Synthesis of chiral thienylpyridines from naturally occurring monoterpenes: Useful ligands for cyclometallated complexes

Article abstract of DOI:10.1055/s-1996-4280

On treatment with ammonium acetate, α,β-unsaturated ketones or aldehydes can easily undergo condensation with acetylpyridinium salts (Krohnke reaction). Four 'thienylpyridine' ligands, derived from (-)-β-pinene, (+)-camphor, (+)-3-carene and (+)-2-carene, were prepared according to this method. The multistep syntheses to get (1R,5R)-3-methylenenopinone (5), (+)-3-methylenecamphor (10), (-)-3-caren-10-al (15) and (1S,6R)-7,7-dimethyl-3-methylenebicyclo[4.1.0]heptan-2-one (18) are also described.