Yile Wu

Mechanistic Insight into the Copper-Catalyzed Phosphorylation of Terminal Alkynes: A Combined Theoretical and Experimental Study

The reaction mechanism of copper-catalyzed phosphorylation of terminal alkynes under different conditions has been investigated experimentally and theoretically. The important role of dioxygen has been elucidated, including the formation of η(1)-superoxocopper(II), η(2)-superoxocopper(III), μ-η(2):η(2)-peroxodicopper(II), and bis(μ-oxo)dicopper(III) complexes. More importantly, the proton transfer from the dialkyl phosphonate (in the form of phosphite) to the bridging oxygen atom entails the migration of the deprotonated phosphonate to the terminal alkyne, leading to the formation of a C-P bond with an activation barrier of only 1.8 kcal/mol. In addition, a particularly stable six-centered dicopper(I) species is formed with the migration of both of the Ph2P(O) groups from the copper atoms to the oxygen atoms of the bis(μ-oxo) bridge, explaining the experimental observation that secondary phosphine oxides can be oxidized to the phosphinic acids. Thus, the diphenylphosphine oxide was added to the reaction mixture dropwise to minimize the concentration during the reaction course. Gratifyingly, the coupling product was generated almost quantitatively when the reaction was completed.

Nickel-Catalyzed Decarboxylative C-P Cross-Coupling of Alkenyl Acids with P(O)H Compounds.

The first nickel-catalyzed decarboxylative C-P coupling of a wide range of alkenyl acids with various P(O)H compounds, especially for H-phosphonates, has been developed, affording a versatile and efficient tool for the preparation of valuable (E)-1-alkenylphosphonates, (E)-1-alkenylphosphinate oxides, and (E)-1-alkenylphosphine oxides with high stereoselectivity and broad substrate applicability. DFT calculation revealed that the phosphine ligand exhibits better catalytic performance than the nitrogen ligand in the reductive elimination step owing to the stronger nucleophilicity and larger size.

Mechanism, Reactivity, and Selectivity in Rh(III)-Catalyzed Phosphoryl-Directed Oxidative C-H Activation/Cyclization: A DFT Study

Density functional theory calculations (DFT) have been performed on Rh(III)-catalyzed phosphoryl-directed oxidative C-H activation/cyclization to investigate the detailed mechanism, including four basic steps: C-H activation, alkyne insertion, reductive elimination, and catalyst recycling, each of which consists of different steps. Interestingly, the Rh(III)-AgOAc catalyst system was found to be more favorable in the C-H activation step in comparison with the Rh(III)-Ag2CO3 system, whereas the Rh(I)-Ag2CO3 catalyst system was more efficient for catalyst recycling. Importantly, our calculations suggest that the alkyne insertion process is a reversible step. Reductive elimination is the rate-determining step with an activation energy of 25.0 kcal/mol. In addition, the origin of the reactivity and selectivity difference between diarylacetylenes and dialkylacetylenes or electron-rich and electron-deficient diarylacetylenes was probed by means of comparative DFT calculations. The calculation results show that the electronic effects of alkynes play a key role in the reactivity and selectivity, in line with the experimental observations that diarylacetylenes and electron-rich diarylacetylenes are more reactive than dialkylacetylenes and electron-deficient diarylacetylenes, respectively. Our findings should be useful for further developments of transition-metal-catalyzed C-H activation reactions.

tert-Butyl Hydroperoxide Mediated Cascade Synthesis of 3-Arylsulfonylquinolines

3-Arylsulfonylquinoline derivatives play important roles as pharmaceutical drugs. A new method for the synthesis of 3-arylsulfonylquinoline derivatives has been achieved through tert-butyl hydroperoxide mediated cycloaddition between N-propargyl aromatic amine derivatives and arylsulfonylhydrazides without the addition of any metals. This transformation offers a straightforward route to the formation of a C-S bond and quinoline ring in one step via a sulfonylation-cyclization-aromatization process.

Main group metal–ligand cooperation of N-heterocyclic germylene: an efficient catalyst for hydroboration of carbonyl compounds

N-heterocyclic ylide-like germylene effectively promotes the hydroboration of aldehydes and ketones under mild conditions with broad substrate tolerance, operational simplicity of procedure and excellent yields. A key intermediate in this catalytic system featuring a bicyclo[2,2,2]octane-like core has been successfully isolated and characterized, suggesting a new type of mechanism that involves the activation mode that mimics that of transition metal catalysts.

Experimental and theoretical studies on nickel–zinc-catalyzed cross-coupling of gem-dibromoalkenes with P(O)–H compounds

A new stereoselective one-pot protocol for the preparation of E-alkenyl-phosphorus compounds under catalysis of an inexpensive nickel–zinc catalyst system has been developed, which provides a potential useful method for C–P bond formation. 31P NMR spectrum and density functional theory calculations were performed to study the reaction mechanism.

Nickel-catalyzed one-pot tandem 1,4-1,2-addition of P(O)H compounds to 1,10-phenanthrolines.

A novel and efficient nickel-catalyzed tandem 1,4-1,2-addition of P(O)H compounds to 1,10-phenanthrolines forming various 2,4-diphosphono-1,2,3,4-tetrahydro-1,10-phenanthrolines has been developed. This reaction breaks up the aromatic stabilization and directly introduces two phosphorus moieties in one single step. This finding is the first example of transition-metal-catalyzed double hydrophosphonylation of 1,10-phenanthrolines.

Catalytic hydroboration of aldehydes, ketones, alkynes and alkenes initiated by NaOH

Commercially available NaOH powder is shown to be an efficient transition-metal-free initiator for the catalytic hydroboration of aldehydes, ketones, alkynes and alkenes with HBpin and 9-BBN under mild conditions. Combined experimental and theoretical studies suggest that the catalytically active species is a boron hydride generated in situ from the reaction mixture.

Mechanism, catalysis and predictions of 1,3,2-diazaphospholenes: theoretical insight into highly polarized P–X bonds

Density functional theory (DFT) calculations were carried out to investigate the hydridic character of several main group hydrides. A P-hydrido-1,3,2-diazaphospholene 1f with two π-electron donor amino groups on the heterocyclic skeleton framework performs as a strong hydride donor owing to the significant n(N)–σ*(P–H) hyperconjugation. The natural bond orbital analysis reveals that high π-electron delocalization exists in both 1f and the corresponding stable phosphenium Ef+. In addition, 1f is calculated to have a similar catalytic ability for the hydroboration of acetone with pinacolborane, compared to 1e. Thus, a variety of organic substrates activated by 1f are explored, including ketone, imine, isocyanate, CO2, diazene, alkene, alkyne and epoxide. The results show that the highly polarized and electron-deficient bonds such as CO π bonds are readily activated, whereas 1f seems difficult to react with electron-rich unsaturated bonds of propene and propyne. More importantly, 1,3,2-diazaphospholene-based compounds, featuring an extremely polarized P–X bond (X = CCMe, NMe2, PMe2 and SMe), are predicted to have a useful catalytic ability. The preliminary computational results suggest that these P–X compounds could catalyze the silylamination, silylphosphination and silylsulfenylation of acetone with TMSNMe2, TMSPMe2 and TMSSMe, respectively. The products are silylethers, which are equivalent to the corresponding alcohols since they easily undergo hydrolysis. Our computational study opens a new avenue to the design of novel main group organocatalysts.

Reactivity of Germylene toward Phosphorus-Containing Compounds: Nucleophilic Addition and Tautomerism

A series of phosphorus-substituted germanium(II) complexes, L(1)GeR [L(1) = CH{(CMe)(2,6-(i)Pr2C6H3N)}2; 2, R = PPh2; 4, R = OPPh2; 5a, R = OP(O)Ph2; 5b, R = OP(O) (O(n)Bu)2; 6a, R = OP(S)Ph2; 6b, R = OP(S)(OEt)2], were synthesized through the direct activation of various organic phosphorus compounds by N-heterocyclic ylide-like germylene 1. These compounds were characterized by IR and NMR spectroscopy, and 4, 5a, 6a, and 6b were further investigated by X-ray crystallography. Interestingly, the reaction of 1 with Ph2P(O)H produced the tricoordinated phosphorus(III) species L(1)GeOPPh2 (4) rather than the expected isomeric product L(1)GeP(O)Ph2. The reaction of 1 with dialkylthiophosphoric acid and diphenylthiophosphinic acid resulted in the products 6a and 6b containing the P═S double bond rather than the P═O double bond.