N-Heterocyclic carbene-catalyzed cascade reaction of 2-aroylvinylcinnamaldehydes with 2-aroylvinylchalcones: rapid assembly of six contiguous stereogenic centers with high diastereoselectivity.

N-Heterocyclic carbene-catalyzed reaction of 2-aroylvinylcinnamaldehydes with 2-aroylvinylchalcones proceeded via a triple Michael addition and intramolecular lactonization cascade to produce novel 9-(2-aroyl-3-aroylmethyl-1-indanyl)-3-arylindeno[2,1-c]pyran-1-ones in good yields with high diastereoselectivity. This reaction constructed six contiguous stereogenic centers in a single reactive event. Among 32 possible diastereoisomers that contain six stereocenters, only two diastereoisomers were detected with diastereomeric ratios being 10 : 1-28 : 1. This work opens up a new avenue for the synthesis of complex indane derivatives, a type of compound that has been reported to possess various biological and pharmaceutical activities.