Stereoselective synthesis of side chain-functionalized tetrahydropyrans from 5-hexenols |
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Authors: | Patrick Fries Melanie Kim MüllerJens Hartung |
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Institution: | Fachbereich Chemie, Organische Chemie, Technische Universität Kaiserslautern, Erwin-Schrödinger-Straße, D-67663 Kaiserslautern, Germany |
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Abstract: | Molecular oxygen stereoselectively converts 5-hexenols into 2,6-trans-, 2,5-trans-, and 2,4-cis-derivatives of 2-methyltetrahydropyran via oxidative cyclization/radical functionalization cascades, when activated by fluoro-substituted cobalt(II) bis-(β-diketonate) complexes in solutions of cyclohexa-1,4-diene (CHD). Aerobic 5-hexenol oxidations in solutions of bromotrichloromethane and CHD furnish products of 6-exo-bromocyclization, as exemplified by synthesis of diastereomerically pure 2,4,6-substituted tetrahydropyrans. The cobalt method extends to intermolecular alkene/alkanol cross-coupling and to multi-component reactions between dimethyl fumarate, CHD, a 5-hexenol, and dioxygen, providing α-tetrahydropyranyl-2-methyl succinates in synthetically useful yields. |
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Keywords: | Addition Aerobic oxidation Alkenol Alkene Bromocyclization Catalysis Dioxygen Cobalt(II) complexes Michael acceptor Radical Stereoselective synthesis Tetrahydropyran |
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