Thiocyanates from amines

Cobaltous chloride potassium thiocyanate Thiocyanates from amines s.680... 

Imino-thiazolidine 93 is prepared directly from the corresponding (9-methanesulfonyl (3-amino alcohol hydrochloride 89 using potassium thiocyanate via aziridine intermediate 90 <05TL233>. Ring opening of 90 with potassium thiocyanate gives amines 91 and 92, which recyclizes to furnish the same cis itnine 93. 

Molina et al. have continued to publish their variation on the use of pyridinium salts for functional-group transformation. In a method which is analogous to that previously reported (Vol. 5, p. 193), arylmethyl thicxiyanates are now available from amines via 4,6-diphenyl-2-methylthiopyridinium thiocyanates (Scheme 62). ... 

Sec. from prim, amines and sulfonic acid esters Thiocyanates from sulfonic acid esters... 

A new synthesis of thiocyanates from aliphatic amines (Scheme 46) utilizes the readily available 2,4,6-triphenylpyrylium thiocyanate (80). The intermediate l-substituted-2,4,6-triphenylpyridinium thiocyanates (81) are smoothly pyrolysed into the corresponding thiocyanates (82) in excellent yields. These promising syntheses complement those available in the aromatic amine series via diazotization. 

Recently nitrosamines have attracted attention because of their marked carcinogenic activity in a wide variety of animal species Q, ). Nitrosamines are likely to be carcinogens in man as well human exposure to these compounds is by ingestion, inhalation, dermal contact and vivo formation from nitrite and amines Nitrite and amines react most rapidly at an acidic pH A variety of factors, however, make nitrosation a potentially important reaction above pH 7 these include the presence of microorganisms, and the possibilities of catalysis by thiocyanate, metals and phenols, and of transnitrosation by other nitroso compounds. 

When hot, ammonia and compounds, which contain nitrogen-hydrogen bonds eg ammonium salts and cyanides react violently with chlorates and alkaline perchlorates. Diammonlum sulphate, ammonium chloride, hydroxyl-amine, hydrazine, sodamide, sodium cyanide and ammonium thiocyanate have been cited. So far as hydrazine is concerned, the danger comes from the formation of a complex with sodium or lithium perchlorate, which is explosive when ground. Many of these interactions are explosive but the factors which determine the seriousness of the accident are not known. 

Phenols79 react with phthalimidesulphenylchloride (PhthNSCl) to yield N-thiophthalimides. These when treated with tertiary amines afford unstable ortho-thioquinones. Base-catalysed CN-elimination from camphoryl thiocyanate yields the a n -l,3-dithietane as the sole stereoisomer via thioketone80 (Scheme 9). 

A direct procedure from isothiocyanates and amines using tetrabutylammo-nium thiocyanate (Bu4NSCN) and PhCH2NMe3Br3 affords functionalized 2-aminobenzo-l,3-thiazoles (Scheme 60).143... 

In addition to benzenoid diazo components, diazotised heterocyclic amines in which the amino group is attached to a nitrogen- or sulphur-containing ring figure prominently in the preparation of disperse dyes [87,88], since these can produce marked bathochromic shifts. The most commonly used of these are the 6-substituted 2-aminobenzothiazoles, prepared by the reaction of a suitable arylamine with bromine and potassium thiocyanate (Scheme 4.31). Intermediates of this type, such as the 6-nitro derivative (4.79), are the source of red dyes, as in Cl Disperse Red 145 (4.80). It has been found that dichloroacetic acid is an effective solvent for the diazotisation of 2-amino-6-nitrobenzothiazole [89]. Subsequent coupling reactions can be carried out in the same solvent system. Monoazo disperse dyes have also been synthesised from other isomeric nitro derivatives of 2-aminobenzothiazole [90]. Various dichloronitro derivatives of this amine can be used to generate reddish blue dyes for polyester [91]. 

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