Zhan-Jiang Zheng

Enantioselective copper-catalyzed azide-alkyne click cycloaddition to desymmetrization of maleimide-based bis(alkynes).

A copper catalyst system derived from TaoPhos and CuF2 was used successfully for catalytic asymmetric Huisgen [3+2] cycloaddition of azides and alkynes to give optically pure products containing succinimide- and triazole-substituted quaternary carbon stereogenic centers. The desired products were obtained in good yields (60-80 %) and 85:15 to >99:1 enantiomeric ratio (e.r.) in this click cycloaddition reaction.

Modulation of Multifunctional N,O,P Ligands for Enantioselective Copper‐Catalyzed Conjugate Addition of Diethylzinc and Trapping of the Zinc Enolate

In this work, we have successfully synthesized a new family of chiral Schiff base–phosphine ligands derived from chiral binaphthol (BINOL) and chiral primary amine. The controllable synthesis of a novel hexadentate and tetradentate N,O,P ligand that contains both axial and sp3-central chirality from axial BINOL and sp3-central primary amine led to the establishment of an efficient multifunctional N,O,P ligand for copper-catalyzed conjugate addition of an organozinc reagent. In the asymmetric conjugate reaction of organozinc reagents to enones, the polymer-like bimetallic multinuclear Cu-Zn complex constructed in situ was found to be substrate-selective and a highly excellent catalyst for diethylzinc reagents in terms of enantioselectivity (up to >99 % ee). More importantly, the chirality matching between different chiral sources, C2-axial binaphthol and sp3-central chiral phosphine, was crucial to the enantioselective induction in this reaction. The experimental results indicated that our chiral ligand (R,S,S)-L1- and (R,S)-L4-based bimetallic complex catalyst system exhibited the highest catalytic performance to date in terms of enantioselectivity and conversion even in the presence of 0.005 mol % of catalyst (S/C = 20 000, turnover number (TON) = 17,600). We also studied the tandem silylation or acylation of enantiomerically enriched zinc enolates that formed in situ from copper-L4-complex-catalyzed conjugate addition, which resulted in the high-yield synthesis of chiral silyl enol ethers and enoacetates, respectively. Furthermore, the specialized structure of the present multifunctional N,O,P ligand L1 or L4, and the corresponding mechanistic study of the copper catalyst system were investigated by 31P NMR spectroscopy, circular dichroism (CD), and UV/Vis absorption.

Modulation of Silver–Titania Nanoparticles on Polymethylhydrosiloxane‐based Semi‐Interpenetrating Networks for Catalytic Alkynylation of Trifluoromethyl Ketones and Aromatic Aldehydes in Water

In this work, we have developed a new approach to monodispersed hybrid Ag@TiO2 nanocomposites using a titanium‐promoted cross‐linking reduction in the SiH functional material, polymethylhydrosiloxane (PMHS)‐based semi‐interpenetrating networks (PMHSIPN). The titania was designed to be highly dispersed on the functional material and then the Ag@TiO2 nanoparticles were formed in uniform size and shape under mild conditions. The experimental results reveal that the nanosilver catalysts (the fabricated Ag@TiO2 located on the PMHSIPNs, namely, nanoAg@TiO2@PMHSIPN) have enhanced catalytic activities in the alkynylation of trifluoromethyl ketones or α,β‐unsaturated trifluoromethyl ketones with terminal alkynes. In this reaction, the hybrid Ag@TiO2 nanoparticles exhibited a high level of catalytic activity for the selective 1,2‐alkynylation of various trifluoromethyl ketones and α,β‐unsaturated trifluoromethyl ketones into a wide range of fluorinated alcohols in water. Finally, on the basis of the nanoAg@TiO2@PMHSIPN‐catalyzed alkynylation of trifluoromethyl ketones, we developed a new concept whereby highly reactive substrates act as a “reactive tractor” or “reactive springboard” to drive the transformation of poorly reactive substrates as springboard chemistry. Consequently, we found that trifluoromethyl ketone can be used as an efficient additive in the nanosilver‐catalyzed alkynylation of aldehydes.

Synthesis of bi- and bis-1,2,3-triazoles by copper-catalyzed Huisgen cycloaddition: A family of valuable products by click chemistry

Summary The Cu(I)-catalyzed azide-alkyne cycloaddition reaction, also known as click chemistry, has become a useful tool for the facile formation of 1,2,3-triazoles. Specifically, the utility of this reaction has been demonstrated by the synthesis of structurally diverse bi- and bis-1,2,3-triazoles. The present review focuses on the synthesis of such bi- and bistriazoles and the importance of using copper-promoted click chemistry (CuAAC) for such transformations. In addition, the application of bitriazoles and the related CuAAAC reaction in different fields, including medicinal chemistry, coordination chemistry, biochemistry, and supramolecular chemistry, have been highlighted.

Copper-Catalyzed Huisgen and Oxidative Huisgen Coupling Reactions Controlled by Polysiloxane-Supported Amines (AFPs) for the Divergent Synthesis of Triazoles and Bistriazoles

An interesting example of a divergent catalysis with a copper(I) and amine-functional macromolecular polysiloxanes system was successfully presented in click chemistry. In this manuscript, we demonstrate the remarkable ability of the secondary amine-functional polysiloxane to induce oxidative coupling in the copper-mediated Huisgen reactions of azides and alkynes, thereby achieving good yields and selectivities. The click reactions mediated by a polysiloxane-supported secondary amine allow the preparation of novel heterocyclic compounds, that is, bistriazoles. Comparably, it is also surprising that the use of a diamine-functional polysiloxane as ligand led to a classic Huisgen [3+2] cycloaddition in excellent yields. From the results of the present amine-functional polysiloxanes-controlled Huisgen reaction or oxidative Huisgen coupling reaction to divergent products and the proposed mechanism, we suggested that the mononuclear bistriazole-copper complex stabilized and dispersed by the secondary amine-functional polysiloxane was beneficial to prevalent the way to oxidative coupling.

Development of a Novel Multifunctional N,P Ligand for Highly Enantioselective Palladium‐Catalyzed Asymmetric Allylic Etherification of Alcohols and Silanols

CycloN2P2-Phos! The use of the multidentate phosphine, CycloN2P2-Phos, which contains four heteroatoms (two nitrogen and two phosphorus atoms), in the palladium-catalyzed asymmetric allylic etherification (AAE) of alcohols and silanols leads to excellent levels of enantioselectivity (up to 99 % ee).

A Chiral Cu‐Salan Catalyst with a Rotatable Aromatic π‐Wall: Molecular Recognition‐Oriented Asymmetric Henry Transformation of Aromatic Aldehydes

the National Natural Science Foundation of China (Nos. 20973051 and 21173064);Program for Excellent Young Teachers in Hangzhou Normal University (HNUEYT, JTAS 2011-01-014)

Dehydrogenation and oxidative coupling of alcohol and amines catalyzed by organosilicon-supported TiO2@PMHSIPN

The catalytic dehydrogenation and tandem transformation of aromatic alcohols, including oxidative coupling of alcohols and amines, were achieved successfully using a catalytic amount of organosilicon-supported titania (TiO2@PMHSIPN), which enables the efficient synthesis of aromatic aldehydes, imines, and benzimidazoles in good to excellent yields.

Multistereogenic Phosphine Ligand‐promoted Palladium‐Catalyzed Allylic Alkylation of Cyanoesters

A palladium‐catalyzed allylic alkylation of unsubstituted 2‐cyanoacetates using a 1,1′‐bi‐2‐naphthol‐derived multifunctional N,O,P ligand is reported. A number of chiral monosubstituted 2‐cyanoacetates with two adjacent stereogenic carbon centers are obtained in this Pd‐catalyzed asymmetric allylic alkylation reaction, in which the multistereogenic and multifunctional 1,1′‐bi‐2‐naphthol‐derived N,O,P ligand‐promoted Pd‐catalyzed asymmetric allylic alkylation reaction proceeds smoothly in high diastereo‐ and enantioselectivity (up to >99:1 dr and up to 96 % ee).

Probing the evolution of an Ar-BINMOL-derived salen–Co(III) complex for asymmetric Henry reactions of aromatic aldehydes: salan–Cu(II) versus salen–Co(III) catalysis

A new type of chiral salen–Co catalyst that features aromatic π-walls and an active Co(III) center has been developed for enantioselective Henry/nitroaldol reactions on the basis of salen–Cu catalysis. The asymmetric Henry reaction of aromatic aldehydes and nitromethane catalyzed by an Ar-BINMOL-derived salen–Co(III) complex was achieved with high yields (up to 93%) and excellent enantioselectivities (up to 98% ee). And more interestingly, it was supposed that either salan–Cu(II) or salen–Co(III) complex-catalyzed Henry reaction was an ideal model reaction for providing direct evidence of noncovalent interaction due to the distinguishable ortho-substituted aromatic aldehydes from meta- or para-substituted benzaldehydes in terms of enantioselectivities and yields.