T. Hudlicky et al., INTRAMOLECULAR DIELS-ALDER REACTIONS OF THE FURAN DIENE (IMDAF) - RAPID CONSTRUCTION OF HIGHLY FUNCTIONALIZED ISOQUINOLINE SKELETONS, Journal of the Chemical Society. Perkin transactions. I, (19), 1995, pp. 2393-2398
Intramolecular Diels-Alder reaction of substituted furans has been inv
estigated as a prelude to focused application to the synthesis of isoq
uinoline 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-cyclode
xtrin catalysis. The. thermal cyclisation of methoxyfuran precursor 11
gave 55% yield of the cycloadduct 13 and 40% yield of anisole derivat
ive 14. Finally, the phenyl-substituted precursor 23 was cyclised in a
yield of 13% at the expense of undesired elimination of 2-phenylbutad
iene. These studies provide preliminary evidence that highly functiona
lised isoquinolines are accessible by the intramolecular Diels-Alder r
eaction of furans.