Four-coordinate boron compounds derived from 2-(2-pyridyl)phenol ligand as novel hole-blocking materials for phosphorescent OLEDs

PdCl2 and N‐Hydroxyphthalimide Co‐catalyzed CH Hydroxylation by Dioxygen Activation

“…[6] Nevertheless, for substrates with other directing groups, the transition-metal-catalyzed direct hydroxylation is still difficult (Scheme 1 c). Functionalized 2-(pyridin-2-yl)phenols are useful building blocks for preparing light-emitting materials [8] and bioactive molecules. Functionalized 2-(pyridin-2-yl)phenols are useful building blocks for preparing light-emitting materials [8] and bioactive molecules.…”

“…[11] A unique and reasonable mechanism is proposed for this reaction, which will probably promote the development of C sp 2 ÀH functionalization by the combination of a radical process with a transition-metal catalysis. [8] 3) Molecular oxygen is employed as a reagent and the sole oxidant under neutral conditions without the addition of any other stoichiometric oxidant and base, thus making this protocol very green and practical. [8] 3) Molecular oxygen is employed as a reagent and the sole oxidant under neutral conditions without the addition of any other stoichiometric oxidant and base, thus making this protocol very green and practical.…”

“…Alternatively, a hydrolysis process assisted by various stoichiometric oxidants (potassium persulfates or periodides) for substrates with carbonyl groups was disclosed by the groups of Rao, [7a] Dong, [7b] Kwong, [7c] and Ackermann [7d-e] (Scheme 1 c). Functionalized 2-(pyridin-2-yl)phenols are useful building blocks for preparing light-emitting materials [8] and bioactive molecules. [9] Recent development for the synthesis of these compounds was realized by this hydrolysis strategy through R-OAc intermediates.…”

“…2) To the best of our knowledge, this reaction is a novel pyridyl group directed [12] hydroxylation with O 2 , thus leading to useful products for preparing various biologically active molecules, [9] organic, and light-emitting materials. [8] 3) Molecular oxygen is employed as a reagent and the sole oxidant under neutral conditions without the addition of any other stoichiometric oxidant and base, thus making this protocol very green and practical.…”

“…[9] In addition, 2-(pyridin-2-yl)phenols are widely used in organic light-emitting materials as a ligand because of their two strong chelating groups (the hydroxy group and the pyridine ring; Schemes 4 b,c,e, and f). [8] For example, the four-coordinate boron compound 3 is a novel hole-blocking material for phosphorescent OLEDs, [8a] and was easily prepared in 70 % yield from our product 2 a (Scheme 4 c). According to the literature, the ligand has an important influence on these materials properties.…”