0009-3122/12/4803-0514©2012 Springer Science+Business Media, Inc. 514 Chemistry of Heterocyclic Compounds, Vol. 48, No. 3, June, 2012 (Russian Original Vol. 48, No. 3, March, 2012) OPENING OF THE EPOXIDE BRIDGE IN 3a,6-EPOXYISOINDOL-1-ONES BY THE ACTION OF BF 3 ·Et 2 O IN ACETIC ANHYDRIDE* F. I. Zubkov 1 **, V. P. Zaytsev 1 , E. S. Puzikova 1 , E. V. Nikitina 1 , V. N. Khrustalev 2 , R. A. Novikov 3 , and A. V. Varlamov 1 The opening of the epoxide bridge in N-substituted 2,3,7,7a-tetrahydro-3a,6-epoxyisoindol-1-ones by the action of BF 3 ·Et 2 O in acetic anhydride at 25°C over 1 h proceeds through an S N 1 mechanism. The allylic type cation formed in the first step is stabilized by the addition of an acetoxy group at C-5 in the isoindole system to give a mixture of cis and trans isomers of 5,6-diacetoxy-2,3,5,6,7,7a-hexa- hydroisoindol-1-ones, which are aromatized under these conditions over 24 h to give 2,3-dihydro- 1H-isoindol-1-ones. Keywords: 3a,6-epoxyisoindole, furan, furfurylamine, isoindole, 7-oxabicyclo[2.2.1]heptene, aromati- zation, intramolecular Diels-Alder reaction. The nucleophilic opening of 7-oxabicyclo[2.2.1]heptenes is known to proceed with high regio- and stereoselectivity, predominantly through an S N 2' mechanism (accompanied by migration of the double bond) [1, 2] and, as a consequence, is commonly used for stereodirected synthesis of polysubstituted cyclohexenes [3, 4]. The regularities of the electrophilic opening of the epoxide bridge in 7-oxabicyclo[2.2.1]heptenes has not been studied as extensively. In this case, depending on the conditions, the formation of an often unpredicted variety of products is possible [5-7]. In the present work, we continue our systematic investigation of the transformations of the oxabicycloheptene ring in 3a,6-epoxyisoindol-1-ones 1 in acidic media [8, 9]. Previous results [10-14] have indicated that these reactions even for similar reagents under similar experimental conditions may lead to different products. Some examples of such transformations are given below. However, most frequently, the action of electrophiles such as H 3 PO 4 [8], HCl [15], p-TsOH [16], and BF 3 ·Et 2 O [17] on oxabicycloheptenes _______ *Dedicated to the memory of Prof. N. S. Prostakov, Honored Science Worker of the Russian Federation, founder of the organic chemistry department at the Peoples' Friendship University of Russia. **To whom correspondence should be addressed, e-mail: fzubkov@sci.pfu.edu.ru. 1 Peoples' Friendship University of Russia, 6 Miklukho-Maklaya St., Moscow 117198, Russia. 2 A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 28 Vavilova St., GSP-1, Moscow 119991, Russia; e-mail: vkh@xrlab.ineos.ac.ru. 3 V. A. Engel'gardt Institute of Molecular Biology, 32 Vavilova St., Russian Academy of Sciences, Moscow 119991, Russia; e-mail: novikovfff@bk.ru. _________________________________________________________________________________________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 549-560, March, 2012. Original article submitted January 17, 2012.