Formation of new 4-isocyanobut-2-enenitriles by thermal ring cleavage of 3-pyridyl azides |
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Authors: | Vegar Stockmann Per Bruheim |
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Institution: | a Department of Chemistry, Sem Saelands v. 8, Norwegian University of Science and Technology, NTNU, NO-7491 Trondheim, Norway b Department of Biotechnology, Sem Saelands v. 8, Norwegian University of Science and Technology, NTNU, NO-7491 Trondheim, Norway |
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Abstract: | A new thermal ring cleavage of 3-pyridyl nitrenes for the formation of 4-isocyanobut-2-enenitrile products is reported. Thermolysis of 4-(thien-3-yl)-3-pyridyl azide 1 and 3-azido-4-(1-TIPS-1H-pyrrol-3-yl)pyridine 5 afforded two new isonitrile-nitrile products by ring cleavage; 4-isocyano-2-(thiophen-3-yl)but-2-enenitrile (3, 27%) and 4-isocyano-2-(1-TIPS-1H-pyrrol-3-yl)but-2-enenitrile (7, 20%), in addition to our previously reported pyrido3,4-b]thienopyrrole (2, 29%) and pyrido3,4-b]pyrrolo3,2-d]pyrrole (6, 71%) products. Minor amounts of 2-(thien-3-yl)-1H-pyrrole-3-carbonitrile (4, 6%), formed by ring contraction, were also isolated after thermolysis of azide 1. Isonitriles 3 and 7 underwent degradation into amine 3b and formamide 7a by acidic hydrolysis. The nature and chemistry of compounds 3, 4 and 7 were investigated. |
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Keywords: | 3-Pyridylazide 3-Pyridyl nitrene Thermolysis 4-Isocyano-2-(thiophen-3-yl)but-2-enenitrile 4-Isocyano-2-(1-TIPS-1H-pyrrol-3-yl)but-2-enenitrile 2-(Thien-3-yl)-1H-pyrrole-3-carbonitrile |
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