C-Quaternary Vinylglycinols by Metal-Catalyzed Cyclization of Allylic Bistrichloroacetimidates
作者:Aigars Jirgensons、Kristine Klimovica、Liene Grigorjeva、Ansis Maleckis、Juris Popelis
DOI:10.1055/s-0031-1289537
日期:2011.12
Bistrichloroacetimidates derived from 2-substituted but-2-ene-1,4-diols are transformed into 4-substituted 4-vinyloxazolines in high yields and excellent regioselectivities when Lewis acids AlCl3, FeCl3, TMSOTf, BF3ËOEt2, and AgBF4 are used as catalysts as well as with the Pd(PPh3)2Cl2/AgBF4 catalytic system. Lower regioselectivity is achieved with a neutral PdCl2(MeCN)2 catalyst and this could be a consequence of a switch to a competitive but less selective reaction mechanism. It is demonstrated that 4-substituted 4-vinyloxazolines can be efficiently transformed to N-Boc-protected C -quaternary vinylglycinols in a one-pot procedure.
由2-取代丁-2-烯-1,4-二醇衍生的双三氯乙酰亚胺酯在Lewis酸催化剂如AlCl3、FeCl3、TMSOTf、BF3·OEt2和AgBF4,以及Pd(PPh3)2Cl2/AgBF4催化体系的作用下,能够高产率且具有优异的区域选择性地转化为4-取代的4-乙烯基噁唑啉。使用中性PdCl2(MeCN)2催化剂时,区域选择性较低,这可能是由于反应机制转变为竞争性但选择性较低的机制。研究表明,4-取代的4-乙烯基噁唑啉可以通过一步反应高效转化为N-Boc保护的C-季铵化乙烯基甘醇。