Some acid-catalysed reactions of indol-3-yl and indol-2-yl disubstituted methanols

1-Substituted indol-3-yl and indol-2-yl disubstituted methanols do not undergo acidcatalysed trimerisation to yield indolocyclotriveratrylenes, unlike the related primary 1-substituted indol-3-yl-and -2-ylmethanols. The 1-substituted indol-3-ylmethanols 10 and 11 gave diindol-3-ylmethanes 12 and 13, respectively, on treatment with p-toluenesulfonic acid in dichloromethane. In contrast, the indol-2-ylmethanols 22 and 23 gave the reduced indolo[3,2-b]carbazoles 24 and 25, respectively, on treatment with boron trifluoride etherate in benzene. An X-ray crystal structure of compound 24 is described.