Simultaneous synthesis of 4,5-dihydro-3H-azepines and 3H-azepines, bearing alkoxy and alkylsulfanyl substituents, through metallation of 2-aza-1,3,5-trienes by t-BuOK |
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Authors: | Nina A. Nedolya,Ol&rsquo ga A. Tarasova,Ol&rsquo ga G. Volostnykh,Alexander I. Albanov,Boris A. Trofimov |
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Affiliation: | A. E. Favorsky Irkutsk Institute of Chemistry of the Russian Academy of Sciences, Siberian Branch, Favorsky Street 1, 664033 Irkutsk, Russia |
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Abstract: | A new range of alkoxy- and alkylsulfanyl-substituted 4,5-dihydro-3H-azepines and 3H-azepines have simultaneously been obtained from conjugated 2-aza-1,3,5-trienes by treatment with t-BuOK under mild reaction conditions (THF/DMSO, ∼−30 °C, 30 min). One-pot synthesis of 1-aza-1,3,4-trienes from α-lithiated alkoxyallenes, isopropyl isothiocyanate and alkyl iodides, followed by the thermally induced sigmatropic [1,5]-H shift, easily leads to starting 2-aza-1,3,5-trienes. The reaction proceeds via generation and [1,7]-electrocyclization of azatrienyl anions and represents a novel simple approach to both azacycloheptadienes and azacycloheptatrienes. |
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Keywords: | 4,5-Dihydro-3H-azepines 3H-Azepines Azatrienes Metallation Hydrogen transfer [1,7]-Electrocyclization |
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