A dynamic open framework exhibiting guest- and/or temperature-induced bicycle-pedal motion in single-crystal to single-crystal transformation

A ligand bis(4-imidazol-1-yl-phenyl)diazene (azim) incorporating an azo moiety at the center and two imidazole groups at the terminals forms two coordination polymers {[Co(azim)(2)(DMF)(2)]·(ClO(4))(2)·2DMF}(n) (1) and {[Cd(azim)(2)(DMF)(2)]·(ClO(4))(2)·2DMF}(n) (2) (DMF = N,N'-dimethylformamide) at room temperature. Both 1 and 2 are isostructural with rhombic two-dimensional sheets stacking in ABAB... fashion resulting in large voids that contain DMF and ClO(4)ˉ as guests. In 1, the azo groups and phenyl rings are disordered over two positions and as in usual cases, the pedal motion cannot be discerned. Upon heating, 1 turns amorphous. In the case of 2, however, heat treatment does not lead to loss of crystallinity. Thus, when a crystal of 2 (mother crystal) is heated slowly, it causes substantial movement or escape of both metal-bound and lattice DMF besides movement of ClO(4)ˉ anions to give daughter crystals 2a, 2b, and 2c without losing crystallinity (single-crystal to single-crystal (SC-SC) transformation). Most interestingly, the X-ray structures of 2 and its daughter products reveal stepwise reversible bicycle-pedal or crankshaft motion of the azo group. When a crystal of 2c is kept in DMF for 10 h, crystal 2' is formed whose structure is similar to that of 2 with slight changes in the bond distances and angles. Also, crystals of 2 are converted to 3 and 4 upon being kept in acetone or DEF (DEF = N,N'-diethylformamide), respectively, for 10 h at ambient temperature in SC-SC transformation. In 3, each lattice DMF molecule is replaced by an acetone molecule, leaving the two coordinated DMF molecules intact. However, in 4, all lattice and coordinated DMF molecules are replaced by equal number of DEF molecules. Both in 3 and 4, the azo moieties show bicycle-pedal motion. Thus, bicycle-pedal motion that normally cannot be observed is shown here to be triggered by heat as well as guest molecules in SC-SC fashion.     

Greener approach toward the generation of dimedone derivatives

The use of dimedone in green chemistry has been described for the synthesis of selective heterocyclic motifs which are both pharmacologically and industrially important. The objective of this review is to summarize some of the selected recent advances of dimedone in the synthesis of organic compounds utilizing green chemistry procedures.     

Condensed cyclic and bridged-ring systems : part 12: A novel synthetic route to 4-p-methoxyphenyl-bicyclo[ 2.2.2 ]octan-2-ones and some bicyclo [ 3.2.1 ] octane derivatives by acid-catalyzed intramolecula

The efficacy of a new acid-catalyzed intramolecular C-alkylation has been demonstrated by the synthesis of 1-methyl-4-$\text{p}$-methoxyphenylbicyclo [2.2.2] octan-2-one ($\text{5}$) and 4-$\text{p}$-methoxyphenylbicyclo [2.2.2] octan-2-one ($\text{6}$) from easily accessible starting materials. The carbinol $\text{20}$, derived from $\text{5}$, undergoes facile rearrangement leading to 1-$\text{p}$-methoxyphenyl-4-methyl bicyclo [3.2.1] oct-3-ene ($\text{22}$), which has been transformed to $\text{endo}$-1-$\text{p}$-methoxyphenyl-4-methylbicyclo [3.2.1] octan-3-one ($\text{25}$).     

Polymeric catalysts. IX. Cobalt complexes of polyureas based on bipyridine pyridine and crown ether for aldol condensation

We report herein studies of Co(OAc)₂ and related transition metal compounds which serve as catalysts for aldol condensations when complexed with bipyridine, triphenyl phosphine, and crown ether. A comparison has been made with polymeric complexes of cobalt(II), which serve the same purpose. Cobalt complexes of built-in polyureas based on bipyridine and crown ether as well as those immobilized to polystyrene by triphenylphosphine and poly(4-vinyl pyridine) are also reported.     

Versatile and facile synthesis of diverse semisynthetic tetracycline derivatives via Pd-catalyzed reactions

A diverse collection of tetracycline derivatives has been synthesized utilizing Heck, Suzuki, and other palladium-coupling reactions via tetracycline arenediazonium and iodoarene salts. Large numbers of tetracyclines are now possible via these reactions, including numerous upper periphery derivatives of doxycycline, minocycline, sancycline, and methacycline modified at positions C7, C9, and C6-C13 on the tetracycline naphthacene ring. Application of palladium-coupling reactions to the tetracyclines has yielded new tetracycline classes with differing structural attributes, greatly increasing the structural diversity of this family of antibiotics, one of the last of the early antibiotic families to be expanded by organic and medicinal chemistry.     

Simultaneous bioanalysis and pharmacokinetic interaction study of acebrophylline,levocetirizine and pranlukast in Sprague–Dawley rats

The combination of acebrophylline (ABP), levocetirizine (LCZ) and pranlukast (PRN) is used to treat allergic rhinitis, asthma, hay‐fever and other conditions where patients experience difficulty in breathing. This study was carried out with the aim of developing and validating a reverse‐phase high‐performance liquid chromatographic bioanalytical method to simultaneously quantitate ABP, LCZ and PRN in rat plasma. The objective also includes determination of the pharmacokinetic interaction of these three drugs after administration via the oral route after individual and combination treatment in rat. Optimum resolution between the analytes was observed with a C₁₈ Kinetex column (250 mm × 4.6 mm × 5 μm). The chromatography was performed in a gradient elution mode with a 1 mL/min flow rate. The calibration curves were linear over the concentration range of 100–1600 ng/mL. The intra‐ and inter‐day precision and accuracy were found to be within acceptable limits as specified in US Food and Drug Administration guideline for bioanalytical method validation. The analytes were stable on the bench‐top (8 h), after three freeze–thaw cycles, in the autosampler (8 h) and as a dry extract (?80°C for 48 h). The statistical results of the pharmacokinetic study in Sprague–Dawley rats showed a significant change in pharmacokinetic parameters for PRN upon co‐administration of the three drugs.     

A Self-Healing Metal–Organic Hydrogel for an All-Solid Flexible Supercapacitor

A zinc containing metal–organic gel (Zn-MOG) with embedded free ions, which exhibits self-healing properties, has been synthesized for application in supercapacitors. The activated carbon-based flexible supercapacitor device with the MOG electrolyte has a broad potential window of 2.1 V, with high retention of specific capacitance compared to the traditional polyvinyl alcohol (PVA)-based gel. The Zn-MOG does not require an additional electrolyte. The sodium and sulphate ions embedded in the MOG are sufficient enough for the charge storage.