Synthesis of Imidazo[1,2- a ] Pyridine Gem -Amido Vinyl Sulfides, Vinyl Sulfoxides And Vinyl Sulfones. Influence of the Degree of Oxidation of the Sulfur on the Stereoselectivity of the Reaction

( E )-Stereoisomers of imidazo[1,2- a ]pyridine gem -amido vinyl sulfoxides and vinyl sulfones are efficiently prepared by condensation of N , N -diethylphenylsulfinyl or z N , N -diethylphenyl- sulfonylacetamide with imidazo[1,2- a ]pyridine-2-carbaldehyde in the presence of NEt 3 .