Pseudoaromatic compounds. Part XXII. Reactions of 2-functionalized tropones with sodium toluene-p-thiolate

Abstract

Relative rates for replacement, without rearrangement, of the X group of some 2-X-tropones by sodium toulene-p-thiolate in dimethyl sulphoxide are in the order 82,2.6,3.5,1.0,and ca. 29 000 for X = F,Cl,Br,I, and N[CH₂CH₂]₃-CHI^–, respectively, whilst with X = OCH₃ slow demethylation occurs instead. The rate of replacement of the quinuclidinium group has been computed for the free reagents present in equilibrium with an adduct which lies off the reaction co-ordinate. These data give support to the idea that ready replacement of strongly bound X groups, such as fluorine or methoxy, of 2-X-tropones by primary or secondary amines is due to stabilisation of the transition state by proton bridging among the protonated nitrogen, the tropone carbonyl oxygen, and for fluorine, the leaving-group.