Batch Versus Flow Lithiation–Substitution of 1,3,4‐Oxadiazoles: Exploitation of Unstable Intermediates Using Flow Chemistry
| Autor: | Filipe Vilela, John M. Tobin, Graeme Barker, Jeff Y. F. Wong |
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| Rok vydání: | 2019 |
| Předmět: |
010405 organic chemistry
Chemistry Metalation Organic Chemistry Mixing (process engineering) General Chemistry Flow chemistry Alkylation 010402 general chemistry Ring (chemistry) 01 natural sciences Decomposition Catalysis 0104 chemical sciences Fragmentation (mass spectrometry) Computational chemistry Electrophile |
| Zdroj: | Chemistry – A European Journal. 25:12439-12445 |
| ISSN: | 1521-3765 0947-6539 |
| DOI: | 10.1002/chem.201902917 |
| Popis: | 1,3,4-Oxadiazoles are a common motif in pharmaceutical chemistry, but few convenient methods for their modification exist. A fast, convenient, high yielding and general α-substitution of 1,3,4-oxadiazoles has been developed using a metalation-electrophilic trapping protocol both in batch and under continuous flow conditions in contradiction to previous reports which suggest that α-metalation of this ring system results in ring fragmentation. In batch, lithiation is accomplished at an industrially convenient temperature, -30 °C, with subsequent trapping giving isolated yields of up to 91 %. Under continuous flow conditions, metalation is carried out at room temperature, and subsequent in flow electrophilic trapping gave up to quantitative isolated yields. Notably, lithiation in batch at room temperature results only in ring fragmentation and we propose that the superior mixing in flow allows interception and exploitation of an unstable intermediate before decomposition can occur. |
| Databáze: | OpenAIRE |
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