Brønsted Acid Promoted Reduction of Tertiary Phosphine Oxides

Abstract

Recently, Brønsted acids, such as phosphoric acids, carboxylic acids, and triflic acid, were found to catalyze the reduction of phosphine oxides to the corresponding phosphines. In this study, we fully characterize the HCl, HOTf, and Me 2 SiHOTf adducts of triphenylphosphine oxide and find that the thermally stable adduct * Prof. Dr. J. C. Slootweg E-Mail: j.c.slootweg@uva.nl [a] Van' 916Ph 3 POH + OTfis efficiently converted into triphenylphosphine at 100°C in the presence of readily available hydrosiloxanes. Under the same reaction conditions, also Ph 3 POSiMe 2 H + OTfselectively affords triphenylphosphine indicating that silylated phosphine oxides are likely intermediates in this process.

Direct and Scalable Electroreduction of Triphenylphosphine Oxide to Triphenylphosphine

“…13 With no industrial applications, TPPO is generally discarded in preference to incineration because incineration causes acidic flashes that necessitate frequent flue-gas scrubbing. 13,14 Thus, TPPO is commonly found in industrial effluents. 13,15,16 The poor biodegradability of TPPO renders it one of the most common organophosphorus compounds in freshwater sources.…”

“…Triphenylphosphine (TPP) is an essential reagent that is stoichiometrically consumed in many of the most reliable organic transformations, including the Appel, , Mitsunobu, − Staudinger, , and Wittig reactions. − As an example, the industrial synthesis of vitamin A relies on a key Wittig olefination that generates multiton quantities of triphenylphosphine oxide (TPPO) as a byproduct . With no industrial applications, TPPO is generally discarded in preference to incineration because incineration causes acidic flashes that necessitate frequent flue-gas scrubbing. , Thus, TPPO is commonly found in industrial effluents. ,, The poor biodegradability of TPPO renders it one of the most common organophosphorus compounds in freshwater sources. , Studies have linked increased concentrations of phosphorus-containing compounds in water to environmental issues, such as algal blooms, that require costly remediation processes. − Another issue associated with an industrial reliance on TPP-based chemistry is the limited global reserve of phosphorus. As the global consumption of phosphorus is increasing, the world’s top phosphorus producers, the United States and China, may face depletion of their reserves by 2050. , Consequently, the development of an inexpensive and sustainable method for the recycling of TPPO to TPP is of great interest to the scientific and industrial communities but remains an unsolved challenge.…”

Dibismuthates as Linking Units for Bis-Zwitterions and Coordination Polymers

“…The 31 P NMR spectrum of the reaction mixture shows a broad singlet resonance at −33.1 ppm (without observable phosphorus− silver coupling) shifted downfield in comparison to the free ligand PS 3 (δ( 31 P) −38.0 ppm in acetonitrile), indicating again a change in the chemical environment of the phosphorus center. Even though the coordination chemical shift change of Δδ( 31 P) = δ(complex) − δ(ligand) = +3.8 ppm is smaller than that for triphenylphosphine complexes [(PPh 3 ) n Ag(OTf)] (Δδ( 31 P) = 13.6−22.1 ppm for n = 1−4 59,60 ), together with the broadening of the resonance this is consistent with an interaction of the phosphorus and the silver centers. Similar behavior is widely known for silver complexes with neutral ligands and is attributed to the fluxionality of the species in solution.…”

Palladium-Catalyzed Aminocyclization–Coupling Cascades: Preparation of Dehydrotryptophan Derivatives and Computational Study

“…In this scenario, reactions of n -butyl acrylate or methyl methacrylate, with low insertion activation energies, would be expected to compete more efficiently with that cycloisomerization pathway than those of α-acetamidoacrylates, where insertion has a much higher barrier . As for the effect of PPh 3 , it is noticed that protodepalladation would be dependent on the availability of HCl (released upon formation of D and also after BHE), which is in turn limited by its consumption during the final Pd(0) oxidation (Scheme ), and possibly by interaction with TPPO produced as a result of PPh 3 air oxidation. , In fact, the formation of the hydrochloride HClTPPO from TPPO and HCl is a very favorable process, calculated to release 13.7 kcal/mol. As a result, TPPO could have a regulatory effect on the available amount of HCl.…”