Application of N‐Acylimidazoles in the Claisen Condensation Reaction. Issue 24 (26th June 2020) - Quan, Haiyuan
Abstract: The Claisen condensation reaction is a classical method used for the formation of C−C bonds. Homo‐ and cross‐Claisen condensation reactions are usually carried out using a Ti(IV)‐based reagent at ultra‐low‐temperatures. In this report, intermediate β‐keto acyl imidazoles were synthesised using a sodium imidazolide‐catalysed homo‐ and cross‐condensation reaction of N ‐acyl imidazoles performed under mild conditions and subsequently used to prepare a range of β‐keto esters and ketones via alcoholysis or hydrolysis. This method is particularly suitable for the synthesis of isotopically‐labelled acetylacetic ester compounds. N ‐acyl imidazole compounds are useful reactants for the Claisen condensation reaction. Abstract : This article describes that β‐keto acyl imidazoles were synthesised using a sodium imidazolide‐catalysed Claisen condensation reaction of N ‐acyl imidazoles and subsequently used to prepare β‐keto ester and ketone products via alcoholysis or hydrolysis. In this work, the effects of temperature, nucleophiles and substituents for the alcoholysis or hydrolysis of β‐keto acyl imidazoles were studied. On the basis of results from products, propose a tentative mechanism for the synthesis and alcoholysis/hydrolysis of β‐keto acyl imidazoles to form their corresponding β‐keto ester and ketone products.