8-Carbolinium salts, 1-alkyl anhydro-bases

Further alkylation of the anhydro-bases derived, by treatment with strong base, from quaternary 1-alkyl-a-, 2-alkyl-j8-, 2-alkyl-y-, and l-alkyl-8-carbolinium salts takes place at the indole nitrogen which in the anhydro-bases is a center of high electron density (see Section VI). 

The third structural possibility, the formulation of the compounds as pseudo-bases (445) was eliminated in the case of the anhydro-bases derived from p /r-iV -alkyl-l-methyl-3,4-dihydro-j8-carbolinium salts on the basis of their ultraviolet absorption spectra. A structure such as 445 demands indole-type absorption (A jax 280 mp) which was not encountered in the spectra of the anhydro-bases under discussion. This is in accord with general experience. Pseudo-bases are generally found only when dehydration to anhydro-bases is structurally impossible Indole-type absorption was indeed found in the case of the product obtained by treatment of 3,4-dihydro-)3-carboline methiodide (452 R = H) with alkali.In acid solution this compound gave the expected absorption (A jax 355 mp). In alkaline solution, however, an indole-type absorption (A jax 285 mp) was observed. On this basis formulation of the product as a derivative of 2-formylindole (454) ( max 315 mp) was rejected. Although the indole-type absorption is in accord with the pseudo-base structure 453 (R = H), the elemental analysis and molecular weight were not compatible with this formulation and the product was regarded as a dimeric anhydro-base (455). 

The third structural possibility, the formulation of the compounds as pseudo-bases (445) was eliminated in the case of the anhydro-bases derived from yr-JV-alkyl-l-methyl-3,4-dihydro-jS-carbolinium salts on the basis of their ultraviolet absorption spectra. A structure such as 445 demands indole-type absorption 280 mfi) which was not... 

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