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-lithiome thylthiazoline(8), and the lithium enolates derived from and 3-pyrroli dinocrotonates(10) with alpha-oxoketene dithioacetals 1 (Scheme 1) hav e 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 al iphatic precursors. The method offers for the first time an one-pot re action process for the construction of aromatic rings from the open-ch ain precursors involving the combination of two three-carbon fragments of which one possessed 1,3-dielectrophilic centres and the other 1,3- dinucleophilic centres.