Thiol-Isocyanate Chemistry

In yet another example of the chemical versatility of thiols, their base-catalyzed reaction with isocyanates is very fast and can be utilized with considerable ease. Such a reaction was used by 

Extrapolating from this work, Hoyle and colleagues combined this chemistry with thiol-ene reactions to achieve segmented polythiourethane elastomers (Shin et al, 2009). A simple mixing of di-thiol prepolymer, diisocyanate linker and a catalytic amount of triethylamine (0.03-0.1 wt%) resulted in 95% conversion of the isocyanate within 10 min. 

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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In amino acid and peptide chemistry, the di-ferf-butyl dicarbonate (BocaO) is an extensively used reagent for the clean and rapid Boc-protection of amine functionalities.It is also an efficient ferf-butoxycarbonylating agent for alcohols, thiols, and carbon nucleophiles, and it has been used for the conversion of amines into isocyanates, carbamates, and urea derivatives.The reaction of amino acids with chloroformates to produce N-urethane-protected amino acids if not performed under optimal conditions is accompanied by the formation of N-protected oligomers this has been well documented in the case of and... 

Instead of matching the polarity of the POSS to the matrix, one can also imbue compatibility through reaction of POSS with the matrix by choosing appropriate chemistry. Virtually all chemistries are available to facilitate reactions such as alcohol, carboxylic acid, sulfonic acid, epoxy, chloroalkyl, acrylate, methacrylate, isocyanate, amine, thiol, silanol, and several others. 

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