Metal‐Free Directed C−H Borylation of Pyrroles

• Published in: Angewandte Chemie International Edition Vol. 60; no. 15; pp. 8500 - 8504
• Main Authors: Wang, Zheng‐Jun, Chen, Xiangyang, Wu, Lei, Wong, Jonathan J., Liang, Yong, Zhao, Yue, Houk, Kendall N., Shi, Zhuangzhi
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 06.04.2021; Wiley Subscription Services, Inc
• Edition: International ed. in English
• Subjects: Chelation; Chemistry; Chemistry, Multidisciplinary; C−H borylation; DFT calculations; metal-free reactions; Physical Sciences; Pyrroles; Science & Technology; Selectivity; site-selectivity; site-selectivity; H borylation; pyrroles; metal-free reactions; C− DFT calculations; C−H borylation
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.202016573

Robust strategies to enable the rapid construction of complex organoboronates in selective, practical, low‐cost, and environmentally friendly modes remain conspicuously underdeveloped. Here, we develop a general strategy for the site‐selective C−H borylation of pyrroles by using only BBr3 directed by pivaloyl groups, avoiding the use of any metal. The site‐selectivity is generally dominated by chelation and electronic effects, thus forming diverse C2‐borylated pyrroles against the steric effect. The formed products can readily engage in downstream transformations, enabling a step‐economic process to access drugs such as Lipitor. DFT calculations (wB97X‐D) demonstrate the preferred positional selectivity of this reaction. An efficient metal‐free system has been uncovered for the site‐selective C−H borylation of pyrroles by using only BBr3 directed by pivaloyl groups. The site‐selectivity is generally dominated by chelation and electronic effects, thus forming diverse C2‐borylated pyrroles against the steric effect.