Thiocarbamate method

Hydroxythiazoles give 2-chIorothiazole derivatives almost quantitatively upon treatment with phosphorus oxychloride (221, 229, 428). This constitutes a convenient synthesis method for these compounds when the conversion of 2-aminothiazoles to 2-chlorothiazole derivatives fails. Esters of thiocarbamic acid or thiourethanes also react with a-halocarbonyl compounds to give the corresponding 2-alkoxythiazoles (50, 68, 209, 272). 

The toxic nature of mercury and its compounds has caused concern over environmental pollution, and governmental agencies have imposed severe restrictions on release of mercury compounds to waterways and the air (see Mercury). Methods of precipitation and agglomeration of mercurial wastes from process water have been developed. These methods generally depend on the formation of relatively insoluble compounds such as mercury sulfides, oxides, and thiocarbamates. MetaUic mercury is invariably formed as a by-product. The use of coprecipitants, which adsorb mercury on their surfaces facihtating removal, is frequent. 

Because of the higher reaction rate, 7V(3)-alkylimidazolium-A ( 1 )-carboxylates or thiocarboxylates have often been used for the synthesis of carbamates and thiocarbamates by the azolide method instead of imidazole-iV-carboxylates. 

Food Wet oxidation with sulfuric acid, complexation with ammonium tetramethylenedi-thiocarbamate followed by extraction with methyl butyl ketone AAS 20 pg/kg No data lARC 1986 (Method 17)... 

Janssen144-146 has successfully used a method resembling the co-technique (self-consistence within the HMO framework) to study the spectral properties of derivatives of thiocarbamic acid and thiourea these compounds lie outside the scope of this review, however. The possibility of using the HMO method to correlate excitation energies of the first (usually intense) bands of various classes of heterocyclic compounds has been investigated see, e.g., refs. 15,17, and 160. The... 

Alkylthiocarbamate or thiocarbamate herbicides have been determined by various analytical methods, e.g., UV spectrometry, thin-layer chromatography, IR spectrometry, and gas chromatography. 

Yu, K., J. Krol, and M. Balogh (2003). A fully automated LC/MS method development and quantification protocol targeting 52 carbamates, thiocarbamates, and phenylureas. Anal. Chem., 75(16) 4103—4112. 

An alternative method for the synthesis of different dextran conjugates with fluorescent dyes is the reaction of a water-soluble amino dextran with the succinimidyl ester of the corresponding dye [360]. The amide linkage is more stable than the corresponding thiocarbamate formed with isothiocyanates. This method is displayed schematically in Fig. 54 for the preparation of 5- (and 6-) carboxynaphthofluorescein-labelled dextran from amino dextran (Fig. 47, [361,362]). 

Other base catalyzed methods for N-carboxylation of amines and hydrazines using CO2 and CS2 to generate the corresponding carbamate or thiocarbamate, respectively, are provided (1). Urea derivatives of Step 1 have also been prepared and are described (2). 

Coupling of a benzoic acid derivative under basic conditions is achieved with alkyl iodides," alkyl chlorides,dimethyl sulfate, or (l,1-dihydroperfluoroalkyl)phenyliodonium triflates. Common bases used arc potassium carbonate or sodium hydroxide (with phase-transfer catalyst). " Again, employing acid chlorides " - or anhydrides, " is the method of choice. The reaction can be performed without further activation, " " but in most cases the transformation takes place in the presence of the usual bases, triethylamine - " or pyridine " " " " " [in some cases 4-(dimethylamino)pyridine is added " ]. In a similar manner carbamates. thiocarbamates, " or thiocarbonates are synthesized. Perfluoropropcn-2-ol... 

A related procedure involves reduction of thiocarbonates or thiocarbamates of primary or secondary alcohols. The alcohols need not be hindered in this case. This ilcoxygcnation procedure is more convenient than many other existing methods and... 

A more efficient method to access single enantiomer thiols and sulfides has been developed using a palladium(0)-catalyzed rearrangement of 0-ally lie thiocarbamates (eq 11). ... 

Miyashita, Y, Ohsako, H., Takayama, C. and Sasaki, S. (1992). Multivariate Structure-Activity Relationships Analysis of Fungicidal and Herbicidal Thiocarbamates Using Partial Least Squares Method. Quant.Struct.-Act.Relat, 11,17-22. 

Improved preparative methods are reported for XPF2(NCO), X = O or S, using the corresponding chloride and silver cyanate at low temperature 300 the oxygen compound gives the expected carbamates and thiocarbamates on treatment with, respectively, alcohols and thiols. 

S. (1992) Multivariate structure-activity relationships analysis of fungicidal and herbiddal thiocarbamates using partial least squares method. Quant. Struct. -Act. Relat., 11, 17—22. 

Immunochemical methods are rapidly gaining acceptance as analytical techniques for pesticide residue analysis. Unlike most quantitative methods for measuring pesticides, they are simple, rapid, precise, cost effective, and adaptable to laboratory or field situations. The technique centers around the development of an antibody for the pesticide or environmental contaminant of interest. The work hinges on the synthesis of a hapten which contains the functional groups necessary for recognition by the antibody. Once this aspect is complete, immunochemical detection methods may take many forms. The enzyme-linked immunosorbent assay (ELISA) is one form that has been found useful in residue applications. This technique will be illustrated by examples from this laboratory, particularly molinate, a thiocarbamate herbicide used in rice culture. Immunoassay development will be traced from hapten synthesis to validation and field testing of the final assay. 

According to Riemschneider and Lorenz (1953) the respective chloroformic acid thiolester is prepared in the first step from metal mercaptide and phosgene this then reacts with the respective amine in the presence of alkali. The following example reaction scheme shows this method for S-ethyl N,N-dipropyl-thiocarbamate ... 

The addition of alcohols to carbohydrate isothiocyanates is a general method for the preparation of linear TV-sugar, O-alkyl thiocarbamates. This reaction is frequently used as a tool for structure confirmation.34,53,54 It requires the use of a large excess of the alcohol and reflux conditions to shift the reaction to the desired thiourethane. 

Replacement of halogen leads to formation of a C-S bond in many cases when alkyl or aryl halides are allowed to react with thiocarbonic acid derivatives such-as thiocarbamates, thiourea, dithiocarbamates, or xanthates. The importance of this method is due to the fact that the intermediates are readily converted into thiols by hydrolysis ... 

A variety of methods is available for preparation of O-esters of thiocarbamic acid ... 

LLE is a widely used technique among the official US-EPA methods for the preconcentration of pesticides in liquid samples. Nonpolar solvents for the LLE of pesticides include w-hexane, benzene, and ethyl acetate. Water-miscible solvents for this purpose include dichloromethane, methanol, acetonitrile, acetone, and water, which have been employed for the extraction of residues from high-moisture commodities. Mixed solvents have often been used to finely adjust the solvent strength. Thus, various carbamate pesticides were extracted from aqueous environmental samples with chloroform and determined by HPLC with a mean recovery of 71 Also, a method based on the extraction by sonication of solid samples placed in small columns with a low volume of ethyl acetate was developed for the extraction of thiocarbamates and other herbicides from soil with recoveries between 89 and 109%. ... 

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