Asymmetric Bromolactonization Using Amino-thiocarbamate Catalyst
摘要:
A novel amino-thiocarbamate-catalyzed bromolactonization of unsaturated carboxylic acids has been developed. The scope of the reaction is evidenced by 22 examples of gamma-lactones with up to 99% yield and 93% ee. The protocol was applied in the enantioselective synthesis of the key intermediates of VLA-4 antagonists.
Dissecting the Stereocontrol Elements of a Catalytic Asymmetric Chlorolactonization: <i>Syn</i> Addition Obviates Bridging Chloronium
作者:Roozbeh Yousefi、Kumar Dilip Ashtekar、Daniel C. Whitehead、James E. Jackson、Babak Borhan
DOI:10.1021/ja4072145
日期:2013.10.2
absolute and relative stereochemistry of addition in enantioselective chlorolactonizations of 4-phenyl-4-pentenoic acid and its related t-butyl ester, catalyzed by (DHQD)2PHAL. Predominant syn addition of the chlorenium and the nucleophile across the olefin is observed. As shown by isotopic labeling, NMR spectroscopy, and derivative studies, the two new stereocenters formed by addition across the double