Dehydrogenative Synthesis of Carbamates from Formamides and Alcohols Using a Pincer-Supported Iron Catalyst was written by Townsend, Tanya M.;Bernskoetter, Wesley H.;Hazari, Nilay;Mercado, Brandon Q.. And the article was included in ACS Catalysis in 2021.Recommanded Product: 2387-23-7 This article mentions the following:
The pincer-ligated iron complex (iPrPNP)Fe(H)(CO) [iPrPNP– = N(CH2CH2PiPr2)2-] is an active catalyst for the dehydrogenative synthesis of N-alkyl- and N-aryl-substituted carbamates RNHC(O)OR1 (R = Me, Ph, Bn, etc.; R1 = Me, Cy, Bn, etc.) from formamides RNHCHO and alcs. R1OH. The reaction is compatible with industrially relevant N-alkyl formamides, as well as N-aryl formamides, and 1°, 2°, and benzylic alcs. Mechanistic studies indicate that the first step in the reaction is the dehydrogenation of the formamide to a transient isocyanate by (iPrPNP)Fe(H)(CO). The cyclohexyl isocyanate then reacts with the alc. to generate the carbamate. However, in a competing reaction, the isocyanate such as benzyl isocyanate, cyclohexyl isocyanate undergoes a reversible cycloaddition with (iPrPNP)Fe(H)(CO) to generate an off-cycle species, which is the resting state in catalysis. Stoichiometric experiments indicate that high temperatures are required in catalysis to facilitate the release of the isocyanate from the cycloaddition product I (R2 = Bn, Cy). Several other off-cycle processes that occur in catalysis, such as the 1,2-addition of the formamide or alc. substrate across the Fe-N bond of (iPrPNP)Fe(H)(CO) were also identified. It has already been demonstrated that the transient isocyanate generated from dehydrogenation of the formamide can be trapped with amines to form ureas and, in principle, the isocyanate could also be trapped with thiols to form thiocarbamates. Competition experiments indicate that trapping of the transient isocyanate with cyclohexanamine to produce 1,3-dicyclohexylurea is faster than trapping with an alc. to produce carbamates and thus ureas can be formed selectively in the presence of alcs. In contrast, thiols such as benzylthiol, cyclohexanethiol bind irreversibly to the iron catalyst through 1,2 addition across the Fe-N bond of (iPrPNP)Fe(H)(CO), and it is not possible to produce thiocarbamates. Overall, the mechanistic studies provide general guidelines for facilitating dehydrogenative coupling reactions using (iPrPNP)Fe(H)(CO) and related catalysts. In the experiment, the researchers used many compounds, for example, 1,3-Dicyclohexylurea (cas: 2387-23-7Recommanded Product: 2387-23-7).
1,3-Dicyclohexylurea (cas: 2387-23-7) belongs to amides. The solubilities of amides and esters are roughly comparable. Typically amides are less soluble than comparable amines and carboxylic acids since these compounds can both donate and accept hydrogen bonds. Tertiary amides, with the important exception of N,N-dimethylformamide, exhibit low solubility in water. The presence of the amide group –C(=O)N– is generally easily established, at least in small molecules. It can be distinguished from nitro and cyano groups in IR spectra. Amides exhibit a moderately intense νCO band near 1650 cm−1. By 1H NMR spectroscopy, CONHR signals occur at low fields. In X-ray crystallography, the C(=O)N center together with the three immediately adjacent atoms characteristically define a plane.Recommanded Product: 2387-23-7
Referemce:
Amide – Wikipedia,
Amide – an overview | ScienceDirect Topics