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

• Published in: Angewandte Chemie International Edition 2022-10, Vol.61 (42), p.e202210207-n/a
• Main Authors: Yang, Wu‐Lin, Shang, Xin‐Yu, Ni, Tao, Yan, Hui, Luo, Xiaoyan, Zheng, Hanliang, Li, Zhong, Deng, Wei‐Ping
• Format: Article
• Language: English
• Subjects: Allyl compounds; Allylation; Aniline; Asymmetric Synthesis; Cascade chemical reactions; Catalysis; Chemical reactions; Enantiomers; Iridium; Isomerization; Phenols; Reaction mechanisms; Silver; Spiroketals; Stereochemistry; Stereoselectivity; Ternary Catalysis
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202210207

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. A cycloisomerization/asymmetric allylation/spiroketalization cascade reaction of o‐alkynylacetophenones and (1‐hydroxyallyl)phenols enabled by Ir/Ag/acid ternary catalysis was developed, affording structurally diverse bisbenzannulated [6,6]‐spiroketals in high efficiency with mostly high diastereoselectivities and excellent enantioselectivities.