SHORT COMMUNICATIONSTetrahydroindolizine fragment is a structural unit of many natural and unnatural compounds possessing diverse biological activity [1][2][3]. Known methods for the preparation of tetrahydroindolizine derivatives are tedious, and the yields of the target products are poor [4,5]. Therefore, development of new procedures for their synthesis is an important problem in medicinal and organic chemistry.In the present communication we report on a new convenient one-step procedure for the synthesis of tetrahydroindolizines via successive intra-and intermolecular alkylations of 2-methyl-and 2-phenyl-1-(4,4-diethoxybutyl)pyrroles I and II in the presence of a catalytic amount of Yb(OTf) 3 (Scheme 1). The yields of compounds III and IV were 40-45% when the reactions were carried out in tetrahydrofuran at room temperature over a period of three days. A probable mechanism of formation of tetrahydroindolizines III and IV (Scheme 2) involves intramolecular nucleophilic addition of C 5 in the pyrrole ring at the acetal carbon atom in the side chain, which bears a partial positive charge enhanced by interaction with the catalyst. Intramolecular ring closure in intermediate complex A gives complex B which reacts with the second substrate molecule, and subsequent elimination of ethanol yields the final product.

SHORT COMMUNICATIONSIsoindoles occupy a particular place in the chemistry of heterocyclic compounds [1,2]. Some isoindole derivatives were found to exhibit antihypertensive, antidiabetic, and antibacterial activity [3,4]. Polymeric composite materials based on isoindoles and methanoisoindoles are used in optoelectronics as fluorescent sensors and laser dyes [5,6]. Aromatic character and high reactivity of isoindoles make them convenient model substrates for theoretical studies [7].Among isoindole derivative, methanoisoindoles have been studied relatively poorly, and available data on these compounds are contradictory [7]. Lebedev et al.[4] described a procedure for the synthesis of 4-aryl-4-azatricyclo[5.2.1.0 2,6 ]deca-2,5,8-trienes ΙΙ in 62-65% yield by reaction of amines with cyclopentadiene adduct Ι with cis/trans-isomeric 2,5-dimethoxy-2,5-dihydrofurans in glacial acetic acid at 70-100°C (Scheme 1). However, we failed to reproduce this procedure. Kobayashi et al. [7] also failed to obtain compound ΙΙ under the conditions described in [4]. The authors [7] developed a four-step procedure for the synthesis of ΙΙ via reaction of aromatic amine with 3-(diethoxymethyl)bicyclo[2.2.1]hepta-2,5-diene-2-carbaldehyde (adduct of cyclopentadiene with 4,4-diethoxybut-2-ynal), followed by reduction of the products to amines and cyclization of the latter to the corresponding methanoisoindoles. However, the yields were relatively poor (18-22%).We succeeded in obtaining compound ΙΙa in 55-60% yield by treatment of adduct Ι with 2 N aqueous HCl at 75°C over a period of 0.5 h (as described in [8]) and subsequent addition of a mixture of 5 equiv of aniline and AcONa · 7 H 2 O in CHCl 3 . Presumably, initial hydrolysis of compound Ι gives intermediate dialdehyde A which then reacts with amine according to Paal-Knorr to afford compounds ΙΙ (Scheme 2). R = Ph (a), PhCH 2 (b). Scheme 2.

A New Synthesis of Methanoisoindoles (III). -(MAGERRAMOV, A. M.; ALIEV, I. A.; ASKEROVA, U. F.; AKHMEDOV, I. M.; FARZALIEV, S. F.; Russ. J. Org. Chem. 48 (2012) 4, 605-606, http://dx.doi.org/10.1134/s1070428012040264 ; Baku State Univ., Baku 370073, Azerbaijan; Eng.) -R. Langenstrassen 41-124

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