Highly Enantioselective Synthesis of 3,4-Dihydropyrans through a Phosphine-Catalyzed [4+2] Annulation of Allenones and β,γ-Unsaturated α-Keto Esters
作者:Weijun Yao、Xiaowei Dou、Yixin Lu
DOI:10.1021/ja5109358
日期:2015.1.14
A phosphine-catalyzed novel [4+2] annulation process was devised employing allene ketones as C2 synthons and β,γ-unsaturated α-keto esters as C4 synthons. In the presence of an L-threonine-derived bifunctional phosphine, 3,4-dihydropyrans were obtained in high yields and with virtually perfect enantioselectivities. The synthetic value of the dihydropyran motif was demonstrated by a concise preparation