Phenyl isothiocyanate, chlorination

A method used to prepare four of six possible thienopyridines (1992S528, 1997S949, 1998S1095) holds considerable promise. In particular, the synthesis of thieno[2,3-6]pyridine derivatives 31 and 32 involves the reaction of 2-chloro-3-(cyanomethyl)pyridine (33) and ethyl 2-chloro-3-pyridylacetate (34) with hetero-cumulenes, such as carbon disulfide and phenyl isothiocyanate. The reaction proceeds through the formation of the corresponding dianions 35 and 36 followed by cyclization through intramolecular nucleophilic substitution of the chlorine atom. 

Phenyl carbylamine chloride is usually prepared by the chlorination of phenyl isothiocyanate ... 

In the laboratory, phenyl isothiocyanate is first prepared from aniline and carbon disulphide and the product then chlorinated. 

The method used by the Germans consisted in preparing the phenyl isothiocyanate first from carbon disulphide, milk of lime and aniline and then chlorinating this. 

The chlorination of isothiocyanates is the classical synthesis of carbonimidoyl dichlorides. Sell and Zierold in 1874 obtained phenyl-carbonimidoyl dichloride (IX) upon chlorination of phenyl isothiocyanate in chloroform at 0°C, and Nef ( ° ) observed that under the conditions... 

Phenylcarbonimidoyl dichloride To a solution of 67.5 g (0.5 mole) of phenyl isothiocyanate in 200 ml of carbon tetrachloride chlorine is added with stirring and ice-cooling below 3°C until the chlorine is no longer absorbed (approximately three to four hours). The solvent and sulfur dichloride, formed in the reaction, are removed by distillation, and vacuum distillation of the residue yields 74-78 g (85-90%) of phenylcarbonimidoyl dichloride, b.p. 103-106°C (31 mm). 

A standard condition has been optimized for this reaction, in which the aryl amine is diazotized in 10 times its amount of acetic acid, followed by the addition of one equivalent of cuprous halide in hydrohalic acid. Under these conditions, the acetate salt of aryl amine is relatively soluble, and less froth and tarry material are formed during diazo transformation. In addition, chlorination, bromination, and iodonation of p-haloaniline to dihalobenzenes under such standard conditions give almost comparable average yields. Other modifications of this reaction include the formation of phenyl selenocyanate by the reaction with potassium selenocyanate, and aryl nitrile by the reaction with nickel cyanide. Moreover, this reaction has been extended to the preparation of phenyl thiocyanate, phenyl isothiocyanate and aromatic sulfonyl chloride. ... 

Compound 129, an intensely blue compound, was obtained by direct functionalization of DDTOMe 20b with LDA and chloro(chloromethyldimethylsilane) at one of the terminal positions followed by conversion of chloride to NCS using sodium thiocyanate in acetone (Scheme 12). The other isothiocyanates were prepared via Stille coupling of mono or dibrominated rigid cores with appropriate thienyl or phenyl stannanes followed by conversion of the chlorine atom of Si(CH3)2CH2Cl attached to a phenyl group into isothiocyanate occurred in rather low yield. 

The addition of halogen to the C=S rather than the C—N bonds, as for example postulated by Gumpert for the bromination of phenyl isocyanate, is in line with the favored participation of the C=S bond in addition reactions of isothiocyanates One is tempted to speculate that the second step involves a-elimination of sulfur dichloride, followed by addition of chlorine to the generated isocyanide. However, further work is needed to establish the mechanism of this reaction. 

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