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The cleavage of alkyl ethers by hydrosilylation is a powerful synthetic tool for the generation of silyl ethers. Previous attempts to apply this transformation to carbohydrate derivatives have been constrained by poor selectivity and preferential reduction of the anomeric position. O -Aryl glycosides are found to be stable under iridium- and borane-catalyzed hydrosilylation conditions, allowing for alkyl ether cleavage without loss of anomeric functionality. A cationic bis(phosphine)iridium complex catalyzes the selective 3-demethylation of a variety of 2,3,4-tri- O -methyl pyranoses, offering a unique approach to 3-hydroxy or 3-acetyl 2,4-di- O -methylpyranoses. 

Abstract The field of catalytic C–H borylation has grown considerably since its founding, providing a means for the preparation of synthetically versatile organoborane products. Although sp2 C–H borylation methods have found widespread and practical use in organic synthesis, the analogous sp3 C–H borylation reaction remains challenging and has seen limited application. Existing catalysts are often hindered by incomplete consumption of the diboron reagent, poor functional-group tolerance, harsh reaction conditions, and the need for excess or neat substrate. These challenges acutely affect the C–H borylation chemistry of unactivated hydrocarbon substrates, which has lagged in comparison to methods for the C–H borylation of activated compounds. Herein, we discuss recent advances in the sp3 C–H borylation of undirected substrates in the context of two particular challenges: (1) utilization of the diboron reagent and (2) the need for excess or neat substrate. Our recent work on the application of dipyridylarylmethane ligands in sp3 C–H borylation has allowed us to make contributions in this space and has presented an additional ligand scaffold to supplement traditional phenanthroline ligands. 

Nucleophilic aromatic substitution (SNAr) of fluorobenzene by morpholine at a bis(diphenylphosphino)pentane-supported ruthenim complex is investigated as a model system for π-arene catalysis through the synthesis and full characterization of proposed intermediates. The SNAr step proceeds quickly at room temperature, however the product N-phenylmorpholine binds tightly to the ruthenium ion. In the case examined, the thermodynamics of arene binding favor product N-phenylmorpholine over fluorobenzene binding by a factor of 2,000, corresponding to significant product inhibition. Observations of the catalyst resting state support this hypothesis and demonstrate an additive-controlled role for a previously-proposed ligand cyclometalation.