A cascade deboronation/regioselective BÀ P coupling of closocarboranes is disclosed using a combination of palladium catalysts and nitrogen or phosphine-containing directing groups. Unsymmetric C-substituted closo-carboranes, including C-monosubstituted and unsymmetric 1,2-disubstituted closocarboranes, are tolerated. Select closo-carboranes bearing other directing groups, such as benzoxazole, and diphenylphosphine, are compatible substrates for this reaction. Phosphine and arsenic can be utilized as effective coupling partners. Furthermore, a catalytic amount of palladium salt mediates the regioselective BÀ H activation process. Readily available closocarboranes as the starting materials for direct one-pot synthesis of functionalized nido-carboranes and the in-situ formation of nido-carborane intermediates without purification are important features in terms of practical applications.
A palladium-catalyzed selective B(3)–H arylation of o-carboranes under room temperature has been developed using readily available arylboronic acids as the aryl source, and the corresponding 3-aryl-o-carboranes were obtained in good to excellent yields.
We
disclose herein an efficient regioselective B(3,4)–H
activation via a ligand strategy, affording B(3)-monoacyloxylated
and B(3,4)-diacyloxylated o-carboranes. The identification
of amino acid and phosphoric acid ligands is crucial for the success
of B(3)-mono- and B(3,4)-diacyloxylation, respectively. This ligand
approach is compatible with a broad range of carboxylic acids. The
functionalization of complex drug molecules is demonstrated. Other
acyloxyl sources, including sodium benzoate, benzoic anhydride, and
iodobenzene diacetate, are also tolerated.
Gluconic acid is a valuable commodity in various industries such as pharmaceuticals, food, and construction. As the demand for gluconic acid grows, the development of its efficient and cost‐effective production methods has become a prominent research priority. Enzymatic synthesis has emerged as a promising approach for the production of gluconic acid due to its numerous advantages such as being eco‐friendly, highly efficient, and cost‐effective. Furthermore, the one‐pot catalytic method simplifies production equipment and operational steps. This concept review discusses the latest development in the field of multi‐enzymatic hybrid catalysts and chemo‐enzymatic hybrid catalysts for the one‐pot cascade catalytic production of gluconic acid. Perspectives for further research in this field are also provided to promote the application of multi‐enzyme complex cascade catalytic systems in extensive areas of organic synthesis.
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