101565-42-8Relevant articles and documents
Phthaloylcobalt complexes in synthesis. Ligand modifications leading to a practical naphthoquinone synthesis
Liebeskind, Lanny S.,Baysdon, Sherrol L.,Goedken, Virgil,Chidambaram, Ramakrishnan
, p. 1086 - 1092 (1986)
Modification of the ligands of trigonal-bipyramidal (phthaloyl)Co(PPh3)2Cl has led to an understanding of how this complex reacts with alkynes to give naphthoquinones when activated with AgBF4. Through X-ray crystal structure determinations and temperature-dependent 1H NMR spectra, it has been determined that reaction with alkynes requires conversion of (phthaloyl)Co(PPh3)2Cl into a six-coordinate complex with a dissociable ligand above or below the plane defined by the phthaloylcobalt ring. Treatment of (phthaloyl)Co(PPh3)2Cl with dimethylglyoxime in pyridine effects such a transformation in high yield, and the resulting air-stable complex (phthaloyl)Co(dimethylglyoxime)(pyridine)Cl reacts with alkynes at 80°C to produce excellent yields of naphthoquinones. A simple synthesis of menaquinones has been realized by using this method. In addition, SnCl4 has been shown to catalyze the quinone forming reaction at room temperature.
