Silicon tetraisothiocyanate, reaction

Silicon tetraisothiocyanate reaction with 2,6-dimethylamhne to yield 2,6 dimethylphenyl thiourea, 46, 70... 

Silicon tetraisothiocyanate, reaction with 2,6-dimethylaniline to yield... 

Silicon tetraisothiocyanate (26.0 g., 0.10 mole) (Note 10) is finely ground under 100 ml. of anhydrous benzene, and the mixture is quickly transferred to a 1-1. round-bottomed flask. The mortar and pestle are washed with two 25-ml. portions of anhydrous benzene, and the washings are added to the flask. A solution of 2,6-dimethylaniline (48.5 g., 0.4 mole) (Note 1) in 100 ml. of anhydrous benzene is added to the well-stirred mixture. The reaction is mildly exothermic. The mixture is heated at the reflux temperature for 30 minutes, and the benzene is then removed using a rotary evaporator. Dilute isopropyl alcohol (200 ml.) (Note 5) is added to the residue, and the resulting mixture is heated at the reflux temperature for 30 minutes. The mixture is then processed in exactly the same manner as described above for the preparation of cyclohexylurea. The crude 2,6-dimethylphenylthiourea (m.p. 193-197°, 71.3 g., 99% yield) is recrystallized from 280 ml. of isopropyl alcohol (Note 8) to give 50 g. (72%) of product, m.p. 201-202°. Concentration of the mother liquor affords 11 g. (15%) of less pure product, m.p, 197-199° (Note 11). 

Silicon tetraisothiocyanate was first prepared by Miquel and Reynolds by treating silicon(IV) chloride with lead thiocyanate. Later, Forbes and Anderson prepared many substituted silicon isothiocyanates by metathetical reaction of the corresponding chlorosilanes with silver thiocyanate. On the bases of molecular refraction studies, the latter workers concluded that the silane derivatives are isothiocyanates rather than the isomeric thiocyanates. Conclusive proof that these compounds are isothiocyanates is their formation in good yield from isocyanosilanes and sulfur ... 

In chemical reactions and physical properties the methylsilicon isothiocyanates are very similar to silicon tetraisothiocyanate. Methylsilicon triisothiocyanate and dimethylsilicon diisothiocyanate are colorless solids at room temperature, whereas trimethylsilicon isothiocyanate is a colorless liquid. All possess pungent odors and are lacrimators. The melting and boiling points are respectively methylsilicon triisothiocyanate, 72.4°, 266.8° dimethylsilicon diisothiocyanate, 18.0°, 217.3° trimethylsilicon isothiocyanate, — 32.8°, 143.1°. 

A soln. of cyclohexylamine in anhydrous benzene added slowly to a stirred soln. of silicon tetraisocyanate in the same solvent, refluxed 0.5 hr. after the exothermic reaction has subsided, the benzene removed by distillation, isopropanol containing up to 10% water added, and refluxed 0.5 hr. cyclo-hexylurea. Y 65-97%. — Similarly 2,6-Dimethylaniline and silicon tetraisothiocyanate 2,6-dimethylphenylthiourea. Y 72-99%. F. e. s. R. G. Neville and J. J. McGee, Org. Synth. 45, 69 (1965). 

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