INTRAMOLECULAR DIELS-ALDER REACTIONS OF THE FURAN DIENE (IMDAF) - RAPID CONSTRUCTION OF HIGHLY FUNCTIONALIZED ISOQUINOLINE SKELETONS

Intramolecular Diels-Alder reaction of substituted furans has been investigated as a prelude to focused application to the synthesis of isoquinoline alkaloids. Several conditions have been investigated for the model compound 6 containing both unactivated dienophile and diene. The best conversion to cycloadduct 8 (84%) was achieved with beta-cyclodextrin catalysis. The. thermal cyclisation of methoxyfuran precursor 11 gave 55% yield of the cycloadduct 13 and 40% yield of anisole derivative 14. Finally, the phenyl-substituted precursor 23 was cyclised in a yield of 13% at the expense of undesired elimination of 2-phenylbutadiene. These studies provide preliminary evidence that highly functionalised isoquinolines are accessible by the intramolecular Diels-Alder reaction of furans.