Carbazoles Moody carbazole synthesis

The first example of an indole-2,3-quinodimethane (IQM) undergoing a Diels-Alder cycloaddition to furnish a carbazole was reported by Plieninger and coworkers in 1964 [9], Thus, indole-3-acetic acid was readily converted to pyrano[3,4-fe]indol-3-ones upon treatment with carboxylic acid anhydrides (Scheme 1, equation 1). These stable synthetic equivalents of IQMs undergo Diels-Alder reactions with electron-deficient dienophiles (A-phenytma-leimide,maleicanhydride,dimethylacetylenedicarboxylate) (equation 2). Plieninger s discovery notwithstanding, it was Moody and coworkers who parlayed this chemistry into a powerful carbazole synthesis (equations 3,4) [10-18],... 

Scheme 2 Moody Carbazole Synthesis from Pyrano[3,4-b]indol-3-ones...

Scheme 4 Variations on the Plieninger-Moody Carbazole Synthesis...

Martin, T., and C.J. Moody A New Route to 1-oxygenated Carbazoles. Synthesis of Murrayafoline-A. Tetrahedron Letters 26, 5841 (1985). 

Murakami et al. reported (575) a total synthesis of murrayaquinone A (107) by oxidation of l-hydroxy-3-methylcarbazole (23) with Fremy s salt, as previously described by Martin and Moody (632). The hydroxycarbazole 23 required for this synthesis was obtained via the Fischer indolization of the O-methanesulfonyl phenylhydrazone 614 (575) (see Scheme 5.38). The oxidation of l-hydroxy-3-methylcarbazole (23) with Fremy s salt afforded murrayaquinone A (107) as the major product, along with a 5% yield of isomeric carbazole-l,2-quinone 876 (575) (Scheme 5.108). 

Recently, Moody et al. reported a biomimetic synthesis of calothrixin B (378) by oxidation of Hibino s 6-formylindole[2,3-fl]carbazole 1555 (870). The key intermediate 6-formyl-indole[2,3-fl]carbazole was readily obtained in six steps from indigo (1458). Using Somei s procedure, indigo (1458) was transformed to the cis-chlorohydrin 1461 in three steps and 50% overall yield (see Scheme 5.247). The reduction of the chlorohydiin 1461 gave 5-hydroxy-indolo[2,3-fl]carbazole 1564, and subsequent Vilsmeier formylation delivered the desired 6-formyl-indole[2,3-fl]carba-zole 1565 in 45% yield. Reaction of hydroxy-indolocarbazole 1565 with an excess of chloromethyl methyl ether (MOMCI) afforded the tiis-MOM-protected compound 1555. Following Hibino s approach, the tris-MOM-protected indolocarbazole 1555... 

Cycloaddition reactions continue to find application in the synthesis of natural products and related substances containing indole and carbazole rings. Moody has published a summary of syntheses of carbazole alkaloids in which cycloadditions of pyrano[3,4-b]indol-3-ones figure prominently. <94SL681>... 

Moody, C.J. and Shah, P. (1989h) Diels-Alder reactivity of pyrano[3,4-b]indol-3-ones. Part 4. Synthesis of the carbazole alkaloids carbazomycin A and B and hyellazole. J. Chem. Soc. Perkin Trans. I, 2463-2471. 

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