New 4-azatetracyclo[5.3.2.02,6.08,10]dodec-11-ene-3,5-diones via the cycloaddition of N-phenylmaleimide and cyclohepta-1,3,5-trienes

The cycloaddition reactions of N-phenylmaleimide with 7-substituted cyclohepta-1,3,5-trienes afforded new 4-aza- tetracyclo[5.3.2.0^2,6.0^8,10]dodec-11-ene-3,5-diones in high yields (87–97%). The true substrates which underwent the [4 + 2] cycloaddition were the 7-R-bicyclo[4.1.0]hepta-2,4-diene tautomers. The structures of the synthesized compounds were proved by NMR spectroscopy and X-ray diffraction analysis.