Aromatic substitution. Part XVI. Reactivity of 3-isopropyl- and 3-cyclohexyl-pyridine and of nicotine towards phenyl-lithium

Abstract

Rates of phenylation relative to pyridine of 3-isopropyl- and 3-cyclohexyl-pyridine and of nicotine with phenyllithium have been measured by means of competitive experiments. All three compounds react more slowly than does pyridine (total rate ratios were found to be 0·31, 0·30, and 0·32, respectively). The partial rate factors (^3-IsoprF₂= 0·46, ^3-IsoprF₆= 0·15; ^3-CyclohexylF₂= 0·37, ^3-CyclohexylF₆= 0·23; ^NicF₂= 0·19, ^NicF₆= 0·45) indicate that, unlike the situation in 3-methyl- and 3-ethyl-pyridine, and as expected, C(2) is not activated compared with the same position in pyridine. The results with nicotine indicate that the competitive technique may not be applicable for that compound. The results are discussed.