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We report studies delineating the speciation, kinetics, and deoxygenation catalysis of phosphine-modified mixtures of B(C 6 F 5 ) 3 (BCF) and R 3 SiH. Combinations of BCF, a tertiary silane, and PAr 3 generate the [H−B(C 6 F 5 ) 3 − ][R 3 Si−PAr 3 + ] ion pair with conversions that depend on the silane and the phosphine. Smaller silanes enhance the ionization of the Si−H, as judged by heteronuclear NMR spectroscopy. Kinetic studies indicate that from BCF•PPh 2 (p-tol), formation of the borohydride/silyl phosphonium ion pair is α [Et 3 SiH] 1 [PPh 2 (p-tol)] 0 . DFT calculations confirmed the intermediacy of the weakly coordinated BCF•••H−SiEt 3 adduct en route to the silyl phosphonium. For the catalytic deoxygenation of anisole with Et 3 SiH, phosphine additives slow the reaction relative to phosphine-free conditions. In situ monitoring confirmed the presence of [H− B(C 6 F 5 ) 3 − ][Et 3 Si−PAr 3 + ] at early times, but this slowly converts to [H−B(C 6 F 5 ) 3 − ][H 3 C−PAr 3 + ], which is catalytically inactive. These data are reconciled by invoking a competitive demethylation of a key PhOMe(SiEt 3 ) + oxonium ion intermediate by H− B(C 6 F 5 ) 3 − (productive) or phosphine (nonproductive).

Tandem oxidation processes enabling one-pot multistep reactions received great attention as an efficient synthetic methodology for construction of complex molecules from simple substrates by a single operation. We report here tandem oxidative transformations of seven different functional groups (imine, imidazole, cyanide, amide, lactone, ester and olefin) from a single substrate (alcohol) by a single cesium promoted mesoporous manganese oxide catalyst (meso Cs/MnOx). High conversions were obtained with a broad range of substrates including aliphatic long chain alcohols. The catalyst can be reused without any loss of catalytic activity. We also demonstrated a unique multiple esterification reaction from a single aliphatic alcohol under aerobic atmospheric conditions catalyzed by meso Cs/MnOx.

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