B(C6F5)3-mediated transformations and hydrogenation of carbodiimides

Abstract

The reactivity of a series of carbodiimides RNCNR (R=tBu (1 a), iPr (1 b), SiMe3 (1 c), and Dipp (2,6-di-iso-propylphenyl (1 d)) with B(C6 F5 )3 was investigated. After initial adduct formation, several distinct reaction pathways were identified. These pathways involve either isomerization of the carbodiimide to cyanamide derivatives or insertion of a carbodiimide into a BC bond of B(C6 F5 )3 to yield four-membered heterocycles. In the presence of dihydrogen, stepwise hydrogenation of the heteroallene moiety in the carbodiimides was achieved, which yielded the respective amidine-B(C6 F5 )3 adducts and amidinium borate salts upon reaction with one or two equivalents of H2 , respectively.

Keywords: amidines; carbodiimides; cyanamides; frustrated Lewis pairs; hydrogenation.