Robert Pollice#RobSelects paper of the week #J_A_C_S: Ortho-carbon-hydrogen-alyklation of bromoarenes catalyzed by an imidazole-olefin-ligated palladium complex. #catalysis https://doi.org/10.1021/jacs.6c02010
#RobSelects paper of the week #J_A_C_S: Pincer-ligated cobalt-catalyzed four-component carbocarbonylation to form unsymmetric aliphatic ketones. #catalysis https://doi.org/10.1021/jacs.6c06343
#RobSelects paper of the week #J_A_C_S: Coupling between two tetrahedral carbon centers from an amine and a carboxylic acid catalyzed by an iron porphyrin forming quaternary carbons. #catalysis https://doi.org/10.1021/jacs.6c05065
#RobSelects paper of the week #J_A_C_S: Excited-state nucleophilic aromatic substitution of nitroarenes. #orgchem https://doi.org/10.1021/jacs.5c21841
#RobSelects paper of the week #J_A_C_S: Asymmetric Sm-catalyzed carbon-carbon coupling between alkenes and ketones forming tertiary alcohols. #catalysis https://doi.org/10.1021/jacs.5c20884
#RobSelects paper of the week #J_A_C_S: Excited-state triplet thiazole-2-thione biradicals as radical covalent catalysts for skeletal reorganization of N-sulfonyl vinylaziridines. #catalysis https://doi.org/10.1021/jacs.5c20284
#RobSelects paper of the week #J_A_C_S: Iridium-catalyzed reduction of beta-boryl amides triggers stereospecific cyclization to form aminocyclopropanes. #catalysis https://doi.org/10.1021/jacs.5c21144
Catalytic Stereospecific Construction of Aminocyclopropanes from β-Boryl Amides
Iridium-catalyzed reduction of β-boryl amides with tetramethyldisiloxane affords iminium ions in situ. These reactive iminium ions are directly trapped by stereospecific (invertive) reaction with the boronate, delivering aminocyclopropanes (ACPs) in excellent yield, diastereoselectivity, and enantiospecificity. The reaction applies to both secondary and tertiary benzylic boronates, allylic boronates, and α-substituted boronates, giving access to many multiply substituted ACPs.
#RobSelects paper of the week #J_A_C_S: Comprehensive investigation of regio- and stereoselectivity of iridium-catalyzed carbon-hydrogen borylation of small substituted aliphatic carbocycles. #catalysis https://doi.org/10.1021/jacs.5c18839
#RobSelects paper of the week #J_A_C_S: Enantioselective cycloaddition of cyclopropanes across alkynes via diamine phosphine oxide-ligated nickel-aluminum bimetallic catalysts. #catalysis https://doi.org/10.1021/jacs.5c18087
Enantioselective Ni–Al Bimetal-Catalyzed Cycloaddition of Cyclopropyl Ketones with Alkynes under Mild Conditions
Transition metal-catalyzed enantioselective intermolecular cycloaddition of cyclopropyl ketones and π-unsaturated compounds represents a long-standing challenge in the asymmetric C–C bond activation of cyclopropanes. Developed strategies rely on substrate modifications to mitigate racemization or to stabilize radical intermediates. In contrast, an efficient approach governed by transition-metal catalysts for general cyclopropyl ketones remains an elusive challenge. Herein, we report a highly active chiral diamine–phosphine oxide-ligated Ni–Al bimetallic catalyst that promotes enantioselective C–C cycloaddition under mild conditions. This system effectively suppresses product racemization and affords a diverse range of cyclopentyl ketones bearing a chiral α-tertiary carbon center in up to 99% yield and 99% ee.
#RobSelects paper of the week #J_A_C_S: Pd-Catalyzed Buchwald-Hartwig amination with a mild and solube potassium alkyl carboxylate salt and a phosphorinane ligand. #catalysis https://doi.org/10.1021/jacs.5c07790
Unleashing the Power of Potassium 2-Ethylhexanoate as a Mild and Soluble Base for Pd-Catalyzed C–N Cross-Coupling
The formation of C–N bonds by Pd-catalyzed cross-coupling is one of the most widely practiced reactions in chemical synthesis. Typical reaction conditions involve either a strong base, which limits the scope of substrates, or an insoluble, inorganic base, which complicates running reactions on a large scale. Reaction conditions for C–N couplings with a base that is both mild and soluble are needed. We report the discovery of a combination of a phosphorinane ligand (L147) and a soluble carboxylate base, potassium 2-ethylhexanoate (K-2-EH), which leads to the coupling of a wide range of base-sensitive coupling partners. To explore the enhanced substrate scope of the reaction with this base and catalyst, we evaluated the scope using representative reactants selected from published partners, using chemical descriptors and clustering to ensure their chemical diversity. These results show that the combination of this phosphorinane ligand and K-2-EH can couple primary aliphatic amines, amides, sulfonamides, and heteroaromatic nucleophiles as well as acidic secondary nitrogen nucleophiles, such as arylamines, heteroarylamines, and amides, with a range of electrophiles. A side-by-side comparison to form selected coupling products in the presence of a range of previously reported bases and ligands showed that the products that decomposed under standard reaction conditions were stable with K-2-EH as a base. Finally, models of quantitative structure–reactivity relationships, trained on ligand screening data, were developed to help reveal the structural features that engender reactivity.