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Synthesis and Local Anesthetic Activity of o-(Cyclopentenyl) ando-(Cyclopentyl)aniline Derivatives.-The synthesis of cyclopentylor cyclopentenyl-substituted N-piperidinylacetanilides (VI), (VII), and tricyclic analogue (VIII) is achieved as described for derivatives (VI) by chloroacetylation of the corresponding anilines (II) followed by amide formation with piperidine. The novel compounds possess local anesthetic activity. -(GATAULLIN, R. R.; KAZHANOVA, T. V.; KARACHURINA, L. T.; IL'YASOVA, L. T.; DAVY-DOVA, V. A.; SAPOZHNIKOVA, T. A.; ZARUDII, F. S.; ABDRAKHMANOV, I. B.; Khim.-Farm. Zh. 35 (2001) 9, 28-32; Inst. org. khim. Ural. otd. Ross.

lntramolecular eyclization of o-alkenylaniUnes was studied. Heating of o-(cyelopcnt-2-ca-l-yl)arylammonium chlorides at 200--220 "12 yields cyelopenta[blindolines as the main reaction products. Cyelization of 4-methyl-2-(pent-3-en-2-yl)aniline under the same conditions gave a mixture of indoline~ and tetrahydroquinolines. An alk-l-enylarylamine containin8 a vinylic double bond does not form cyclization products on the nitrogen atom.Key words: 2-methyl-6-(cyclopent-2-en-l-yl)aniline, 2,4-dimethyl-6-(cyelopent-2-enl-yl)aniline, inttamolecular eyclization, cyclopenta [b]indolines,2,4,2,3,3,1,2,3,3a,4,indoles.Depending on catalysts, intramolecular cyclization of 2-(alk-2-enyl)anilines can occur on either the aromatic ring or the nitrogen atom. t,2 The character of substituents in the allylic fragment significantly influences the structure of the final products. 3 Earlier, it was shown that eyclopenta [b]indolines result only from a photochemical cyclization of 2-(cyclopent-2-en-l-yl)-N-ethylaniline or N-methyl-N-(cyclopent-l-en-l-yl)aniline, 4 whereas N-unsubstituted 2-(cyclopent-2-enl-yl)aniline does not undergo photochemical transformation into indoline. Scarce literature data on acidcatalyzed heterocyclization of alkenylarylamines mainly deals with compounds containing acyclic allylic fragments. It is of theoretical and practical interest to study the catalyzed cyclization of o-(cycloalk-2-enyl)anilines because compounds having the indoline or tetrahydroquinoline structure are precursors of stable nitroxyl radicals s and can be used in the synthesis of valuable alkaloids. 6,7In the present work, we studied intramolecular cyclization of o-(alk-2-en-l-yl)anilines in the presence of HC! at 200--220 ~ It was shown that this reaction is a convenient method for the synthesis of cyclopenta [b]indotines (Scheme 1). Thus, when heated under these conditions, o-eyclopentenylarylammonium (2a--e) chlorides, obtained according to the-known procedure g by condensation of anilines la--e with chlorocyclopentene, are isomerized into indolines 3a--e. Heating of N-cyclopentenylarylammonium 9 (4a--e),chlorides in an excess of the corresponding amine la--e at 200--220 oC for 9--10 h also yields heterocycles 3a--e. An analysis of this reaction mixture in the course of the heating shows the presence of the corresponding o-cyclopentenylanilines 2a--e, which are gradually transformed into indolines 3a--e. Thus, the condensation of arylamines la--e with chlorocyclopentene $ followed by heating to 200--220 *C allows the one-pot synthesis of indolines 3a--e in high yields.The structures of heterocycles 3a--e were unambiguousiy proven by tH and 13C NMR and IR spectroscopy and elemental analysis. Thus, the IR spectra ~ of compounds 3a--e exhibit a band at 3390 cm -1 characteristic of the NH group, l~ The formation of tricyclic compounds 3a--e is evidenced by signals for the angular methine protons observed in IH NMR spectra at 5 3.80 and 4.40. These signals have a large vicinal coupling constant (Jl-lrt = 8.8 Hz), which suggests their cis-arran...