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An I2/TBHP-mediated intramolecular dehydrogenative coupling reaction is developed for the synthesis of a library of medicinally important 5,11-dialkylindolo[3,2-c]quinoline salts and 5,7-dimethylindolo[2,3-c]quinoline salts. The annulation reaction is followed by aromatization to yield tetracycles in good yield. This protocol is also demonstrated for the synthesis of the naturally occurring isocryptolepine in salt form.

A two step synthesis of a benzo analog of alpkinidine is described via Negishi coupling followed by a base mediated annulation reaction strategy. The organozinc compound prepared from ethyl 2‐iodobenzoate was coupled with 4‐chloro‐2‐methyl‐2,3‐dihydro‐1H‐pyrrolo[3,4‐c]quinolin‐1‐one to obtain ethyl 2‐(2‐methyl‐1‐oxo‐2,3‐dihydro‐1H‐pyrrolo[3,4‐c]quinolin‐4‐yl)‐benzoate which on further treatment with a base provided ABCD ring system of alpkinidine.

A new and convenient synthesis of the indoloquinoline alkaloid cryptolepine hydroiodide is described through a tandem reductive cyclization–dehydration approach. This methodology employs a C–C bond formation through the C‐2 lithiation of a benzenesulfonyl‐protected indole and a C–N bond formation through a nitrene intermediate, which is produced from different organophosphorus reagents, to give a fused tetracyclic compound. The versatility of this method is demonstrated by the syntheses of a series of cryptolepine salts with substituents on the indole as well as the quinoline ring.

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