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Reaction of the pyrazoles (I) with excess cis‐1,4‐dichloro‐2‐butene (II) gives the bicyclic salts (III), whereas with excess trans‐1,4‐dichloro‐2‐butene (IV) the mono‐substituted products (V) and (VI) are obtained.

Given are experimental data indicating that base-catalyzed intramolecular cyclization of ammonium salts containing a 2-propynyl-like group together with a 3-alkenyl-or 3-aryl-2-propynyl group follows a concerted mechanism involving the 3-alkenyl-or 3-aryl-2-propynyl moiety as π 4 -fragment.We previously showed that ammonium salts containing β,γ-unsaturated groups and various 4-en-2-ynyl fragments on the nitrogen atom readily undergo basecatalyzed intramolecular cyclization (like Diels-Alder reaction) to afford 2,2-dialkylisoindolium or 2,2-dialkyldihydroisoindolium salts and their fused analogs in almost quantitative yield [1-7] (Scheme 1). Scheme 1. N N or OH -N Two schemes were proposed for cyclization of the above systems [1, 3, 8-15]. According to the first of these, the cyclization involves intermediate formation of species A or B which undergoes fast aromatization via hydride (pathway a) or proton transfer (pathway b;Scheme 2). The other scheme includes isomerization of the 3-alkenyl-or 3-aryl-2-propynyl group to allenyl fragment, cyclization of the salt thus formed, and aromatization of the latter to dihydroisoindole derivative (Scheme 3). Scheme 3 is consistent with published data on cyclization of acetylenic compounds [16][17][18][19][20]. For example, base-catalyzed intramolecular cyclization of compounds with the general formula X(CH 2 C≡CC 6 H 5 ) 2 (X = CH 2 , S, NCH 3 , O), as well as of allyl and 2-propynyl ethers derived from 3-isopropenyl-2-propynyl and 3-phenyl-2-propynyl alcohols, was presumed to be preceded by isomerization into the corresponding α-allenyl derivative [16][17][18].With the goal of establishing the true mechanism of the cyclization, Babayan and co-workers previously performed kinetic studies using UV spectroscopy [8][9][10][11][12][13][14][15]. However, this method did not allow the authors to detect formation of intermediate species, in N OH -N H A N H B H OH b a N Scheme 2.

Fused pyrrole derivatives R 0160Investigations in the Area of Amines and Ammonium Compounds. Part 237. Synthesis of 2,2-Dialkyl-4-hydroxymethylbenzo[f]isoindolinium and 2,2-Dialkyl--4-hydroxymethylisoindolinium Salts. -Base-catalyzed cyclization of the ammonium salts (I) and (III) gives rise to benzoisoindolinium and isoindolinium salts (II) and (IV), resp., in good yields under mild reaction conditions. -(CHUKHADZHYAN, E. O.; GEVORKYAN. A. R.; CHUKHADZHYAN, E. O.; SHAKHATUNI, K. G.; KINOYAN, F. S.; PANOSYAN, G. A.; Chem. Heterocycl.