In-Depth Assessment of the Palladium-Catalyzed Fluorination of Five-Membered Heteroaryl Bromides
作者:Phillip J. Milner、Yang Yang、Stephen L. Buchwald
DOI:10.1021/acs.organomet.5b00631
日期:2015.10.12
A thorough investigation of the challenging Pd-catalyzed fluorination of five-membered heteroaryl bromides is presented. Crystallographic studies and density functional theory (DFT) calculations suggest that the challenging step of this transformation is C-F reductive elimination of five-membered heteroaryl fluorides from Pd(II) complexes. On the basis of these studies, we have found that various heteroaryl bromides bearing phenyl groups in the ortho position can be effectively fluorinated under catalytic conditions. Highly activated 2-bromoazoles, such as 8-bromocaffeine, are also viable substrates for this reaction.
Synthesis of sulfonamides from azoles and sodium sulfinates at ambient temperature
reaction shows good substrate scope and tolerates a wide range of functionalities in both azoles and sodium sulfinate substrates. Pyrazoles are also suitable for this method, various 4-halopyrazoles derivatives were obtained by using N-halosuccinimide (NXS) as the halogen source.