Photochemical nitration by tetranitromethane. Part XXXIX. The photolysis of tetranitromethane with 2,8-dimethyl- and 1,3,7,9-tetramethyl-dibenzofuran

The photolysis of the charge transfer complex of 2,8-dimethyldibenzofuran in dichloromethane gives 2,8-dimethyl-3-trinitromethyldibenzofuran (11) and 2,8-dimethyl-3-nitrodibenzofuran (12) as the major products, with minor amounts of 2,8-dimethyl-4-nitrodibenzofuran (13) and the 4-hydroxy-3-trinitromethyl adduct 14. In 1,1,1,3,3,3-hexafluoropropan-2-ol the yield of the 3-trinitromethyl compound 11 is much reduced, and the adduct 14 is not detected. Similar photolysis of 1,3,7,9-tetramethyldibenzofuran gives predominantly 1,3,7,9-tetramethyl-2-nitrodibenzofuran (15) accompanied by the epimeric 1,3,7,9-tetramethyl-1-nitro-4-trinitromethyl-1,4-dihydrodibenzofurans 16 and 17. For reactions in dichloromethane containing trifluoroacetic acid (0.8 M), or in 1,1,1,3,3,3-hexafluoropropan-2-ol, adducts 16 and 17 are not seen among the products and the 2-nitroarene 15 is close to the exclusive reaction product.