Copper‐Catalyzed Tandem Cyclization Approach toN,O‐Chelated Boron Difluoride Complexes

Abstract

A strategy for synthesizing N,O‐chelated boron difluoride complexes via copper‐catalyzed tandem cyclization of readily available 2‐aryl pyridines has been developed. This reaction tolerates a wide range of functional groups, providing the corresponding products in 43–91% yield. Furthermore, the photophysical properties were investigated by measuring the UV/Vis absorption and fluorescence spectra of several product derivatives.

Recent advances in oxidative chlorination

“…On the basis of the previous study on oxidative functionalization of indoles, Xu, Ma and Tong continued to establish a oxone/halide-mediated halogenation of indoles (Scheme 42). 68 The presence of electron-withdrawing groups on the N1 of indole enables C2 chlorination with oxone and KCl (22 examples, 50-88% yield). C3 chlorination of indoles can be reached selectively by the use of KCl and oxone, without dependence on the electronic nature of N1 protective groups (14 examples, 62-91% yield).…”

Iron(III) and BF3·OEt2-Promoted O-Transfer Reaction of N-Aryl-α,β-Unsaturated Nitrones to Prepare Difluoroboron β-Ketoiminates

“…Some N , O -difluoroboron scaffolds have been designed, and their photophysical properties have been studied in the past decades (Scheme A) . The vast majority of reported methods toward the preparation of N , O -difluoroboron complex included the condensation of β-diketones with a primary amine and subsequent reaction with BF 3 , multiple component cascade reactions of alkyne/amines/acyl chlorides/BF 3 , the condensation of β-epoxy ketones with a primary amine and subsequent reaction with BF 3 , the condensation of 2-pyridylacetophenones or nitrogen-containing heterocycle with BF 3 , or oxidative C–H activation of pyridine derivatives and sequential reaction with BF 3 . Although these strategies have shown efficient approaches to access N , O -difluoroboron complexes, regioselectivity issues in the condensation step limit in these cases of preparation of unsymmetrical β-diketones, β-epoxy ketones, or C–H activation.…”