INTRAMOLECULAR DIELS-ALDER REACTIONS OF VINYLFURANS LEADING TO FURANODECALINS

Thermolysis of the (2E,8Z)-9-(2-furyl)nonadienoate 25 at 290-degrees-C leads to an essentially quantitative yield of a single furanodecalin 26, whereas the corresponding (2E,8E)-isomer 34 undergoes a non-stereo selective cyclisation leading to the furanodecalins 26 and 35. (Z)-Alk enoate functions undergo partial isomerisation prior to cyclisation an d so lead to mixtures of isomers. Alkyl groups can be incorporated aro und the reaction sites, but this can result in overwhelming competitio n from side reactions. The corresponding 3-furyl analogues 56 and 59 d isplay very similar reactivities.