Vinylidenecyclopropanes have value as synthons in organic synthesis, in particular in the preparation of heterocyclic compounds [1][2][3][4][5][6]. Catalysis by Lewis acids has recently been reported in the reaction of vinylidenecyclopropanes with acetals to give indene derivatives [7]. It has previously been shown that the reaction of vinylidenecyclopropanes with aromatic imines or ethyl (arylimino)acetates in the presence of a Lewis acids gives pyrrolidine or 1,2,3,4-tetrahydroquinoline derivatives depending on the nature of the substituent on the multiple bond or in the cyclopropane ring [8,9]. We have found that the reaction of aromatic imines with vinylidenecyclopropanes containing alkyl substituents in the cyclopropane ring and on the multiple bond gives only the formation of products which occurs via a cyclopropyl-allyl rearrangement stage, i.e. substituted pyrrolidines. Vinylidenecyclopropanes containing an aryl and alkyl substituent simultaneously in the cyclopropane ring and aryl substituents on the double bond gave products the formation of which occurs via an intramolecular Friedel-Crafts reaction stage, i.e. tetrahydroquinoline derivatives [8]. Vinylidene-cyclopropanes containing two aryl substituents in the cyclopropane ring have not been included in this reaction hence the aim of this work was a study of the reaction of vinylidenecyclopropanes containing aryl substituents in the cyclopropane ring and on the double bond with aromatic imines in the presence of BF 3 ·Et 2 O.It was found that treating the 1,1-diaryl-2-(diphenylvinylidene)cyclopropanes 1a,b with the imines 2a,b in the presence of BF 3 ·Et 2 O (15 mol %) in methylene chloride gave the 2-aryl-4-diarylmethylene-3-diphenylmethylene-1-phenylpyrrolidines 3a-d in yields up to 27%. In all cases the target compounds were separated using preparative TLC. The structure and composition of compounds 3a-d were established from their spectroscopic and elemental analytical data. The 1 H NMR spectra of these compounds show doublet signals for the methylene group protons at 4.2 and 4.6 ppm (J = 12 Hz) and a methine proton singlet at 5.0 ppm assigned to the pyrrolidine ring. The 13 C NMR spectra show the signals for atoms C-2 and C-5 of the pyrrolidine ring at 66 and 53 ppm respectively. _________________________________________________________________________________________St.
2 O. -Pyrrolidines (III) are synthesized by reaction of vinylidenecyclopropanes (I) with imines (II) via a cyclopropyl-allyl rearrangement stage and subsequent cyclization. -(STEPAKOV*, A. V.; LARINA, A. G.; RADINA, O. V.; BOITSOV, V. M.; MOLCHANOV, A. P.; Chem. Heterocycl. Compd. (N. Y.) 44 (2008) 4, 430-434; St. Petersburg State Univ., St. Petersburg 198504, Russia; Eng.) -R. Langenstrassen 21-105
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