Amines isothiocyanate

Synthesis of 2-thioxotetrahydropyrimidin-4-(lH)-ones Libraries of 2-thioxotetrahy-dropyrimidin-4-(lH)-ones can be prepared by multicomponent reaction of amine, isothiocyanate, and yS-dielectrophile components (Scheme 7.23). [PEG -RMIM]X ionic liquids have been used in this reaction with microwave irradiation (Scheme 7.24) [75]. In a step-by-step approach, treatment of [PEG -RMIM]X with acryloyl chloride provided a supported acryloyl ionic liquid phase which was reacted with an amine and then isothiocyanate to give a thiourea. Cyclization-cleavage from the ionic liquid support to give the desired 2-thioxotetrahydropyrimidin-4-(lH)-one was achieved by using low-power microwaves at 120 °C for 15-45 min in the presence of diethylamine. 

Keywords 1,2-Diaza-l,3-dienes, amines, isothiocyanates, chloroform, room temperature, sequential three-component reaction, one-pot synthesis, 2-thiohydantions... 

Attanasi, O. A., Bartoccini, S., Favi, G., Giorgi, G., Pemilli, F. R., and Santeusanio, S. (2012a). Powerful approach to heterocyclic skeletal diversity by sequential three-component reaction of amines, isothiocyanates, and 1,2-diaza-l,3-dienes. J. Org. Chem., 77, 1161-1167. 

Add 0 -5 ml. of phenyl isothiocyanate to the distillate and shake the mixture vigorously for 3-4 minutes. If no derivative separates, crystallisation may be induced by cooling the flask in ice and scratching the walls with a glass rod. Filter off the crude product, wash it with a little 50 per nent. ethanol, and recrystaUise from hot dilute alcohol. (See Table 111,123 for melting points of phenylthiourea derivatives of amines.)... 

Phenylthioureas. Primary and secondary amines react with phenyl isothiocyanate to yield phenylthioureas ... 

Phenyl isothiocyanate is not sensitive to water the reaction may be carried out with an aqueous solution of an amine. 

Alternatively, mix equal amounts (say, 0-2 g. of each) of the amine and phenyl isothiocyanate in a test-tube and shake for 2 minutes. If no reaction occurs, heat the mixture gently for 2 minutes and then cool in ice until the mass soUdifies. Powder the soUd, wash it with a little light petroleum (b.p. 100-120°), and recrystallise from rectified spirit. 

Aryl and alkyl isothiocyanates are converted ia good yields by IF ia pyridine to thiohis(/V-trifluoromethy1 amines) (89,90) ... 

Chemical Properties The formation of salts with acids is the most characteristic reaction of amines. Since the amines are soluble in organic solvents and the salts are usually not soluble, acidic products can be conveniendy separated by the reaction with an amine, the unshared electron pair on the amine nitrogen acting as proton acceptor. Amines are good nucleophiles reactions of amines at the nitrogen atom have as a first step the formation of a bond with the unshared electron pair of nitrogen, eg, reactions with acid anhydrides, haUdes, and esters, with carbon dioxide or carbon disulfide, and with isocyanic or isothiocyanic acid derivatives. 

AletalHydrides. Metal hydrides can sometimes be used to prepare amines by reduction of various functional groups, but they are seldom the preferred method. Most metal hydrides do not reduce nitro compounds at all (64), although aUphatic nitro compounds can be reduced to amines with lithium aluminum hydride. When aromatic amines are reduced with this reagent, a2o compounds are produced. Nitriles, on the other hand, can be reduced to amines with lithium aluminum hydride or sodium borohydride under certain conditions. Other functional groups which can be reduced to amines using metal hydrides include amides, oximes, isocyanates, isothiocyanates, and a2ides (64). 

Thiophosgene reacts with alcohols and phenols to form chlorothionoformates or thiocarbonates. The most studied reactions of thiophosgene are with primary amines to give isothiocyanates and with secondary amines to give thiocarbamyl chlorides ... 

Determination of ethyleneamines in air can be accomplished by absorbing the amines on NITC (1-naphthyl isothiocyanate) treated XAD-2 resin, then desorbing the derivative from the treated tubes and quantifying the amount using high performance Hquid chromatography (hplc). Sensitivity is reported as 0.37 and 0.016 mg/m for EDA and DETA, respectively, pet sample (153,154). 

Ethoxy-6-methylpyrimidine 1-oxide (499) reacts with phenyl isocyanate to eliminate carbon dioxide and give a mixture of 4-ethoxy-6-methyl-N-phenylpyrimidin-2-amine (SOO) and (the derived) 7V-(4-ethoxy-6-methylpyrimidin-2-yl)-7V,7V -diphenylurea (SOI) phenyl isothiocyanate reacts quite differently (79CPB2642). 

K A L U Z A Isothiocyanate synthesis Formation of isothiocyanates from amines. 

Aryl isothiocyanates can be prepared by the action of thio-phosgene on the arylamine (this reaction fails with naphthyl compounds), by fission of a 5ym-diaryIthiourea with acidic reagents (this reaction involves the loss of half the amine used), and by the decomposition of an ammonium aryldithiocar-bamate (low yields are reported for naphthyl and other compounds).The procedure described here is that of Baxter, Cymerman-Craig, Moyle, and White. ... 

Elemental sulfur undergoes nucleophilic attack by amines at low temperatures. Therefore the conjugate position of an enamine is sufficiently nucleophilic to attack elemental sulfur and yield thiolated intermediate 103. When 103 is treated when phenyl isothiocyanate, the cyclic adduct 104... 

N,N Disubstituted thioureas from secondary amines and silicon tetra-isothiocyanate, 46, 69 N,N-Disubstituted ureas from secondary ammes and silicon tetraiso-cyanate, 46, 69... 

Amines, preparation from isothiocyanates, 18, 5 from ketones, 17, 76 m-Aminobenzaldehyde, 13, 28... 

Bazureau et al. have reported a similar protocol to that described in Sect. 8.1 for the rapid synthesis of 2-thioxo tetrahydropyrimidin-4-(lH)-ones via cycli-zation of a primary amine with an isothiocyanate and a /1-dielectrophile (Fig. 35) [138]. First a j6-amino ester was linked to the ionic hquid support... 

Related to this process is the hydrolysis of isocyanates or isothiocyanates" where addition of water to the carbon-nitrogen double bond would give an N-substituted carbamic acid (3). Such compounds are unstable and break down to carbon dioxide (or COS in the case of isothiocyanates) and the amine ... 

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