Heating enables solid-state motion and improves the yield of a [2 + 2] cycloaddition reaction within an organic cocrystal

The cocrystallization of either 2,3,5,6-tetrachloroaniline (C6H3Cl4N) or 2,4,6-trichloroaniline (C6H4Cl3N) with trans-1,2-bis-(4-pyridyl)-ethylene (BPE) results in a pair of three-component hydrogen-bonded cocrystals, namely 2-(C6H3Cl4N)·(BPE) and 2-(C6H4Cl3N)·(BPE). These cocrystals undergo up to a quantitative [2 + 2] cycloaddition reaction in the organic solid state upon exposure to ultraviolet light. Utilizing the ability of these chlorinated anilines to engage in both N-H···N hydrogen bonds along with homogeneous and face-to-face π-π stacking interactions ultimately positions BPE in a suitable location to photoreact and generate the stereoselective photoproduct rctt-tetrakis-(4-pyridyl)-cyclobutane (TPCB). The tendencies for these chlorinated anilines to form homogeneous π-stacks were investigated by means of density functional theory calculations with the goal to determine not only the overall strength but also the preference for this stacking pattern. In addition, a series of isostructural cocrystals were also achieved by incorporating two isosteric hydrogen-bond acceptors, namely 1,2-bis-(4-pyridyl)-acetylene (BPA) and azobipyridine (Azo), with these chlorinated anilines.

The formation of three isostructural co-crystals that utilize iodoperchlorobenzene as a dual halogen-bond donor is reported.

Cocrystals for photochemical solid-state reactions: An account on crystal engineering perspective

Organocatalytic Stereoselective [8+2] Cycloaddition of Tropones with Azlactones

Eight types of cationic glycidyl triazole polymers (GTPs) are prepared from combinations of four quaternary ammonium cationic units (pyrrolidinium, piperidinium, morpholinium, and N,N‐diethyl‐substituted ammonium) and two N‐alkyl substituents (methyl and ethyl groups). These poly(ionic liquid)s are prepared using Cu(I)‐catalyzed azide‐alkyne cycloaddition reaction between the alkyne derivatives of ionic liquids and glycidyl azide polymer. The ionic conductivity is characterized by impedance measurement. The ionic conductivity depends on the type of the cationic unit, but the type of the N‐alkyl substituent shows little influence on the ionic conductivity. The order of the cationic units that afford high ionic conductivity is as follows: pyrrolidinium >N,N‐diethyl‐substituted ammonium > piperidinium > morpholinium. The highest anhydrous ionic conductivity obtained in this study is 9.8 × 10−6 S cm−1 at 30 °C for the GTPs with the 1‐methylpyrrolidinium unit. Based on electrode polarization analysis, the conducting ion (carrier) concentration and mobility are calculated.image

Simultaneous tuning of permanent porosity and modulation of magnetic properties by postsynthetic modification (PSM) with light in a metal-organic framework is unprecedented. With the aim of achieving such a photoresponsive porous magnetic material, a 3D photoresponsive biporous framework, MOF1, which has 2D channels occupied by the guest 1,2-bis(4-pyridyl)ethylene (bpee), H2 O, and EtOH molecules, has been synthesized. The guest bpee in 1 is aligned parallel to pillared bpee with a distance of 3.9 Å between the ethylenic groups; this allows photoinduced PSM of the pore surface through a [2+2] cycloaddition reaction to yield MOF2. Such photoinduced PSM of the framework structure introduces enhanced CO2 selectivity over that of N2 . The higher selectivity in MOF2 than that of MOF1 is studied through theoretical calculations. Moreover, MOF2 unveils reversible changes in Tc with response to dehydration-rehydration. This result demonstrates that photoinduced PSM is a powerful tool for fabricating novel functional materials.

A series of asymmetrical spirohomo- and methanofullerenes were synthesized for the first time in reactions of selective cycloaddition of adamantane diazo compounds to C<sub>60</sub> fullerene in the presence of the catalyst Pd(PPh<sub>3</sub>)<sub>2</sub>Cl<sub>2</sub>. Adamantane diazoalkanes were obtained <i>in situ</i> in the oxidation reactions of adamantane hydrazones with manganese oxide MnO<sub>2</sub>. It has been established that the presence of adamantyl on the methylene bridge (in the case of symmetry of the spirocyclic fragment), methyl and ethyl substituents, or no substituents (in the case of asymmetry of the spirocyclic fragment) leads to the formation of exclusively [5,6]-open isomers (homofullerenes); when the hydrocarbon radical (butyl and nonyl radical) is extended on the methylene bridge of the asymmetric spirocyclic fragment, only [6,6]-closed isomers (methanofullerenes) are formed. All homofullerenes obtained in this work do not isomerize into the corresponding methanofullerenes under thermal conditions (180°C, 100 hours). Homofullerenes containing an adamantyl radical (in the case of symmetry of the spirocyclic fragment) or not containing substituents (in the case of asymmetry of the spirocyclic fragment) on the methylene bridge do not isomerize into the corresponding methanofullerenes under the influence of ultrasound (room temperature, 5 hours). For the first time, sonochemical isomerization of spirohomofullerenes containing electron-donating methyl and ethyl groups on the methylene bridge into methanofullerenes was carried out under mild conditions (1.5 hours, toluene, room temperature, air). Atmospheric oxygen does not affect the isomerization reaction. The presence of CCl<sub>4</sub>, which forms CCl<sub>3</sub><sup>●</sup> radicals during sonolysis, suppresses isomerization reactions, which indicates the participation of radical particles in the rearrangement process. A probable mechanism for the structural rearrangement of homofullerenes into methanofullerenes under the action of ultrasound is proposed.

The ability to achieve a series of solid-state [2 + 2] cycloaddition reactions within related hydrogen-bonded co-crystals is reported. These multicomponent molecular solids contain either trans-1,2-bis(3-pyridyl)ethylene (3,3-BPE) or trans-1,2-bis(2-pyridyl)ethylene (2,2-BPE) as the reactant, along with one of two chlorinated anilines that behave as a template, namely 2,3,5,6-tetrachloroaniline (C6H3Cl4N) or 2,4,6-trichloroaniline (C6H4Cl3N). For each of the four unique organic solids, the co-crystallization process yields a three-component hydrogen-bonded assembly with a formula of either 2(C6H3Cl4N)·(3,3-BPE), 2(C6H4Cl3N)·(3,3-BPE), 2(C6H3Cl4N)·(2,2-BPE), or 2(C6H4Cl3N)·(2,2-BPE). In all co-crystals, these anilines template up to a quantitative yield for the photoreaction since they are able to engage in both N-H···N hydrogen bonds and homogeneous face-to-face π–π stacking interactions, which position the ethylene groups within the different reactant molecules in a suitable location to photoreact. These results complete the series for the remaining symmetric bipyridine-based reactants to undergo a solid-state [2 + 2] cycloaddition reaction utilizing these chlorinated anilines. This work expands and illustrates the potential for these chlorinated anilines to serve as reliable molecular templates that crystal engineers can utilize to control the organic solid state and achieve photoreactions.

The formation of a photoreactive cocrystal based upon 1,2-diiodoperchlorobenzene (1,2-C6I2Cl4) and trans-1,2-bis(pyridin-4-yl)ethylene (BPE) has been achieved. The resulting cocrystal, 2(1,2-C6I2Cl4)·(BPE) or C6Cl4I2·0.5C12H10N2, comprises planar sheets of the components held together by the combination of I...N halogen bonds and halogen-halogen contacts. Notably, the 1,2-C6I2Cl4 molecules π-stack in a homogeneous and face-to-face orientation that results in an infinite column of the halogen-bond donor. As a consequence of this stacking arrangement and I...N halogen bonds, molecules of BPE also stack in this type of pattern. In particular, neighbouring ethylene groups in BPE are found to be parallel and within the accepted distance for a photoreaction. Upon exposure to ultraviolet light, the cocrystal undergoes a solid-state [2 + 2] cycloaddition reaction that produces rctt-tetrakis(pyridin-4-yl)cyclobutane (TPCB) with an overall yield of 89%. A solvent-free approach utilizing dry vortex grinding of the components also resulted in a photoreactive material with a similar yield.

A quantum mechanistic insight into the chemo- and regio-selective [3 + 2]-cycloaddition reaction of aryl hetaryl thioketones with diazoalkanes and nitrile oxide derivatives

Polar [4 + 2 +] Diels—Alder cycloaddition to nitrilium and immonium ions in the gas phase: Applications of multiple stage mass spectrometry in a pentaquadrupole instrument

Synthesis and reactions of dimolybdenum(II,II), diruthenium(II,III) and dicopper(II,II) complexes containing unsaturated aliphatic carboxylate bridging ligands: X-ray crystal structure of [Ru 2(μ-O 2C(CH 3)Cz.dbnd&2;CH 2) 4Cl

A strategy was developed to construct dihydropyran and multifunctional cyclopentene derivatives from the same starting materials by using different phosphine catalysts. By exploiting the different nucleophilicities of the phosphine catalysts, the γ‐substituted allenoates selectively acted as C3 or C2 synthons. Under the catalysis of different organophosphine catalysts, the domino reaction proceeded smoothly with broad substrate tolerance and excellent total yields. The results suggest that the ethyl group of the γ‐substituted allenoates played a key role in the domino reaction.