Enantioselective [4+2] Cycloadditions of 2-Vinyl-1 H-indoles with 3-Nitro-2 H-chromenes Catalyzed by a Zn(OTf)2/Bis(oxazoline) Complex: An Efficient Approach to Fused Heterocycles with a Quaternary Stereocenter
There's a ringer: The asymmetric [4+2] cycloaddition reaction of 3‐nitro‐2H‐chromenes with 1‐benzyl‐2‐vinyl‐1H‐indoles catalyzed by Zn(OTf)2 with bis(oxazoline) ligands offers a practical and efficient method to synthesize a variety of fused heterocycles bearing a quaternary stereocenter with good reaction efficiency (up to 94% yield) and excellent stereoselectivities (up to 96% ee, >95:5 d.r.).