preparing (E)- and (Z)-stereodefined fully substituted enol tosylates is described. α-Substituted β-keto esters undergo (E)-selective enol tosylations using TsCl–Me2N(CH2)6NMe2 as the reagent (method A, 13 examples; 63–96%) and (Z)-selective enol tosylations using TsCl–TMEDA–LiCl as the reagent (method B, 13 examples; 62–99%). A plausible mechanism for the (E)- and (Z)-enol tosylation selectivity is proposed
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
Catalytic TMSCl promoted powerful aldol addition and Claisen condensation mediated by TiCl4/Bu3N agent: comparison and evaluation with the Mukaiyama aldol addition
catalyst (0.05 equiv) signifiantly promoted the TiCl4/Bu3N-mediated direct cross aldol additions of sterically crowded ketones and α-hetero substituted ketones, and also the direct Claisencondensation between methyl esters.
MSCl催化剂(0.05当量)显着促进了空间拥挤的酮和α-杂取代的酮的TiCl 4 / Bu 3 N介导的直接交叉羟醛加成,以及甲酯之间的直接Claisen缩合。
Indium Tribromide Catalyzed Cross-Claisen Condensation between Carboxylic Acids and Ketene Silyl Acetals Using Alkoxyhydrosilanes
作者:Yoshihiro Nishimoto、Aya Okita、Makoto Yasuda、Akio Baba
DOI:10.1002/anie.201104140
日期:2011.9.5
Acylations achieved: The title reaction between carboxylic acids and ketene silyl acetals has been accomplished (see scheme). The additive, (MeO)3SiH, is believed to play an important role in the promotion of the condensation reaction. This reaction system was compatible with a diverse range of functional groups, including alkenes, alkynes, chlorides, alcohols, esters, and nitro groups.