Trisulfonamide Calix[6]arene-Catalysed Michael Addition to Nitroalkenes

We describe the application of a novel family of trisulfonamide calix[6]arenes TSA in general acid catalysis. Hydrogen-bonding interactions between acidic TSA and methanol boosted the reactivity of a Michael addition of indoles to nitroalkene derivatives. The transformation occurs at a low catalyst loading of 5 mol % allowing for the synthesis of nitroalkanes in good yields and functional group tolerance.