Identification of a potent palladium-aryldiphosphine catalytic system for high-performance carbonylation of alkenes

The development of stable and efficient ligands is of vital significance to enhance the catalytic performance of carbonylation reactions of alkenes. Herein, an aryldiphosphine ligand (L11) bearing the [Ph2P(ortho-C6H4)]2CH2 skeleton is reported for palladium-catalyzed regioselective carbonylation of alkenes. Compared with the industrially successful Pd/1,2-bis(di-tert-butylphosphinomethyl)benzene catalyst, catalytic efficiency catalyzed by Pd/L11 on methoxycarbonylation of ethylene is obtained, exhibiting better catalytic performance (TON: >2,390,000; TOF: 100,000 h-1; selectivity: >99%) and stronger oxygen-resistance stability. Moreover, a substrate compatibility (122 examples) including chiral and bioactive alkenes or alcohols is achieved with up to 99% yield and 99% regioselectivity. Experimental and computational investigations show that the appropriate bite angle of aryldiphosphine ligand and the favorable interaction of 1,4-dioxane with Pd/L11 synergistically contribute to high activity and selectivity while the electron deficient phosphines originated from electron delocalization endow L11 with excellent oxygen-resistance stability.

Synthesis, structures and properties of metal–organic frameworks prepared using a semi-rigid tricarboxylate linker

A series of MOFs constructed from 5-((carboxymethyl)amino)isophthalic acid (H3cmai) have been prepared and characterised, with [Cd3(cmai)2(H2O)4]·4H2O demonstrating loss of water in a single-crystal-to-single-crystal transformation.

Solvent-mediated structural transformations of copper(II) coordination polymers induced by different short-chain alcohols

A three-dimensional copper(II) coordination polymer (CP), {Cu(L-F)(N₃)}_n (1), was synthesized by reacting Cu(NO₃)₂ with 5-fluoronicotinic acid (HL-F) and NaN₃ in a water medium. Complex (1) shows a 3D network, in which the 1D [Cu₂(COO)N₃]_n chains are interconnected via L-F ligands. By immersing (1) into different short-chain alcohols (CH₃OH, C₂H₅OH and HOC₂H₄OH), three different CPs were isolated, including {Cu₃(L-F)₄(N₃)₂(CH₃OH)₂}_n (2), {Cu₃(L-F)₄(N₃)₂(C₂H₅OH)₂}_n (3) and {Cu_2.5(L-F)₃(N₃)₂(HOC₂H₄OH)_0.5}_n (4). CPs (2) and (3) display a similar structure, in which trinuclear subunit [Cu₃(COO)₂(N₃)₂(solvent)₂] is generated. Furthermore, such entities are interconnected via L-F ligands to give rise to a 3D network. As for (4), there are trinuclear [Cu₃(COO)₂(N₃)₂] and binuclear [Cu₂(COO)N₃] units, which are interconnected by L-F ligands to generate a 3D network. Notably, in (2) and (3), the coordination modes of CH₃OH and C₂H₅OH solvents are monodentate; whereas for (4), the HOC₂H₄OH solvent adopts a bridging mode to link two Cu atoms. Of further interest, these processes are solvent-mediated structural transformations, with obvious colour changes in the crystals. Structural changes and mechanisms of transformation are discussed in detail.

TEMPO-catalyzed synthesis of 5-substituted isoxazoles from propargylic ketones and TMSN3

A novel and efficient TEMPO-catalyzed synthesis of 5-substituted isoxazoles from propargylic ketones and TMSN₃via the radical mechanism process is described. A plausible reaction mechanism for this process is proposed.

Synthesis of 3,4,5-trisubstituted isoxazoles via 1,3-dipolar cycloaddition/SO2 extrusion of benzoisothiazole-2,2-dioxide-3-ylidenes with nitrile oxides

An straightforward synthesis of 3,4,5-trisubstituted isoxazole derivatives via 1,3-dipolar cycloaddtion/SO₂ extrusion of benzoisothiazole-2,2-dioxide-3-ylidenes with nitrile oxides is reported using 4 Å molecular sieves as dehydrochlorinating agent.

Synthesis of 3,4,5-Trisubstituted Isoxazoles from Morita-Baylis-Hillman Acetates by an NaNO2 /I2 -Mediated Domino Reaction

An efficient NaNO2 /I2 -mediated one-pot transformation of Morita-Baylis-Hillman (MBH) acetates into alkyl 3-nitro-5-(aryl/alkyl)isoxazole-4-carboxylates is described. In a cascade event, initial Michael addition of NaNO2 to the MBH acetate furnishes the allylnitro intermediate which undergoes I2 -catalyzed oxidative α-CH nitration of the nitromethyl subunit followed by [3+2] cycloaddition to afford the title compounds. Structural elaborations of these highly substituted isoxazoles by SN Ar reactions and hydrogenolysis allows access to useful products.

Coordination assembly of Borromean structures

The state-of-art advances in the assembly of coordination supramolecular structures featuring Borromean topological character have been introduced.

Post‐synthetic Modification of MOFs

Post‐synthetic modification is increasingly recognised as an important and versatile tool in the preparation of functionalised metal organic frameworks (MOFs). The process involves one or more reactions on a pre‐formed MOF, and it can be used to prepare MOFs that are not accessible by direct combination of metal and linker. This review explores the methods and strategies that have been developed for post‐synthetically modifying MOFs, concentrating on four classes of reaction: covalent transformations of the linker, coordination of a metal centre to a linker, modification of the inorganic part of the MOF and exchange of counter‐ions. Examples of the use of the modified MOFs are given, with a focus on their utility in catalysis.