Synthesis and reactions of 2-(4-pyridyl)indole anhydro bases

The corresponding anhydro bases are formed from quaternary salts of 2-(4--pyridyl)indole under the influence of a methanol solution of alkali. The 2-(4-pyridyl)indole cation and 1H-4-(2-indolenylidene)-1,4-dihydropyridine were subjected to quantum-chemical calculation, and the possibility of electrophilic substitution of the anhydro bases in the position of indole was predicted on the basis of the results of the calculations. Thus, the reaction of the anhydro bases with acetyl nitrate and a solution of bromine in acetic acid leads to quaternary salts with a substituent in the position of the indole ring, which are reconverted to anhydro bases under the influence of alkali with retention of the substituent in the position. When the anhydro bases are refluxed in nitromethane and cyanoacetic and malonic esters in the presence of triethylamine, they form the corresponding adducts, which give the starting compounds under the influence of alkali, whereas upon reaction with methyl iodide in ethanol they give quaternary salts. All of these chemical transformations were confirmed by the IR, UV, PMR, and mass spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 52–58, January, 1982.