Zinc-Catalyzed Alkyne Oxidation/CH Functionalization: Highly Site-Selective Synthesis of Versatile Isoquinolones and β-Carbolines

• Published in: Angewandte Chemie International Edition Vol. 54; no. 28; pp. 8245 - 8249
• Main Authors: Li, Long, Zhou, Bo, Wang, Yong-Heng, Shu, Chao, Pan, Yi-Fei, Lu, Xin, Ye, Long-Wu
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 06.07.2015; WILEY‐VCH Verlag
• Subjects: Acids, Heterocyclic - chemistry; Carbolines - chemistry; Catalysis; heterocycles; homogeneous catalysis; nitrogen oxides; Nitrogen Oxides - chemistry; Oxidation-Reduction; synthetic methods; zinc; Zinc - chemistry; homogeneous catalysis; heterocycles; zinc; nitrogen oxides; synthetic methods
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.201502553

An efficient zinc(II)‐catalyzed alkyne oxidation/CH functionalization sequence was developed, thus leading to highly site‐selective synthesis of a variety of isoquinolones and β‐carbolines. Importantly, in contrast to the well‐established gold‐catalyzed intermolecular alkyne oxidation, over‐oxidation can be completely suppressed in this system and the reaction most likely proceeds by a Friedel–Crafts‐type pathway. Mechanistic studies and theoretical calculations are described. Swap gold for zinc: The title reaction was achieved by a zinc(II)‐catalyzed alkyne oxidation/CH functionalization sequence. In contrast to the well‐established gold‐catalyzed intermolecular alkyne oxidation, the over‐oxidation can be suppressed in this system and the reaction most likely proceeds by a Friedel–Crafts‐type pathway. Tf=trifluoromethanesulfonyl, PG=protecting group.