Electron transfer reactions. Reaction of tetracyclone, tetraphenylfuran and related substrates with potassium

Abstract

The reaction of tetracyclone (1) with potassium in THF gave a mixture of benzoic acid (4), tetraphenylfuran (5) and cis-1,2-dibenzoylstilbene (6). The reaction of 1 with potassium in oxygen-saturated THF gave a mixture of 2-hydroxy-2,4,5-triphenyl-3(2H)furanone (3), 4, 5 and 6, whereas the reaction of 1 with potassium superoxide gave a moderate yield of 3,4,5,6-tetraphenyl-2-pyrartone (7), besides 3, 4, 5, and 6. The reaction of tetraphenylfuran (5) itself with potassium in THF gave a mixture of 6, 1,2,3,4-tetraphenylbutan-1-one (9), 2,3-diphenyl-1-indenone (10) and 2,3-epoxy-4-hydroxy-2,3,4-tnphenyltetralone-l (11), whereas practically no reaction occurred on treatment of 5 with potassium superoxide. Treatment of 10 with potassium in THF, however, gave a mixture of 4, dibenzo[a,c]-13-fluorenone (13), 2,3-diphenyl-2-hydroxyl-1-indanone (14) and 2,3-diphenylbenzofuran (15). A similar mixture of products consisting of 4, 13, 14 and 15 was obtained when the reaction of 10 with potassium was carried out in oxygen-saturated THF or when 10 was treated with potassium superoxide. Treatment of 2,3-diphenyl-2,3-epoxy-1-indanone (16) with potassium on the other hand, gave 10 in excellent yield. Cyclic voltammetric studies have been carried out to measure the reduction potentials of 1, 5, 10 and 16 in the generation of their radical anions. The radical anions of 1, 5, 10 and 16 were also generated pulse radiolytically in methanol and their spectra showed absorption maxima in the region 320–380 nm.