PROCESS FOR PREPARING ISOCYANATE AND CARBAMATE ESTER PRODUCTS

摘要

A process for preparing an isocyanate having at least two -N=C=O groups is provided which comprises preparing a substituted aromatic amine having at least two -NH2 groups, recovering the substituted aromatic amine having at least two -NH2 groups, and preparing an isocyanate from the substituted aromatic amine having at least two -NH2 groups by (1) contacting the substituted aromatic amine with CO2 under conditions sufficient to produce the corresponding ammonium carbamate salt, and reacting the ammonium carbamate salt with an electrophilic or oxophilic dehydrating agent under conditions sufficient to produce the corresponding isocyanate, or (2) contacting the substituted aromatic amine with CO2 under conditions sufficient to produce the corresponding ammonium carbamate salt, reacting the ammonium carbamate salt with a primary or secondary hydrocarbyl halide in a polar aprotic solvent under conditions sufficient to produce the corresponding carbamate ester, and cracking the carbamate ester under conditions sufficient to produce the corresponding isocyanate. In another embodiment, a process for preparing a carbamate ester having at least two -NH-COOR1 groups is provided which comprises preparing a substituted aromatic amine having at least two -NH¿2? groups, recovering the substituted aromatic amine having at least two -NH2 groups, and preparing a carbamate ester by contacting the substituted aromatic amine with CO2 under conditions sufficient to produce the corresponding ammonium carbamate salt, and reacting the ammonium carbamate salt with a primary or secondary hydrocarbyl halide in a polar aprotic solvent under conditions sufficient to produce the corresponding carbamate ester.