Trimethylsilylcyanid als Umpolungsreagenz, XIX [1] Dreikomponentenreaktionen zur Synthese von ungesättigten γ ‐Ketoestern

Trimethylsilyl Cyanide – A Reagent for Umpolung, XIX [1] . – Unsaturated γ‐Keto Esters by Three‐Component Reactions Addition products 1a–c of α,β‐unsaturated aldehydes and trimethylsilyl cyanide are deprotonated and added to methyl acrylate ( 2 ). On alkylation with the allylic bromo dienes 3a, b the intermediate ester enolates yield the final adducts 4aa–4cb (83–95%). Deprotection transforms these adducts into 5aa‐5cb (72–98%), which contain the functionalities of an α,β‐unsaturated ketone, a carboxylic ester group, and a diene in the appropriate arrangement for intramolecular Diels‐Alder reactions. Yields between 64 and 79% of 5 are achieved if the reaction sequence 1 + 2 + 3 → 4 → 5 is performed without isolation of 4 .