Thiol on silica as a ‘catch and release’ support for isocyanates to afford ureas

Silica-bound thiocarbamates were prepared by Curtius rearrangement of carboxylic acids in the presence of thiol on silica gel. The solid supported thiocarbamates were found to be stable isocyanate equivalents, which upon treatment with amines efficiently afforded di- and tri-substituted ureas. The urea products released from the catch and release support were, in the majority of cases, greater than 95% pure and required no further work up.     

Iron-promoted one-pot approach: Synthesis of isothiocyanates

Abstract

We have established a facile and versatile synthesis for the construction of isothiocyanates from their respective amines in the presence of an eco-friendly, inexpensive, easily available Iron catalyst under mild conditions. This reaction provides the target products through the formation of thiocarbamate salt as an intermediate. Both aromatic amines and aliphatic amines provided the respective target products in moderate to high yield under optimized reaction conditions. However, electron withdrawing substituents were difficult to give target product at room temperature, whereas, they obtained final products in good yield at moderate temperature. In addition, mechanistic studies were revealed that the synthetic route involved iron based subsequent reactions of addition and removal of sulfur.     

硒作用下苯胺和硫醇羰基化合成硫代氨基甲酸酯

报道了一种新颖且简易的合成硫代氨基甲酸酯的方法. 在硒作用下, 苯胺和硫醇的羰基化反应在室温常压条件下顺利进行, 大多数目标产物硫代氨基甲酸酯的收率从中等到较高. 硒在反应结束后可方便地回收并能循环使用.     

(英)硫代氨基甲酸酯和草酰胺酯的合成、表征及抑菌活性

为发现具有农业生物活性的先导化合物,本文以三聚光气和草酸二乙酯或乙基草酰氯为酰化试剂,在不同条件下合成了硫代氨基甲酸酯和草酰胺酯或草酰苯胺酯,所有目标化合物的结构都经过质谱、1H NMR和13C NMR表征。生物活性测试表明,硫代氨基甲酸酯1b和1f在浓度为6.25 mg/L时,表现出较好的体外抑菌活性,而草酰胺酯和草酰苯胺酯没有表现出任何农业生物活性。     

Thiobencarb Degradation by TiO2 Photocatalysis: Parameter and Reaction Pathway Investigations

The present study deals with the photocatalytic degradation of the thiocarbamate herbicide, thiobencarb (TBC), in the presence of TiO₂ particles and UV‐A (λ = 365 nm) radiation. Results show rapid and complete oxidation of TBC after 90 min, and slightly over 70% of TBC was mineralized after 32‐h treatment. Factors such as solution pH, TiO₂ dosage, and the presence of anions are found to influence the degradation rate. The establishment of the reaction pathway is made possible by a thorough analysis of the reaction mixture identifying the main intermediate products generated. Results suggest that possible transformation pathways may include hydroxylation, dealkylation and C—S bond cleavage processes. The possible degradation pathways are proposed and discussed on the basis of the evidence of oxidative intermediate formation.     

液相色谱-串联质谱法同时测定红茶和绿茶中7种硫代氨基甲酸酯类除草剂

建立了红茶和绿茶中7种硫代氨基甲酸酯类除草剂(禾草敌、克草敌、灭草敌、野麦畏、禾草丹、茵草敌和丁草敌)的高效液相色谱-串联质谱(LC-MS/MS)检测方法.样品制备后,取2.0 g样品,加6 mL水浸润1 h.然后加入2.5 g NaCl,并用20 mL乙腈分两次进行提取,提取液吹氮浓缩后过HLB柱,并用3 mL乙腈洗脱.洗脱液浓缩后用2.0 mL正己烷-丙酮(7∶ 3,V/V)溶解残渣,然后过Envi-Carb固相萃取柱,再用5 mL正己烷-丙酮洗脱,洗脱液浓缩后用乙腈-水(5∶ 5,V/V)定容.采用LC-MS/MS电喷雾电离,多反应监测模式对样品进行分析.以D_3-甲萘威为内标,测定7种硫代氨基甲酸酯除草剂的线性范围为0～200 μg/L,线性相关系数在0.9954～0.9988范围内,检出限在0.093～1.77 μg/L范围内.在添加浓度5～20 μg/kg范围内,7种硫代氨基甲酸酯除草剂的回收率均在77.3%～91.5%,相对标准偏差(RSD)小于15%.本方法被成功用于红茶和绿茶样品中硫代氨基甲酸酯除草剂的测定.     

Preparation and characterization of a new HPLC C18 reversed phase containing thiocarbamate groups

A HPLC stationary phase that possesses an internal thiocarbamate functional group is described. The new C18-thiocarbamate silane was synthesized by the reaction of a trifunctional alkoxysilane with a mercaptan. The silylant agent was bonded to silica (5 μm) and the new stationary phase was then endcapped. Surface characteristics of the packing before and after chemical modification with HMDS and TMCS were determined by different physico-chemical methods, such as elemental analysis and infrared and solid-state ¹³C and ²⁹Si nuclear magnetic resonance spectroscopies. Chromatographic properties of the C18-thiocarbamate silica were evaluated under reversed phase conditions by separation of four different test mixtures that including compounds from the Engelhardt, Tanaka, and Neue test mixtures. Chromatographic evaluations of the C18-thiocarbamate phase show promising results for the separation of basic analytes.     

Analysis of carbamate pesticides by micellar electrokinetic chromatography

Capillary elcctrophoresis (CE) was used for the qualitative and quantitative analysis of eleven compounds of the carbamate, thio-carhamate, and dithiocarbamate classes of pesticides. Micellar elec-trokinetic chromatography (MEKC) was employed for the separation of these substances. The analysis was performed using an uncoated fused silica column, in borate buffer containing SDS and 10% methanol at basic pH, and UV detection at 230 nm. The addition of methanol to the buffer increased the separation and affected intrinsic migration of analytes. The working standard solutions were prepared in acetonitrile/water 50:50. Although these compounds are structurally different, with a large spectrum of chemical properties, such as polarity and solubility, good separation and sensitivity were obtained. Moreover, good recovery of car-bamates was obtained from tap-water using a styrene-divinylben-zene polymer column with the solid phase extraction (SPE) technique.