Carbazoles, hexahydro-, reaction with

N-, 2- and 2,3- alkylsubstituted indoles are reduced in acid solution to give good yields of the dihydroindolc [63]. Indole itself is polymerised under the acid conditions. Reaction was originally carried out in a medium of 60 % sulphuric acid at a lead cathode with no attempt made to find the optimum acid concentration. More recently, 20 % sulphuric acid has been proposed as the solvent in these reactions [64], Reduction of tetrahydrocarbazole 17 gives predominately cis-hexahydro-carbazole, the thermodynamically favoured isomer, along with 1 -2 % of the trans-isomer [65], 2,3-Dimethyl-indole yields a mixture of the cis- and trans-dihydro-indole isomers [63,66],... 

The main product of the reaction of the biphenyl derivative (143) with triethyl phosphite is 9-ethyl-4,5-dimethylcarbazole (144). Treatment of the diamine (145) with phosphoric acid yields a mixture of carbazole and 2-t-butylcarbazole. Di-lithiation of the o-bromoaniline derivative (146), followed by addition of 2-chlorocyclohexanone, affords the hexahydro-carbazole (147). ... 

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