A Catalyst and Solvent Free Route for the Synthesis of N-Substituted Pyrrolidones from Levulinic Acid

An efficient, metal-free, catalyst-free and solvent-free methodology for the reductive amination of levulinic acid with different anilines has been developed using HBpin as the reducing reagent. This protocol offers an excellent method to avoid solvents and added catalysts on the synthesis of different kinds of N-substituted pyrrolidones under metal free conditions. It is also the first report for the synthesis of different pyrrolidones by solvent-free as well as catalyst-free methods. The proposed mechanism for the formation of pyrrolidone has been supported by DFT calculations and control experiments.     

Gold-Catalyzed Cross-Coupling Reactions: An Overview of Design Strategies,Mechanistic Studies,and Applications

Transition-metal-catalyzed cross-coupling reactions are central to many organic synthesis methodologies. Traditionally, Pd, Ni, Cu, and Fe catalysts are used to promote these reactions. Recently, many studies have showed that both homogeneous and heterogeneous Au catalysts can be used for activating selective cross-coupling reactions. Here, an overview of the past studies, current trends, and future directions in the field of gold-catalyzed coupling reactions is presented. Design strategies to accomplish selective homocoupling and cross-coupling reactions under both homogeneous and heterogeneous conditions, computational and experimental mechanistic studies, and their applications in diverse fields are critically reviewed. Specific topics covered are: oxidant-assisted and oxidant-free reactions; strain-assisted reactions; dual Au and photoredox catalysis; bimetallic synergistic reactions; mechanisms of reductive elimination processes; enzyme-mimicking Au chemistry; cluster and surface reactions; and plasmonic catalysis. In the relevant sections, theoretical and computational studies of Au^I/Au^III chemistry are discussed and the predictions from the calculations are compared with the experimental observations to derive useful design strategies.     

Mechanistic Insights into C(sp2)−C(sp)N Reductive Elimination from Gold(III) Cyanide Complexes

A new family of phosphine-ligated dicyanoarylgold(III) complexes has been prepared and their reactivity towards reductive elimination has been studied in detail. Both, a highly positive entropy of activation and a primary ^12/13C KIE suggest a late concerted transition state while Hammett analysis and DFT calculations indicate that the process is asynchronous. As a result, a distinct mechanism involving an asynchronous concerted reductive elimination for the overall C(sp²)−C(sp)N bond forming reaction is characterized herein, for the first time, complementing previous studies reported for C(sp³)−C(sp³), C(sp²)−C(sp²), and C(sp³)−C(sp²) bond formation processes taking place on gold(III) species.     

Subdirectly irreducible medial quandles

We describe all subdirectly irreducible medial quandles. We show that they fall within one of four disjoint classes. In particular, in the finite case they are either connected (and therefore Alexander quandles) or reductive. Moreover, we provide a representation of all non-connected subdirectly irreducible medial quandles.     

Palladium on activated carbon catalyzed reductive amination of aldehydes and ketones by triethylsilane

Various aldehydes and ketones were efficiently transformed into the corresponding amines using amine derivatives in the presence of triethylsilane and a catalytic amount of palladium on activated carbon in ethanol. The proposed method provides a one‐pot synthesis of various amines in excellent yields after short reaction times. Copyright © 2013 John Wiley & Sons, Ltd.     

Reduced graphene oxide supported copper oxide nanocomposites: An efficient heterogeneous and reusable catalyst for the synthesis of ynones, 1,3-diynes and 1,5-benzodiazepines in one-pot under sustainable reaction conditions

A greener and efficient method for the synthesis of ynones and 1,3-diynes using copper oxide nanoparticles (CuONPs) doped reduced graphene oxide (CuO@rGO) catalyst under palladium, ligand and solvent free conditions have been developed. The catalyst was subsequently utilized for the synthesis of biologically active 1,5-benzodiazepines in one pot via sequential addition of acyl chlorides, terminal alkynes and o-phenylenediamines. The methodology initially involves in situ formation of ynones which react with o-phenylenediamines in presence of ethanol to afford a wide variety of benzodiazepines. Mild reaction conditions, good to an excellent yield of the products, cheap and recyclable catalyst make this methodology environmentally benign and sustainable.     

A Convenient Heterogeneous Reduction of Knoevenagel Product by Hantzsch Ester and Its Development into Reductive Alkylation of Malononitrile

Poor solubility of Hantzsch ester is used as indicator in the reduction of methylidene malononitrile. The Knoevenagel reaction is integrated to develop a reductive alkylation of malononitrile with aryl and aliphatic aldehyde as the carbonyl substrate.     

B(C6F5)3催化的醛与烷氧基羟胺的一锅法还原胺化反应

近年路易斯酸B（C₆F₅）₃催化的醛酮还原及胺化反应研究表明,缺电子的路易斯酸B（C₆F₅）₃也可以作为一种"耐水"的催化剂在"有水"条件下进行催化反应.这些研究成果对进一步扩展受限路易斯酸碱对（FLPs）化学的研究领域和应用前景提供了更多可能.本文以硅烷作为还原剂,在路易斯酸B（C₆F₅）₃催化下可在温和条件下实现醛与烷基羟胺类化合物的直接还原胺化反应,并且在还原过程中N-O键不会发生断裂,可中等至高产率地制备各种烷氧基取代的羟胺衍生物.对反应机理研究发现,在中性条件下苯甲醛与苄氧基羟胺的反应仅得到缩合中间产物肟醚,而在HCl或过量H₂O的参与下苯甲醛与苄氧基羟胺的直接还原胺化均可顺利进行;对反应机理的研究表明苄氧基羟胺会与路易斯酸硼烷在过量H₂O的参与下发生质子化,在硅烷的作用下转化成具有一定还原性的"硼氢化胺盐"活性中间体并进而促使中间产物肟醚的还原.对醛与羟胺的直接还原胺化反应研究表明,在"有水"条件下路易斯酸B（C₆F₅）₃不仅仅是一种"耐水"的催化剂,在某些反应中水可能直接影响着催化反应,尤其是对醛酮的直接还原胺化反应.因此,继续深入研究有"水"条件下路易斯酸硼烷参与的催化反应机理不仅对FLPs化学的发展至关重要,对其他相应催化体系的研究也具有重要的参考价值.     

Synthesis of Functionalized (η5‐Indenyl)rhodium(III) Complexes and Their Application to C−H Bond Functionalization

It has been established that reductive complexation of functionalized benzofulvenes, which are readily prepared from commercially available indene and 2‐methylindene, with RhCl₃ in ethanol affords the corresponding indenyl–rhodium(III) dichlorides bearing substituents at the 1‐ (H or CO₂Et), 2‐ (H or Me), and 3‐ [CH₂Ph or CH₂(2‐MeOC₆H₄)] positions. The indenyl–rhodium(III) complexes bearing one ethoxycarbonyl group showed higher thermal stability and regioselectivity than our previously reported Cp^ERh^III complex toward the oxidative [3+2] annulation of acetanilides with internal alkynes.