Isocyanates hetero-substituted

Reviews of the Cope reaction, electronic quantum fluxes during the rearrangement of semibullvalene," the chemistry of hetero-substituted isocyanates and isothiocyanates RX-NCY (X = R2N, RO, RS Y = 0, S) and the isomeric cyanates RX-OCN, thiocyanates RX-SCN, nitrile oxides RX-CNO, and nitrile sulfides RX-CNS have appeared. ... 

The anodic oxidation of substituted allenes [76-79] and hetero-allenes [80-85] has been extensively studied by Becker and coworkers. Oxidation of secondary and tertiary alkyl isothiocyanates resulted in an ot-cleavage processes [77]. Primary alkyl isocyanates yielded amides and carbonyl compounds due to the nucleophilic involvement of either acetonitrile or water [80]. Primary alkyl isothiocyanates 48 afforded five-membered thiadiazolidine 49 and 50 and... 

There are many reactions in which pyridines are used as bases. However in a large number of reactions only pyridine itself is reactive. a-Substituted pyridines behave differently, e.g. in the catalysis of acylation reactions with acyl chlorides or anhydrides [45]. The sterical hinderance of the a-substituents decelerates reactions in which a pyridine reacts as a nucleophile. A reaction which can be base-catalyzed by a-substituted pyridines is the addition of alcohols to hetero-cumulenes such as ketenes and isocyanates. Therefore this reaction was investigated as a model reaction for base catalysis by concave pyridines. 

Carbodiimides are a unique class of reactive organic compounds having the hetero-cumulene structure R-N=C=N-R. They can be formally considered to be the diimides of carbon dioxide and they are closely related to the monoimides of carbon dioxide, the isocyanates. The substituent R can be alkyl, aryl, acyl, aroyl, imidoyl, or sulfonyl, but nitrogen, phosphorous and metal-substituted carbodiimides are also known. The unsubstituted carbodiimide is isomeric with cyanamide, H2NCN. Also, monosubstituted carbodiimides exist only in the isomeric cyanamide structure. 

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