Other catalytic approaches
BINOL and its derivatives are widely used classes of ligands in asymmetric synthesis, such as in Diels–Alder reactions, carbonyl
addition, and reductions (7). Researchers at the University of Texas, Austin, recently developed a bifunctional catalyst derived
from BINOL for producing highly enantioselective bromolactonizations of unsaturated carboxylic acids (8, 9). Specifically,
the catalyst promoted highly enantioselective bromolactonizations of 4- and 5-aryl-4-pentenoic acids, but it also catalyzed
the highly enantioselective bromolactonizations of 5-alkyl-4(Z)-pentenoic acids. The researchers assert that these reactions
represent the first catalytic bromolactonizations of alkyl-substituted olefinic acids that proceeded by means of 5-exo mode
cyclizations to give lactones in which new carbon–bromine bonds are formed at a stereogenic center with high enantioselectivity.
The researchers also reported on what they say is the first catalytic desymmetrization of a prochiral dienoic acid by enantioselective
bromolactonization (8, 9).
Patricia Van Arnum is executive editor of Pharmaceutical Technology, 485 Route One South, Bldg F, First Floor, Iselin, NJ 08830 tel. 732.346.3072, firstname.lastname@example.org
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