One-Pot Synthesis of 1H-Benzimidazole Derivatives Using Thiamine Hydrochloride as a Reusable Organocatalyst

A simple and efficient one-pot synthesis of 1H-benzimidazole derivatives using thiamine hydrochloride (VB₁) as the organocatalyst from o-phenylenediamine and aldehyde in dimethylformamide is described. Compared to classical reaction conditions, this new method consistently has the advantages of excellent yields, metal-ion-free procedure, and good recovery and reusablity of catalyst.     

N-heterocyclic carbene (thiamine) promoted eco-friendly synthesis of quinoxalines under mild reaction conditions

Abstract

An efficient and convenient protocol of broad scope for the synthesis of quinoxaline by cyclization-oxidation of phenacyl bromide with equimolar amount of phenylenediamine at room temperature catalyzed by thiamine in the form of N-heterocyclic carbene (NHC). High efficiency, inexpensiveness, and non-toxicity are the interesting features of the catalyst, which make it eco-friendly and highly attractive.     

Indication Ion Square Wave Voltammetric Determination of Thiamine and Ascorbic Acid

Abstract

Cd²⁺ ion was used as an electrochemical indicator to detect V_B1 or Vc using square ware voltammetry (SWV) at a mercury film‐coated glassy carbon (GC) electrode. At pH=10 NH₃‐NH₄Cl buffer, a new cathodic peak was found at ?0.360 V (vs.SCE) by addition of thiamine, and the peak current of SWV was linear with the concentration of thiamine in the range of 1×10^?6 to 4×10^?3 M. On the other hand, the SWV peak current of Cd²⁺ at ?0.856 V linearly decreased with addition of ascorbic acid in the range of 6×10^?6～10^?3 M. The effects of interference, such as citric acid, DL‐malic acid, and calcium panlothenate, on thiamine or ascorbic acid determination were investigated. This method was successfully applied to the determination of thiamine or in pharmaceutical preparation.     

Performance of the Continuous Addition of Reagent Technique in Fluorimetric Reaction-Rate Methods. Determination of Thiamine at the Nanomolar Level

Abstract

The potential of the continuous addition of reagent (CAR) technique, developed for reactions on the millisecond time scale, in fluorimetric reaction-rate methods, is evaluated. The approach was applied to the classical fast reaction involving the oxidation of thiamine to fluorescent thiochrome effected by potassium ferricyanide in basic solutions. Practical problems associated with this system were readily avoided by using the CAR technique. Several kinetic methods have been developed for the determination of thiamine; all are very sentitive (detection limit, 2. 5x10^?9 M) compared to other fluorimetric equilibrium and reaction-rate methods and are suitable for routine analyses (sample throughput, 100 h^?1).     

钴-硫胺素-Triton X-100体系的荧光特性及其分析应用

在碱性介质中，钴与硫胺素反应产生荧光物质，表面活性剂 Ｔｒｉｔｏｎ Ｘ－１００对该反应具有敏化作用，据此建立了测定微量钻的荧光分析法，其荧光光谱的激发波长λｅｘ＝３７５ ｎｍ，发射波长 λｅｍ＝ ４４０ ｎｍ。在 ６．０ ×１０－８～ ２．４ × １０－７ｍｏｌ／Ｌ范围内荧光强度与钻离子的浓度呈良好线性关系。将其用于合金钢和维生素Ｂ１２针剂中微量钻的测定，取得了满意结果。并对发 光机理进行了探讨。     

Artificial Ribozyme Switches Containing Natural Riboswitch Aptamer Domains

RNA Lego : The use of natural riboswitch aptamers in synthetic RNA switches (see picture) should broaden the scope of artificial RNA regulators dramatically. It is shown that thiamine pyrophosphate (TPP) aptamers can be used in engineered devices as very sensitive switches of gene expression in unmodified organisms. The approach demonstrates that intrinsic metabolites can be utilized as external effectors of cellular functions.

     

Secondary Weak Interactions in the Crystal Structure of Thiamine Bromide

The x-ray crystal structure of thiamine bromide hydrate was studied. The crystals are monoclinic, a = 12.348, b = 24.852, c = 11.682 ,= 113.67°, Z = 4, space group P2 ₁ /c. The crystal structure is constructed of two crystallographically independent thiamine cations, bromide anions, and water molecules. The thiamine cations have the F-conformation. The structure contains intermolecular short contacts involving S and N atoms of the thiazole ring.