A Diastereoselective, Nucleophile-Promoted Aldol-Lactonization of Ketoacids Leading to Bicyclic-β-Lactones
摘要:
An improved, tandem acid activation/aldol-lactonization process is described. This more practical protocol shortens reaction times for the construction of bicyclic beta-lactones from ketoacids and implements the use of commercially available reagents p-toluenesulfonyl chloride (p-TsC1) as activator and 4-dimethylaminopyridine (4-DMAP) as nucleophllic promoter (Lewis base). Substrates with beta-substituents, with respect to the carboxylic acid, consistently showed excellent levels of diastereoselectivity during the bis-cyclization event.
Enantioselective Synthesis of Functionalized β-Lactones by NHC-Catalyzed Aldol Lactonization of Ketoacids
作者:Santigopal Mondal、Subrata Mukherjee、Tamal Kanti Das、Rajesh G. Gonnade、Akkattu T. Biju
DOI:10.1021/acs.joc.7b01526
日期:2017.9.1
leading to the enantioselectivesynthesis of cyclopentane-fused β-lactones is presented. The reaction proceeds via the generation of NHC-bound enolate intermediates formed from the ketoacids in the presence of the peptide coupling reagent HATU and NHC generated from the chiral triazolium salt. The functionalized β-lactones are formed under mild conditions in high yields and enantioselectivities.