Toward the Selection of Sustainable Catalysts for Suzuki–Miyaura Coupling: A Gate-to-Gate Analysis

Reports
of homogeneous and heterogeneous methods for Pd-catalyzed
Suzuki–Miyaura coupling provide a vast data set to establish
sustainability targets and parameters for future catalyst development.
In this gate-to-gate inventory we estimate energy and palladium usage
along with reaction mass efficiency (RME) for a range of palladium
catalysts (both single- and multiuse) for the generation of (a) 4-phenylphenol
from 4-iodophenol and phenylboronic acid or (b) 4-methoxybiphenyl
from 4-chloroanisole and phenylboronic acid. Small differences were
found in calculated energy usage, RME values, and non-palladium reagent
toxicities. Palladium usage, however, varied substantially and stood
out as the main differentiating consideration from a sustainability
standpoint. Reusable heterogeneous catalysts still use more palladium
when compared to ultra-low-loading homogeneous techniques that are
effective for conversion of aryl iodides. For aryl chloride substrates,
highly active and reusable heterogeneous catalysts become a viable,
sustainable alternative to traditional homogeneous systems.