A mixture of 4.28 mmol (1.1328 g) bibenzil-4,4-di-yl-diisocyanate (1) [1] and 84 mmol (6.14 g) of redistilled N,N-dimethylformamide (2) was refluxed under stirring using a magnetically stirring-bar for 12 h, with complete absorption for any carbon dioxide in aqueous potassium hydroxide solution [2].[...]