Highly Regioselective Alkylation at the More Hindered <i>γ</i>-Site of Unsymmetrical Ketones by Use of Their Potassium Enolates. A Comparative Study with Lithium Enolates
Alkylation of regioisomeric potassium enolates 4 and 6 obtained from corresponding silyl enol ethers 2 and 3 occurs at the most substituted site affording ketones 8. Alkylation of corresponding lithium enolates 5 and 7 occurs at the expected site affording ketones 8 or 9. As an application the one pot synthesis of spiroketones 13 from silyl enol ethers 12 is described.