Ti-<i>Crossed</i>-Claisen Condensation between Carboxylic Esters and Acid Chlorides or Acids: A Highly Selective and General Method for the Preparation of Various β-Keto Esters
condensation between a 1:1 mixture of carboxylic esters and acidchlorides promoted by TiCl4-Bu3N-N-methylimidazole proceeded successfully to give various beta-keto esters in good yields with excellent selectivities (19 examples, approximately 48-95% yield; cross/self-selectivity = approximately 96/4-99/1). The present method was extended to the condensation between a 1:1 mixture of carboxylicacids and carboxylic