Dearomative tandem annulation to access chiral indoline-fused bicyclo[2.2.2]octanes using modularly designed organocatalysts

Abstract

Herein, we describe an asymmetric dearomative tandem annulation between 3-nitroindoles and 7-oxo-5-heptenals. The cascade reactions proceeded smoothly using modularly designed organocatalysts self-assembled from cinchona-squaramide and D-proline. As a result, a collection of enantioenriched indoline-fused bicyclo[2.2.2]octanes featuring six vicinal stereocenters were smoothly obtained in good yields with excellent enantioselectivities (up to >99% ee). This protocol provides an economical and practical approach for the asymmetric synthesis of structurally complex indolines.