Synthesis of 5-aminoisoxazolines from N-allyl compounds and nitrile oxides via tandem isomerization-1,3-dipolar cycloaddition |
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Authors: | Piotr Bujak Stanis?aw Krompiec Micha? Krompiec Witold Danikiewicz Katarzyna G?barowska |
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Institution: | a Institute of Chemistry, Faculty of Mathematics, Physics and Chemistry, University of Silesia ul. Szkolna 9, 40-007 Katowice, Poland b Institute of Organic Chemistry, Polish Academy of Science, ul. Kasprzaka 44/52, 01-224 Warszawa 42, PO Box 58, Poland c Centre of Polymer Chemistry, Polish Academy of Science, ul. Sk?odowskiej-Curie 34, 41-819 Zabrze, Poland |
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Abstract: | A new strategy for the synthesis of derivatives of 5-aminoisoxazolines via tandem catalytic isomerization (of N-allyl systems to N-(1-propenyl) systems)—1,3-dipolar cycloaddition (of a stable nitrile oxide to N-(1-propenyl) systems) is presented. Rhodium and ruthenium complexes, Verkade’s superbase, and 18-crown-6/KOH system were used for the syntheses of the N-(1-propenyl) systems. 4-P-substituted isoxazoline was also synthesized via cycloaddition of diphenyl(1-propenyl)phosphine (prepared via isomerization of allyldiphenylphosphine) to 2,6-dichlorobenzonitrile oxide. All cycloadditions were regioselective but not stereoselective and not concerted. Cycloaddition to all N-(1-propenyl) systems yielded 5-N-substituted isoxazolines, but cycloaddition to P-(1-propenyl) system lead to the formation of a 4-P-regioisomer. This difference in regioselectivity is predicted by opposite FMO reactivity indices calculated for model compounds: N-(1-propenyl)amine and N-(1-propenyl)phosphine. |
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Keywords: | N-Allyl systems Isomerization 1 3-Dipolar cycloaddition Isoxazoline Verkade&rsquo s base |
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