Sulphoxide substituted pyridines as phase-transfer catalysts for nucleophilic displacements and alkylations

Abstract

2-Methylsulphinyl-, 2-methylsulphinylmethyl-, 2,6-bis(methylsulphinyl)-, 2,6-bis(methylsulphinylmethyl)-pyridines, bis(2-pyridylmethyl) sulphoxide, and 2-methylsulphinylpyridine N-oxide have been prepared. These sulphoxides served as good phase-transfer catalysts which accelerate SN2 type displacements of octyl bromide with various nucleophiles (thiolate, cyanide, thiocyanate, and phenoxide) in solid–liquid two-phase systems. Alkylations of phenylacetonitrile and benzyl methyl ketone with alkyl halides were also carried out in liquid–liquid two-phase systems in the presence of the above sulphoxides to afford the corresponding monoalkylated products in high yields. Pyridine derivatives bearing polysulphinyl groups were found to be even more effective catalysts for these two-phase alkylations. Neither 2-methylthio- nor 2-methylsulphonyl-pyridine catalysed SN2 type displacement reactions effectively.