AROMATIC SUBSTITUTION: PART VII. COMPETITIVE REACTIONS OF PYRIDINE, 3-PICOLINE, AND 3-ETHYLPYRIDINE WITH PHENYLLITHIUM. ACTIVATION OF A NUCLEOPHILIC AROMATIC SUBSTITUTION BY ALKYL GROUPS

Abstract

The relative reactivities of pyridine, 3-picoline, and 3-ethylpyridine towards phenyllithium have been measured under various conditions by a competitive technique and have been found to be in the order: 3-picoline > pyridine > 3-ethylpyridine. A 3-methyl or ethyl substituent activates the 2-position relative to that in pyridine itself, while C 6 is deactivated as expected. A possible explanation is put forward for these observations and for the somewhat low yields that are obtained in such reactions. A method is described whereby arylation of pyridines with aryllithium compounds may be effected in high yields.