THE PHOTOCHEMICAL APPROACH TO THE FUNCTIONALIZATION OF OPEN-CHAIN ANDCYCLIC ALKANES .2. HYDROGEN ABSTRACTION

Chloranil (Chl) has been irradiated in the presence of the alkanes 2,3 -dimethylbutane, cyclohexane, norbornane, adamantane in acetonitrile. The primary step is hydrogen abstraction by triplet Chl, k(H) 0.8 to 2 x10(6) M(-1)s(-1), as confirmed by the detection of the ChlH(.) radica l. Hydrogen abstraction from the alkanes is unselective. The thus form ed alkyl radicals undergo different reaction, viz: coupling with ChlH( .) (both C-Q coupling to give hydroquinonemonoethers and C-C coupling to give hydroxydihydrobenzoflurans are observed); addition to ground s tate Chl to yield ultimately alkoxyphenoxyquinones; oxidation by groud state Chl (this process is fast only with tertiary radicals, and the cations formed in this case are trapped by the solvent MeCN to yield a cetamides). Different methods for alkane funtionalization are compared . Copyright (C) 1996 Elsevier Science Ltd