Abstract
Solvent-free reactions of 2- and 3-halopyridines with PPh 3 , PBu 3 , and PCy 3 were studied under conventional heating, as well as under microwave irradiation. No difference was observed in the reaction course between classical and microwave reactions. 2-Bromopyridine gave quantitative yields of 2-pyridyltriphenylphosphonium bromide within few minutes at 190°C. Equimolar amounts of some inorganic salts (LiPF 6 , LiOTf, LiBr, NaPF 6 , KPF 6 ) were necessary for the reactions of the other 2-halopyridines. 3-Halopyridines did not react with PPh 3 even in the presence of LiPF 6 . Their reactions with PCy 3 in the presence of LiPF 6 resulted in the quantitative formation of dicyclohexylphosphine oxide.
Acknowledgments
This work was carried out under the auspices of COST D32 project No. 0010/04 and Slovak grant agency VTP grant No. 1012/2003. NMR measurements were performed on the equipment supported by the Slovak State Program Project No. 2003SP200280203.
Notes
a Only starting materials were detected in the reaction mixture.
a Only starting materials were recovered from the reaction mixture.