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Achiral Counterion Control of Enantioselectivity in a Brønsted Acid-Catalyzed Iodolactonization

Author:
Dobish, Mark C., Johnston, Jeffrey N.
Source:
Journal of the American Chemical Society 2012 v.134 no.14 pp. 6068-6071
ISSN:
1520-5126
Subject:
carboxylic acids, catalysts, enantiomers
Abstract:
Highly enantioselective halolactonizations have been developed that employ a chiral proton catalyst–N-iodosuccinimide (NIS) reagent system in which the Brønsted acid is used at catalyst loadings as low as 1 mol %. An approach that modulates the achiral counterion (equimolar to the neutral chiral ligand–proton complex present at low catalyst loadings) to optimize the enantioselection is documented for the first time in this transformation. In this way, unsaturated carboxylic acids are converted to γ-lactones in high yields (up to 98% ee) using commercially available NIS.
Agid:
5385080