Chiral Brønsted acids have become an invaluable tool for achieving a variety of asymmetric chemical transformations under catalytic conditions while avoiding the use of toxic and expensive metals1–8. While the catalysts developed so far are remarkably effective at activating polarized functional groups, chemists have not yet been able to use organic Brønsted acids to catalyze highly enantioselective transformations of unactivated carbon-carbon multiple bonds. This deficiency persists despite the fact that racemic acid-catalyzed “Markovnikov” additions to olefins are a well-established part of the chemist’s toolbox. Here we show that chiral dithiophosphoric acids catalyze the intramolecular hydroamination and hydroarylation of dienes and allenes to generate heterocyclic products in exceptional yield and enantiomeric excess. To help rationalize the unique success of this catalytic system, we present a mechanistic hypothesis that involves the addition of the acid catalyst to the diene followed by SN2′ displacement of the resulting dithiophosphate intermediate. Mass spectrometry and deuterium labelling studies are presented in support of the proposed mechanism. The catalysts and concepts revealed in this study should prove applicable to other asymmetric functionalizations of unsaturated systems.

A chiral anion phase-transfer system for enantioselective halogenation is described. Highly insoluble, ionic reagents were developed as electrophilic bromine and iodine sources, and application of this system to o-anilidostyrenes afforded halogenated 4H-3,1-benzoxazines with excellent yield and enantioselectivity.

The effect localized surface plasmon resonance (LSPR) of Au nanoparticles was studied on the photocatalytic activity of TiO2 film. We used the thermal hydrolysis method to prepare 300 nm TiO2 film and the sodium citrate reduced method to synthesize gold nanoparticles. The photocatalytic activities of Au/TiO2, Au@SiO2/TiO2, and TiO2 films were evaluated by the degree of MB photodegradation under similar conditions with simultaneous UV (365 nm) and visible-light (400 nm < λ < 700 nm) irradiation for 5 h. The degree of MB photodegradation was in the following order: Au@SiO2/TiO2 > Au/TiO2 > TiO2. Although the SiO2 shell prevented the electron trap effect, the MB photodegradation efficiency of Au@SiO2/TiO2 was superior to that of Au/TiO2 because its LSPR was much higher. To validate the experimental results, the electric field intensity around the gold nanoparticles was simulated by the finite element method (FEM). In the presence of gold nanoparticles, the LSPR effect increased the surrounding intensity of electric field that enhanced the photocatalytic activities. Furthermore, from the simulation results, Au@SiO2/TiO2 showed EM field improvement of nearly 9 times compared with Au/TiO2. The SiO2 coating significantly increased the LSPR effect of gold nanoparticles. We named this new core–shell structure “shell-isolated plasmonic photocatalyst”.

We report a catalytic enantioselective electrophilic fluorination of alkenes to form tertiary and quaternary C(sp3)-F bonds and generate β-amino-and β-aryl-allylic fluorides. The reaction takes advantage of the ability of chiral phosphate anions to serve as solid-liquid phase transfer catalysts and hydrogen bond with directing groups on the substrate. A variety of heterocyclic, carbocyclic, and acyclic alkenes react with good to excellent yields and high enantioselectivities. Further, we demonstrate a one-pot, tandem dihalogenation-cyclization reaction, using the same catalytic system twice in series, with an analogous electrophilic brominating reagent in the second step.asymmetric | organocatalysis | hydrogen-bonding

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