Alkene , reactivity toward Isocyanates

The availability of the unshared pair of electrons on the heteratcm(s) dictates the potential reactivity of these compounds. For enamines (vinylamines) or ketene aminals, the more basic -NR2 groups give more reactive ccnpounds. Secondly, the orbital containing the available electron pair must be ooplanar with the pi orbital of the alkene for polarization, 4, to occur. Clearly, greater polarization gives more nucleophilic character to the /3-carbon and enchaneed reactivity towards isocyanates. 

The reactivity of electron-rich alkenes towards isocyanates is... 

It is important to note that the thiol-isocyanate reaction is not orthogonal to the base-catalyzed Michael addition of thiols to alkenes, as was observed by Lowe when attempting to conjugate 2-isocyanoethyl methacrylate, although this system still showed significant selectivity towards the thiocarbamate adduct (Li et al, 2009). Furthermore, it should be noted that isocyanates are very reactive (and toxic) compounds that can react with hydroxyl functionality. 

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