Nitrogen Ligand Complexes of Metal Chlorides as Effective Catalysts for the Highly Regio- and Chemoselective Silylation of Hydroxyl Groups with Hexamethyldisilazane (HMDS) at Room Temperature

Zn(bipy)₃Cl₂, Fe(bipy)Cl₃, and Fe(tpp)Cl are effective catalysts for silylation of hydroxy groups with HMDS at room temperature in dry CH₃CN. High selectivity is observed between primary and secondary hydroxy functional groups. This method absolutely discriminates other functional groups containing labile hydrogen atoms.     

Tetrakis (Pyridine)silver Dichromate Py4Ag2Cr207 - A Mild and Efficient Reagent for the Conversion of Benzylic and Allylic Alcohols to Their Corresponding Carbonyl Compounds

Tetrakis(pyridine)silver dichromate is prepared and used for the oxidation of benzylic and allylic alcohols in refluxing benzene in high yields.     

Convenient and Regioselective One‐Pot Solvent‐Free Synthesis of ß‐Hydroxyphosphonates

A simple, efficient, regioselective, and solvent‐free method has been developed for the synthesis of β‐hydroxyphosphonates from epoxides and triethyl phosphite using ZnCl₂ in high yields under mild conditions.     

Zirconyl triflate as an efficient and reusable catalyst for one-pot synthesis of 1-amidoalkyl-2-naphthols under solvent-free conditions

In the present work, the preparation of 1-amidoalkyl-2-naphthols via one-pot three-component condensation of amides, aldehydes, and β-naphthol in the presence of catalytic amounts of zirconyl triflate, as a highly efficient, low toxic, stable and non-hygroscopic catalyst under solvent-free conditions is reported. This low-cost procedure offers several other advantages such as short reaction times and good to excellent yields.     

Oxidation of Thiols to Their Disulfides with Bis Trinitratocerium (IV)l Chromate [Ce(NO3)312 CrO4 and Pyridinum Chlorochromate

Oxidation of thiophenols, benzyl thiol, and alkyl thiols with bis [trinitratocerium (IV)] chromate and pyridinum chlorochromate are investigated. Pyridinum chlorochromate is quite ineffective for the oxidative dimerization of alkyl thiols.     

Bis(2,2'-bipyridyl)copper(II) permanganate (BBCP): A mild and versatile oxidant in organic synthesis

The preparation of bis(2,2'-bipyridyl)copper(II) permanganate (BBCP) is described. The reagent converts alcohols to the corresponding carbonyl compounds, α-hydroxy ketones to diketones, hydroquinone to p-benzoquinone, and compounds with benzylic double bonds to benzaldehyde in high yield. Benzophenone oxime, acetophenone oxime and various benzaldoximes are converted to the corresponding carbonyl compounds, aromatic amines to azo compounds, and benzylamine to benzaldehyde, usually in high yields, under mild condition.     

Detection of nucleic acids in situ: novel oligonucleotide analogues for target-assembled DNA-mounted exciplexes

This research describes the effects of structural variation and medium effects for the novel split-oligonucleotide (tandem) probe systems for exciplex-based fluorescence detection of DNA. In this approach the detection system is split at a molecular level into signal-silent components, which must be assembled correctly into a specific 3-dimensional structure to ensure close proximity of the exciplex partners and the consequent exciplex fluorescence emission on excitation. The model system consists of two 8-mer oligonucleotides, complementary to adjacent sites of a 16-mer DNA target. Each probe oligonucleotide is equipped with functions able to form an exciplex on correct, contiguous hybridization. This study investigates the influence of a number of structural aspects (i.e. chemical structure and composition of exciplex partners, length and structure of linker groups, locations of exciplex partner attachment, as well as effects of media) on the performance of DNA-mounted exciplex systems. The extremely rigorous structural demands for exciplex formation and emission required careful structural design of linkers and partners for exciplex formation, which are here described. Certain organic solvents (especially trifluoroethanol) specifically favour emission of the DNA-mounted exciplexes, probably the net result of the particular duplex structure and specific solvation of the exciplex partners. The exciplexes formed emitted at approximately 480 nm with large Stokes shifts ( approximately 130-140 nm). Comparative studies with pyrene excimer systems were also carried out.     

KF/Al2O3: an efficient solid heterogeneous base catalyst in one-pot synthesis of benzimidazoles and bis-benzimidazoles at room temperature

Abstract  

KF/Al₂O₃ is an efficient solid heterogeneous base catalyst in the one-pot synthesis of 2-substituted benzimidazoles and 2,2′-disubstituted bis-benzimidazoles from 1,2-phenylenediamines or 3,3′-diaminobenzidines and acid chlorides, anhydrides, and esters at room temperature.