The Cyclization Reactions of Lawesson''''s Reagent with Bifunctional Substrates

2,4-Bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane-2,4-d,common1yknoWnaSLawesson'sreagent(LR),isnotonlythethiatingagentfordiversecarbonylcomPounds'-',butalsoundergoesring-closurereactionswithtWofunctionalgroupstogivephosphorusheterocycleswhichcontalnthe4-methoXyPhenylphosphonothioylienemoiety.Theseheterocycliccompoundsareofpotentialinterestasherbicides,insecticidesandfungicides".Inthebifunctionalsysteminwhichthesubstraesarelocatedl,2orl,3toeachother,theopportUnityexiStsforring-closurerea…     

Reactions of S-Silyl Esters of Tetracoordinated Phosphorus Thioacids with Acetals and Ortho Esters

The reactions of S-trimethylsilyl esters of dithiophosphoric, diamidodithiophosphoric, aryldithiophosphonic, aryltrithiophosphonic, and arylamidodithiophosphonic acids with diethyl acetal of benzaldehyde and ortho formiate and acetate were studied. On the basis of these studies, new derivatives of tetracoordinated phosphorus thioacids were obtained.     

A Facile Preparation of Tebbe Reagent and its Subsequent Reactions

A facile preparation of Tebbe reagent (1) by reacting AlMe₃ solution with Cp₁TiCl₂ is reported. After complete removal of solvent and excess of AlMe₃, the crude Tebbe reagent could be used without purification to react with ketones in a Wittig-type manner.     

Kinetics of Arylsulfonation of Aminobenzoic Acids with m-and p-Nitrobenzenesulfonyl Chlorides in the System Water-2-Propanol

The concentrations of the uncharged and anionic forms of m- and p-aminobenzoic acids participating in arylsulfonation of the acids with m- and p-nitrobenzenesulfonyl chlorides in the system water-2-propanol at 298 K at various water contents and pHs were estimated. The resulting data were used to estimate the rate constants for the reactions of the above forms with nitrobenzenesulfonyl chlorides, based on experimental kinetic data.     

Fluorine-containing Vinyl Ethers: I. Reactions with Carboxylic Acids

Polyfluoroalkyl vinyl ethers take up aliphatic and aromatic carboxylic acids in the presence of 0.2-5 wt% of trifluoroacetic acid at 55-105°C to give fluorine-containing hemiacetals in 60-100% yields.     

Coupling Reactions of Anhydro-Aldose Tosylhydrazones with Boronic Acids

A catalyst-free coupling reaction between O-peracetylated, O-perbenzoylated, O-permethylated, and O-permethoxymethylated 2,6-anhydro-aldose tosylhydrazones (C-(β-d-glycopyranosyl)formaldehyde tosylhydrazones) and aromatic boronic acids is reported. The base-promoted reaction is operationally simple and exhibits a broad substrate scope. The main products in most of the transformations were open-chain 1-C-aryl-hept-1-enitol type compounds while the expected β-d-glycopyranosylmethyl arenes (benzyl C-glycosides) were formed in subordinate yields only. A mechanistic rationale is provided to explain how a complex substrate may change the well-established course of the reaction.     

Reactions of 1-Germatranol Hydrate with Dicarboxylic Acids

Russian Journal of General Chemistry - The reactions of 1-germatranol hydrate with malonic, succinic, maleic, cork, sebacic acids, and bistrimethylsilyl ester of succinic acid, and also of...     

Reactions of Unsaturated Phosphonic Acids with 2-Aminopyridine

Abstract

Different unsaturated phosphonic acids of the general formula (R=C1, OCH₃, OH, NMe₂, C₆H₅; R′=C1, OCH₃, H, NMe₂) have been prepared starting from propargyl alcohol. Reaction of chlorophosphonic acids with 2-amino-pyridine yields phosphoramidates, which in the next step undergo a base-catalyzed cyclization by addition of the ring nitrogen across the unsaturated bond, leading to the unstable derivative 1. In the case of the allenic phosphonic acid in which R=R′=NMe₂, the NH₂ group of 2-aminopyridine adds first to the allenic system yielding an enamine, which on heating cyclizes to give a new phosphorus-nitrogen heterocyclic system 2.     

Reactions of Acetylenic Hydrocarbons with Various CH Acids

Russian Journal of Organic Chemistry -     

二氟沙星激发态氧化损伤氨基酸和脱氧鸟苷酸的激光光解研究

The reactions of triplet-state difloxacin (DFX) with various amino acids and deoxyguanylic acid in aqueous media were studied using laser flash photolysis. Tryptophan, tyrosine, cysteine, and 2'-deoxyguanosine-5'-monophosphate (dGMP) were found to completely quench the triplet state of DFX in aqueous solution, the corresponding second-order rate constants being 1.97×10⁸, 1.48×10⁸, 1.72×10⁸, and 6.92×10⁷ dm³·mol^－1·s^－1. The quenching mechanism involves electron transfer to the photoexcited triplet state of DFX from the tryptophan, tyrosine, cysteine, and dGMP moieties, followed by fast protonation of the resulting DFX anion radical.     

Reactions of Phenols with Lewis Acids: XX. Tautomerism of Naphthols

Thermodynamic parameters of tautomeric transformations of naphthols and their derivatives were estimated on the basis of experimental data and quantum-chemical calculations.     

测定手性有机酸对映体纯度的新试剂

用NMR技术测定微量手性化合物的对映体纯度,已有多种方法。其中,加手性镧化物位移试剂法适用面最广,但对有机酸,结果常不理想。另一种使用较广的方法是加手性试剂,将样品中两对映体转变成非对映异构体,然后比较非对映基因NMR信号的强度,确定原样品中对映体的组成比例。国外已出售的手性试     

A Spray Reagent for Identification of Amino Acids on Thin-Layer Chromatography Plates

JPC – Journal of Planar Chromatography – Modern TLC -     

A ChemiluminesClent Precolumn Labelling Reagent for High-Performance Liquid Chromatography of Amino Acids

Abstract

A chemiluminescent tag for precolumn derivatization of amino acids has been developed. The tag, 4-isocyanatophthalhydrazide, couples with 17 amino acids tested, including proline and hydroxyproline, in less than ten minutes. Twelve derivatized amino acids have been separated and detected with an average detection limit of 10 femptomoles per 20 μL injection.     

A New Reagent for Identification of Amino Acids on Thin-Layer Chromatography Plates

JPC – Journal of Planar Chromatography – Modern TLC -     

Ligand-free Suzuki-Miyaura Cross-Coupling Reactions of Aryltriazenes with Arylboronic Acids

The boron trifluoride induced Suzuki‐Miyaura cross‐coupling of aryltriazenes with arylboronic acids catalyzed by Pd(OAc)₂ without added ligands has been achieved for the first time. The reactions performed at room temperature under an argon atmosphere give biaryls in good to excellent yields. It is noteworthy that the reactions were conducted under mild and ligand‐free conditions.