Highly enantioselective synthesis of 3,4-dihydropyrans through a phosphine-catalyzed [4+2] annulation of allenones and β,γ-unsaturated α-keto esters.
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 of an anti-hypercholesterolemic agent.
Department of Chemistry, National University of Singapore , 3 Science Drive 3, 117543 Singapore.
Weijun
W
Yao
Xiaowei
X
Dou
Yixin
Y
Lu