GB1065767A - Process for preparing carbodiimides - Google Patents

Abstract

Carbodiimides are prepared by thermally decomposing N,N1 - disubstituted S - alkyl-isothioureas of the formula <FORM:1065767/C2/1> or <FORM:1065767/C2/2> wherein R and R1 each represents primary, secondary or tertiary alkyl, cycloalkyl, aralkyl, or aryl, R and R1 being so chosen that not more than one represents aryl, and the total number of hydrogen atoms attached to the two carbon atoms linked directly to the nitrogen atoms of the isothiourea group is not greater than 2 or not greater than 1 when one of R and R1 is aryl, R111 represents cycloalkyl or primary, secondary or tertiary alkyl, R11 represents an aliphatic or cycloaliphatic hydrocarbon chain containing at least 3 carbon atoms and optionally interrupted by oxygen atoms, sulphur atoms or nitrogen-free hetero groups separated from the nearest isothiourea groups by at least 2 carbon atoms, R11 and R111 being so selected that a total of at most 2 hydrogen atoms are attached to the 2 carbon atoms linked directly to the nitrogen atoms of each isothiourea group, and n represents a positive integer, preferably 1. The thermal decomposition may be carried out in the presence of a high-boiling inert organic solvent, and the crude reaction product obtained may be purified by a treatment with active aluminium oxide. A suitable substituted S-alkyl isothiourea starting material is prepared by reacting ethylene glycol - bis - (gamma - aminopropylether) with tertiary - butyl mustard oil, followed by S-methylation of the product with dimethyl sulphate.