A simple catalytic racemic synthesis of benzopyranes, benzothiopyranes and 1,2-dihydroquinolines is presented. The organocatalytic domino reactions between 2-heteroatom substituted aldehyde derivatives and ?,?-unsaturated aldehydes or ?,?-unsaturated cyclic ketones proceed with excellent chemoselectivity to give the corresponding products in good to high yields.
Ethyl-3-formyl-6-methoxy-(2H)-chromene-2-carboxylate was transformed to N-substituted 1,2-dihydrochromeno[2,3-c]pyrrol-3-ones in a domino reductive amination–lactamization reaction. Isomerization of the double bond and the inherently labile stereogenic center was studied, and HPLC-ECD analysis of a chiral 1,2-dihydrochromeno[2,3-c]pyrrol-3(3aH)-one derivative aided by TDDFT-ECD calculation allowed configurational assignment of the separated enantiomers. Antiproliferative activity of the products was demonstrated on the CaCo-2 human epithelial colorectal adenocarcinoma cell line.