Cu(II)-Catalyzed Hydroboration Reactions of 1,1-Disubstituted α,ß-Unsaturated Ketones, Esters, and Amides in Pure Water.

Here, a Cu2(OH)2CO3-catalyzed hydroboration reaction of 1,1-disubstituted α,ß-unsaturated compounds has been developed. The reaction was carried out using water as a solvent at room temperature except for N-monosubstituted α,ß-unsaturated amides. This method is applicable to diverse 1,1-disubstituted α,ß-unsaturated ketones, esters, and amides, showing excellent reactivity (up to 98% yield). Gram-scale experiments and functional group transformations further demonstrated the practicality of this method.

Preparation of Chitosan-Composite-Film-Supported Copper Nanoparticles and Their Application in 1,6-Hydroboration Reactions of p-Quinone Methides.

Here, we describe the preparation of copper nanoparticles that are stabilized on a chitosan composite film (CP@Cu). This material could catalyze the 1,6-hydroboration reactions of p-quinone methides with B2pin2 as a boron source under mild conditions. This reaction exhibited very good functional group compatibility, and the organoboron compounds that were formed could easily be converted into corresponding hydroxyl products with good to excellent yields. This newly developed methodology provides an efficient and sequential pathway for the synthesis of gem-disubstituted methanols.

Enantioselective Synthesis of Fused Isocoumarins via Palladium-Catalyzed Annulation of Alkyne-Tethered Malononitriles.

An enantioselective palladium-catalyzed annulation of alkyne-tethered malononitriles for the synthesis of 3,4-ring-fused isocoumarins is described. This cascade strategy involves oxypalladation of ortho-alkynylbenzoates and desymmetrizing addition onto one cyano group of the pendant malononitriles, which enables the concurrent construction of two rings and an all-carbon quaternary stereocenter in a single operation.

Synthesis of 2,3-Ring Fused Pyrroles via Cu-Catalyzed 5-exo-dig Annulation of Alkyne-Tethered Enaminones.

A copper-catalyzed annulation of alkyne-tethered enaminones for the synthesis of 2,3-ring fused pyrroles is reported. The 5-exo-dig cyclization/olefin migration reaction delivers the multisubstituted pyrroles in 59-99% yields with 16 examples. This strategy features easily available starting materials, mild reaction conditions, and a cheap ligand-free copper catalyst. The atom-economic transformation provides a simple access to a variety of synthetic useful pyrroles and their derivatives.

Cu-Catalyzed Arylation/Acyl Migration Cascade Reaction of Enaminones: Access to N-Fused Polycyclic and 2,3-Disubstituted Indoles.

An efficient synthesis of N-fused polycyclic and 2,3-disubstituted indoles by copper-catalyzed direct annulation/acyl migration reaction of enaminones is reported. This strategy features cheap and low loading of the catalyst/ligand, readily available starting materials, and good functional group compatibilities. Notably, allyl-containing substrates are also tolerated, which allows the downstream derivatization toward indole alkaloids.

Cellulose supported TiO2/Cu2O for highly asymmetric conjugate addition of α,ß-unsaturated compounds in aqueous phase.

A series of new kind green cellulose-supported bimetallic TiO2/Cu2O (Cell@TiO2/Cu2O) catalytic materials were obtained by in-situ reduction method employing cellulose as the carrier. The effects of metal percentage composition on the morphology and construction of the catalytic materials were systematically investigated. The Cell@TiO2/Cu2O were characterized by FT-IR, TG, XPS, SEM, TEM, EDS, and the element content was obtained by elemental analysis. Then, the achieved catalytic materials were applied to the chiral borylation reaction of α,ß-unsaturated compounds, including nitrile compounds, esters, and α,ß-unsaturated ketones. Remarkably, this approach provides an efficient strategy to gain an important class of chiral organic boron compounds with target chiral products in high yields as well as enantioselectivities. Besides, the Cell@TiO2/Cu2O could be easily recycled and effectively reused. This work constructed bimetallic TiO2/Cu2O on cellulose as a newly catalyst to obtain chiral boron compounds in aqueous phase.

8-Aminoquinoline-based ratiometric zinc probe: unexpected binding mode and its application in living cells.

PMQA, an 8-aminoquinoline-based ratiometric fluorescent sensor, demonstrates the Zn(2+)-induced red-shift of emission (85nm), and was successfully applied to image zinc in living cells. Compared to 2:1 stoichiometry in PMQA-Zn(2+), PMQA-Cu(2+) shows 1:1 composition. Both nitrogen atoms from the aminoquinoline are missing in binding of zinc, while they are critically involved in Cu(2+) chelation. The structure difference between PMQA-Zn(2+) and PMQA-Cu(2+) might shed light in designing novel zinc probes without suffering from copper interference.

FeCl2-Mediated Regioselective Aminochlorination and Aminoazidation of Styrenes with Trifluoromethanesulfonyl Azide.

An efficient aminochlorination reaction of stryenes is described using N3SO2CF3 as an amination reagent and FeCl2 as a chloride source. The operationally simple procedure features mild reaction conditions, good functional group compatibility, and high regioselectivity. An example of aminobromination using FeBr2 is also realized. Additionally, a one-pot aminoazidation of styrenes is achieved by adding sodium azide to the reaction. The gram-scale synthesis and downstream derivatization of the products are showcased as well.

Trifluoromethanesulfonyl azide as a bifunctional reagent for metal-free azidotrifluoromethylation of unactivated alkenes.

Vicinal trifluoromethyl azides have widespread applications in organic synthesis and drug development. However, their preparation is generally limited to transition-metal-catalyzed three-component reactions. We report here a simple and metal-free method that rapidly provides these building blocks from abundant alkenes and trifluoromethanesulfonyl azide (N3SO2CF3). This unprecedented two-component reaction employs readily available N3SO2CF3 as a bifunctional reagent to concurrently incorporate both CF3 and N3 groups, which avoids the use of their expensive and low atom economic precursors. A wide range of functional groups, including bio-relevant heterocycles and amino acids, were tolerated. Application of this method was further demonstrated by scale-up synthesis (5 mmol), product derivatization to CF3-containing medicinal chemistry motifs, as well as late-stage modification of natural product and drug derivatives.

Synthesis of N-Fused Polycyclic Indoles via Ligand-Free Palladium-Catalyzed Annulation/Acyl Migration Reaction.

An efficient synthesis of N-fused polycyclic indoles by a palladium-catalyzed annulation/acyl migration cascade reaction is described. The reaction is ligand-free, scalable, and provides access to a diverse range of useful indole scaffolds from readily available starting materials. Supporting mechanistic studies indicate that the reaction likely proceeds via an intramolecular α-arylation mechanism. The synthetic utility of this protocol is demonstrated by a gram-scale reaction and syntheses toward indole alkaloids and a HSP90 inhibitor.