Theoretical studies of metallo (Li and Na)-ene reaction mechanisms

The reaction mechanisms of allyl-lithium and allyl-sodium with ethylene were studied by ab initio molecular orbital (MO) methods. The reaction mechanisms were analyzed by a CiLC-IRC method on the basis of ab initio CASSCF MOs. The ene reaction pathways of allyl-Li and allyl-Na with ethylene were located. The complex between allyl-metal and ethylene for both systems is found in the first step of the reaction, and then the metal migration and new C-C bond formation occur synchronously through the transition state. The complexation energies are -13.2 and -9.6 kcal/mol for Li and Na systems, respectively. The activation energy barriers from the reactants are 3.5 kcal/mol for the Li system and 2.0 kcal/mol for the Na system at the MRMP2 calculation level. These barriers are significantly lower than that of the ene reaction of propene with ethylene as the parent reaction. The CiLC-IRC analysis shows that the reaction of allyl-metal with ethylene is a concerted ene reaction mechanism, not a metal catalysis and/or a stepwise reaction.     

中孔硫酸化氧化锆-氧化硅催化甘油转化制丙烯醛

一种中孔硫酸化的、只含Br?nsted酸位的氧化锆-氧化硅催化剂可将甘油转化为丙烯醛,其产率和选择性分别为81%和82%.即使在低温(523 K)下,产物时空收率可高达9.0 mmol h–1 gcat–1.本催化剂的活性和选择性高于典型的硫酸化的ZrO2催化剂.氧化硅稀释了锆物种而使得催化剂酸性更温和,较大的孔径使得传质更快,因此催化剂性能提高.     

(Pi-allyl)palladium complexes bearing diphosphinidenecyclobutene ligands (DPCB): highly active catalysts for direct conversion of allylic alcohols

The (pi-allyl)palladium complex bearing an sp2-hybridized phosphorus ligand (DPCB-OMe: 1,2-bis(4-methoxyphenyl)-3,4-bis[(2,4,6-tri-tert-butylphenyl)phosphinidene]cyclobutene) efficiently catalyzes direct conversion of allylic alcohols in the absence of activating agents of alcohols such as Lewis acids. N-Allylation of aniline proceeds at room temperature to afford monoallylated anilines in 90-97% yields. C-Allylation of active methylene compounds is also successful at 50 degrees C using a catalytic amount of pyridine as a base, giving monoallylation products in 85-95% yields. The catalytic mechanism involving hydrido- and (pi-allyl)palladium intermediates has been proposed on the basis of stoichiometric examinations using model compounds of presumed intermediates.     

Preparation and properties of polymers with biphenyl units in the chain: Syntheses of solvent-soluble substituted polyphenylenes

Benzidinetetrazonium chloride (BTC)–CuCl and BTC–FeCl₂ complexes were thermally converted to benzene-soluble poly-4,4′-biphenylene plus small amounts of insoluble material. The soluble fraction was more stable than the insoluble fraction when heated at 300–500°C, although the solubility decreased. BTC in water was converted to an insoluble material by addition of alkali or cuprous ammonia solution. The C/(H + Cl) ratio indicated the existence of three to five side groups for each twenty phenyl groups of the insoluble fraction, while that of the soluble fraction showed few such groups. The number increased to one or more side groups for each phenyl nucleus as both soluble and insoluble fractions were heated to 500°C. A thin film of soluble fraction deposited on a copper plate showed an electrical conductivity in the range 10^?2–10^?3 ohm^?1 cm^?1 at 25°C and an energy gap (ΔE_g) of 0.2–0.3 eV. However, a compressed specimen of the same soluble fraction showed little conductivity. Solventsoluble samples of substituted poly-4,4,-biphenylene were prepared by the same procedure. These materials cracked on processing, and accurate conductivity measurements could not be made.     

Total Synthesis of (+)-Sch 725680: Inhibitor of Mammalian A-, B-, and Y-Family DNA Polymerases

The total synthesis of (+)-Sch 725680, a member of the hydrogenated azaphilone family, has been accomplished. The synthesis confirmed the absolute configuration and biological activities of the natural product. A key reaction to construct a hydrogenated azaphilone core skeleton is a Ti-mediated aldol reaction.     

Control of photochemistry of stilbazolium ion by adsorption to poly(potassium vinylsulfate) and to hectorite clay

Adsorption or intercalation of trans-1-methyl-4-(2-phenylvinyl)pyridinium ion (stilbazolium ion, SB ( 1 )) to a polyelectrolyte, i. e., poly(potassium vinylsulfate) (PVSK), and to a hectorite clay is studied and its effect on the photochemistry of SB examined. trans-cis Photoisomerization of SB molecularly adsorbed to PVSK proceeds efficiently as with free SB in water, while that of SB molecularly intercalated in the clay is markedly suppressed. Photodimerization proceeds efficiently with SB intercalated in the clay in the aggregated form. Overall photodecoloration, however, proceeds more efficiently with SB adsorbed to PVSK under multiple adsorption conditions apparently due to the higher mobility of PVSK-adsorbed SB compared to that of clay-intercalated SB.     

Inside Back Cover: Integrated Soft Porosity and Electrical Properties of Conductive-on-Insulating Metal-Organic Framework Nanocrystals (Angew. Chem. Int. Ed. 35/2023)

A one-stone, two-bird method to integrate the soft porosity and electrical properties of distinct metal–organic frameworks (MOFs) into a single material involves the design of conductive-on-insulating MOF (cMOF-on-iMOF) heterostructures that allow for direct electrical control. Herein, we report the synthesis of cMOF-on-iMOF heterostructures using a seeded layer-by-layer method, in which the sorptive iMOF core is combined with chemiresistive cMOF shells. The resulting cMOF-on-iMOF heterostructures exhibit enhanced selective sorption of CO₂ compared to the pristine iMOF (298 K, 1 bar, S from 15.4 of ZIF-7 to 43.2–152.8). This enhancement is attributed to the porous interface formed by the hybridization of both frameworks at the molecular level. Furthermore, owing to the flexible structure of the iMOF core, the cMOF-on-iMOF heterostructures with semiconductive soft porous interfaces demonstrated high flexibility in sensing and electrical “shape memory” toward acetone and CO₂. This behavior was observed through the guest-induced structural changes of the iMOF core, as revealed by the operando synchrotron grazing incidence wide-angle X-ray scattering measurements.