Trimethylsilylcyanid als Umpolungsreagens, XXIII. Umpolungsprodukte aus α,β1‐ungesättigten Aldehyden mit α,β1‐ungesättigten Carbonyl‐Verbindungen: Folgereaktionen

Abstract

Trimethylsilyl Cyanide – A Reagent for Umpolung, XXIII[1]. – Products from Umpolung of α,β1‐Unsaturated Aldehydes and α,β1‐Unsaturated Carbonyl Compounds: Consecutive ReactionsThe unsaturated nitrile 1 is transformed by TiCl4 into chloronitrile 2, whereas reaction with [BzNMe3]+F− and treatment with acids yields cyanocyclopentenone 4. Removal of the umpolung groups from 1 and 5–8 by [BzNMe3]F− results in the unsaturated 1,4‐diketones 9–13 only if the cyanide ions formed are prevented by ZnO from adding to the double bond. Condensation of ketones 9 and 11–13 with tBuOK yields cyclopentenones 14–18 with conjugated vinylic groups. In the presence of [BzNMe3H]+F− α1‐cyano enol silyl ethers 22–24 are smoothly converted in methanol into ϵ1‐oxo‐carboxylic esters 19–21, whereas in pure methanol α1‐hydroxycyclopentanecarboxylic esters 25–27 are produced in high yied.