An efficient synthesis of 6 H,7 H-chromeno[4,3- b]chromenes and 6,7-dihydrothio chromeno[3,2- c]chromenes as 9-substituted xanthene like analogs

Abstract

An efficient synthetic route with good overall yields to access 7-aryl/heteroaryl/alkyl substituted 6 H,7 H-chromeno[4,3- b]chromene, and 6,7-dihydrothiochromeno[3,2- c]chromene scaffolds has been developed. The route to these xanthene-like analogs involves a three-step reaction sequence: (1) Michael addition of readily available phenol and thiophenol to 4-chloro-2,2-dimethyl-2 H-chromene-3-carbaldehyde, (2) Grignard reaction of different aryl, heteroaryl and alkyl magnesium bromides on the resulting carbaldehydes followed by (3) FeCl 3 catalyzed spontaneous intramolecular Friedel–Craft’s reaction on the diarylmethyl carbinols.