HETEROAROMATIC ANNELATIONS FOR THE SYNTHESIS OF BRIDGE-HEAD NITROGEN-COMPOUNDS VIA ALPHA-OXOKETENE DITHIOACETALS

The discovery of our aromatic and heteroaromatic annelations involving the reaction of allyl(1), benzyl(2), propargyl(3) magnesium halides, lithioacetonitrile(4), Reformatsky reagents(5), 2-picolyl-lithium(6), 5-lithiomethylisoxazoline(7), 2-lithiomethyl- thiazoles and 2-lithiomethylthiazoline(8), and the lithium enolates derived from and 3-pyrrolidinocrotonates(10) with alpha-oxoketene dithioacetals 1 (Scheme 1) have been shown to be of general applications to yield the corresponding aromatic and heteroaromatic compounds with diverse structural features in high yields. The overall process was aimed at creating an aromatic (or heteroaromatic) ring systems from the easily available acyclic aliphatic precursors. The method offers for the first time an one-pot reaction process for the construction of aromatic rings from the open-chain precursors involving the combination of two three-carbon fragments of which one possessed 1,3-dielectrophilic centres and the other 1,3-dinucleophilic centres.