Anthony John Nelson

Colour and constitution of azo compounds derived from diaminoazines

Abstract Visible absorption spectra have been recorded for azo compounds derived from 2,5-dichlorosulphanilic acid azo-coupled with N , N -diethyl-m-phenylenediamine, and with azine analogues. The effects of the ring-aza substituents as well as cyano on the spectra indicate a surprising difference in sensitivity of the two ring positions meta to the azo group. M.O. calculations show chat the amino group ortho to the azo linkage introduces asymmetry into the HOMO, and this is responsible for the differing effects of substitution.

Transformations of trichloromethyl groups during reactions of 3-trichloromethylpyridines with methoxide

When methoxide ion attacks an unsubstituted 2- or 6-position of a 3-trichloromethylpyridine, a hydrogen shift leads to a methoxy-substituted 3-dichloromethylpyridine. Further reaction of the dichloromethyl group with methoxide gives the corresponding acetal. This type of reaction has been applied to several chlorinated 3-trichloromethylpyridines and to 3-trichloromethylpyridine itself; a convenient synthesis of the latter is described.

Contrasting reactions of 2,6-dichloro-4-trichloromethylpyridine, 2,6-dichloro-3-trichloromethylpyridine and their N-oxides with nucleophiles

Various nucleophiles react with 2,6-dichloro-4-trichloromethylpyridine and 2-chloro-6-trichloromethylpyridine as expected, by displacement of ring chlorine atoms. But in the reactions of nucleophiles with 2,6-dichloro-3-trichloromethylpyridine and 2,6-difluoro-3-trifluoromethylpyridine, displacement of ring halogen atoms is accompanied or followed by multiple attack at the trihalogenomethyl group. The reactivity of the trihalogenomethyl groups is modified by N-oxidation. A mechanism for the peculiar reactivity of the trihalogenomethyl groups is proposed, involving loss of halide ion from the CX3 group assisted by lone pairs on substituents or negative charge in Meisenheimer intermediates. Both geometrical isomers of 1,2-dichloro- 1,2-bis(2,6-dichloro-3-pyridyl)ethene are described.

Polyhalogenoaromatic compounds. Part 49. Synthesis of carbolines by the reaction of enamines with tetrachloro-4-cyanopyridine

Reactions of tetrachloro-4-cyanopyridine with 1-(dialkylamino)cyclohexenes gave tetrahydro-5H-pyrido[3,2-b]indoles and tetrahydro-9H-pyrido[2,3-b]indoles, in proportions varying with the dialkyl-amino-group. The tetrahydrocarbolines could be dehydrogenated by treatment with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone. 2,3-Dichloro-4-cyano-9-ethyl-9H-pyrido[2,3-b]indole was synthesised independently by photolysis of trichloro-4-cyano-6-(N-ethylanilino)pyridine.