Amines aromatic, thiocyanation

Phenols and aromatic amines are thiocyanated on electrolysis in an aqueous solution of SCN" [13]. The reaction is indirect since there is compelling evidence that the thiocyanat-ing reagent must be (SCN)2, formed by anodic oxidation of SCN"" [156]. In MeCN solution oxidation of SCN"" and SeCN in the presence of phenol of various aromatic amines leads to thiocyanation and selenocyanation in 55-80% yields 157 [109]. 

Aromatic secondary and tertiary amines undergo thiocyanation, often more readily than primary amines. N,N-Dimethylaniline gives N,N-dimethyl-4-thiocyanoaniline (92% 3deld), and N,N-dimethyl-p-tolui-dine gives N,N-dimethyl-2-thiocyano-p-toluidine (21% yield). Di-phenylamine and triphenylamine are converted into dithiocyano derivatives, each with two of the phenyl rings substituted in the para positions. ... 

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). 

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. 

Thiocarbonates, synthesis of, 17, 3 Thiocyanation of aromatic amines, phenols, and polynuclear hydrocarbons, 3, 6 Thiophenes, synthesis of, 6, 9 Thorpe-Ziegler condensation, 15, 1 31 Tiemann reaction, 3, 9 Tiffeneau-Demjanov reaction, 11, 2 Tin(n) enolates, 46, 1 Tin hydride method to prepare radicals,... 

As a result of interaction of 843 and pyridine, the adduct 845 is formed [53], The structures of coordination compounds 844 and 845 were proved by x-ray diffraction. As shown above (Sec. 3.4.3.2), the direct ammonia synthesis [55,56] with participation of various ligands (especially aliphatic, aromatic, and heterocyclic amines, aminoalcohols), elemental metals (or their oxides), and NH4SCN in mostly non-aqueous media, opens definite possibilities for obtaining thiocyanate complexes. In this respect, transformation (4.9) should be mentioned [57] ... 

MPO (Myeloperoxidase) [EC 1.11.1.7] catalyzes the hydrogen peroxide dependent two-electron oxidation of halides (CD, I, Br ) and thiocyanate to the corresponding hypohalous acids and hypothiocyanate which are cytotoxic to invading pathogens. In addition, MPO is capable of the singleelectron oxidation of a wide variety of aromatic alcohols and amines. " ... 

Silicon tetraisothiocyanate is rapidly hydrolyzed to gelatinous silica and thiocyanic acid on exposure to moist air or water. With primary or secondary aliphatic or aromatic amines, silicon tetraisothiocyanate reacts to produce N-mono- or iV,iV-disubstituted thioureas, respectively, in essentially 100% yields. ... 

In its reactions thiocyanogen is somewhat like bromine without a catalyst. Direct replacement of hydrogen by the thiocyano group, thiocyanation, is limited to aromatic amines and phenols, and a few very reactive hydrocarbons. Aniline is converted into 4-thiocyanoaniline in 97% yield, o-toluidine into 4-thiocyano-2-methylaniline in 80% yield, anthranilic acid into 5-thiocyanoanthranilic acid in 80% yield. Phenols likewise are thiocyanated in the para position if available, otherwise in the ortho position. 

Cyanogen chloride reacts with sodium sulfide, Na2S, to form sodium thiocyanate, NaSCN. An extension of this involves the reaction of thiolate anions, RS, with CICN to form thiocyanates, RSCN. Similarly, the reaction of phenols produces aromatic cyanates (Kaupp et al., 1998). In such reactions, 3° amines are used to trap hydrogen chloride. 

The procedure given above is a convenient method involving the formation of an active thiocyanogen derivative in the presence of dimethylaniline. Thiocyanation of aromatic amines and phenols has also been accomplished electrochemically. ... 

A one-pot synthesis of imidazolidines (30-67%) reacts aromatic aldehydes with diethyl keto-malonate and a benzylamine with a catalytic quantity of p-toluenesulfonic acid <94H(38)587>. The Ugi four-component eondensation of l,l-diethoxy-2-isocyanoethane, cycloketones, amine hydrochlorides, and potassium thiocyanate gives rise to 2-spiro-2W-imidazoles (10-48%) <93LAI229>. 

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