of various functionalized biaryl frameworks in good to excellent yield through palladium-catalyzed denitrogenative cross-coupling...     

Palladium-catalyzed oxidative coupling of trialkylamines with aryl iodides leading to alkyl aryl ketones

A new, simple method for selectively synthesizing alkyl aryl ketones has been developed by palladium-catalyzed oxidative coupling of trialkylamines with aryl iodides. In the presence of PdCl(2)(MeCN)(2), TBAB, and ZnO, a variety of aryl iodides underwent an oxidative coupling reaction with tertiary amines and water to afford the corresponding alkyl aryl ketones in moderate to excellent yields. It is noteworthy that this method is the first example of using trialkylamines as the carbonyl sources for constructing alkyl aryl ketone skeletons.     

Palladium-catalyzed coupling of thiol esters with aryl and primary and secondary alkyl organoindium reagents

Thiol esters and organoindium reagents undergo palladium-catalyzed cross-coupling under mild conditions to give ketones in moderate to excellent yields. Aryl and primary/secondary alkyl organoindium reagents can be used as coupling partners. This method has two advantages over the cross-coupling of thiol esters with boron and tin reagents: (1) no added copper reagent is required to mediate the reaction and (2) for the case of alkyl transfer, no added base is required to activate organoindium reagents for cross-coupling as is required for the coupling of alkyl boron reagents with thiol esters.     

Palladium-catalyzed carbonylation of aryl tosylates and mesylates

A general protocol for the palladium-catalyzed carbonylation of aryl tosylates and mesylates to form esters has been developed using a catalyst system derived from Pd(OAc)2 and the bulky, bidentate dcpp ligand. The system operates under mild conditions: atmospheric CO pressure and temperatures of 80-110 degrees C. A broad substrate scope has been demonstrated allowing carbonylation of electron-rich, electron-poor, and heterocyclic tosylates and mesylates, and the reaction shows wide functional group tolerance.     

Palladium-catalyzed reactions of arylindium reagents prepared directly from aryl iodides and indium metal

Treatment of aryl iodides with indium metal in the presence of lithium chloride leads to the formation of an organoindium reagent capable of participating in cross-coupling reactions under transition-metal catalysis. Combination with aryl halides in the presence of 5 mol % Cl2Pd(dppf) furnishes biaryl compounds in good yields; similarly, reaction with acyl halides or allylic acetates/carbonates in the presence of 5-10 mol % palladium catalyst leads to arylketones and allylic substitution products, respectively, in moderate yields. The reactions are tolerant of the presence of protic solvents, and approximately 85% of the indium metal employed can be recovered by reduction of the residual indium salts with zinc(0).     

Palladium-catalyzed Heck reaction of aryl chlorides under mild conditions promoted by organic ionic bases

An efficient Pd-catalyzed Heck reaction of aryl chlorides with olefins under mild conditions is described. High yields of products were achieved with n-Bu(4)N(+)OAc(-) as base. Significantly, the temperature of the Heck reaction of diverse nonactivated aryl chlorides can be lowered to 80 °C. The new reaction system can also tolerate a wider range of olefins.     

Palladium-catalyzed cross-coupling of aryl electrophiles with dimethylalkynylaluminum reagents

[reaction: see text] Alkynyldimethylaluminum reagents are easily available from terminal alkynes and trimethylaluminum via a triethylamine-catalyzed metalation. These compounds can react with various aromatic and heterocyclic halides in the presence of palladium in a fast and efficient way. This catalyzed cross-coupling reaction provides a simple entry to numerous internal alkynes, using a readily available, inexpensive, and nontoxic metalating agent.     

Palladium-catalyzed hydrophenylation of alkynes with sodium tetraphenylborate under mild conditions

In an aqueous solution of acetic acid, PdCl2(PPh3)2 showed high catalytic activity for the hydrophenylation of both terminal and internal alkynes with sodium tetraphenylborate (NaBPh4) under mild conditions, affording phenyl alkenes in moderate to excellent yields.     

Selenium assisted carbonylation of alkyl aryl ketones with carbon monoxide

Selenium assisted carbonylation of alkyl aryl ketones with carbon monoxide leading to formation of 1,3-dicarbonyl compounds as C-carbonylated products is described. o-Hydroxyacetophenone 7a and its derivatives7b,7c, and 7d have been converted to the corresponding 4-hydroxycoumarins 8a,8b,8c and 8d in moderate to quantitative yields by treatment with an equivalent of selenium and carbon monoxide with concomitant formation of hydrogen selenide 9 (Eq.(8)). It was further revealed that oxidation of in situ formed hydrogen selenide to selenium with an appropriate oxidizing agent such as nitrobenzene permitted catalytic use of selenium for the carbonylation of 7. Possible rationalizations for the formation of 4-hydroxycoumarins are suggested.     

Palladium-catalyzed cyclization and cross-coupling of acetylenic aryl triflates with organotin reagents

Acetylenic aryl triflates reacted readily with vinyltributyltin, allyltributyltin, 1-(trimethylsilyl)-2-(tributylstannyl)acetylene, and trimethylsilyltributyltin in the presence of a palladium catalyst to produce (Z)-indanylidene and (Z)-tetralinylidene substituted compounds, the stereospecificity of the reactions for the synthesis of these compounds being ≥98%.     

Palladium-catalyzed C2-acylation of indoles with aryl and alkyl aldehydes

A palladium-catalyzed C2-acylation of indoles with aryl and alkyl aldehydes via C–H functionalization is reported. The method shows excellent functional group tolerance and provides a straightforward way for the preparation of 2-aroylindoles.     

Palladium-catalyzed carbonylation of aryl, alkenyl, and allyl halides with phenyl formate

Highly efficient palladium-catalyzed carbonylation of aryl, alkenyl, and allyl halides with phenyl formate is reported. This procedure does not use carbon monoxide and affords one-carbon-elongated carboxylic acid phenyl esters in excellent yields. The reaction proceeds smoothly under mild conditions and tolerates a wide range of functional groups including aldehyde, ether, ketone, ester, and cyano groups. Furthermore, a variety of heteroaromatic bromides can be converted to the corresponding phenyl esters in high yields.     

Silver-catalyzed cross-coupling reactions of alkyl bromides with alkyl or aryl Grignard reagents

Treatment of secondary or tertiary alkyl bromides with alkyl Grignard reagents in the presence of catalytic amounts of silver bromide and potassium fluoride in CH₂Cl₂ afforded the corresponding cross-coupling products in reasonable yields. Moreover, silver showed catalytic activity for the cross-coupling reactions of alkyl bromides with aryl Grignard reagents.     

Copper-catalyzed N-arylation of sulfonamides with aryl bromides under mild conditions

This Letter describes a copper catalyzed sulfonamide coupling reaction with aryl bromides to form N-aryl sulfonamides under mild conditions, including the first examples of Cu-catalyzed sulfonamide coupling at room temperature. The reaction protocol tolerates a broad range of substrates including a variety of primary and secondary sulfonamides and challenging heteroaryl bromides such as 2-bromothiazole.     

Novel C-C bond cleavage under mild, neutral conditions: conversion of electron-deficient aryl alkyl ketones to aryl carboxylic esters

A novel, unique way to cleave the carbon-carbon bond in aryl alkyl ketones under mild, neutral conditions is described. Treatment of aryl alkyl ketones in a refluxing mixture of N,N-dimethylformamide dimethyl acetal and methanol for 16 h provided aryl carboxylic esters. The scope and limitations of the reaction are discussed. Useful yields of the reaction can be obtained with electron-deficient aryl groups, and the yields are higher when the alkyl group is larger than a methyl group. Studies toward elucidation of the reaction mechanism led to a proposed mechanism that is consistent with all the observations.