An Oxidant-Free and Mild Strategy for Quinazolin-4(3H)-One Synthesis via CuAAC/Ring Cleavage Reaction.

An oxidant-free and highly efficient synthesis of phenolic quinazolin-4(3H)-ones was achieved by simply stirring a mixture of 2-aminobenzamides, sulfonyl azides, and terminal alkynes. The intermediate N-sulfonylketenimine underwent two nucleophilic additions and the sulfonyl group eliminated through the power of aromatization. The natural product 2-(4-hydroxybenzyl)quinazolin-4(3H)-one can be synthesized on a large scale under mild conditions with this method.

CuX Dual Catalysis: Construction of Oxazolo[2,3-b][1,3]oxazines via a Tandem CuAAC/Ring Cleavage/[4+2+3] Annulation Reaction.

CuX as a simple dual catalyst strategy that promotes the tandem transformations of fused oxazolo[2,3-b][1,3]oxazines has been developed. Copper catalyzed terminal ynones, sulfonyl azides, and nitriles for the CuAAC/ring cleavage/[4+2] annulation reaction, while the halogen catalyzed ring cleavage and [2+3] annulation of oxiranes to form the final fused products. This study provides a four-component, one-pot strategy for synthesizing complex fused heterocycles from simple ingredients and expands the application of CuAAC in organic synthesis.

Layer-by-Layer Growth of AA-Stacking MoS2 for Tunable Broadband Phototransistors.

The stacking configuration has been considered as an important additional degree of freedom to tune the physical property of layered materials, such as superconductivity and interlayer excitons. However, the facile growth of highly uniform stacking configuration is still a challenge. Herein, the AA-stacking MoS2 domains with a ratio up to 99.5% has been grown by using the modified chemical vapor deposition through introducing NaCl molecules in the confined space. By tuning the growth time, MoS2 domains would transit from an AA-stacking bilayer to an AAAAA-stacking five-layer. The epitaxial growth mechanism has been insightfully studied, revealing that the critical nucleation size of the AA-stacking bilayer is 5.0 ± 3.0 µm. Through investigation of the photoluminescence, the photoemission, especially the indirect photoexcitation, is dependent on both the stacking fashion and layer number. Furthermore, by studying the gate-tuned MoS2 phototransistors, we found a significant dependence on the stacking configuration of MoS2 of the photoexcitation and a different gate tunable photoresponse. The AAA-stacking trilayer MoS2 phototransistor delivers a photoresponse of 978.14 A W-1 at 550 nm. By correction of the external quantum efficiency with external field and illumination power density, it has been found that the photoresponse tunability is dependent on the layer number due to the strong photogating effect. This strategy provides a general avenue for the epitaxial growth of van der Waals film which will further facilitate the applications in a tunable photodetector.

Me3SiSiMe2(O n Bu): a disilane reagent for the synthesis of diverse silacycles via Brook- and retro-Brook-type rearrangement.

Herein, a readily available disilane Me3SiSiMe2(O n Bu) has been developed for the synthesis of diverse silacycles via Brook- and retro-Brook-type rearrangement. This protocol enables the incorporation of a silylene into different starting materials, including acrylamides, alkene-tethered 2-(2-iodophenyl)-1H-indoles, and 2-iodobiaryls, via the cleavage of Si-Si, Si-C, and Si-O bonds, leading to the formation of spirobenzosiloles, fused benzosiloles, and π-conjugated dibenzosiloles in moderate to good yields. Preliminary mechanistic studies indicate that this transformation is realized by successive palladium-catalyzed bis-silylation and Brook- and retro-Brook-type rearrangement of silane-tethered silanols.

A simple and efficient copper-catalyzed three-component reaction to synthesize (Z)-1,2-dihydro-2-iminoquinolines.

A operationally simple synthesis of (Z)-1,2-dihydro-2-iminoquinolines that proceeds under mild conditions is achieved by copper-catalyzed reaction of 1-(2-aminophenyl)ethan-1-ones, sulfonyl azides and terminal ynones. In particular, the reaction goes through a base-free CuAAC/ring-opening process to obtain the Z-configured products due to hydrogen bonding.

Design and Synthesis of Novel Podophyllotoxins Hybrids and the Effects of Different Functional Groups on Cytotoxicity.

Development of novel anticancer therapeutic candidates is one of the key challenges in medicinal chemistry. Podophyllotoxin and its derivatives, as a potent cytotoxic agent, have been at the center of extensive chemical amendment and pharmacological investigation. Herein, a new series of podophyllotoxin-N-sulfonyl amidine hybrids (4a-4v, 5a-5f) were synthesized by a CuAAC/ring-opening procedure. All the synthesized podophyllotoxins derivatives were evaluated for in vitro cytotoxic activity against a panel of human lung (A-549) cancer cell lines. Different substituents', or functional groups' antiproliferative activities were discussed. The -CF3 group performed best (IC50: 1.65 µM) and exhibited more potent activity than etoposide. Furthermore, molecular docking and dynamics studies were also conducted for active compounds and the results were in good agreement with the observed IC50 values.

Palladium-Catalyzed Domino Heck/C-H Activation/Decarboxylation: A Rapid Entry to Fused Isoquinolinediones and Isoquinolinones.

A new palladium-catalyzed tandem cyclization of various alkene-tethered aryl iodides has been presented. In this protocol, o-bromobenzoic acids are employed as coupling parters to achieve the insertion of aromatic rings by the cleavage of C(sp2)-Br and decarboxylation, thus assembling various dibenzoisoquinolinediones and dibenzoisoquinolinones. In addition, a seven-membered ring can be constructed by the use of 8-bromo-1-naphthoic acid. Notably, this approach enables regioselective product formation and features broad substrate scope.

Palladium-Catalyzed Tandem Reaction of Three Aryl Iodides Involving Triple C-H Activation.

A novel palladium-catalyzed tandem reaction of N-(2-iodoaryl)acrylamides with two aryl iodides for the synthesis of spirooxindole has been achieved. The reaction underwent the process of triple C-H activation and four C-C bond formations based on the double trapping of transient spirocyclic palladacycles which are obtained through remote C-H activation.