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Unexpected Stereoselective Access to 2-Aminooxazolines from Propargyl Ureas by Silver Salts under Mild Conditions
Advanced Synthesis & Catalysis ( IF 5.4 ) Pub Date : 2022-10-17 , DOI: 10.1002/adsc.202200950
Aleksandr Voronov 1 , Alessandra Casnati 1 , Paolo P. Mazzeo 1, 2 , Paolo Pelagatti 1, 3 , Alessia Bacchi 1, 2 , Raffaella Mancuso 4 , Bartolo Gabriele 4 , Elena Motti 1, 3 , Giovanni Maestri 1, 3 , Péter Pál Fehér 5 , András Stirling 5, 6 , Nicola Della Ca' 1, 3
Affiliation  

Propargyl ureas can lead to a range of possible heterocyclic compounds, mainly depending on the employed catalyst. Silver salts are known to promote the N-5-exo-dig cyclization mode to imidazolidinone derivatives. Conversely, a versatile and stereoselective O-5-exo-dig cyclization of propargyl ureas to 2-aminooxazolines by Ag(I) catalysis is here disclosed. Good to excellent yields and complete stereoselectivity of the external double bond have been achieved under milder reaction conditions (50–60 °C). A one-pot protocol starting from the corresponding propargylic amines and isocyanates has been developed as well. N,N’-Dipropargyl ureas underwent a uncommon O-5-exo-dig/N-5-endo-dig double cyclization sequence. Finally, insights into the tautomeric equilibrium of 2-aminooxazoles and on their relative reactivity are provided.

中文翻译:

银盐在温和条件下从炔丙基脲中意外立体选择性获得 2-氨基恶唑啉

炔丙基脲可导致一系列可能的杂环化合物,主要取决于所使用的催化剂。已知银盐促进N -5 -exo-dig环化模式生成咪唑啉酮衍生物。相反,此处公开了通过 Ag(I) 催化将炔丙基脲生成 2-氨基恶唑啉的多功能和立体选择性O -5-外切环化。在较温和的反应条件 (50–60 °C) 下,已经实现了良好到极好的收率和外部双键的完全立体选择性。还开发了从相应的炔丙基胺和异氰酸酯开始的一锅法方案。N , N '-二炔丙基脲经历了罕见的O-5- exo-dig/N -5 -endo-dig双环化序列。最后,提供了对 2-氨基恶唑的互变异构平衡及其相对反应性的见解。
更新日期:2022-10-17
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