Furfuryl vinyl ethers in [4+2]-cycloaddition reactions

For the first time [4+2]-cycloaddition reactions were carried out between furfuryl vinyl ethers and typical dienophiles and heterodienes proceeding in uncatalyzed conditions and resulting in previously unknown heterocyclic systems containing either free vinyloxy groups or furfuryl substituents. With maleic anhydride and maleimide furfuryl vinyl ethers afforded 1-(vinyloxyalkyl)tricyclodec-8-ene-3,5-diones in up to 72% yields, and with N-benzylideneaniline or acrolein the corresponding functionally substituted tetrahydroquinolines (yield up to 65%) or 3,4-dihydropyrans (yield 23–50%) were obtained.