One-Pot, Two-Step Synthesis of Highly Functionalized 4-Indolyl/Pyrrolyl-Chromanes via para-Quinone Methide Formation-1,8-Addition Sequence

An efficient one-pot, two-step synthesis of structurally diverse 4-indolyl-/pyrrolyl-chromanes was developed starting from o-propargylated salicylaldehydes, 2,6-dialkylphenols and indoles/pyrrole. This process begins with a sequential secondary amine-catalyzed formation of p-quinone methides followed by Brønsted acid catalyzed 1,8-addition with indoles/pyrrole to access the functionalized chromanes in high yields (up to 91%). This sequential reaction generates three new C–C bonds, shows high step- and atom-economy with only one molecule of water as the side product and gives access to complex molecular frameworks without the need for the isolation of the intermediates.