Addition of Enolates and Silyl Enol Ethers of Cycloalkanones to Levoglucosenone in the Presence of Lewis Acids

Abstract

The addition of lithium enolates and TMS ethers of cyclohexanone and cyclododecanone to levoglucosenone in the presence of Lewis acids was studied. It was established that the optimal way to obtain of Michael adducts involves the reaction levoglucosenone at −78°C with lithium enolates of cyclohexanone and cyclododecanone in the presence of ZnCl₂. Additional amounts of Michael adducts can be obtained by treatment of 1,2-adducts with lithium diisopropylamine. 1,2-Adducts are best prepared by the reaction of the corresponding lithium enolates with levoglucosenone in the presence of Ti(Oi-Pr)₄.