Using catalysts is a powerful way to make chemistry greener and produce less waste. Organocatalysts are powerful alternatives to commonly used metal catalysts because they are often less expensive, not as reactive with oxygen and water, and less toxic. Trityl catalysts are Lewis acid catalysts that are electronically tunable, allowing for fine adjustments of reactivity for specific applications. Previously we optimized trityl catalysts for the synthesis of bisindoylmethanes with antibiotic properties, but the reaction was limited to symmetric bisindolylmethanes due to a faster second addition of indole. To address this limitation the substrate was modified to slow down the second addition step, which allows for effective isolation of a single addition product. Optimization of the reaction parameters led to high yields for a variety of substrates, including electron-rich, electron poor, and sterically hindered aromatic imines. The process is also amenable to a one-pot two-step sequence in which a second indole nucleophile is added after the first addition is complete to generate a non-symmetric bisindolylmethane. Future work on this project includes completing the substrate scope and characterization of the products as well as biological testing of the novel non-symmetric bisindolylmethane substrates.

Trityl catalyzed synthesis of bisindolylmethanes from imines

2019 Spring National Meeting

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