Metal-free regio- and chemoselective hydroboration of pyridines catalyzed by 1, 3, 2-diazaphosphenium triflate

• Main Authors: Rao, Bin, Chong, Che Chang, Kinjo, Rei
• Other Authors: School of Physical and Mathematical Sciences
• Format: Article
• Language: English
• Published: 2020
• Subjects: Science::Chemistry; Catalysts; Catalytic Reactions
• Online Access: https://hdl.handle.net/10356/137702
• Institution: Nanyang Technological University

N-Heterocyclic phosphenium triflates (NHP-OTf) 1 serve as efficient catalysts for the regio- and chemoselective hydroboration of pyridines under ambient condition with good functional group tolerance. Mechanistic studies indicate that a boronium salt, [(Py)2·Bpin]OTf 4, is generated concomitant with NHP-H 5 via hydride abstraction from HBpin by 1 in the initial reaction step. Hydride reduction of the activated pyridine in [(Py)2·Bpin]OTf 4 by NHP-H 5 affords the 1,4-hydroboration product selectively. Thus, the phosphenium species act as a hydrogen transfer reagent in the catalytic cycle.