Carbamate halosilyl

Union Carbide also patented a phosgene-free process for making hexamethylene diisocyanates [40] (Scheme5.5). In this later process, 1,6-hexanediamine was reacted with dry-ice, trimethylchlorosilane, and trichlorophenylsilane to form a halosilyl carbamate intermediate and then converted to the corresponding diisocyanate. However, it should be noted that trichlorophenylsilane used in this process is on the EPA s Extremely Hazardous Chemicals List (40 CFR Part 355, Appendix A). 

Hedaya, E. and Spyros,T. (1981) Halosilyl carbamates and isocyanates derived therefrom. Canadian Patent Application, 278,460, Union Carbide. 

Aliphatic isocyanates from halosilyl or O-silyl carbamates of amines... 

A method for the preparation of halosilyl carbamates and isocyanate involves direct synthesis from amines via halosilyl carbamate intermediates [277]. A primary amine is converted to its carbamic acid salt, which is then treated with a silane containing > 2 halogen atoms bonded to Si. Gentle heating of the resulting halosilyl carbamate gives the isocyanate. In an alternative (exchange) procedure, the carbamic acid salt is treated with any halosilane to form a silyl carbamate, which is trans-silylated. 

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See also in sourсe #XX -- [ ]

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