Organocatalytic SOMO reactions can provide access to various α-functionalized carbonyl compounds. Chiral imidazolidinones catalysed the organo-SOMO reactions of aldehydes and ketones with cyclic and acyclic enol silanes. The resulting chiral dicarbonyl compounds were obtained in yields of up to 80% and enantiomeric purities of up to 90% ee. Under the SOMO conditions, silyl ketene acetals did not afford the desired products. However, silyl ketene thioacetal could be employed, and the corresponding product was isolated with useful enantiomeric purity of 82% ee.