Phenylthioureas, from amines

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.)... 

N— compounds used as acid inhibitors include heterocyclic bases, such as pyridine, quinoline and various amines. Carassiti describes the inhibitive action of decylamine and quinoline, as well as phenylthiourea and dibenzyl-sulphoxides for the protection of stainless steels in hydrochloric acid pickling. Hudson e/a/. refer to coal tar base fractions for inhibition in sulphuric and hydrochloric acid solutions. Good results are reported with 0-25 vol. Vo of distilled quinoline bases with addition of 0 05m sodium chloride in 4n sulphuric acid at 93°C. The sodium chloride is acting synergistically, e.g. 0-05m NaCl raises the percentage inhibition given by 0-1% quinoline in 2n H2SO4 from 43 to 79%. Similarly, potassium iodide improves the action of phenylthiourea . 

Reaction of aromatic or heterocyclic amines with formaldehyde and urea or phenylthioureas gave 2-(oxo)thioxohexahydro-l,3,5-triazines 90. Regioselective cyclization and isomerization of propargylthio-l,2,4-triazinones were achieved to give the fused heterocycles 91-93. Cyclization of isatin 3-thiosemicarbazones gave 94 which can be alkylated to 95 . The imidazotriazepines 96 were obtained from heating a mixture of hydrazide and ortho-ester. 

In this extensive study of thiourea synthesis by coupling isothiocyanates with amines under mechanochemical conditions of neat and LAG, a total of 49 different thiourea derivatives were prepared. Since the supramolecular chemistry of simple synunetrical and nonsymmetrical diarylthiouieas had not previously been studied in detail, the information from the PXRD patterns of the milling products in this work also allowed for a systematic analysis of structural features of diarylthio-ureas. The three main self-assembly motifs were identified. A characteristic supramolecular synthon based on bifurcated N—H - S hydrogen bonds was found in most cases, whereby the individual thiourea molecules were assembled into chains aligned in a head-to-head (parallel molecular dipoles) or head-to-tail (antiparallel molecular dipoles) manner. In the case of slerically hindered thioureas, such as A -(2,6-dimethylphenyl)-A -phenylthiourea, the third motif arising from discrete cen-trosymmetric dimers based on rI(S) supramolecular synthon was found. A detailed look at the measured PXRD patterns for aU diarylthioureas revealed that solid-state structures of these compounds could be classified into two structural families, denoted as family I and family II (Fig. 1.11). 

---