Light-induced and related reactions of quinones. Part IX. t-Butyl-1,4-benzoquinones

Abstract

Irradiation of t-butyl-1,4-benzoquinone with visible light in dry acetaldehyde gives an 80% yield of 4,5-dihydro-2,4,4-trimethyl-1,3-benzodioxepin-7-ol, but irradiation in aqueous acetaldehyde yields 72% of 1-(2,5-dihydroxy-phenyl)-2-methylpropan-2-ol. The latter compound is also the major product when the quinone is irradiated in aqueous t-butyl alcohol, although only a poor yield results when the t-butyl alcohol is dry. With isopropyl alcohol, ethanol, and methanol the major products are the corresponding 2-alkoxy-1-(2,5-dihydroxyphenyl)-2-methyl-propanes.

Irradiation of 2,5-di-t-butyl-1,4-benzoquinone in acetaldehyde gives the expected t-butyldihydrobenzodioxepin, although in low yield, but no dihydrobenzodioxepin was detected amongst the products similarly obtained from 2,6-di-t-butyl-1,4-benzoquinone.

Irradiation of the quinones in dry benzene gives very low yields of 2,3-dihydro-2,2-dimethylbenzofuran-5-ols and 3-(2,5-dihydroxyphenyl)-2-methylpropenes.

Reorganisation of the carbon skeleton of a t-butyl group is involved in the formation of all these compounds, and mechanisms for this are discussed. Structural assignments are based on spectroscopic examination, and, on comparison of derivatives with synthetic materials.