14 Horn M\EC, Dick MC, Frost B, et al. Neonatal screening for sickle cell diseases in Camberwcll: results and recommendations of a two year pilot study. BrMedJ 1986;292:737-40. 15 Rowley PT. Newborn screening for sickle cell disease. Benefits and burdens.
FTIR spectroscopy is a common in
situ reaction monitoring technique
used in modern academic and industrial environments. The FTIR signals
collected during the course of a reaction are proportional to the
concentration of the reaction components but not intrinsically quantitative.
To make FTIR data quantitative, precalibration or offline analyses
of reaction samples are required, which diminishes the unique benefits
of in situ reaction monitoring techniques. Herein, we report the use
of standard addition as a convenient method to obtain quantitative
FTIR data.
The enantioselective aminocatalytic α-chlorination of aldehydes is a challenging reaction because of its tendency to proceed through neutral intermediates in unselective pathways. Herein we report the rational shift to a highly selective reaction pathway involving charged intermediates using hexafluoroisopropanol as solvent. This change in mechanism has enabled us to match and improve upon the yields and enantioselectivities displayed by previous methods while using cheaper aminocatalysts and chlorinating agents, 80−95% less amount of catalyst, convenient temperatures, and shorter reaction times.
A series
of chiral-at-metal aluminum complexes have been synthesized
using chiral catam ligands. Reactivity studies demonstrate the importance
of alkoxide bulkiness and complex chirality in inducing catalyst aggregation.
This has been exploited in cyclic ester ring-opening polymerization
(ROP). For ε-Cl ROP, enantiopure catalysts were found to outperform
a racemic mixture of catalysts, as the racemic mixture resulted in
lower activity heterodimeric catalytic species and reduced polymerization
rates. In the case of L-LA, one catalyst enantiomer was found to be
the most active of the series and outperformed both the other enantiomer
and the corresponding achiral catalyst. Very high activities were
observed and up to 9,200 equivalents of L-LA were polymerized in 4.5
min at 150 °C with TOF > 100,000 h–1 under
industrially relevant conditions. Analysis of the catalyst orders
for these reactions provided a meaningful catalyst speciation-activity
relationship enabling improved understanding of both catalyst speciation
and the activity of each catalytic species involved in cyclic ester
ROP using chiral aluminum catalysts.
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