An efficient method to synthesize N/O, O-difluoroboron complexes from alkynes

Harnessing reductive BF2-complexation via Ru(II)-catalyzed N-O cleavage of isoxazoles

Developed here is a highly fluorescent organic N,O bidentate BF2 complex from isoxazole in the presence of a Ru(II) catalyst. Herein, the complexation proceeds via a selective N-O cleavage of the isoxazole ring. The complex shows absorption (λmax,abs) in the range of 352-363 nm with an extinction coefficient (ε) in the range of 8000-64 000 M-1 cm-1, and fluorescence emission (λmax,em) in the range of 413-485 nm with a Stokes shift of 61-125 nm having quantum yield up to 33%. Apart from the solution state, the solid BF2 complex 2u exhibits absorption at 405 nm and strong fluorescence emission at 550 nm with a quantum yield of 26.9%.

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

We described an iron(III) and BF3·OEt2-promoted oxygen transfer reaction of N-aryl-α,β-unsaturated nitrones to prepare various N,O-difluoroboron β-ketoiminates in good yields ranging from 24% to 87%. Control experiments revealed that the enaminone was the vital intermediate for the formation of N,O-difluoroboron β-ketoiminates, and iron(III) combined with BF3·OEt2 played as cocatalyst to promote the oxygen transfer reaction through intramolecular cyclization and N-O bond cleavage. More importantly, an estrone-derived N,O-difluoroboron β-ketoiminate was easily prepared in 40% yield from estrone in four steps.

De Novo Synthesis of α-Oligo(arylfuran)s and Its Application in OLED as Hole-Transporting Material

Tuning the photophysical properties of π-conjugated oligomers by functionalization of skeleton, to achieve an optically and electronically advantageous building block for organic semiconductor materials is a vital yet challenging task. In this work, a series of structurally well-defined polyaryl-functionalized α-oligofurans, in which aryl groups are introduced precisely into each of the furan units, are rapidly and efficiently synthesized by de novo metal-free synthesis of α-bi(arylfuran) monomers for the first time. This new synthetic strategy nicely circumvents the cumbersome substituent introduction process in the later stage by the preinstallation of the desired aryl groups in the starting material. The characterization of α-oligo(arylfuran)s demonstrates that photoelectric properties of coplanar α-oligo(arylfuran)s can be tuned through varying aryl groups with different electrical properties. These novel α-oligo(arylfuran)s have good hole transport capacity and can function as hole-transporting layers in organic light-emitting diodes, which is indicative of significant breakthrough in the application of α-oligofurans materials in OLEDs. And our findings offer an avenue for the ingenious use of α-oligo(arylfuran)s as p-type organic semiconductors for OLEDs.

Deconstructive Cycloaromatization Strategy toward N,O-Bidentate Ligands from Indolizines and Cyclopropenones

The innovative construction of novel N,O-bidentate ligands represents a long-standing challenge for chemists. Here, we report an unprecedented approach for the construction of N,O-bidentate derivatives via the merging of ring deconstruction with cycloaromatization of indolizines and cyclopropenones. Without any catalysts, our method can deliver a series of polyaryl 2-(pyridin-2-yl)phenols in excellent yields. In addition, N,O-bidentate organic BF₂ complexes can also be constructed via this one-pot protocol.

Modular construction of α-furanyl ketones via semi-pinacol rearrangement-mediated ring expansion

An efficient semi-pinacol rearrangement strategy of enynals involving a metal carbene intermediate has been developed, which allows the practical synthesis of various functionalized α-furanyl ketones in moderate to good yields under mild reaction conditions.