Organocatalyzed [4+2] Annulation of All-Carbon Tetrasubstituted Alkenes with Allenoates:Synthesis of Highly Functionalized 2H- and 4H-Pyran Derivatives

A stereoselective [4+ 2] annulation of acyclic all-carbon tetrasubstituted alkenes with allenoates was described. The reaction with DABCO proceeded smoothly leading to the formation of highly functionalized 4H-pyran derivatives in good yields. We have also reported first beta-ICD-catalyzed [4+ 2] annulation affording functionalized enantioenriched 2H-pyran derivatives bearing a chiral all-carbon quaternary center.