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New derivatives of 2-arylindoles containing (4-pyridyl)alkyl substituents at various positions of the pyrrole ring were synthesized. They react with 2,3-dimethoxycarbonylspirofluorenylcyclopropene with the formation of light-sensitive systems belonging to the photochromic dihydroindolizine class.Photochromic dihydroindolizines form a rich and varied class of light-sensitive compounds [2,3]. Among the multitude of photochromic materials they are distinguished by high their efficiency, their cheapness, and their accessibility. This forms the basis of their prospective use in optical lenses, the recording and storage of data [4], and dental materials [5].In the present work we describe the synthesis and photochromic characteristics of novel 2-arylindole systems containing a dihydroindolizine ring. It seemed to us important to couple the qualities of 2-arylindoles, which form the fundamental unit in many biologically active systems [6,7], and those of photochromic molecules. Model systems of such a type are promising for use as marker molecules in the study of biological processes.A standard and effective method for the production of photochromic dihydroindolizines is the addition of electron-excessive N-heterocyclic bases to spirocyclopropene. Such bases for us were the 1-and 3-(4-pyridyl)alkyl-substituted 2-arylindoles 4a-d and 5a-c that we had synthesized.Indolepyridine is the main structural element of many natural products [8], among which there are antitumor [9] and antidiabetic [10] agents. On this basis compounds 4a-d and 5a-c are of interest in themselves as possible biologically active substances.The initial bases 4a-d and 5a-c were produced by alkylation of the respective 2-arylindoles, obtained by the Fischer method [11] (Scheme 1).The 1-(4-pyridylmethyl)-2-arylindoles 4a-d were obtained by N-alkylation of 2-arylindoles (1) with 4-(chloromethyl)pyridine in the 50% aqueous potassium hydroxide-benzene two-phase system in the presence of tetrabutylammonium bromide.It is known that 4-vinylpyridine in an acidic medium alkylates the indole ring at position 3 [12]. In our case too by boiling 2-arylindoles 1a-c with 4-vinylpyridine 3 we obtained the corresponding 3-[2-(4-pyridyl)ethyl] derivatives 5a-c.

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Indole derivatives R 0140 Derivatives of Indole. Part 143. Synthesis of Photochromic Derivatives of 2-Arylindoles. -During exposure to UV light the light-yellow solution of title derivatives (V) and (VIII) becomes dark-green as a result of ring opening and transformation to betaines. -(GOGRICHIANI, E. O.; KATSADZE, E. A.; GAVTADZE, N. G.; SAMSONIYA, S. A.; DUERR, H.; Chem. Heterocycl.