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Iron-based catalysts for atom-transfer radical polymerization (ATRP) are attractive in the sustainability aspects of green polymer chemistry but usually exhibit lower efficiency and controllability...

A side-armed bis(oxazoline) (SaBOX)/copper catalyst, possessing a low equilibrium constant (KATRP = kact/kdeact) and bearing large side-arm groups, was employed for supplemental activation and redu...

Crystallinity (Xc) is a crucial crystallographic factor that related closely to mechanical properties in linear polyethylene or high density polyethylene (HDPE), whose molecular weight (MW) is at a 105 level. However, as a typically intractable-processing polymer, the structure-property relationship concerned Xc is still ambiguous for ultrahigh molecular weight polyethylene (UHMWPE) with MW﹥1.5 × 106. The reason is that high entanglement density hinders chain mobility in the course of UHMWPE crystallization, thus crystalline degree in UHMWPE molding parts is difficult to be artificially modulated within a wide scope. In this study, low chain-entanglement status of UHMWPE melt was achieved by (1) utilizing lowly entangled nascent UHMWPE synthesized via the single-site Ziegler-Natta catalyst, and (2) decreasing the sintered temperature. It is impressive that partial disentanglement reserved in the melt is favorable for obtaining higher crystallinity. Meanwhile, an isothermal crystallization treatment was additionally adopted to further improve the capacity of regulating crystallization after the traditional two-step sintering procedure. By a combination of varying the initial entanglement in nascent powders, sintering temperature, isothermal crystallization duration, and molecular weight of UHMWPE, the Xc of the compression-sintered products has been successfully adjusted in the relatively broad range of 29%≦ Xc ≦ 65%, which offered an opportunity to validly survey the correlation between mechanical property and crystallinity. Particular attention was paid to the yield strength. A linear master straight-line can be plotted as yield strength vs. Xc for all of the samples inspected, indicating crystallinity also plays a dominant role on mechanical performances of UHMWPE sintering parts, as same in the case of HDPE. However, the mechanical reinforcement induced by increment of Xc in UHMWPE is more efficient than in HDPE. The yield strength of UHMWPE is much higher than that of HDPE at the same Xc, indicating the amorphous phase or entanglements in UHMWPE is crucial to determine the mechanical property. These findings are of significance for guiding the manufacturing of high-performance UHMWPE materials via crystallization manipulation.

New pseudo-C3-symmetric hetero-trisoxazoline can be easily prepared on a gram scale in good yield. Its combination with copper(II) triflate exhibits high enantiomeric induction in the asymmetric Friedel-Crafts alkylation between indoles and alkylidene malonates, with up to 97% ee and good to excellent yields. The catalyst loading can be lowered to 0.5 mol% without loss of the enantiomeric excess.

Highly diastereoselective synthesis of cis-trisubstituted vinylaziridines containing a quaternary carbon center is realized by a one-pot protocol in which the combination of sulfur ylide-mediated aziridination of cyclic ketimines and Pd(0)-catalyzed isomerization is employed successfully.

A facile multistep one-pot synthesis of single or fused cyclopentenones has been developed. The sequence involves a transition metal-catalyzed ylide formation/Wittig Olefination/Nazarov Cyclization.

A pyridine-catalyzed ylide cyclization affording dihydrofurans and dihydropyrroles has been developed. In the presence of a catalytic amount of pyridine and Fe(Tcpp)Cl, α-ylidene-β-diketones and α,β-unsaturated imines react with diazoacetates providing dihydrofurans and dihydropyrroles respectively, in up to 96% yield with high diastereoselectivities.

The new pseudo-C3-symmetric hetero-trisoxazolines are prepared on a gram scale and in combination with copper triflate applied to the asymmetric Friedel—Crafts alkylation of both indoles (II) and pyrrole (V) with alkylidene malonates (I) and (IV), respectively.

In the presence of Fe(Cl4tpp) and pyridine base, α-ylidene-β-diketones and α,β-unsaturated imines react with diazoacetates to provide the title heterocycles as single diastereomers.

Treatment of α,β-unsaturated ketones with the sulfonium salt (I) and the weak base Cs2CO3 results in efficient and stereoselective formation of cyclohexadiene epoxides like (III).

Highly diastereoselective synthesis of cis-trisubstituted vinylaziridines containing a quaternary carbon center is realized by a one-pot protocol in which the combination of sulfur ylide-mediated aziridination of cyclic ketimines and Pd(0)-catalyzed isomerization is employed successfully.

On the basis of the reactions of camphor-derived sulfur ylide with alpha,beta-unsaturated ketone, highly efficient and selective synthesis of optically active cyclohexadiene epoxides and vinylcyclopropanes with excellent diastereoselectivities, moderate to high enantioselectivities, and yields has been achieved.

A facile multistep one-pot synthesis of single or fused cyclopentenones has been developed. The sequence involves a transition metal-catalyzed ylide formation/Wittig Olefination/Nazarov Cyclization.

A highly efficient diastereoselective synthesis of cyclohexadiene epoxide derivatives with a multi-stereocenter has been developed via a tandem ylide Michael addition/epoxidation. By employing a chiral sulfonium ylide, up to 96% ee can be achieved in good yields.

A highly efficient diastereoselective synthesis of cyclohexadiene epoxide derivatives with a multi-stereocenter has been developed via a tandem ylide Michael addition/epoxidation. By employing a chiral sulfonium ylide, up to 96% ee can be achieved in good yields.

Pseudo-C2-symmetric chiral phosphorus ylide is designed and synthesized for the enantioselective preparation of allenic esters, amides, ketone, and nitrile. Up to 92% ee is achieved.