Carbamoylation of Aryl Halides by Molybdenum or Tungsten Carbonyl Amine Complexes

Preparation of Functionalized Amides Using Dicarbamoylzincs

We report a new convenient preparation of dicarbamoylzincs of type (R¹R²NCO)₂Zn by the treatment of ZnCl₂ and formamides R¹R²NCHO with LiTMP in THF (15 °C, 15 min) or by the reaction of formamides R¹R²NCHO with TMP₂Zn (25 °C, 16 h). This second method tolerates sensitive groups such as an ester, ketone or nitro function. Reaction of these dicarbamoylzincs with allylic, benzylic, aryl, alkenyl bromides, acid chlorides, aldehydes or enones provided various polyfunctional amides in 47–97 % yields. ¹³C NMR characterization of these new carbamoylzinc derivatives is reported.

Synthesis of unprotected glyco-alkynones via molybdenum-catalyzed carbonylative Sonogashira cross-coupling reaction

Herein we report a novel Mo-catalyzed carbonylative Sonogashira cross-coupling between 2-iodoglycals and terminal alkynes. The reaction displays major improvements compared to a related Pd-catalyzed procedure previously published by our group, such as utilizing unprotected sugar derivatives as starting materials and tolerance to substrates bearing chelating groups. In this work we also demonstrate the utility of the glyco-alkynone products as platform for further functionalization by synthesizing glyco-flavones via Au-catalyzed 6-endo-dig cyclization.

Tandem Homologation-Acylation Chemistry: Single and Double Homologation

Treatment of β-dicarbonyls with the Furakawa-variant of the Simmons-Smith reagent results in homologation and production of an intermediate zinc enolate. Treatment of the enolate with various acylating agents generate products with both γ-dicarbonyl functionality and β-dicarbonyl functionality. In situ exposure of the acylated product to additional zinc carbenoid effects a second regiospecific homologation reaction.

Carboxyboronate as a Versatile In Situ CO Surrogate in Palladium-Catalyzed Carbonylative Transformations

The application of carboxy-MIDA-boronate (MIDA=N-methyliminodiacetic acid) as an in situ CO surrogate for various palladium-catalyzed transformations is described. Carboxy-MIDA-boronate was previously shown to be a bench-stable boron-containing building block for the synthesis of borylated heterocycles. The present study demonstrates that, in addition to its utility as a precursor to heterocycle synthesis, carboxy-MIDA-boronate is an excellent in situ CO surrogate that is tolerant of reactive functionalities such as amines, alcohols, and carbon-based nucleophiles. Its wide functional-group compatibility is highlighted in the palladium-catalyzed aminocarbonylation, alkoxycarbonylation, carbonylative Sonogashira coupling, and carbonylative Suzuki-Miyaura coupling of aryl halides. A variety of amides, esters, (hetero)aromatic ynones, and bis(hetero)aryl ketones were synthesized in good-to-excellent yields in a one-pot fashion.

Amide Synthesis through the In Situ Generation of Chloro- and Imido-Phosphonium Salts

We describe a methodology for the amidation of carboxylic acids by generating phosphonium salts in situ from N-chlorophthalimide and triphenylphosphine. Aliphatic, benzylic, and aromatic carboxylic acids can be transformed into their amide counter parts using primary and secondary amines. This functional group interconversion is achieved at room temperature in good to excellent yields. Mechanistic work shows the in situ formation of chloro- and imido-phosphonium salts that react as activating agents for carboxylic acids and generate an acyloxy-phosphonium species.

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.

Mechanistic investigation of palladium-catalyzed amidation of aryl halides

A mechanistic investigation using Becke3LYP density functional theory (DFT) was carried out on the palladium-catalyzed amidition of bromobenzene and (t)Bu-isocyanide. The whole catalytic cycle consists of five steps: oxidative addition, migratory insertion, anion exchange, reductive elimination, and hydrogen migration. The rate-determining step is oxidative addition, with a small Gibbs free energy of 14.6 kcal mol(-1). In the migratory insertion step, (t)Bu-isocyanide provides an important source of carboxy and amino groups to establish the amide group. For anion exchange, path 1a is suggested as the most favorable pathway with the help of the base, and water provides a source of oxygen which is perfectly in line with experimental observations. Finally, in the hydrogen migration step, we illustrate that the six-membered ring path is energetically favored due to the assisting influence of water. In addition, our calculations indicate that using dimethyl sulfoxide as a solvent does not change the rate-determining step.

Palladium-catalyzed oxidative carbamoylation of isoquinoline N-oxides with formylamides by means of dual C–H oxidative coupling

A new palladium-catalyzed oxidative carbamoylation reaction of isoquinoline N-oxides with formylamides for the synthesis of isoquinoline-1-carboxamides is described.

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 amides via palladium-catalyzed amidation of aryl halides

A new and efficient method for the synthesis of amides via palladium-catalyzed C-C coupling of aryl halides with isocyanides is reported, by which a series of amides were formed from readily available starting materials under mild conditions. This transformation could extend its use to the synthesis of natural products and significant pharmaceuticals.

Mo(CO)(6)-mediated carbamoylation of aryl halides

A simple method for the synthesis of amides has been developed by molybdenum-mediated carbamoylation of aryl halides. Whereas the conventional palladium-catalyzed three-component coupling reaction requires a large excess of gaseous carbon monoxide, the incorporation of carbon monoxide in this Mo-mediated carbamoylation reaction is so efficient that it requires only a slight excess amount of carbon monoxide in the form of its molybdenum complex, Mo(CO)(6). The reaction is applicable for the synthesis of a wide variety of not only secondary and tertiary amides but also primary amides by using aqueous ammonia.