Reaction of alkyl-3-nitro-and-3-bromo-3-nitroacrylates with 2-(2-nitroethenyl)furan

The diene condensation of β-nitro and β-bromo-β-nitroacrylates with 2-(2-nitroethenyl)furan as 1,3-diene leads to a mixture of regioisomeric tetrahydrobenzofurans transforming under the reaction conditions into benzofurancarboxylates due to the easy dehydrohalogenation, denitration, and dehydration. In the case of a gem-bromonitroacrylate reaction takes two routes: diene synthesis and alkylation of the furan ring, the latter process prevailing. The structure of products formed was established by spectral methods. The investigation of geometry of 2-(1-methoxycarbonyl-2-nitroethenyl)-5-(2-nitroethenyl)furan by XRD analysis showed that its vinyl fragments have the coplanar chelate-like structure with the cisoid orientation of the CO2Me and NO2 groups. The ester group deviates from the plane of the the carbon-carbon multiple bond.