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SiCl4-catalyzed/PR3-mediated β-C(sp3)−H functionalization of nitrones to α,β-unsaturated imines and aromatic heterocycles
- Zhu, De-Ping, Xu, Bao-Hua, Du, Yi-Ran, Zhang, Suo-Jiang
- Tetrahedron 2018 v.74 no.18 pp. 2230-2238
- Lewis acids, Lewis bases, acidity, aldehydes, aromatization, chemical structure, condensation reactions, imines, ketones, phosphine
- A novel method of SiCl4-catalyzed/PR3-mediated β-C(sp3)−H functionalization of nitrones with aldehydes/ketones to α,β-unsaturated imines was developed. The synthesis of α,β-unsaturated imines mainly invovles deoxygenation and aldol condensation, each proceeding under a cooperation effect between Lewis acid and Lewis base. In addition, both the acidity and hydrolytic stability of the weak SiCl4 were supposed to be enhanced by coordination with phosphine oxide (R = Et) or phosphoric triamide (R = NMe2) that originated from deoxygenation of nitrones by PR3. In the case of 6-membered nitrone, a [1,3]-hydride shift within the resulted α,β-unsaturated imines renders the aromatization leading to 3,5-dialkylpyridines.