The reaction between acetoxy oxiranes and lithium dialkylcuprates proceeds at low temperatures (−78 °C) to produce the desired α-alkyl ketones in yields which vary greatly with the cuprate and acetoxy oxirane used (2.3−43%). Lithium dimethylcuprate generally gives the best yields, with lithium di-n-butyl- and diphenylcuprate giving more complex product mixtures which contain less of the desired substituted ketone. Formation of the nonalkylated ketone is consistently observed and several potential mechanisms for the reaction are considered in light of its formation. The use of cuprates having a nontransferable ligand and also the use of the epoxides of enol pivalates, benzoates, and mesitoates, as substrates, were explored as a means of controlling formation of the unsubstituted ketone.
ASJC Scopus subject areas
- Organic Chemistry