3173-53-3Relevant articles and documents
Free-Radical Halogenations. 5. Reaction of Chlorosulfonyl Isocyanate with Alkanes
Mosher, Melvyn W.
, p. 1875 - 1879 (1982)
The free-radical chain reactions of chlorosulfonyl isocyanate with alkanes can be initiated with either light or thermal initiators.The major products in these reactions are chlorides, with low yields of isocyanates and sulfonyl chlorides.On the basis of tertiary to primary hydrogen selectivity of about 120:1 and the relative reactivities of various substrates toward the abstracting radical from chlorosulfonyl isocyanate, the hydrogen-abstracting radical is suggested to be the NCO radical.
POLYMERIZATION, OXYGENATION AND ISOMERIZATION OF ISOCYANIDES UNDER IRRADIATION
Boyer, Joseph H.,Ramakrishnan, V. T.,Srinivasan, K. G.,Spak, A. J.
, p. 43 - 46 (1981)
Irradiation in the presence of triplet oxygen polymerized both 2,4-dimethoxyphenyl and cyclohexyl isocyanide and photoautoxidized each into the corresponding isocyanate.The aryl, but not the alicyclic, isocyanide also photoisomerized into a cyanide.The consumption of an isocyanide was enhanced in the presence of certain aromatic hydrocarbons, e. g., naphthalene and phenanthrene, but was diminished in the presence of pyrene.Two bisisocyanides were unaffected by the presence of oxygen during irradiation.
Supporting-Electrolyte-Free Anodic Oxidation of Oxamic Acids into Isocyanates: An Expedient Way to Access Ureas, Carbamates, and Thiocarbamates
Petti, Alessia,Fagnan, Corentin,van Melis, Carlo G. W.,Tanbouza, Nour,Garcia, Anthony D.,Mastrodonato, Andrea,Leech, Matthew C.,Goodall, Iain C. A.,Dobbs, Adrian P.,Ollevier, Thierry,Lam, Kevin
supporting information, p. 2614 - 2621 (2021/06/27)
We report a new electrochemical supporting-electrolyte-free method for synthesizing ureas, carbamates, and thiocarbamates via the oxidation of oxamic acids. This simple, practical, and phosgene-free route includes the generation of an isocyanate intermediate in situ via anodic decarboxylation of an oxamic acid in the presence of an organic base, followed by the one-pot addition of suitable nucleophiles to afford the corresponding ureas, carbamates, and thiocarbamates. This procedure is applicable to different amines, alcohols, and thiols. Furthermore, when single-pass continuous electrochemical flow conditions were used and this reaction was run in a carbon graphite Cgr/Cgr flow cell, urea compounds could be obtained in high yields within a residence time of 6 min, unlocking access to substrates that were inaccessible under batch conditions while being easily scalable.
Dehydrogenative Synthesis of Carbamates from Formamides and Alcohols Using a Pincer-Supported Iron Catalyst
Bernskoetter, Wesley H.,Hazari, Nilay,Mercado, Brandon Q.,Townsend, Tanya M.
, p. 10614 - 10624 (2021/09/02)
We report that the pincer-ligated iron complex (iPrPNP)Fe(H)(CO) [1, iPrPNP- = N(CH2CH2PiPr2)2-] is an active catalyst for the dehydrogenative synthesis of N-alkyl- and N-aryl-substituted carbamates from formamides and alcohols. The reaction is compatible with industrially relevant N-alkyl formamides, as well as N-aryl formamides, and 1°, 2°, and benzylic alcohols. Mechanistic studies indicate that the first step in the reaction is the dehydrogenation of the formamide to a transient isocyanate by 1. The isocyanate then reacts with the alcohol to generate the carbamate. However, in a competing reaction, the isocyanate undergoes a reversible cycloaddition with 1 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. We also identified several other off-cycle processes that occur in catalysis, such as the 1,2-addition of the formamide or alcohol substrate across the Fe-N bond of 1. 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 amines to produce ureas is faster than trapping with an alcohol to produce carbamates and thus ureas can be formed selectively in the presence of alcohols. In contrast, thiols bind irreversibly to the iron catalyst through 1,2 addition across the Fe-N bond of 1, and it is not possible to produce thiocarbamates. Overall, our mechanistic studies provide general guidelines for facilitating dehydrogenative coupling reactions using 1 and related catalysts.