Palladium-Catalyzed Three-Component Coupling Reaction via Benzylpalladium Intermediate

Transition-metal catalyzed multi-component reactions have captured the attention of researchers in organic synthesis and drug synthesis due to their advantages of simple operation, easy availability of raw materials and without separation of intermediates. Among the multi-component reactions, the three-component processes have been developed into effective organic procedures. This personal account reviews our and other group's studies on the development of three-component coupling reaction for the rapid construction of two new chemical bonds simultaneously via benzylpalladium intermediates. Catalyst-switched three-component reactions of benzyl halides, activated olefins, and allyltributylstannane were successfully conducted to produce the corresponding benzylallylation products. Activation and conversion of carbon monoxide and carbon dioxide via π-benzylpalladium intermediates provide access to a wide range of unsaturated ketones and esters with excellent functional group tolerance. Meanwhile, other methods to produce benzylpalladium intermediates, including Heck insertion of alkenes into arylpalladium complexes, the oxidative addition of benzyl carbonate to palladium complexes and palladium-carbene migratory insertion, were also highlighted.

Nickel-Catalyzed Formal Aminocarbonylation of Secondary Benzyl Chlorides with Isocyanides

Phenylacetamides represent versatile feedstocks in synthetic chemistry, widely existing in drug molecules and natural products. Herein, we disclose a nickel-catalyzed formal aminocarbonylation of secondary benzyl chlorides with isocyanides yielding α-substituted phenylacetamide with steric hindrance, which is synthetically challenging via palladium-catalyzed aminocarbonylation. The reaction features wide functional group tolerance under mild conditions, highlighted by the tolerance of various aromatic halide (-Cl, -Br, -I) and heteroaromatic rings (pyridine and pyrazine).

An Efficient Palladium-Catalysed Aminocarbonylation of Benzyl Chlorides

An improved procedure for the aminocarbonylation of benzyl chloride derivatives using carbon monoxide and either primary or secondary amines has been developed. Studying the competing background alkylation reaction allowed the solvent and base to be selected for a simple catalyst screen, which, in turn, enabled the discovery of a method for the preparation of 2-arylacetamides under mild conditions, with minimal side-products using an inexpensive phosphine ligand. This non-traditional optimisation strategy allowed us to overcome the background alkylation, which has been cited as justification for the development of more complex and less atom-economical approaches.

Palladium-catalyzed carbonylative synthesis of arylacetamides from benzyl formates and tertiary amines

A palladium-catalyzed carbonylative synthesis of arylacetamides via a C–N bond cleavage of tertiary amines with benzyl formates as the CO source has been disclosed. A variety of arylacetamides were obtained in very good yields under oxidant-free conditions.

Pd-catalysed carbonylative annulation of salicylaldehydes with benzyl chlorides using N-formylsaccharin as a CO surrogate

A highly efficient synthesis of 3-arylcoumarins by Pd-catalysed carbonylative cyclisation of salicylaldehydes with benzyl chlorides using N-formylsaccharin as a CO source is developed.

Palladium-catalyzed carbonylation of benzylic ammonium salts to amides and esters via C–N bond activation

An efficient palladium-catalyzed carbonylation reaction of readily available quaternary ammonium salts with CO is reported for the first time to afford arylacetamides and arylacetic acid esters via benzylic C–N bond cleavage.

Palladium-catalyzed regiodivergent hydroaminocarbonylation of alkenes to primary amides with ammonium chloride

A new and efficient process for transferring NH₄Cl to both linear and branched primary amides has been achieved via palladium-catalyzed hydroaminocarbonylation of alkenes.

Palladium-catalyzed hydroaminocarbonylation of alkenes for the synthesis of primary amides has long been an elusive aim. Here, we report an efficient catalytic system which enables inexpensive NH₄Cl to be utilized as a practical alternative to gaseous ammonia for the palladium-catalyzed alkene-hydroaminocarbonylation reaction. Through appropriate choice of the palladium precursors and ligands, either branched or linear primary amides can be obtained in good yields with good to excellent regioselectivities. Primary mechanistic studies were conducted and disclosed that electrophilic acylpalladium species were capable of capturing the NH₂-moiety from ammonium salts to form amides in the presence of CO with NMP as a base.

Pd/C-catalyzed facile synthesis of primary aromatic amides by aminocarbonylation of aryl iodides using ammonia surrogates

Use of Pd/C as an efficient, phosphine free, heterogeneous and recyclable catalyst for one pot carbonylative synthesis of primary aromatic amides has been demonstrated.

Palladium-catalyzed synthesis of primary benzamides from aryl bromides via a cyanation and hydration sequence

An interesting and effective procedure for the synthesis of primary benzamides from aryl bromides via cyanation and in situ hydration sequence has been developed.

Palladium on manganese ferrite: an efficient catalyst for one pot synthesis of primary amides from iodobenzene

Amidation of aryl iodide in one pot is reported using Pd–MnFe₂O₄ as a catalyst.

Synthesis of conformationally restricted glutamate and glutamine derivatives from carbonylation of orthopalladated phenylglycine derivatives

A new method for the regioselective synthesis of 2-alkoxycarbonyl- and 2-(aminocarbonyl)phenylglycinate methyl esters has been developed. The reaction of the orthopalladated complex [Pd(μ-Cl)(C(6)H(4)(CH(CO(2)Me)NMe(2))-2)](2) (1) with nucleophiles HNu under a CO atmosphere results in the selective incorporation of the C(O)Nu moiety to the phenyl ring and formation of the carbonyl species ortho-C(6)H(4)(C(O)Nu)(CH(CO(2)Me)NMe(2)) (2a-j) (Nu = OR, NHR, NR(2)). Compounds 2a-j are conformationally restricted analogues of glutamic acid and glutamine and are interesting due to their biological and pharmacological properties. The reaction of [Pd(μ-Cl)(C(6)H(4)(CH(CO(2)Me)NHTf)-2)](2) (3) with nucleophiles in a CO atmosphere results, however, in the formation of the cyclic isoindolinone or the open 2-carboxyphenylglycine methyl esters, with the reaction outcome being driven by the choice of the solvent.