Tohru Kitamura

Photochemical reactions of allylphenoxide anions

Abstract Photochemical behaviour of sodium allylphenoxides 1a–3a was compared with that of corresponding neutral allylphenols 1b–3b, and a striking difference was found in reactivity as well as in course of the reaction. Remarkably higher photoreactivity of allylphenoxide anions, especially that of o-allylphenoxide 1a, is ascribed to the efficiency of electron transfer. The characteristic reaction products derived only from the anions were as follows: (a) intramolecular cyclization products, indanols 9, from 2a, (b) rearranged reduction products 10 from both 2a and 3a, and (c) degradative methanol-adduct 11 from 3a. Methanol-adducts 7 and photo-reduction products 6 were formed in either case. In addition cyclization products with the participation of O atom, 4 and 5, were obtained from 1a and 1b. Occurrence of the di-π-methane rearrangement was restricted to the reaction of neutral species 1b–3b. A mechanism based on electron transfer in the excited state is suggested for the course of the photoreaction.

A synthesis of γ-alkylidenebutenolides photochemical rearrangement of 2,3-epoxy-1,4-cyclohexanediones

Abstract Photo-induced rearrangement of 2,3-epoxy-1,4-cyclohexanediones was investigated for a synthesis of γ-alkylidene-γ-butyrolactones and γ-alkylidenebutenolides. Irradiation of epoxy diketones 1 and 4 in acetone gave γ-lactones, 2 and 5 , and triketones, 3 and 6 . On the other hand, in CH 2 Cl 2 , EtOAc, or PhH solution epoxy diketones 1 and 4 gave only triketones, 3 and 6 . Retro-Diels-Alder reaction of γ-lactones 5aE or 5aZ at 230° (20 mmHg) afforded γ-alkylidenebutenolides 7aE and 7aZ in addition to anthracene. According to the procedure, butenolide 7bZ , a key intermediate for the synthesis of freelingyne, was prepared. The dramatic solvent effect in the photochemical rearrangement was also discussed.

Photo-induced dimerization of 1-naphthoxide anion: a new type of photochemical reaction

Irradiation of the 1-naphthoxide anion (1) gave 5′,8′-dihydro-4,8′-bi-1-naphthol (2) probably via photoinduced nucleophilic addition.