Copper-catalyzed coupling of amides and carbamates with vinyl halides

[reaction: see text] A general and efficient copper-catalyzed method for the amidation of vinyl bromides and iodides has been developed. This protocol uses a combination of 5 mol % copper iodide and 20 mol % N,N'-dimethyl ethylenediamine. Substrates bearing ester, silyl ether, and amino groups were successfully coupled under the reaction conditions. The double bond geometry of the vinyl halides was retained under the reaction conditions.     

The stereodivergent aziridination of allylic carbamates, amides and sulfonamides

A stereodivergent protocol for the aziridination of a range of cyclic allylic amine derivatives has been developed. syn-Products can be obtained in >99:1 dr under H-bonded control and anti-products are obtained in >99:1 dr under steric control by judicious choice of the N-protecting groups.     

The direct conversion of carbamates to ureas using aluminum amides

The conversion of carbamates into ureas using aluminum amide complexes is reported. This reaction is a convenient method to prepare bi-, tri- and tetra-substituted ureas from carbamate-protected primary or secondary amines by reaction with primary or secondary amines in the presence of stoichometric quantities of trimethylaluminum. A reactivity trend of the various carbamates was observed and methyl and benzyl carbamates were reacted selectively in the presence of t-butyl carbamates.     

N-Alkylation of carbamates and amides with alcohols catalyzed by a CpIr complex

New atom-economical catalytic systems consisting of [Cp^∗IrCl₂]₂/NaOAc (Cp^∗=pentamethylcyclopentadienyl) for the N-alkylation of carbamates and amides using alcohols as alkylating agents under solvent-free conditions have been developed. For example, the reaction of n-butyl carbamate with benzyl alcohol in the presence of [Cp^∗IrCl₂]₂ (5.0 mol % Ir) and NaOAc (5.0 mol %) at 130 °C under the absence of solvent gives n-butyl N-benzylcarbamate in the yield of 94%. The present catalytic system is applicable to not only carbamates but also amides, and only harmless water is produced as co-product.     

First carbamates conversion to amides by simple alkyl group transfer from trialkylalanes

[reaction: see text] N-Monosubstituted carbamates are cleanly converted to amides under treatment with trialkylaluminum. This reaction involves an aluminum-assisted internal delivery of alkyl groups. It can be applied to new and mild protecting group strategies for alcohols.     

The development of efficient protocols for the palladium-catalyzed cyclization reactions of secondary amides and carbamates

[formula: see text] With the proper choice of palladium catalyst, ligand, and base, five-, six-, and seven-membered rings are formed efficiently from secondary amide or secondary carbamate precursors, offering significant improvements to currently existing methodology.     

CuI/N,N-dimethylglycine-catalyzed coupling of vinyl halides with amides or carbamates

The CuI-catalyzed coupling reaction of vinyl halides with amides or carbamates proceeds well at room temperature to 80 degrees C in dioxane to give enamides using N,N-dimethylglycine as the promoter and Cs(2)CO(3) as the base. The geometry of the C-C double bond is retained during the reaction course. [reaction: see text]     

Gold(I)-catalyzed regioselective cyclizations of silyl ketene amides and carbamates with alkynes

The gold(I)-catalyzed regioselective cyclizations of silyl ketene amides or carbamates with alkynes were utilized to construct cyclopentanes or dehydro-delta-lactams.     

Nucleophilic behaviour of DBU towards imidazolides: one-pot synthesis of ε-caprolactam derived carbamates and amides

Herein, we report the DBU ring opening reactions with imidazolide which can be a facile method to generate the library of ε-caprolactam derived carbamates and amides under one-pot condition.     

Synthesis of allenamides by copper-catalyzed coupling of allenyl halides with amides, carbamates, and ureas

[reaction: see text]. A variety of N-substituted allenes have been synthesized by the copper-catalyzed coupling reaction between allenyl halides and amides, carbamates, and ureas. The reactions proceed in good to excellent yield using 7 mol % copper thiophenecarboxylate and 15 mol % of a diamine catalyst.     

N-Fluorination of bis(polynitroalkyl)amines

Conclusions The fluorination of bis(polynitroalkyl)amines by elemental fluorine in acetic acid gave a series of bis(polynitroalkyl)-N-fluoramines.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2859–2860, December, 1987.     

N-carbonylation of lithium azaenolates of amides, formamides, ureas, and carbamates with carbon monoxide mediated by selenium

N-Carbonylation of less nucleophilic nitrogen compounds was achieved by the reaction of the lithium azaenolates with carbon monoxide and selenium. This reaction proceeds in the cases of amides, formamides, ureas, and carbamates, leading to the formation of the corresponding carbamoselenoates in good to high yields after trapping with BuI.     

Carbamoylimidazolium and thiocarbamoylimidazolium salts: novel reagents for the synthesis of ureas, thioureas, carbamates, thiocarbamates and amides

Carbamoylimidazolium salts act as efficient N,N-disubstituted carbamoylating reagents. These salts are readily prepared by the sequential treatment of secondary amines with N,N′-carbonyldiimidazole (CDI) and iodomethane. The carbamoylimidazolium salts are more efficient carbamoyl transfer reagents than the intermediate carbamoylimidazoles, as a result of the ‘imidazolium’ effect. Kinetic studies on the base promoted hydrolysis of both carbamoylimidazoles and carbamoylimidazolium salts reveal over a hundred-fold rate acceleration. The salts react with amines, thiols, phenols/alcohols, and carboxylic acids in high yields, without the need for subsequent chromatographic purification of the products, producing ureas, thiocarbamates, carbamates, and amides, respectively. Analogous thiocarbamoylimidazolium salts were also synthesized from secondary amines and N,N′-thiocarbonyldiimidazole (TCDI), followed by methylation with iodomethane.     

Indirect reduction of CO2 and recycling of polymers by manganese-catalyzed transfer hydrogenation of amides,carbamates, urea derivatives,and polyurethanes

The reduction of polar bonds, in particular carbonyl groups, is of fundamental importance in organic chemistry and biology. Herein, we report a manganese pincer complex as a versatile catalyst for the transfer hydrogenation of amides, carbamates, urea derivatives, and even polyurethanes leading to the corresponding alcohols, amines, and methanol as products. Since these compound classes can be prepared using CO₂ as a C1 building block the reported reaction represents an approach to the indirect reduction of CO₂. Notably, these are the first examples on the reduction of carbamates and urea derivatives as well as on the C–N bond cleavage in amides by transfer hydrogenation. The general applicability of this methodology is highlighted by the successful reduction of 12 urea derivatives, 26 carbamates and 11 amides. The corresponding amines, alcohols and methanol were obtained in good to excellent yields up to 97%. Furthermore, polyurethanes were successfully converted which represents a viable strategy towards a circular economy. Based on control experiments and the observed intermediates a feasible mechanism is proposed.

A Mn–PNP complex proved to be a suitable catalyst for the transfer hydrogenation of amides, carbamates, urea derivatives and even polyurethanes.     

Conversion of carbamates to amidosulfones and amides. Synthesis of the [14C]-labeled antiobesity agent Ro23-7637

[reaction: see text] Carbamates of primary and secondary amines react with the dianion of methyl phenyl sulfone to yield amidosulfones. Alylation of the amidosulfone followed by reductive removal of the sulfonyl residue gives an amide.     

Solvolysis of trimethylsilyl-N-aryl carbamates

The kinetics of the solvolysis reaction of various trimethylsilyl esters of N-aryl carbamic acid with isopropanol was studied. UV spectrophotometry was used to monitor the reaction and the pseudo first order rate constants were determined. The experiments were carried out in dioxane solutions containing lithium chloride. A reaction mechanism is suggested on the basis of the dependence of the reaction rate on ionic strength, the parameters of activation, the reaction constant (ϱ) and the isotope effect.     

Atropisomerism of aromatic carbamates

ortho‐Haloarylcarbamates like 1 – 4 show a high rotational barrier about the N? aryl bond of up to 91.6 kJ mol^?1 as found for 1 , which was determined by 2D exchange NMR spectroscopy (EXSY). It was further demonstrated that the height of the barrier not only depends on the substituents at the axis of chirality, but is also influenced by electronic effects.