A One-Pot Direct Iodination of the Fischer–Borsche Ring Using Molecular Iodine and Its Utility in the Synthesis of 6-Oxygenated Carbazole Alkaloids

Abstract

An efficient regioselective iodination of the Fischer-Borsche ring has been achieved using molecular iodine, in a one-pot synthesis. The acid-, metal-, and oxidant-free conditions of the present method are highly convenient and practical. Furthermore, the one-pot direct iodination process is extended to the concise synthesis of glycozoline, 3-formyl-6-methoxy-carbazole, and 6-methoxy-carbazole-3-methylcarboxylate natural alkaloids. This method has been proven to be tolerant to a broad range of functional groups, with good to excellent yields.

I2‐Catalyzed Total Synthesis of Collective 7‐Oxygenated Carbazole Alkaloids: Clauszoline‐K, ‐L, Clausine‐M, ‐N and Formal Synthesis of Siamenol

“…Next, we smoothly achieved 7‐methoxy‐3‐methyltetrahydrocarbazole 5 from substrate 3 a using NaOMe/CuI in DMF at 120 °C, in 86 % yield. Recently, we reported the one‐pot iodination of tetrahydrocarbazoles using a stoichiometric amount of molecular iodine . When the similar condition was employed, a remarkable change was observed.…”

Iodine(III)-Mediated, Controlled Di- or Monoiodination of Phenols

“…3-Iodo-9H-carbazole (48). 61,64 The following compound was obtained according to a modified general procedure A, by using 9H-carbazole as starting material and NH 4 I (reaction was in reflux overnight). The crude material was purified by flash column chromatography over silica gel with the system (3% EtOAc/Hexane) to afford the product 48 (58 mg, 47%) as a liquid.…”

“…1-Bromo-6-(p-tolyl)naphthalen-2-ol (61). The following compound was obtained according to the general procedure A, by using 6-(p-tolyl)naphthalen-2-ol as starting material and NH 4 Br.…”

Site-Specific Synthesis of Carbazole Derivatives through Aryl Homocoupling and Amination

“…In view of the paramount significance of carbazoles, numerous methods for the synthesis of carbazole derivatives have been reported. 2,22,23 Recently, transition metals such as rhodium-, 24 palladium-, [25][26][27] copper-, 28 and cobalt-catalyzed, 29 some other heterogeneous catalysts, 30,31 and even iodine- 32,33 and acid-catalyzed [34][35][36] reactions have been utilized in the key step in carbazole syntheses. Visible-lightinduced synthetic routes 37,38 have also made notable contributions to carbazole synthetic protocols.…”