Tautomerism in ketomethyl quinolines. Part 3. 4-Ketomethylquinolines

Abstract

A series of 4-ketomethylquinolines has been prepared and their tautomerism investigated. The compounds were prepared from 4-methylquinoline deprotonated with lithium diisopropylamide or potassium ethoxide and treated with esters. Attempted deprotonation with tert-butyllithium or phenyllithium led to 2-substituted-4-methylquinolines. The simple alkyl or aryl 4-keto methylquinolines exist essentially as the keto forms, but the quinoline-4-pyruvates are exclusively or substantially in the enol forms. Key words: ketomethyl quinolines, pyruvates, tautomerism, enols.