Poly(ethylene glycol) (400) as superior solvent medium against ionic liquids for catalytic hydrogenations with PtO2

Adams' catalyst in poly(ethylene glycol) (PEG) (400) has been found to be a superior solvent over the ionic liquids by severalfold in promoting the hydrogenation of various functional groups. Both the catalyst and PEG were recycled efficiently over 10 runs without loss of activity, and substrate cross contamination was not observed despite a change in the substrate four times.     

Identification of chromium and nickel sites in zinc phosphate glasses

Optical and EPR investigations of chromium and nickel doped zinc phosphate glasses are carried out at room temperature to evaluate crystal field, spin-Hamiltonian and bonding parameters. For Cr³⁺ ion, the site symmetry is ascribed to a distorted octahedron, whereas the Ni²⁺ ion is located in a near octahedral site. In addition, the bonding parameters suggest covalent nature for Cr³⁺ and a moderate covalent nature for Ni²⁺ in the zinc phosphate glasses.     

Pd/ligand-free synthesis of thienopyranones via Cu-catalyzed coupling-cyclization in PEG 400 under ultrasound

A greener and practical synthesis of 5-substituted thieno[2,3-c]pyran-7-ones has been achieved via Cu-catalyzed coupling-cyclization of 3-iodothiophene-2-carboxylic acid with terminal alkynes in the presence of K₂CO₃ in PEG 400 under ultrasound irradiation. A range of thienopyranone derivatives were synthesized by using this inexpensive and Pd- and ligand-free methodology.     

Tantalum(V) Chloride–Silica Gel: An Efficient Catalyst for Conversion of Carbonyl Compounds to 1,3‐Oxathiolanes

A variety of carbonyl compounds can be easily converted to the corresponding 1,3‐oxathiolanes in the presence of a catalytic amount of tantalum(V) chloride [TaCl₅] on silica gel in dichloromethane. Mild reaction conditions, efficiency, high yields, operational simplicity, and only 2.5 mol% of TaCl₅ catalyst are some of the major advantages of the procedure.     

CAAC‐Based Thiele and Schlenk Hydrocarbons

Diradicals have been of tremendous interest for over a century ever since the first reports of p‐ and m‐phenylene‐bridged diphenylmethylradicals in 1904 by Thiele and 1915 by Schlenk. Reported here are the first examples of cyclic(alkyl)(amino)carbene (CAAC) analogues of Thiele's hydrocarbon, a Kekulé diradical, and Schlenk's hydrocarbon, a non‐Kekulé diradical, without using CAAC as a precursor. The CAAC analogue of Thiele's hydrocarbon has a singlet ground state, whereas the CAAC analogue of Schlenk's hydrocarbon contains two unpaired electrons. The latter forms a dimer, by an intermolecular double head‐to‐tail dimerization. This straightforward synthetic methodology is modular and can be extended for the generation of redox‐active organic compounds.     

The thermal C2-C6/[2 + 2] cyclisation of enyne-allenes: reversible diradical formation

New enyne-allenes, structurally designed toward the thermal C(2)-C(6)/[2 + 2] cyclisation mode, were prepared and characterised, one of them even by X-ray crystallography. The mechanism of their transformation to formal [2 + 2] cycloadducts was interrogated by trapping experiments and DFT computations. The results support a stepwise mechanism that involves the reversible formation of the C(2)-C(6) diradical intermediate.     

Reactions of in situ generated hydrated organotin cations with chelating O,O- or O,N-ligands: a possible structure-directing influence of the organic substituent on tin

The reaction of [n-Bu(2)SnO](n) with 1,5-naphthalenedisulfonic acid tetrahydrate in a 1:1 stoichiometry followed by reaction with 2,2'-bipyridine-N,N'-dioxide (BPDO-I) afforded a 1D-coordination polymer [n-Bu(2)Sn(BPDO-I)(1,5-C(10)H(6)(SO(3))(2))](n) (1) where the disulfonate ligand acts as a bridging ligand between two tin centers. An analogous reaction involving [Ph(2)SnO](n) afforded a trihydrated O,O'-chelated diorganotin cation [{Ph(2)Sn(BPDO-I)(H(2)O)(3)}(2+)][C(10)H(6)(SO(3)(-))(2)]·2CH(3)OH (2·2CH(3)OH). Utilizing two equivalents of BPDO-I in this reaction resulted in the ionic complex [{Ph(2)Sn(BPDO-I)(2)(H(2)O)}(2+)][C(10)H(6)(SO(3)(-))(2)]·3H(2)O (3·3H(2)O). In 2 and 3 the sulfonate ligands are not present in the coordination sphere of tin. Reaction of [n-Bu(2)SnO](n) and 1,5-naphthalenedisulfonic acid tetrahydrate, followed by reaction with [bis(diphenylphosphoryl)methane (DPPOM)] resulted in the formation of, [{n-Bu(2)Sn(DPPOM)(2)(H(2)O)(1,5-C(10)H(6)(SO(3))(SO(3)(-))}]·H(2)O (4·H(2)O). Of the two coordinating groups present in DPPOM, only one P=O group is coordinated to the tin atom. The remaining P=O motif is free and is involved in intramolecular H-bonding with the tin-bound water molecule. Using [Ph(2)SnO](n) instead of [n-Bu(2)SnO](n) afforded the ionic complex [{Ph(2)Sn(DPPOM)(2)}(2+){1,5-C(10)H(6)(SO(3)(-))(2)}] (5) where the DPPOM functions as a chelating ligand. The reaction of [n-Bu(2)SnO](n) with 1,5-naphthalenedisulfonic acid tetrahydrate followed by addition of one equivalent of 8-hydroxyquinoline (8-HQ) in presence of triethylamine afforded the neutral dinuclear complex, [(H(2)O)(8-Q)n-Bu(2)Sn(μ-1,5-C(10)H(6)(SO(3))(2))n-Bu(2)Sn(8-Q)(H(2)O)] (6) where the two tin atoms are bridged by the disulfonate ligand. Compounds 1-6 are thermally stable as shown by their thermogravimetric analyses.     

Total synthesis of pyrrolidine alkaloid, Radicamine-B via Stille coupling

Total synthesis of (−) Radicamine-B is achieved in eight steps from (R)-(+)-Garner aldehyde in a stereoflexible manner involving Stille coupling and one-pot domino epoxidation-pyrrolidine formation as key steps.