Chiral Phosphoric Acid-Catalyzed Asymmetric [4 + 2] Cycloadditions of Photogenerated o -Quinodimethanes with Vinylazaarenes

Chiral cyclohexyl-appended azaarenes are highly sought synthetic targets in biochemistry and medicinal chemistry. Herein we report a chiral phosphoric acid-catalyzed asymmetric [4 + 2] cycloaddition reaction between photogenerated o -quinodimethanes and alkenylazaarenes. A wide range of cyclohexyl-appended azaarenes are obtained in moderate to high yields (up to 85%) with high diastereoselectivities (up to 20:1 dr) and excellent enantioselectivities (up to 98% ee). A scale-up experiment and derivatizations of products demonstrate the practical utility of this synthetic method.