ACETYLENE CHEMISTRY .33. SYNTHESIS OF 2-S UBSTITUTED DIHYDROFURO[2,3-B]QUINOLINES

The reaction of 3-iodo-4-methoxy-2(1H)-quinolinone (1) and 3-iodo-4,6, 8-trimethoxy-2(1H)-quinolinone (2) with 2-methyl-3-butyn-2-ol under mo dified Heck-conditions gave the 2-substituted derivatives droxy-1-meth ylethyl)4-methoxyfuro[2,3-b]-quinoline (3) and -methylethyl-4,6,8-trim ethoxyfuro[2,3-b]-quinoline (4). By a subsequent hydrogenation-reactio n with a homogeneous catalyst (PtO2/Rh2O3), the furoquinoline-derivati ves yielded the dihytrofuro[2,3-b]quinolines, identified as hylethyl-4 -methoxy-2,3-dihydrofuro[2,3-b]quinoline (5) (racemic platydesmine) an d )-4,6,8-trimethoxy-2,3-dihydrofuro[2,3-b]quinoline (6) (racemic prec ursor of O4-methylptelefolonium salt).