PURPOSE: To prepare the bis-compound of the titled compound useful as a starting raw material for the preparation of polyurethane, with little production of by-product, in high selectivity, by reacting an N-phenylcarbamic acid ester with a methylene introducing agent using a specific compound as a catalyst.

CONSTITUTION: Methylene group is introduced into an N-phenylcarbamic acid ester of formula (R is alkyl, aromatic group, etc.; R' is H, alkyl, halogen, etc.; r is 0W4, etc.), by reacting the ester with a methylene introducing agent (e.g. formaldehyde, paraformaldehyde, etc.) using a compound having a fluorinated sulfonic acid group of formula CF2SO3H or CFSO3H and a carboxyl group (e.g. difluorosulfoacetic acid, perfluoro-3-sulfopropionic acid, etc.) as a catalyst. The characteristic feature of the catalyst is high rate of reaction and the capability of proceeding the reaction at a temperature of as low as ≤100°C.