General synthetic approach towards annelated 3a,6-epoxyisoindoles by tandem acylation/IMDAF reaction of furylazaheterocycles. Scope and limitations |
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Authors: | Fedor I Zubkov Eugenia V Nikitina Timur R Galeev Vladimir P Zaytsev Victor N Khrustalev Roman A Novikov Daria N Orlova Alexey V Varlamov |
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Institution: | 1. Department of Organic Chemistry, Peoples'' Friendship University of Russia, 6 Miklukho-Maklaya St., Moscow 117198, Russian Federation;2. Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84322, USA;3. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 28 Vavilov St., Moscow 119991, Russian Federation;4. V.A. Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, 32 Vavilov St., Moscow 119991, Russian Federation |
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Abstract: | An efficient and versatile one-pot synthesis of 3,6a-epoxyisoindoles annelated with oxazine, oxazole, thiazine, thiazole, pyrimidine fragments and with their benzoannelated analogues is presented. The method is based on tandem N-acylation/intramolecular cycloaddition (the intramolecular Diels–Alder reaction of furan, IMDAF) reaction between α,β-unsaturated acid anhydrides and α-furyl substituted azaheterocycles. The latter can be easily prepared by condensation of diverse furfurals and 1,2- or 1,3-N,X-binucleophiles (aminoalcohols, aminothiols, diamines). The observed IMDAF reaction is stereoselective: exo-adducts are formed exclusively with large prevalence of one of the diastereoisomers. In most cases, the condensation/N-acylation/IMDAF reaction sequence may be carried out via a one-pot domino protocol. The scope and limitations of the proposed approach are thoroughly investigated. The obtained Diels–Alder adducts are attractive and useful substrates for further transformations. Fused isoindoles can be prepared from them in one-step by aromatization of the 7-oxabicyclo2.2.1]heptene ring. Other transformations, including halogenation, ring cleavage, and Wagner–Meerwein skeletal rearrangement, are also demonstrated. The spatial structures of the obtained compounds have been established by X-ray diffraction analyses. |
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Keywords: | Furan Cycloaddition IMDAF Isoindole Wagner&ndash Meerwein rearrangement |
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