Three chiral TADDOL (alpha,alpha,alpha,alpha '-tetraaryl-2,2-disubstituted 1,3-dioxolane-4,5-dimethanol) host molecules were employed to yield inclusion compounds with three isomers of methylcyclohexanones as guests. Although 4-methylcyclohexanone was not a chiral compound due to its internal symmetry, the other two isomers were racemates, and TADDOLs acted as potential resolving agents. The selectivity preference of the methylcyclohexanones for each host was established using solution nuclear magnetic resonance (NMR) spectroscopy, and the crystal structure of each host-guest compound was elucidated by single-crystal X-ray diffraction. The packing of the structures was analysed to explain the resulting resolution of the enantiomeric guests. The kinetics of decomposition were investigated for a representative TADDOL host.

The host compound, (4RS,5RS)-alpha,alpha,alpha',alpha'-tetra-p-tolyl-2,2-dimethyl-1,3-dioxolane-4,5-dimethanol (one of the TADDOL series of hosts), H, forms inclusion compounds with the six isomers of lutidine. The six structures derived from exposing the host, H, to each individual lutidine yielded similar structures, each exhibiting both intramolecular and intermolecular hydrogen bonds. The host was also exposed to pairs of lutidine isomers, and the resulting structures were analyzed by NMR. The sequence of selectivity found by NMR was 2,6 > 2,3 > 3,4 > 2,5 > 2,4 > 3,5-lutidine. In total, 21 structures were also analyzed by single- crystal X-ray diffraction; however, 5 of the structures from mixed lutidine pairs yielded highly disordered guest molecules that could not be modeled.

The host 9,10-[2-(9-hydroxy-9-fluorenyl)ethynyl] anthracene forms inclusion compounds with guests of pyridine and each of the picoline isomers. Pairwise competition with equimolar guests yielded crystals from both mother liquor and gels. The selectivity sequence resulted in the preference 4PIC > 3PIC > 2PIC > PYR. The kinetics of the desorption was analyzed by thermogravimetric analysis at variable temperatures and yielded activation energies varying from 13.2 to 16.7 k J mol(-1).

Herein, we describe a Cinchona-aminocatalyzed enantioselective α-hydrazination of an α-formyl amide for the production of protected quaternized serines as tertiary amides with ee's of generally >98% and ≤99% yields. The proposed TS model supported by density functional theory calculations involves a quinuclidinium ion Brønsted acid-assisted delivery of DtBAD, which occurs from the Re face of an H-bonded enaminone when using a 9S-cinchonamine catalyst, resulting in a hydrazide with the R-configuration as determined by X-ray analysis.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Lithocholic acid (LCA), one of the bile acids, is an efficient resolving agent of racemic phenylethylamine (PEA). It enclathrates the (S)-enantiomer down to the point where the mole fraction of the starting PEA liquid is 0.25 (S)-PEA. The structures of LCA(R)-(+)-PEA, the p salt, and LCA(S)-(-)-PEA, the n salt, have been elucidated, showing a notable difference in the relative locations of the guest PEA. Thermal analysis confirms that the LCA(S)-(-)-PEA structure is more stable.

Effluents from dyeing companies are a major polluter of the environment and water bodies. An estimated 70 tons of dye are generated globally each year, with more than one-third of this amount lost to the environment. To combat this issue, novel chemical compounds that are more efficient than existing ones are proposed. The soft synthetic approach was used to create [Ni(II)(Tpy) 2 ] MOF by reacting nickel nitrate with terpyridine (Tpy). The melting point of the MOF was determined, as well as the EA, HSM, TGA, PXRD, and X-ray crystallographic studies. The MOF results support the synthesis and coordination of the nickel (II) ion with the two Tpy molecules. In application, [Ni(II)(Tpy) 2 ] MOF was utilized to study the adsorption of Congo red. After 30 min of adsorption time, 1 g of [Ni(II)(Tpy) 2 ] MOF adsorbed a high amount of Congo red (138.26 mg) at [Formula: see text]C and a pH of 2. When compared to other isotherms, the Langmuir isotherm provided the best fit. Adsorption kinetics demonstrating electrostatic interaction between MOF and Congo red might be interpreted using the pseudo-second-order model. Density functional theory, Monte Carlo, and molecular dynamics simulations of the [Ni(II)(Tpy) 2 ] MOF over Congo red dye were computed. Density functional theory calculations provide insights into the reactivity of the novel [Ni(II)(Tpy) 2 ] MOF by furnishing chemical reactivity parameters that explain the interactions and adsorption processes between the [Ni(II)(Tpy) 2 ] MOF and Congo red. The quantum mechanical calculations provide data for an insightful understanding of the reactivity of the MOF and its high adsorption on the Congo red surface. Low band gaps (1.40 and 1.43 eV in the gas phase and water, respectively) obtained for the [Ni(II)(Tpy) 2 ] MOF suggest that this will make an extrinsic semiconductor with high electrical conductivity. Thus, it would readily interact with and be adsorbed on the Congo red.

The host compound 3,3′-bis(9-hydroxy-9-fluorenyl)-2–2′-binaphthyl, H1, has been employed to separate the six isomers of lutidine. Competition experiments showed that the preference for enclathration is in the sequence 3,4-LUT > 2,6-LUT > 2,3-LUT > 2,5-LUT > 2,4-LUT ≈ 3,5-LUT. The structures yielded results that agree with the 1H NMR analyses and with the thermal analysis. The effects of mixed hosts and vapor-phase competitions were briefly explored with two extra hosts, namely, 2,2′-bis(1-hydroxy-4,5-dihydro-2:3,6:7-dibenzocycloheptadien-1-yl)biphenyl (H2) or 3,3′-bis(di-p-tolylhydroxymethyl)-1,1′-binaphthyl (H3).

The host tetrakis (p-bromophenyl) ethylene forms inclusion compounds with 1,4-dioxane (chiral and racemic polymorph pair), cyclohexanone, dimethyl sulfoxide, and 3-pentanone. Their structures have been elucidated, and their nonbonded host-guest interactions have been analyzed. The thermal decomposition of the two Host center dot dioxane polymorphs yielded activation energies of 84 kJ.mol(-1) and 90 kJ.mol(-1). Guest exchange kinetics have been measured for the Host.dimethyl sulfoxide -> Host.acetone by differential scanning calorimetry and for the Host center dot cyclohexanone -> Host.3-pentanone by powder X-ray diffraction. The latter reaction is deceleratory and follows the decreasing area law, with a half-life of 42 min at 25 degrees C.

To explore the reactivity of the amine in oxahexacycloundecylamines and its effect on biological properties, two di-substituted N-benzamido-oxahexacycloundecylamine derivatives were synthesized. These compounds exhibited favourable biological properties in cytotoxicity, neuroprotection and calcium influx experiments. Steric and conformational factors are proposed to play an important role in the biological activities observed and X-ray crystallographic experiments were conducted in an attempt to gain insight into the structural features of these compounds. The propyl derivative, 3-(N-(8,11-oxahexacyclo [5.4.0.0(2,6).0(3,10).0(5,9)]-undecyl)benzamido)propyl benzoate, crystallizes in the monoclinic space group P2(1)/c with unit cell parameters: a = 6.2838(11) angstrom; b = 27.833(5) angstrom; c = 12.630(2) angstrom; beta = 95.457(3) angstrom; V = 2199.0(7) angstrom(3); Z = 4. The crystal structure revealed the existence of enantiomerism in the oxa-bridged polycycloundecylamine residue as a result of the nitrogen attached on either side of the oxa-bridge. This enantiomerism leads to molecular disorder of this residue in the crystal over two positions with refined site-occupancy factors (s.o.f.s) of x (= 0.774(2)) and 1-x (= 0.226(2)) corresponding to the respective enantiomeric residues with S- and R-configurations at partial atoms C18A and C18B in one molecule. For each two-fold disordered chiral atom, the presence of a centre of symmetry in the crystal generates the complementary pair of partial atoms within the crystal (s.o.f.s x and 1-x), thus rendering it racemic. DFT optimization studies on the two individual enantiomers corresponding to the two residues with S- and R-configurations at C18 within the disordered structure showed almost identical geometric parameters, indicating that the disorder observed is linked to the crystal packing. The ethyl derivative also showed similar geometric parameters to its propyl counterpart according to the DFT results. These findings correspond to earlier observations in that a number of steric and electronic factors could collectively be responsible for the biological activities observed for these compounds. (C) 2020 Elsevier B.V. All rights reserved.

The six xylenol (XYL) isomers can be separated by selective enclathration with the host 4,4-isopropylidene bisphenol, H1. This selectivity is enhanced by the use of a second, complementary host in combination with H1.

The structures of six inclusion compounds with the two isomers of methylnaphthalene and the Werner host Ni(NCS)(2)(4-phenylpyridine)(4) were determined. We report on the polymorphism and concomitant color change of the 1-methylnapthalene clathrates and the formation of a host dimer in a 2-methylnapthalene clathrate. We investigated the selectivity of the host toward an equimolar mixture of the naphthalene isomers and found that the selectivity varies from 87% 1-methylnapthalene to 54% 1-methylnapthalene with time and increasing evaporation of cosolvent, rendering a labile system.

A concise, asymmetric synthesis of the indole alkaloid (+)-tacamonine is reported involving a stereoselective radical cyclization of a 1-phenylsulfanyl tetrahydro-β-carboline bearing a pendant enoate ester side chain as a key step. In this process, a single stereocenter in the side chain allows for the formation of two stereocenters of the natural product in a highly diastereoselective fashion. Computational investigations of this key cyclization support the experimentally observed outcome and shed light on the factors impacting its stereoselectivity.

The Host compound 2,2ʹ bis(1-hydroxy-4,5-dihydro-2,3:6,7-dibenzocycloheptatrien-1-yl)-biphenyl, H1, has been employed to discriminate between all the pairs of lutidine isomers. The preference for guest enclathration follows the sequence 3,4-LUT>2,4-LUT≈3,5-LUT>2,5-LUT>2,3-LUT>2,6-LUT. This has been confirmed by guest-release endotherms measured by DSC. Four other diol host compounds, H2–H5, were tested on pairs of lutidine isomers which were poorly separated by H1.

Deoxycholic acid (DCA) includes all the isomers of methylcyclohexanones (MCH). Competition experiments showed that the preference is 2MCH > 3MCH > 4MCH confirmed by crystal structure analysis, NMR, and thermal analysis. DCA resolves 2MCH, enclathrating the S-conformer, whereas 3MCH remains unresolved. However, in competition experiments of rac-2MCH/rac-3MCH, both guests are resolved yielding S-conformers, suggesting that 2MCH has a templating effect on the final structures. The activation energies of desolvation of the clathrates with 2MCH and 3MCH are similar (∼74 kJ/mol) but significantly lower for 4MCH (∼48 kJ/mol).

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.