GB1022641A - A process for the preparation of dicarbamates with non-identical carbamate groups from diols - Google Patents

Abstract

Non-symmetric dicarbamates of the formula <FORM:1022641/C2/1> where R1 is a C1- 6 alkyl group and R2 and R3 are different and may be hydrogen or a C1- 6 alkyl group, are made by reacting (a) one mol. of a diol <FORM:1022641/C2/2> with 2 mols. phosgene in the presence of 2 mols. of an acid acceptor to form the dichlorocarbonate, (b) blocking one of the chlorocarbonate groups by reacting the dichlorocarbonate with one mol. of a tertiary amine, (c) converting the unblocked chlorocarbonate group into a carbamate group by reaction with two mols. of ammonia or a primary amine NH2R, at a temperature not exceeding 20 DEG C., and (d) converting the blocked carbonate group into a carbamate group different from that of step (c) by reaction with 2 mols. of ammonia or a primary amine, NH2R3, under more active conditions than those of step (c). In steps (c) and (d) the second mol. of ammonia or amine acts as an acidacceptor. Step (d) is suitably effected at super-atmospheric pressures and/or temperatures up to 50 DEG C. The reaction may be effected in a solvent, e.g. halogenated aliphatic hydrocarbons or aromatic hydrocarbons. Examples relate to (1) and (3) N-isopropyl-2-methyl-2-n-propyl-1,3-propanediol dicarbamate, and (2) N - n - butyl - 2 - methyl - 2 - n - propyl - 1,3-propanediol dicarbamate.