Base and catalyst-free synthesis of nitrobenzodiazepines via a cascade N-nitroallylation-intramolecular aza-Michael addition involving o-phenylenediamines and nitroallylic acetates |
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Authors: | Divya K. Nair Sudheesh T. Sivanandan Pravin Kendrekar Irishi N.N. Namboothiri |
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Affiliation: | 1. Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400 076, India;2. Unit for Drug Discovery Research (UDDR), Department of Health Sciences, Central University of Technology, Free State (CUT), Private Bag X20539, Bloemfontein 9300, South Africa |
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Abstract: | A [4+3] annulation of o-phenylenediamines with primary nitroallylic acetates affords nitrobenzodiazepines (NBDZs) in good to excellent yield. The reaction which proceeds in MeOH at room temperature in the absence of any base or catalyst involves a cascade SN2 N-nitroallylation-intramolecular aza-Michael addition sequence. In the case of mono-N-arylated o-phenylenediamines and o-aminobenzamides, the reaction stops at the SN2 stage affording nitroallylic amines. On the other hand, reaction of o-aminobenzamides with secondary nitroallylic acetates delivers SN2′ products. Formation of stable SN2 and SN2′ products provides insights into the reactivity of primary and secondary nitroallylic acetates and also the mechanism of formation of nitrobenzodiazepines. |
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Keywords: | Corresponding author. Morita-Baylis-Hillman Benzodiazepine Aza-Michael addition Nitroallylic acetates |
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