Thiocyanates esters

Condensation of 1 in acetone with silver or potassium thiocyanate, under mild conditions, results212,213 in the formation of the corresponding 1-thiocyanic ester which, on heating, readily rearranges to the 1-isothiocyanate isomer (see Section VI). 

The carbon resonance of the S-C=N group of thiocyanate esters absorbs over a narrow chemical shift range from 110-114 ppm compared to 111 - 126 ppm for the nitrile (R-C=N) group. The thiocyanate salts show a C=N resonance near 133 ppm in D20 solution. 

Treatment of alkyl halides with alkali thiocyanates leads to replacement of the halogen with formation of thiocyanic esters (organic thiocyanates). However, it is impossible to foretell whether thiocyanic esters or the isothiocyanic esters ( mustard oils ) will be products by this method but in all cases the latter is the more stable, so that thiocyanates can be converted into isothiocyanates by heat. 

There are also preparatively important methods for preparation of thiocyanic esters that start from dithiocyanogen, which behaves in its reactions as a pseudohalogen, so that it can add to olefinic double-bond systems and substitute aromatic compounds. Kaufmann362 and also Wood363 have reviewed the preparation of organic thiocyanates, which has been described previously (pages 203, 213 ) in the present volume. 

Thiocyanic esters can also be obtained by treating arene-364 or alkane-sulfenyl chlorides,365 including trichloromethanesulfenyl chloride,366 with potassium cyanide ... 

Disulfides are formed, with elimination of the cyano group, when the C-S bond of thiocyanic esters is cleaved by alkali 637-639 and sulfides are obtained,... 

Arabic acid, isothiocyanic esters (e.g., allyl isothiocyanate and methyl isothiocyanate), thiocyanic esters (e.g., ethyl thiocyanate and methyl thiocyanate), Cu+, Fe +, La +, HCl, acetate... 

The above-mentioned plants, as Brassicacea, contain mustard oil glucosides (glucosinolates, cf. 17.1.2.6.5) which, immediately after seed crushing, are hydrolyzed to esters of isothio-cyanic acid. The hydrolysis is dependent on seed moisture and is catalyzed by a thioglucosidase enzyme called myrosinase (EC 3.2.3.1). In the presence of the enzyme, some of the isocyanates are isomerized into thiocyanates (esters of normal thiocyanic acid or rhodanides) and, in part, are decomposed into nitrile compounds which do not contain sulfur. All these compounds are volatile and, when dissolved in oil, are hazardous to health and detrimental to oil flavor. Moreover, they interfere with hydrogenation of the oil by acting as Ni-catalyst poisons (cf. 14.4.2.2). Therefore, in the production of rapeseed oil, a dry conditioning step is used (without live steam) to... 

In 1902, Wheeler and Johnson (63) obtained 5-substituted rhodanines (54) by condensing substituted bromornalonic esters with postassium thiocyanate, then thiolacetic acid, the cydization resulting from an alkaline treatment. 

Compounds of type 184 were prepared similarly with R, = methyl and R2 = alkanoic esters (136, 229, 304) or carboxyethyl (4, 10, 13, 22, 220) (Table 11-27). Dichloroacetone reacts with ammonium thiocyanate, but... 

Nitrates Aluminum, BP, cyanides, esters, phosphorus, tin(II) chloride, sodium hypophos-phite, thiocyanates... 

In an analogous manner, DCPD reacts with alcohols and phenols to form ether derivatives, and with halogen acids, thiocyanic acid, and various carboxyhc acids to form esters. These esters are used as perfume components (67). Dicyclopentadiene alcohol and a number of the ethers, esters, and glycol adducts have been claimed as coal and ore flotation aids (68). 

Other functional groups that are easily differentiated are cyanide (5c =110-120) from isocyanide (5c = 135- 150), thiocyanate (5c =110-120) from isothiocyanate (5c = 125 - 140), cyanate (5c = 105- 120) from isocyanate (5c = 120- 135) and aliphatic C atoms which are bonded to different heteroatoms or substituents (Table 2.2). Thus ether-methoxy generally appears between 5c = 55 and 62, ester-methoxy at 5c = 52 N-methyl generally lies between 5c = 30 and 45 and. S-methyl at about 5c = 25. However, methyl signals at 5c = 20 may also arise from methyl groups attached to C=X or C=C double bonds, e.g. as in acetyl, C//j-CO-. 

The effect of a substituent may be substantially modified by fast, concurrent, reversible addition of the nucleophile to an electrophilic center in the substituent. Ortho- and para-CS.0 and pam-CN groups have been found by Miller and co-workers to have a much reduced activating effect on the displacement of halogen in 2-nitrohaloben-zenes with methoxide ion [reversible formation of hemiacetal (143) and imido ester anions (144)] than with azide ion (less interaction) or thiocyanate (little, if any, interaction). Formation of 0-acyl derivatives of 0x0 derivatives or of A-oxides, hydrogen bonding to these moieties, and ionization of substituents are other examples of reversible and often relatively complete modifications under reaction conditions. If the interaction is irreversible, such as hydrolysis of a... 

Alkyl halides or sulfuric or sulfonic esters can be heated with sodium or potassium thiocyanate to give alkyl thiocyanates, though the attack by the analogous cyanate ion (10-66) gives exclusive N-alkylation. Primary amines can be converted to thiocyanates by the Katritzky pyrylium-pyridinium method (pp. 447, 489). "... 

Thiolates, generated in situ by the action of ammonium tetra-thiomolybdate on alkyl halides, thiocyanates, and disulfides, undergo conjugate addition to a, (1-unsaturatcd esters, nitriles, and ketones in water under neutral conditions (Eq. 10. II).29 Conjugate addition of thiols was also carried out in a hydrophobic ionic liquid [bmim]PF6/water-solvent system (2 1) in the absence of any acid catalyst to afford the corresponding Michael adducts in high to quantitative yields with excellent 1,4-selectivity under mild and neutral conditions (Eq. 10.12). The use of ionic liquids helps to avoid the use of either acid or base catalysts... 

Lysine Acid anhydrides, succinimidyl esters, iso thiocyanates, trinitrobenzenesulfonic acid... 

The pairs of dyes more commonly used to generate FRET have been extensively reviewed [86-88] and their conjugation to different types of molecules has been facilitated by the incorporation of a range of reactive groups. Some examples are activated esters and iso thiocyanates for reaction with amino groups of proteins or peptides,... 

A-Thiazolyl a-amino acids 56 have been prepared. The preferred route to these compounds would utilise the Hantzsch synthesis, however in this case the in situ formation of the required thiourea derivatives of a-aminoacids 52 failed. A variety of isothiocyanate reagents were tried, with the result being either no reaction, decomposition or the corresponding thiohydantoin 53. A modified version of the Hantzsch synthesis was developed. If the bromoketone 54 is initially treated with sodium thiocyanate an a-thiocyanatoketone 55 is formed, subsequent addition of the amino acid ester 51 yields A-thiazolyl a-amino acids 56 <00T3161>. 

Metabolism of the 2,S -isomers proceeds sequentially hydroxylation at the phenoxy group, hydrolysis of the cyano group, and cleavage of the ester linkage (Coats et al. 1989). Fenvalerate and the IS-isomers yield two ester metabolites in feces from hydroxylation at the 4 - and 2 -phenoxy positions. Other significant metabolites were 3-phenoxybenzoic acid and its hydroxy derivatives from the alcohol moiety, 3-(4-chlorophenyl) isovaleric acid and its hydroxy derivatives from the acid moiety, and thiocyanate and carbon dioxide from the cyano moiety (Ohkawa et al. 1979). A slow elimination rate characterizes fenvalerate and other a-cyano pyrethroids when compared with... 

The efficiency of the extraction depends on the coordinating ability of the solvent, and on the acidity of the aqueous solution which determines the concentration of the metal complex. Coordinating ability follows the sequence ketones > esters > alcohols > ethers. Many metals can be extracted as fluoride, chloride, bromide, iodide or thiocyanate complexes. Table 4.5 shows how the extraction of some metals as their chloro complexes into diethyl ether varies with acid concentration. By controlling... 

Samarium enolates 60 can be easily prepared by reduction of ct-bromocarboxylic acid esters with SmT. These enolates mediated well-defined synthesis of star-shaped block co-polymers 61 (Scheme 21 ).32 32l Sml3 also mediated the formation of samarium enolates. Phenacyl thiocyanate 6233 and cr-haloketone 6434 are converted to samarium(lll) enolate intermediates 63 and 65, respectively, which undergo addition to benzaldehyde derivatives affording the corresponding oy i-unsaturatcd ketones as shown in Schemes 22 and 23. 

ABS AE AE/P AES AG AOS APEO APG AS BiAS BM c6(EO)3 CNPEC CTAS D DATS DCPEG DEEDMAC branched alkylbenzene sulfonate alcohol ethoxylate alcohol ethoxylate/propoxylate alkylether sulfate alkyl glucamide a-olefin sulfonate alkylphenol ethoxylate alkyl polyglucoside alkyl sulfate bismuth active substances alkyldimethylbenzyl ammonium triethylene glycol monohexyl ether carboxylated nonylphenoxy carboxylates cobalt thiocyanate active substances R2S10(o.5)2 dialkyl tetralinsulfonate dicarboxylated PEG ditallow ester of di(hydroxyethyl)dimethyl ammonium chloride... 

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