Formation of N-substituted 4- and 7-oxo-4,5,6,7-tetrahydroindoles revisited: a mechanistic interpretation and conversion into 4- and 7-oxoindoles |
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Authors: | Antonio Garrido Montalban Sven M. BaumJustin Cowell Alexander McKillop |
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Affiliation: | School of Chemical Sciences, University of East Anglia, Norwich NR4 7TJ, UK |
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Abstract: | An efficient method for the preparation of 4-oxo-4,5,6,7-tetrahydroindoles was successfully applied to the synthesis of N-substituted 7-oxo-4,5,6,7-tetrahydroindoles for the first time. Both isomers where converted into their corresponding 4- and 7-oxoindoles in good yields utilizing a novel aromatization protocol. Based on the impurity profile obtained, however, different mechanisms for the formation of the 4- and 7-oxo-4,5,6,7-tetrahydroindole derivatives are discussed. In addition, the reaction sequences appear to be stereospecific allowing for the direct introduction of a chiral center α to the nitrogen and preparation of enantiomerically enriched products. |
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Keywords: | Indoles Tetrahydroindoles Cyclization Aromatization Chirality |
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