Thermal and catalytic intramolecular [4+2]-cycloaddition in 2-alkenylfurans

The published data on the intramolecular Diels–Alder reaction in compounds of the 2-alkenylfuran series are generalised. The methods and conditions for the preparation of tricyclic systems are considered. The effects of the substituents in the furan and the unsaturated fragments on the cycloaddition are discussed. The application of this reaction to the synthesis of alkaloids and terpenoids is exemplified.