Palladium-catalyzed synthesis of N-aryloxazolidinones from aryl chlorides

An efficient method for intermolecular N-arylation of oxazolidinones using Pd(2)dba(3) and various phosphine ligands in the presence of a weak base is reported. The conditions allow the use of cheaper aryl chlorides containing functionalities such as enolizable ketones, amides, etc., which would be incompatible with other coupling methods. The coupling reaction can be used to prepare enantiopure N-aryl beta-amino alcohols. Depending on the stereoelectronic nature of the aryl chloride, careful choice of ligand was necessary for the success of these reactions. [reaction: see text]     

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.     

Palladium-catalyzed multicomponent coupling of alkynes, imines, and acid chlorides: a direct and modular approach to pyrrole synthesis

A new palladium-catalyzed method to prepare pyrroles directly from three basic building blocks-imines, alkynes, and acid chlorides-is described. This approach provides a straightforward method both to prepare pyrroles in one step and to diversify their structure by simple variation of any of the three starting materials. Mechanistic studies suggest that this process occurs via a complex series of eight individual steps, and this is discussed.     

meta-Selective C–H functionalisation of aryl boronic acids directed by a MIDA-derived boronate ester

N-Methyliminodiacetic acid (MIDA) boronates are boronic acid derivatives which are stable to reduction, oxidation and transmetalation. This has led to their widespread use as boronic acid protecting groups (PGs) and in iterative cross-couplings. We describe herein the development of a novel MIDA derivative that acts in a dual manner, as a protecting group and a directing group (DG) for meta C(sp²)–H functionalisation of arylboronic acids. Palladium catalysed C–H alkenylations, acetoxylations and arylations are possible, at room temperature and under aerobic conditions. Deprotection to reveal the functionalised boronic acids is rapid and allows for full recovery of the DG. The technique allows the facile diversification of aryl boronic acids and their subsequent use in a range of reactions or in iterative processes.

An N-methyliminodiacetic acid derivative allows the meta-C–H functionalisation of boronic acids, acting simultaneously as a directing and protecting group.     

A direct copper-catalyzed route to pyrrolo-fused heterocycles from boronic acids

A convenient route to prepare azaindoles and related pyrrolo-fused heterocycles from boronic acids, DBAD (di-tert-butyl-diazodicarboxylate) and enolizable aldehydes and ketones is presented. The reaction proceeds via a one-pot four-step cascade sequence with key steps involving a copper-catalyzed boronic acid coupling to DBAD and a Fischer indolization providing access to a variety of pharmaceutically interesting heterocycles including pyrrolo-pyridines, -pyrimidines, -quinolines, and -isoquinolines from readily available aza–aryl boronic acid precursors.     

Addition of grignard reagents to aryl acid chlorides: an efficient synthesis of aryl ketones

[chemical reaction: see text]. Direct addition of Grignard reagents to acid chlorides in the presence of bis[2-(N,N-dimethylamino)ethyl] ether proceeds selectively to provide aryl ketones in high yields. A possible tridentate interaction between Grignard reagents and bis[2-(N,N-dimethylamino)ethyl] ether moderates the reactivity of Grignard reagents, preventing the newly formed ketones from nucleophilic addition by Grignard reagents.     

Palladium-catalyzed C-O bond formation: direct synthesis of phenols and aryl/alkyl ethers from activated aryl halides

A simple and efficient palladium-catalyzed carbon-oxygen bond formation is reported. The palladium-tri-tert-butylphosphine complex was found to be effective in converting haloarenes to corresponding substituted phenols. This methodology offers a direct transformation of aryl halides to phenols, as well as the straightforward application to generate a wide variety of diaryl or alkyl/aryl ethers.     

Palladium-catalyzed synthesis of alpha-iminoamides from imidoyl chlorides and a carbamoylsilane

A series of pure imidoyl chlorides were converted into alpha-iminoamides by treatment with a carbamoylsilane under catalysis by palladium(0) complexes.     

Palladium-catalyzed cross-coupling of aryl chlorides and triflates with sodium cyanate: a practical synthesis of unsymmetrical ureas

An efficient method for palladium-catalyzed cross-coupling of aryl chlorides and triflates with sodium cyanate is reported. The protocol allows for the synthesis of unsymmetrical N,N'-di- and N,N,N'-trisubstituted ureas in one pot and is tolerant of a wide range of functional groups. Insight into the mechanism of aryl isocyanate formation was gleaned through studies of the transmetalation and reductive elimination steps of the reaction, including the first demonstration of reductive elimination from an arylpalladium isocyanate complex to produce an aryl isocyanate.     

One-step synthesis of alpha-chloro acetophenones from acid chlorides and aryl precursors

A direct and efficient method was developed for the preparation of a variety of substituted acetophenone derivatives from readily available arene precursors and acid chlorides. This method has significant generality and affords access to substitution patterns on aryl rings not directly achievable by Friedel-Crafts chemistry. [reaction: see text].     

Palladium-catalyzed carbonylation of aryl triplates. Synthesis of arenecarboxylic acid derivatives from phenols

Various aryl triflates derived from phenols were converted into aryl esters or amides in good yields by a palladium-catalyzed reaction with carbon monoxide and alcohols or amines.     

Palladium-catalyzed carbopalladation and carbocyclization of arynes with aryl halides: a highly efficient route to functionalized triphenylenes

Highly substituted triphenylene derivatives were prepared in good yields via the palladium-catalyzed carbocyclization of arynes with aryl iodides.     

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.     

Copper-catalyzed coupling of imines, acid chlorides, and alkynes: a multicomponent route to propargylamides

The use of imines in a metal-catalyzed coupling with alkynes and acid chlorides is described. This process proceeds rapidly with CuI as the catalyst and provides an efficient and general three-component coupling method to prepare propargylamides. The coupling can also be diversified to allow the formation of N-carbamate-protected propargylamines with the use of chloroformates.     

A direct, one step synthesis of imidazoles from imines and acid chlorides: a palladium catalyzed multicomponent coupling approach

A palladium-catalyzed one-step synthesis of imidazoles from imines and acid chlorides is described. A plausible mechanism for this multicomponent reaction is provided, which explains the selective incorporation of two different imines into the final product with perfect regiocontrol. Overall, this catalytic process provides a modular method to prepare imidazoles directly from building blocks that are all either commercially available or readily generated.