SET Photochemical Reactions between 1,4-Naphthalenedicarbonitrile and Benzylic Donors. Medium Effects
摘要:
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.
SET Photochemical Reactions between 1,4-Naphthalenedicarbonitrile and Benzylic Donors. Medium Effects
作者:E. Fasani、N. d'Alessandro、A. Albini、P. S. Mariano
DOI:10.1021/jo00083a025
日期:1994.2
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.
Benzyl Radicals from Toluene by Photosensitization with Naphthalene-1,4-dicarbonitrile – Benzylation and Hydroxymethylation of Unsaturated Compounds
transfer fromtoluene to 1,4-naphthalenedicarbonitrile (DCN) is followed by in-cage proton transfer and radical coupling. However, in the presence of a protic co-solvent, the radical ions diffuse out of the cage and deprotonation of the tolueneradical cation takes place from the free solvated species. With tBuOH, this results in reductive benzylation of DCN through coupling of benzylradicals with DCN–·