Studies on the rearrangement of ortho-nitro- benzylidenemalonates and their analogues to 2-aminobenzoate derivatives

Reaction of the diethyl 2-nitro-4-(trifluoromethyl)benzylidenemalonate with diethylamine in alcohols resulted in the reduction of the nitro group and the oxidation of the vinylic carbon attached to the phenyl ring. Simultaneous migration of the malonic fragment gave the appropriate 2-amino-4-(trifluoromethyl)benzoate esters. The presence of at least two nitro groups, or one nitro group and trifluoromethyl group on the phenyl ring, attached to the α-carbon and strongly electron withdrawing substituents at the β-carbon (CO2Et, CN) in ortho-nitrobenzylidene systems is necessary for this reductive–oxidative rearrangement to proceed. Reaction of nitrocinnamates with thiols in the presence of triethylamine in tetrahydrofuran gave Michael addition products with different regioselectivity of addition. Ethyl 2nitrocinnamate undergoes standard β-addition of thiols to a carbon–carbon double bond. However, 2,4-dinitroand 2,4,6-trinitrocinnamates undergo α-addition of thiols, indicating that the presence of two nitro groups on the phenyl ring can reverse polarity of the carbon–carbon double bond in cinnamate acceptors.