Synthesis and isolation of iodocarbazoles. Direct iodination reaction 933 of N-substituted carbazoles

Abstract

Iododerivatives of N-methylcarbazole (1), N-phenylcarbazole (2), N-benzylcarbazole (3), 2-methoxy-N-methylcarbazole (4) and 3-acetamido-N-ethylcarbazole (5) are synthesised. N-Iodosuccinimide (NIS) in tetrahydrofurane/H2SO4 (catalyst), a mixture of KIO3 - KI - H2SO4 (catalyst) in ethanol and a mixture of KIO3 - KI in glacial AcOH as iodinating agents have been used and their uses have been compared. The preparation, isolation and characterization of compounds 1a, 1b, 1c, 1d, 2a, 2b, 3a, 3b, 4a, 4b, 4c and 5a are reported (mp, tR, Rf, 1H-nmr, 13C-nmr, IR and ms). All of them are described for the first time except 3,6-diiodo-N-phenylcarbazole (2b). Semiempirical PM3 calculations have been performed to predict reactivity of N-substituted carbazoles and their iododerivatives. Theoretical and experimental results are discussed briefly.