Synthesis of 5-(2-hydroxyphenyl)-5-methyl-6H-benzo[c]carbazole-6-ones via photo-induced rearrangement and oxidation

A concise and efficient photo-induced rearrangement and oxidation of 2-(3-methylbenzofuran-2-yl)-3-phenyl-1H-indoles 1 for the syn-thesis of 5-(2-hydroxyphenyl)-5-methyl-5,7-dihydro-6H-benzocarbazol-6-ones 2 is described. Irradiation of 1 in the solution of di-chloromethane with a 313 nm UV light in the air atmosphere gave 2 in good yields. Using the 6π-electric cyclization strategy of 1 con-taining a methyl, a quaternary carbon stereocenter was introduced in the target compound 2. The carbonyl group of 2 was formed by the photo-induced oxidation of C-H bond to C-OH and hemiketal-keto tautomerization. Additionally, the antitumor activities of 2 was evaluated and showed similar or better activity compared to the Cisplatin against tumor cell lines of leukemia HL-60, lung cancer A594, liver cancer HepG2, breast cancer MDA-MB-231 and colon cancer SW480.