Reactions on (R) and (S)-1,1,2-triphenyl-1,2-ethandiols induced by aminium salts and protic acids. Solvent effect.

(R) and (S) 1,1,2-triphenyl-1,2-ethandiols (1a) and (1b), upon treatment of their dichloromethane solutions with catalytic amounts of aminium salt cation radicals afforded mixtures of the corresponding pinacolones (Ph3CCHO, 90 %) (2), (Ph2CHCOPh, 10%) (3), whereas similar reactions, carried out in acetonitrile, led to consistent amounts of both pinacolones, together with benzophenone (4), benzaldehyde (5) (minor amounts), and new products (30 %), fully characterized as (R) and (S) 4,4,5-triphenyl-2-methyloxazolines (7a,b). The formation of these latter was selectively inhibited in the aminium salt induced reactions, modified by 2,6-di-tert-butylpyridine (DBP). (C) 1997 Published by Elsevier Science Ltd.