Organic isocyanates, generation from

Generation of Organic Isocyanates from Amines, Carbon Dioxide, and Electrophilic Dehydrating Agents... 

Kumar and Ramakrishnan synthesized hyperbranched polyurethanes via the in-situ generation of 3,5-dihydroxyphenyl isocyanate from the corresponding carbonyl azide [98]. The degree of branching was determined as being close to 0.6 using NMR spectroscopy. The hyperbranched polyurethane was completely soluble in common organic solvents while the linear counterpart was completely insoluble. 

The chemical reactivity of the cumulenes under discussion ranges from highly reactive species to almost inert compounds. While some cumulenes can only be generated in a matrix at low temperatures, others are indefinitely stable at room temperature. For example, sulfines and sulfenes are only generated in situ, but some cumulenes with bulky substituents are sometimes isolated at room temperature for example, C=C=S was detected in interstellar space by microwave spectroscopy, and its spectrum was later verified by matrix isolation spectroscopy. In contrast, some cumulenes, such as carbon dioxide and carbon disulfide, are often used as solvents in organic reactions or in the extraction of natural products. The reactivity of some center carbon heterocumulenes in nucleophilic reactions is as follows isocyanates > ketenes > carbodiimides > isothiocyanates. However these reactivities do not relate to the reactivities in cycloaddition reactions. Often reactive cumulenes are isolated as their cyclodimers. Aromatic diisocyanates are more reactive than aliphatic diisocyanates in nucleophilic as well as cycloaddition reactions. 

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