The fluoride ion-induced intramolecular conjugate addition of propargylsilanes to dihydropyridones. A novel method for the stereoselective construction of azabicyclic ring systems

The fluoride ion-induced intramolecular conjugate addition of propargylsilanes to dihydropyridones is reported. Our results revealed that tetrabutylammonium triphenyldifluorosilicate (TBAT), an air-stable, non-hygroscopic fluoride ion source, catalyzes cyclocondensation to provide the corresponding 1-vinylidene indolizidines in a high yield as single isomers, while Lewis acid catalysts were ineffective. The scope of this method was further investigated in the reactions leading to compounds with larger ring size. In these cases dihydropyridones with the propargylsilane located in the side-chain underwent cyclization to give 9-vinylidene quinolizidines with significantly lower yields.