Aromatic thiocyanate

Agbalyan et al 9 recently employed this reaction in the synthesis of several 3,4-dihydroisoquinoline derivatives with unsaturated substituents in the 1-position. The Madrid group50 has shown that (with the exception of benzyl thiocyanate) aliphatic and aromatic thiocyanates yield 1-alkylthio- and l-arvlthio-3,4-dihydroisoquinolines as expected (cf. Table V). 

Cuprous thiocyanate, CuCNS.—The thiocyanate is produced by dissolving cuprous oxide or carbonate in thiocyanic acid, and by the interaction of solutions of potassium thiocyanate and a cupric salt in presence of a reducer, such as ferrous sulphate or sulphurous acid.2 It is a white substance, its solubility at 18° C. being 0 23 mg. in 1 litre of water.3 It dissolves in ammonium hydroxide and concentrated hydrochloric acid, and also in concentrated nitric acid with formation of cupric sulphate. It is employed in the preparation of aromatic thiocyanates.4... 

Thiocyanates. Thiocyanates are obtained in yields usually over 80% by reaction of sulfenyl chlorides with this silane in dry acetonitrile (1 hour, 25°). The advantage of this method is that isothiocyanates are not formed and that even aromatic thiocyanates are easily prepared. The paper reports that the most satisfactory method for preparation of sulfenyl chlorides is reaction of sulfuryl chloride with a thiol or disulfide (80-90% yield). 

Figure 11. Aromatic thiocyanate tubulin assembly inhibitors. DCBT (20) and WR85915 (21).

Although DCBT (20) is known to covalently modify mammalian tubulin with selectivity, the mechanism of action of aromatic thiocyanates against kinetoplastid parasites is unclear. WR85915 (21) is an interesting antileishmanial lead compound in its own right given its oral activity versus L. donovani in vivo. Such studies indicate that aromatic thiocyanates possess acceptable pharmacokinetic properties. Further work with aromatic thiocyanates may be useful in identifying compounds that selectively interact with parasite tubulin and interfere with the function of this critical protein in the cell. 

Fragmentation Dominant loss of NCS (Am 58). In contrast to aromatic thiocyanates, the loss of HCN (Am 27) or CS (Am 44) leads to very weak fragments only. 

Sulphur.—There is a rapid exchange of C-labelled cyanide ion with aromatic thiocyanates in acetonitrile solution, followed by the formation of an adduct (23), ... 

Ateya et al. tested thiosemicarbazide and Pevneva et al. examined pyrazo-lene derivatives both types of compounds worked well in HCI at low concentrations. Methylene Blue (3,9-bisdimethylamlnophenazothionium chloride) is another efficient inhibitor. Aliphatic and aromatic thiocyanates work well on steel in HCI. ° Here again, caution must be used when alloyed steels are cleaned as with many othar... 

Aromatic thiocyanates have also been prepared by the action of potassium thiocyanate or cuprous thiocyanate on diazonium salts. 

Solvent for Displacement Reactions. As the most polar of the common aprotic solvents, DMSO is a favored solvent for displacement reactions because of its high dielectric constant and because anions are less solvated in it (87). Rates for these reactions are sometimes a thousand times faster in DMSO than in alcohols. Suitable nucleophiles include acetyUde ion, alkoxide ion, hydroxide ion, azide ion, carbanions, carboxylate ions, cyanide ion, hahde ions, mercaptide ions, phenoxide ions, nitrite ions, and thiocyanate ions (31). Rates of displacement by amides or amines are also greater in DMSO than in alcohol or aqueous solutions. Dimethyl sulfoxide is used as the reaction solvent in the manufacture of high performance, polyaryl ether polymers by reaction of bis(4,4 -chlorophenyl) sulfone with the disodium salts of dihydroxyphenols, eg, bisphenol A or 4,4 -sulfonylbisphenol (88). These and related reactions are made more economical by efficient recycling of DMSO (89). Nucleophilic displacement of activated aromatic nitro groups with aryloxy anion in DMSO is a versatile and useful reaction for the synthesis of aromatic ethers and polyethers (90). 

Hydrazinopyridazines are easily formylated with formic acid or ethyl formate and acety-lated with acetic anhydride. A-Pyridazinylthiosemicarbazides are obtained from thiocyanates or alkyl- and aryl-isothiocyanates. Hydrazinopyridazines condense with aliphatic and aromatic aldehydes and ketones to give hydrazones. 

Aliphatic methyl ketones (CH3C(0)CH3) Simple aromatic nitro compounds (NO+CO) Straight-chain mercaptans Thiocyanates and isothiocyanates... 

It has also been argued10,40 that the second mechanism (rapid, reversible interconversion of II and IV) cannot be general. The basis for this contention is the fact that electrophilic catalysis is rare in nucleophilic aromatic substitution of non-heterocyclic substrates, an exception being the 2000-fold acceleration by thorium ion of the rate of reaction of 2,4-dinitrofluorobenzene with thiocyanate... 

Similarly, a high-density brine, useful as a drilling fluid for deep wells, is made corrosion resistant by adding an aliphatic or aromatic aldehyde and thiocyanates [817]. The aldehyde can be reacted with a primary amine before use. 

Another important click reaction is the cycloaddition of azides. The addition of sodium azide to nitriles to give l//-tetrazoles is shown to proceed readily in water with zinc salts as catalysts (Eq. 11.71).122 The scope of the reaction is quite broad a variety of aromatic nitriles, activated and nonactivated alkyl nitriles, substituted vinyl nitriles, thiocyanates, and cyanamides have all been shown to be viable substrates for this reaction. The reaction of an arylacetylene with an azide in hot water gave 1,4-disubstituted 1,2,3-triazoles in high yields,123 while a similar reaction between a terminal aliphatic alkyne and an azide (except 111 - nitroazidobenzcnc) afforded a mixture of regioisomers with... 

About 100 gal of process wastewater is typically generated from 1 t of coke produced.15 These wastewaters from byproduct coke making contain high levels of oil and grease, ammonia nitrogen, sulfides, cyanides, thiocyanates, phenols, benzenes, toluene, xylene, other aromatic volatile components, and polynuclear aromatic compounds. They may also contain toxic metals such as antimony, arsenic, selenium, and zinc. Water-to-air transfer of pollutants may take place due to the escape of volatile pollutants from open equalization and storage tanks and other wastewater treatment systems in the plant. 

Tellurium Tetrahydrofuran Tetranitroaniline Tetranitromethane Thiocyanates Thionyl chloride Thiophene Thymol Halogens, metals Tetrahydridoaluminates, KOH, NaOH Reducing materials Aluminum, cotton, aromatic nitro compounds, hydrocarbons, cotton, toluene Chlorates, nitric acid, peroxides Ammonia, dimethylsulfoxide, linseed oil, quinoline, sodium Nitric acid Acetanilide, antipyrine, camphor, chlorohydrate, menthol, quinine sulfate, ure- thene... 

Unisulf [Unocal sulfur removal] A process for removing sulfur compounds from petroleum fractions, similar to the Stretford process, but including in the catalytic solution vanadium, a thiocyanate, a carboxylate (usually citrate), and an aromatic sulfonate complexing agent. Developed by the Union Oil Company of California in 1979, commercialized in 1985, and operated in three commercial plants in 1989. 

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