Some aspects of azide reactions

The reported work on the reactions between indoles and arylsulphonyl azides was extended with a view to identifying any intermediates involved and establishing the relationships between the products formed. The effect of varying the structures of the indoles on these products has also been investigated.
Compounds of type (I) appear to be key intermediates in the reactions of alkyl indoles with azides. Compound (I) has recently been prepared . The suggested intermediacy of this compound in the reaction between tosyl azide and 9-methyltetrahydrocarbazole was proved, the reaction of (I) with p-chlorobenzenesulphonyl azide yielding (II).
As an extension of the work on tetrahydrocarbazoles, the reactions of 5,6,7,8,9,10-hexahydrocyclohept[b]indole, 6,7,8,9,10,11-hexahydro-5H-cyclooct[b]indole and their N-methyl derivatives have been examined. From the reactions of the N-H compounds have been isolated the products (III, n = 5, Z = Ts), (III, n = 6, Z = Ts) and (III, n = 6, Z = Cbs).
The action of heat on (III, n = 6, Z = Ts) has been investigated and the products (IV) and (V) isolated. In acetic acid solution (III, n = 6, Z = Ts) was oxidised to (VI); a plausible mechanism for this oxidation was proposed. On heating, (VI) isomerised to (VII), and on treatment with base (VI) added water, giving (VIII).
5,6,7,8,9,10-Hexahydro-5-methylcyclohept[b]indole gave four products on treatment with tosyl azide, (IX–XII, n = 4). The structures of the latter two products .were proved by degradation to the compounds (XIII) and (XIV), and synthesis of these degradation products. The homologous compounds (IX–XII, n = 5) were obtained when 6,7,8,9,10,11-hexahydro-5-methyl-5H-cyclooct[b]indole was treated with tosyl azide. The stereochemistry of the compounds (XI, n = 4) and (XI, n = 5) has been determined and the transformation of (X, n = 5) into (XII, n = 5) on heating was demonstrated.
Rapoport has reported the high reactivity of indoles with structures of the type (XV), this reactivity being due to a high degree of strain in the molecule. It was of interest, therefore, to extend the present work by synthesising the compounds (XV, n = 4) and (XV, n - 5) and investigating their reactions with arylsulphonyl azides.
The former yielded the products (XVI), (XVII), (XVIII, n = 3) and (XIX), depending on the conditions used. From the reaction of p-nitrobenzenesulphonyl azide in methanol a further product (XX) was obtained. The effect of heat on the compounds (XVI) and (XX) has been examined, both yielding (XXI).
(XV, n = 5) reacted with azides to give the compounds (XXII) as major product. Also obtained were compounds (XVIII, n = 4) and from the reaction with p-nitrobenzenesulphonyl azide (XXIII) was also isolated. Since this was the first time that compounds of the type of structure (XXII) had been obtained in good yield, the chemistry of these products was studied in some detail. A number of interesting rearrangements were observed. Treatment with base gave the compounds (XXIV, R = NZ) and (XXIV, R = O), while the effect of acid was to produce the ion (XXV). This was not isolated, products resulting from the addition of hydroxylic solvents to the molecule being the only compounds obtained. A similar rearrangement occurred on heating (XXII) in hydroxylic solvents. The rearrangement in acidic solvent was studied by means of n.m.r. spectroscopy.
The reactions of 2-alkylthioindoles with azides were investigated, the major products being the azobisindoles (XXVI). Prom the reaction of 1-methyl-2-methylthioindole compound (XXVII) was also obtained; the formation of this compound involves a 1,2-shift of the alkylthio group.
2-Indolinethiones gave two products on treatment with arylsulphonyl azides, compounds (XXVIII) and the 1,2,3-thiadiazoles (XXIX).
Finally, the reported work on 1,2,3,4-tetrahydro-2,5-dimethyl-5H-pyrido[4,3-b]indole was repeated and a further product (XXX) was obtained.
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Advisor: Bailey, A