SET PHOTOCHEMICAL-REACTIONS BETWEEN 1,4-NAPHTHALENEDICARBONITRILE AND BENZYLIC DONORS - MEDIUM EFFECTS

The electron transfer induced photochemical reactions of 1,4-naphthalenedicarbonitrile (NDN) with toluene (1a), diphenylmethane (1b), p-methoxytoluene (1c), and benzyltrimethylsilane (1d) in MeOH-MeCN and 0.1 M KOH-MeOH-MeCN were examined. The results were compared with those of reactions occurring in neat MeCN. Under the former conditions, the cation radical derived from 1a undergoes deprotonation after diffusion from (rather than within) the geminate ion pair (as in MeCN). The formed benzyl radical abstracts a hydrogen from MeOH leading to hydroxymethylation of NDN competitively with its benzylation. Under basic conditions MeO(-) adds to 1a(+.) yielding 1c. The reaction of 1b in MeOH-MeCN and 0.1 M KOH-MeOH-MeCN is similar to that of 1a. However, in the reaction of 1c under these conditions, the arene cation radical undergoes deprotonation out of cage. Finally, desilylation of the cation radical from 1d is a fast process occurring from the geminate pair in all the media explored.