|Budget Amount *help
¥3,400,000 (Direct Cost : ¥3,400,000)
Fiscal Year 1999 : ¥1,300,000 (Direct Cost : ¥1,300,000)
Fiscal Year 1998 : ¥2,100,000 (Direct Cost : ¥2,100,000)
We have studied photoinduced electron-transfer reactions of the following four compounds, a precursor of the 1,1-diaryl- or 1,4-diaryl-substituted tetramethyleneethane (TME) cation radicals and diradicals.
1.1-diaryl-substituted TME system
・ 2,3-bis(2-phenylvinyl)-5,5-dimethylcyclopenta-1,3-diene (1)
・ 1,4-diphenyl-5,6-dimethylene-2,3-diazabicyclo[2.2.2]oct-2-ene (2)
1.4-diaryl-substituted TME system
・ 1-methylene-3,3-bis(4-methoxyphenyl)spiropentane (3)
・ 3,3-diphenyl-2-methylene-1-(methylethylidence)cyclobutane (4)
As a result, 9,10-dicyanoanthracene (DCA)-photoinduced electron-transfer reaction of 1 in the presence of N-methylmaleimide (NMI) as a diylophile gave the adducts with NMI (5) in good yields, suggesting generation of a 1,1-diaryl-substituted TME diradical (6). This was most likely generated by back electron transfer from sensitizer anion radical to the corresponding 1,1-diaryl-substituted TME cation radical (6ィイD1・+ィエD1). Further supports were obtained by laser flash photolyses of 1. Similar photoinduced electron-transfer reactions of 2 underwent deazetation to give 3,4-dimethylene-2,5-diphenyl-1,5-hexadiene (7) quantitatively. Trapping experiment with NMI gave two adducts (8 and 9), suggesting generation of the corresponding 1,1-diaryl-substituted TME diradical (10).
In contrast, compounds (3) and (4) did not gave any products through 1,4-diaryl-substituted TME intermediates but underwent novel reactions under photoinduced electron-transfer conditions. Surprisingly, 3 gave 1,3-dimethylene-2,2-bis(4-methoxyphenyl)cyclobutane (11) under the DCA-sensitized photoconditions. Similar photoreactions of 4 underwent formal [4+4] cyloadditions to give two kinds of dimer (syn-12, anti-12) and an adduct (13) of 4 with DCA.