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A novel and uncommon macrocyclization reaction between 3-triflyloxybenzynes and tetrahydrofuran has been developed for the first time, providing a direct method for the synthesis of a range of functionalized 19-membered polyether macrocycles in moderate to good yields. The process was proposed to proceed through an anionic thia-Fris rearrangement under transition metal-free conditions, leading to the formation of four new C-O bonds and one new C-S bond in a single step.

The engineering of highly stable metal-organic frameworks (MOFs) will unveil the intrinsic potential of these materials for practical applications, especially for heterogeneous catalyzes. However, it is fairly challenging to rationally design robust MOFs serving as highly effective and reusable heterogeneous catalysts. Here, for the first time, we report the construction of four robust UiO-type chiral zirconium-metallosalen frameworks, denoted ZSF-1-4. Single-crystal X-ray-diffraction reveals that the frameworks consist of twelve-connected Zr6O8 clusters with privileged chiral metallosalen ligands anchored at ideal positions, generating confined chiral cages that enable synergistic activation. Unlike UiO-68 that is highly sensitive to aqueous solutions, ZSF-1-4 exhibit excellent chemical stability in aqueous solutions with a wide range of pH owing to the abundant hydrophobic groups within metallosalen ligands. These features render ZSF-1 and ZSF-2 to be excellent recycled heterogeneous catalysts for the conversion of imitated industrial CO2 with epoxides into cyclic carbonates with the highest reported turnover numbers in Zr-MOFs. With regard to asymmetric catalysis, ZSF-3 and ZSF-4 can effectively catalyze C-H azidation reaction in water medium with ee value up to 94%. Moreover, these robust ZSFs can be further extended to other analogues with various metal centers through demetallization-remetallization strategy, which renders them to be an excellent platform for broader fields.

The development of well-defined multimetallic porous metal–organic frameworks (MOFs) will add a new dimension to the application of MOF catalysis. From this perspective, the understanding and tailoring of the catalytic metal sites in MOFs are key fundamental challenges that could reveal the intrinsic potential of these materials. In this work, a series of porphyrin–salen chiral MOFs (ps-CMOFs 2–7) have been synthesized through postsynthetic metalation (PSMet) of the parent ps-CMOF via single-crystal to single-crystal transformation. Crystal structures of these ps-CMOF analogues revealed the same topological structure but varied metal entities compared to those of the parent framework. Note that the PSMet process involves three methods involving cation exchange at the nodes, cation exchange at the metalated porphyrin, and cation addition at the free porphyrin, which has been systematically investigated using single-crystal X-ray diffraction and other physicochemical methods. The N2 adsorption tests, thermo...

Bipyridine(bpy)/phenanthroline(phen)-based ligands have been utilized widely to coordinate metals for homogeneous organic catalysis. The immobilization of M(bpy)/M(phen) active sites into porous supports is an intriguing approach to combine the appealing activities of homogeneous catalysts with the heterogeneity of the host materials. Herein we review the recent research progress of M(bpy)/M(phen)-functionalized metal–organic frameworks (MOFs) and covalent organic frameworks (COFs). Emphasis is focused on the synthetic strategies of these porous materials, as well as their catalytic performances in thermocatalysis, photocatalysis and electrocatalysis.

A three-dimensional (3D) chiral metal-organic framework [Cd2(Ni(salen))(DMF)3]*4DMF*7H2O (1) based on a new enantiopure tetracarboxyl-functionalized metallosalen Ni(H4salen) [where H6salen is (R,R)-N,N′-bis(3-tert-butyl-5-(3,5-dicarboxybenzyl)salicylidene)-1,2-diphenylethylenediame], has been synthesized and characterized by Infrared spectrum, thermogravimetric analysis, nitrogen and carbon dioxide adsorption, powder and single-crystal X-ray diffractions. In 1, the dinuclear Cd2 cluster [Cd2(COO)4(DMF)3] as node is cross-linked by four isophthalate groups on salen ligands, forming a 2D lamellar structure, which are further linked by Ni(salen) into the 3D network with 1D open channel (∼7.0 × 8.0 A2) along a axis. On account of its porosity, Lewis acid sites and moderate uptake for CO2, 1 can be used as an efficiently heterogeneous catalyst for the CO2 cycloaddition with epoxides under relatively mild conditions. Moreover, the bulky epoxide shows a decrease in the activity with an increase in the alkyl chain length of the substrate due to the confinement effect of 1, showing size-dependent selectivity.

We report a protocol for palladium-catalyzed dearomatizing alkoxydiarylation of furan rings via aerobic oxidative coupling between arylboronic acids and 5-aryl-2-hydroxyalkylfurans. This green protocol starting from furan derivatives, which can be sustainably sourced, provides rapid access to polysubstituted 2,3,3a,6a-tetrahydrofuro[3,2-b]furans and hexahydrofuro[3,2-b]furans, oxabicyclic frameworks that are shared by various natural products and synthetic molecules with important biological activities.

Four metal-organic frameworks (MOFs), {[Mn3.5L(OH)(HCOO)4(DMF)]·H2O} (1), {[In2.5L2O(OH)1.5(H2O)2]·DMF·CH3CN·2H2O} (2), {[Pb4L3O(DMA)]·CH3CN} (3), and {[LaL(NO3)(DMF)2]·2H2O} (4) were synthesized by utilizing the ligand 2,2′,6,6′-tetramethoxy-4,4′-biphenyldicarboxylic acid (H2L) via solvothermal methods. All MOFs were characterized by single-crystal X-ray diffraction, powder X-ray diffraction, thermogravimetric analysis, and infrared spectroscopy. In 1, the Mn2+ ions are interconnected by formic groups in situ produced via DMF decomposition to form a rare 2D macrocyclic plane, which is further linked by L2– to construct the final 3D network. In 2, 1D zip-like infinite chain is formed and then interconnected to build the 3D framework. In 3, a [Pb6(μ4-O)2(O2C)10(DMA)2] cluster with a centrosymmetric [Pb6(μ4-O)2]8+ octahedral core is formed in the 3D structure. In 4, the La3+ ions are connected with each other through carboxylate groups of L2– to generate 1D zigzag chain, which is further linked by L2– to construct a 3D network with sra topology. Solid photoluminescence properties of 3 and 4 were also investigated.

Fully meta-substituted 2,2′,6,6′-tetramethoxy-4,4′-biphenyldicarboxylic acid (H2L) was synthesized and applied in the construction of three metal–organic frameworks (MOFs), {[Cu3L3(H2O)2(DMF)]n (1), [Zn4OL3]n (2), and [Zn4OL3(H2O)(DEF)]n (3)}. For 1, the approximately vertical twist of two benzene rings in L leads to the formation of a twofold-interpenetrated 3D structure with 1D open channels (11 × 15 A). MOFs 2 and 3 have classical twofold-interpenetrated isoreticular MOF structures, and reversible transformation of the oxozinc carboxylate clusters of 2 and 3 could be realized via a solvent-exchange-induced single-crystal-to-single-crystal pathway, which provides direct structural evidence for a Zn4O core as Lewis acidic site in MOFs. Desolvated framework 1′ exhibits high permanent porosity (Langmuir surface area = 555 m2/g), high thermal stability (up to 300 °C), and highly active catalytic properties for cyanosilylation and olefin epoxidation. MOF 2 exhibits moderate carbon dioxide uptake ability and can efficiently catalyze the cycloaddition of CO2 with epoxides under mild conditions.

The first porphyrin-salen based chiral metal-organic framework (ps-CMOF) constructed by judiciously incorporating metalloporphyrin and metallosalen struts into one MOF structure is reported, which can serve as an effective heterogeneous catalyst for the asymmetric cyanosilylation of aldehydes owing to the synergistic function between Lewis acid activation (from metalloporphyrin) and chiral induction (from metallosalen).

Described here is a new and viable approach to achieve Pd catalysis for aerobic oxidation systems (AOSs) by circumventing problems associated with both the oxidation and the catalysis through an all-in-one strategy, employing a robust metal-organic framework (MOF). The rational assembly of a PdII catalyst, phenanthroline ligand, and CuII species (electron-transfer mediator) into a MOF facilitates the fast regeneration of the PdII active species, through an enhanced electron transfer from in situ generated Pd0 to CuII , and then CuI to O2 , trapped in the framework, thus leading to a 10 times higher turnover number than that of the homogeneous counterpart for Pd-catalyzed desulfitative oxidative coupling reactions. Moreover, the MOF catalyst can be reused five times without losing activity. This work provides the first exploration of using a MOF as a promising platform for the development of Pd catalysis for AOSs with high efficiency, low catalyst loading, and reusability.

The first example of the epoxidation reaction of trifluoromethylketones with N-tosylhydrazones under transition-metal free conditions is reported. This epoxidation reaction provided tetrasubstituted trifluoromethylated oxiranes with excellent yields and diastereoselectivities. The salient features of this reaction include readily available starting materials, mild conditions, broad substrate scope, high efficiency, and valuable further applications. Remarkably, this reaction proceeded through an unprecedented nucleophilic addition process, and the ammonium O-anion intermediate was detected and characterized by NMR and HRMS analysis.

A heterometallic organic framework {Pb[Pd(bpydc)Cl2]DMF}n (1) (H2bpydc = 2,2′-bipyridine-5,5′-dicarboxylic acid) was synthesized via a one-pot solvothermal method and characterized using thermogravimetric analysis, X-ray photoelectron spectroscopy as well as powder and single-crystal X-ray diffraction. The crystal structure of 1 indicates that, in metalloligand Pd(bpydc)Cl2, every Pd atom adopts a square planar coordination mode with two chloride ions and two nitrogen atoms from bpydc, and the carboxyl groups of Pd(bpydc)Cl2 connect Pb atoms to form a one-dimensional chain along the crystallographic a-axis, which is interlinked via metalloligands to form a two-dimensional layer structure. This complex is highly active, stable and recyclable as a catalyst for the Suzuki–Miyaura and Heck reactions of a wide range of aryl halides including electron-rich and electron-poor aryl iodides/bromides, affording the corresponding products in good to excellent yields. Copyright © 2016 John Wiley & Sons, Ltd.

Cyclopropanation of 2-aminoacrylates with N-tosylhydrazones could proceed smoothly under transition-metal-free conditions via a [3 + 2] cycloaddition process. This robust protocol exhibits excellent generality, delivering a wide spectrum of cyclopropane α-amino acid esters bearing contiguous quaternary carbon centers in high yields and diastereoselectivities. With these readily available products, the steric convergence of cyclopropane α-amino acids could be readily obtained.

Two Lewis acid–base bifunctional monometallic aluminum–salen complexes were prepared based on a new type of salen ligand with two N-methylhomopiperazine moieties at the 3,3′-position. The Al(salen) complexes proved to be efficient and recyclable homogeneous catalysts towards the organic solvent-free synthesis of cyclic carbonates from epoxides and CO2 in the absence of a co-catalyst, in which >90% yield of cyclic carbonate could be obtained under relatively mild conditions. The catalysts can be easily recovered and reused five times without significant loss of activity and selectivity. Furthermore, the Lewis acid–base cooperative activation mechanism by the bifunctional Al(salen) complexes was proposed according to experimental data.

Metal–organic frameworks (MOFs) imbedded privileged molecular catalysts are of particular interest due to their higher catalytic activities derived from the MOFs pore/channel confinement effect, improved lifetime through eliminating intermolecular deactivation pathway, and the recyclability based on their heterogeneity. In this work, a 3D chiral metallosalen-based MOF [Cd2(Cu(salen))(DMF)3]·DMF·3H2O (1) with a 1D open channel was synthesized and characterized by single-crystal X-ray diffraction and other physicochemical methods. Upon postsynthetic reduction modification with NaBH4, the conversion from imino to amino group on salen cores of 1 generates the reduction product 2 with a more flexible chiral group and more alkaline backbone, meanwhile still maintaining the original porous framework. 2 can be used as an efficient heterogeneous catalyst for the asymmetric Henry reaction with broad substrate applicability and exhibits higher activity and enantioselectivity (ee up to 98%) compared with the unreduce...

A copper-catalyzed [2 + 3] formal cyclization reaction between α-hydroxyl ketones and arylacetonitriles has been developed. The reaction outcome was ultimately dependent on the structure of the α-hydroxy ketones employed. Tertiary α-hydroxy ketones gave 3,4,5,5-tetrasubstituted butenolides as the sole products, while secondary α-hydroxy ketones furnished 2,4,5-trisubstituted oxazoles selectively. This method has many advantages, such as the use of easily available substrates, broad substrate scope, good functional tolerance, and milder reaction conditions.

A highly stable chiral salen-based metal–organic framework [(Cu4I4)2L4]·20DMF·3CH3CN (1) [L = (R,R)-N,N′-bis(3-tert-butyl-5-(4-pyridyl)salicylidene)-1,2-diphenylethylenediamine nickel(II)] has been synthesized and characterized by single crystal X-ray diffraction and other physicochemical methods. 1 exhibits a rare 8-fold interpenetrated 3D framework constructed by a 4-connecting Cu4I4 cluster and a 2-coordinating L ligand. Remarkably, in spite of 8-fold interpenetration, 1 still possesses two types of 1D chiral hydrophobic channels with pore window sizes of 6.77 × 8.64 A2 and 6.09 × 10.96 A2 along the crystallographic a axis. All Ni(salen) moieties of L lie inside the 1D channels and the empty coordination sites of Ni2+ are oriented to the cavities. PXRD and N2 adsorption measurements confirmed that 1 is extremely stable under high temperature (>400 °C), in water vapor (90% relative humidity), in acid/base aqueous solution (pH 0–14), and in saturated NaOH solution at 100 °C, as well as in 30 wt% H2O2 and 70 wt% tert-butyl hydroperoxide solution. 1 was proved to be an excellent recycled heterogeneous catalyst for the conversion of simulated industrial CO2 (that is, involving tiny amounts of water vapor and other acidic gases) with epoxides into cyclic carbonates under mild conditions for the first time. The synthesis of β-hydroxy-1,2,3-triazoles from the same epoxides, alkyne and sodium azide was also catalyzed by 1 in aqueous solution with high yield. Interestingly, the cycloaddition reaction of CO2 to bulky epoxides shows a decrease in the activity with an increase in the alkyl chain length of the substrate because of confinement of the channel size of 1, showing size-dependent selectivity. The plausible catalytic mechanisms for these two reactions have also been proposed.

A palladium-catalyzed fluoroalkylative cyclization of olefins with readily available Rf–I reagents to afford the corresponding fluoroalkylated 2,3-dihydrobenzofuran and indolin derivatives with moderate to excellent yields is reported. This novel procedure provides an efficient method for the construction of Csp3–CF2 and C–O/N bonds in one step. A wide range of functional groups are tolerated. It is proposed that a radical/SET (single electron transfer) pathway proceeding via the fluoroalkyl radical may be involved in the catalytic cycle.

A palladium-catalyzed multicomponent reaction (MCR) of propargylic carbonates with isocyanides is reported. Remarkably, the orderly insertion of isocyanides affords two types of valuable N-heterocyclic products (Z)-6-imino-4,6-dihydro-1H-furo[3,4-b]pyrrol-2-amines and (E)-5-iminopyrrolones in high yields. Systematic analysis of the reaction conditions indicates that the selectivity of these N-heterocyclic products can be controlled by ligands and temperature.

The first base-promoted formal [4 + 3] annulation between 2-fluorophenylacetylenes and ketones has been disclosed. The reaction proceeds through a tandem α-vinylation of ketones followed by an intramolecular nucleophilic aromatic substitution (SNAr) reaction of the in situ generated β,γ-unsaturated ketone intermediates, providing a straightforward access to a wide range of functionalized benzoxepines in moderate to high yields. The transition-metal-free methodology featured a wide substrate scope, the use of easily available starting materials, and a high functional group tolerance.