Synthesis of Chiral Thienylpyridines from Naturally Occurring Monoterpenes: Useful Ligands for Cyclometallated Complexes
作者:Michel Gianini、Alex von Zelewsky
DOI:10.1055/s-1996-4280
日期:1996.6
On treatment with ammonium acetate, α,β-unsaturated ketones or aldehydes can easily undergo condensation with acetylpyridinium salts (Kröhnke 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-methyleneopinone (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.
Oxidation of (-) (1R:6S)-Δ4(10)-carene-trans-3-ol (I) with chromic acid in benzene leads to (-) (1R:6S)-Δ3-caren-10-al (II), which is reduced to (+) (1R:6S):Δ4(10)-carene (V) by the method of Huang-Minlon