Maximizing sinusoidal channels of HZSM-5 for high shape-selectivity to p-xylene.

The shape-selective catalysis enabled by zeolite micropore's molecular-sized sieving is an efficient way to reduce the cost of chemical separation in the chemical industry. Although well studied since its discovery, HZSM-5's shape-selective capability has never been fully exploited due to the co-existence of its different-sized straight channels and sinusoidal channels, which makes the shape-selective p-xylene production from toluene alkylation with the least m-xylene and o-xylene continue to be one of the few industrial challenges in the chemical industry. Rather than modifications which promote zeolite shape-selectivity at the cost of stability and reactivity loss, here inverse Al zoned HZSM-5 with sinusoidal channels predominantly opened to their external surfaces is constructed to maximize the shape-selectivity of HZSM-5 sinusoidal channels and reach > 99 % p-xylene selectivity, while keeping a very high activity and good stability ( > 220 h) in toluene methylation reactions. The strategy shows good prospects for shape-selective control of molecules with tiny differences in size.

Assembly of Sub-Crystals on the Macroscale and Construction of Composite Building Units on the Microscale for SAPO-34.

The nucleation and growth of SAPO-34 crystals with triethylamine (TEA) as a single template was monitored with ex situ time-resolved characterization methods. The investigation focused on the evolution of the intermediate phases at different crystallization stages of SAPO-34. The morphology transformation of the intermediate phases at different crystallization times revealed the unique self-assembly process of the sub-crystals. The cubic SAPO-34 crystals can be constructed from eight pyramidal subunits. Additionally, the construction order of cha cages and double-six-membered ring (d6r) units in the initial crystallization stage was determined. The appearance of cha cages prior to d6r units can be attributed to the structure-directing effect of protonated TEA, which is charge balanced with the negative charge of the framework from Si incorporation. Further analysis showed that Si species were incorporated into the framework by direct participation in the initial crystallization stage and substitution for framework P atoms during the later stage.

Nitrene equivalent mediated metal-free ring expansions of alkylidenecyclopropanes and an alkylidenecyclobutane.

The ring expansion of small-ring compounds provides a powerful method for the construction of various cyclic compounds. Herein, nitrene equivalent mediated metal-free ring expansions of alkylidenecyclopropanes (ACPs) and an alkylidenecyclobutane (ACB) were described. In this synthesis, a series of aryl-substituted cyclobutylidene and cyclopentylidene hydrazine derivatives were obtained under mild conditions in moderate to good yields. [reaction: see text]

Asymmetric aziridination of 1,3-dienes catalyzed by bisoxazoline-copper complexes.

The asymmetric aziridination of 1,3-dienes catalyzed by bisoxazoline-CuOTf complexes with PhI=NTs as a nitrene precursor has been achieved in moderate yields with up to >99:1 regioselectivity, up to >99% diastereoselectivity, and up to 80% enantioselectivity. alpha,beta,gamma,delta-Unsaturated ketones usually produced cis-gamma,delta-aziridinated products, while 1,4-diphenyl-1,3-butadiene afforded both of cis- and trans-aziridine derivatives as major products by the use of different bisoxazoline ligands. The configuration of cis-aziridine derivatives was proposed on the basis of the reaction mechanism.

Rational tuning chelate size of bis-oxazoline ligands to improve enantioselectivity in the asymmetric aziridination of chalcones.

[reaction: see text] Chalcones were asymmetrically aziridinated with [N-(p-toluenesulfonyl)imino]phenyliodinane (PhI=NTs) as a nitrene source under catalysis of CuOTf and a series of cyclohexane-linked bis-oxazolines (cHBOXes), which are chelate size rationally tuned bis-oxazolines. The results indicate that highly enantioselective aziridination of chalcones with up to >99% ee have been achieved under catalysis of (S,S)-1,2-bis[(S)-(4-phenyl)oxazolin-2-yl]cyclohexane, which is the most-matched stereoisomer among cyclohexane-linked bis-oxazolines. It was also found that the enantioselectivity is not substituent-dependent with respect to chalcones in the present case, unlike with 1,8-anthracene-linked bis-oxazolines (AnBOXes).

Asymmetric aziridination of chalcones catalyzed by a novel backbone 1,8-bisoxazolinylanthracene (AnBOX)-copper complex.

Highly enantioselective aziridination of chalcones catalyzed by a novel backbone 1,8-bisoxazolidinylanthracene (AnBOX) and CuOTf with up to >99% ee and the opposite enantioselectivity compared with the ligands of Evans are described.