Diastereo‐ and Enantioselective Synthesis of Bisbenzannulated Spiroketals and Spiroaminals by Ir/Ag/Acid Ternary Catalysis

Abstract We reported herein an iridium/silver/acid ternary catalytic system to access bisbenzannulated [6,6]‐spiroketals in high efficiency with generally high diastereo‐ and enantioselectivities (up to >20 : 1 dr, >99 % ee). In this procedure, readily available o ‐alkynylacetophenones undergo cycloisomerization to generate isochromenes in situ that participate in stereoselective allylation/spiroketalization sequence with 2‐(1‐hydroxyallyl)phenols. Meanwhile, 2‐(1‐hydroxyallyl)anilines were also compatible in this cascade reaction, furnishing structurally novel bisbenzannulated [6,6]‐spiroaminals with good diastereoselectivities (8 : 1–12 : 1 dr) and excellent enantioselectivities (98 %–>99 % ee). Moreover, experimental studies and theoretical calculations were performed to illustrate the reaction mechanism and stereochemistry.