Domino reaction of 3-nitro-2-(trifluoromethyl)-2H-chromenes with 2-(1-phenylalkylidene)malononitriles: synthesis of functionalized 6-(trifluoromethyl)-6H-dibenzo[b,d]pyrans and a rare case of [1,5] sigmatropic shift of the nitro group

A variety of functionalized 6-(trifluoromethyl)-6H-dibenzo[b,d]pyrans were easily synthesized in good yields under mild conditions by a domino reaction of 3-nitro-2-(trifluoromethyl)-2H-chromenes with 2-(1-phenylethylidene)- and 2-(1-phenylpropylidene)malononitriles. In the latter case, intermediate 7-amino-10-methyl-10-nitro-9-phenyl-6-(trifluoromethyl)-10,10a-dihydro-6H-benzo[c]chromene-8-carbonitriles were isolated as a result of a rare [1,5] sigmatropic shift of the nitro group.