The
generalization of related asymmetric processes in organocatalyzed
reactions is an ongoing challenge due to subtle, noncovalent interactions
that
drive selectivity. The lack of transferability is often met with a
largely empirical approach to optimizing catalyst structure and reaction
conditions. This has led to the development of diverse structural
catalyst motifs and inspired unique design principles in this field.
Bifunctional hydrogen bond donor (HBD) catalysis exemplifies this
in which a broad collection of enantioselective transformations has
been successfully developed. Herein, we describe the use of data science
methods to connect catalyst and substrate structural features of an
array of reported enantioselective bifunctional HBD catalysis through
an iterative statistical modeling process. The computational parameters
used to build the correlations are mechanism-specific based on the
proposed transition states, which allows for analysis into the noncovalent
interactions responsible for asymmetric induction. The resulting statistical
models also allow for extrapolation to out-of-sample examples to provide
a prediction platform that can be used for future applications of
bifunctional hydrogen bond donor catalysis. Finally, this multireaction
workflow presents an opportunity to build statistical models unifying
various modes of activation relevant to asymmetric organocatalysis.
Multivariate
linear regression (MLR) analysis is used to unify
and correlate different categories of asymmetric Cu-bisoxazoline (BOX)
catalysis. The versatility of Cu-BOX complexes has been leveraged
for several types of enantioselective transformations including cyclopropanation,
Diels–Alder cycloadditions, and difunctionalization of alkenes.
Statistical tools and extensive molecular featurization have guided
the development of an inclusive linear regression model, providing
a predictive platform and readily interpretable descriptors. Mechanism-specific
categorization of curated data sets and parameterization of reaction
components allow for simultaneous analysis of disparate organometallic
intermediates such as carbenes and Lewis acid adducts, all unified
by a common ligand scaffold and metal ion. Additionally, this workflow
permitted the development of a complementary linear regression model
correlating analogous BOX-catalyzed reactions employing Ni, Fe, Mg,
and Pd complexes. Comparison of ligand parameters in each model reveals
the relevant structural requirements necessary for high selectivity.
Overall, this strategy highlights the utility of MLR analysis in exploring
mechanistically driven correlations across a diverse chemical space
in organometallic chemistry and presents an applicable workflow for
related ligand classes.
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