RELATIVELY STABLE N-BENZHYDRYLKETENE AND N-BENZYLDIARYLKETENE IMINES AND THEIR CONVERSION TO CYANODIARYLMETHANES VIA AN ISOLABLE RADICAL

An efficient synthetic route to the sterically hindered ketene imines N-benzyl- and N-benzylhydrylbis(pentamethylphenyl)ketene imines 8 from dipentamethylphenyl ketene 6 is described. The thermal stability of these ketene imines is in marked contrast to the diphenylketene imine analogues which rearrange rapidly to C-tri-substituted nitriles. On heating 8b is converted to the relatively stable free radical 13 which can be reduced to the nitrile 10 in a variety of solvents. These radicals are proposed intermediates in the ketene imine-nitrile rearrangement, and the mechanism of this reaction is considered in in terms of these results.