S Salprima Yudha

Biosynthesis of gold nanoparticles: A green approach

Nanotechnology is an immensely developing field due to its extensive range of applications in different areas of technology and science. Different types of methods are employed for synthesis of nanoparticles due to their wide applications. The conventional chemical methods have certain limitations with them either in the form of chemical contaminations during their syntheses procedures or in later applications and use of higher energy. During the last decade research have been focussed on developing simple, clean, non-toxic, cost effective and eco-friendly protocols for synthesis of nanoparticles. In order to get this objective, biosynthesis methods have been developed in order to fill this gap. The biosynthesis of nanoparticles is simple, single step, eco-friendly and a green approach. The biochemical processes in biological agents reduce the dissolved metal ions into nano metals. The various biological agents like plant tissues, fungi, bacteria, etc. are used for biosynthesis for metal nanoparticles. In this review article, we summarised recent literature on biosynthesis of gold nanoparticles which have revolutionised technique of synthesis for their applications in different fields. Due to biocompatibility of gold nanoparticles, it has find its applications in biomedical applications. The protocol and mechanism of biosynthesis of gold nanoparticles along with various applications have also been discussed.

Rhenium- and Manganese-Catalyzed Insertion of Alkynes into a Carbon–Carbon Single Bond of Cyclic and Acyclic 1,3-Dicarbonyl Compounds

Treatment of alkynes with cyclic and acyclic 1,3-dicarbonyl compounds in the presence of a catalytic amount of a rhenium or manganese complex gives ring-expanded and carbon-chain extension products, respectively. In these reactions, alkynes insert into a non-strained carbon-carbon single bond of 1,3-dicarbonyl compounds. The ring-expansion reaction is also promoted by the addition of 4-A molecular sieves instead of a catalytic amount of an isocyanide.

Manganese-Catalyzed Construction of Tetrasubstituted Benzenes from 1,3-Dicarbonyl Compounds and Terminal Acetylenes

Treatment of beta-keto esters with terminal acetylenes in the presence of a catalytic amount of a manganese complex, MnBr(CO)5, and molecular sieves, gave multisubstituted aromatic compounds in good to excellent yields. This reaction employs [2 + 2 + 2] cycloaddition of beta-keto esters and 2 equiv of terminal acetylenes with dehydration. In the case of a 1,3-diketone, the corresponding acetophenone derivative and its deacylated compound can be synthesized selectively.

Rhenium- and Manganese-Catalyzed Synthesis of Aromatic Compounds from 1,3-Dicarbonyl Compounds and Alkynes

We have succeeded in the development of three approaches to the synthesis of aromatic compounds from 1,3-dicarbonyl compounds and alkynes. The first approach is a manganese-catalyzed [2+2+2] cycloaddition between 1,3-dicarbonyl compounds, which have no substituents at the active methylene moiety, and terminal alkynes. This reaction proceeds with high regioselectivity when aryl acetylenes are employed as the alkyne component. The second approach is a rhenium- or manganese-catalyzed formal [2+1+2+1] cycloaddition between beta-keto esters and two kinds of alkynes. In this reaction, the aromatic compounds are obtained by the following reaction sequence: (1) insertion of the first alkyne into a carbon-carbon single bond of a beta-keto ester, (2) formation of 2-pyranones via intramolecular cyclization with the elimination of ethanol, and (3) Diels-Alder reaction between the formed 2-pyranone and the second alkyne. This reaction provides multisubstituted aromatic compounds in a regioselective manner. The third approach is a rhenium-catalyzed formal [2+2+1+1] cycloaddition reaction from two 1,3-diketones and one alkyne. In this reaction, the aromatic skeleton is constructed from three carbons of the first 1,3-diketone, two carbons of the alkyne, and one carbon of the second 1,3-diketone.

Rhenium‐Catalyzed Synthesis of Stereodefined Cyclopentenes from β‐Ketoesters and Aliphatic Allenes

Approaches to construct complex organic molecules, such as carbocyclic compounds, from simple starting materials as building blocks are of great interest. Five-membered carbocycles are especially important, and remarkable progress has been made in their syntheses. Among them, [3+2] cycloaddition reactions have been studied intensively because the five-membered carbocycles can be derived from simpler molecules. The synthesis of five-membered carbocycles starting from allenes have also been reported; for example (trimethylsilyl)cyclopentene annulation mediated by titanium complexes, gold-catalyzed [3+2] cycloaddition of enones/ enals with allenyl methoxymethyl ethers, and cobalt-catalyzed reductive [3+2] cycloaddition of allenes and enones. Herein, we report the unprecedented synthesis of polysubstituted cyclopentenes from b-ketoesters and aliphatic allenes. Previous work on the use of rhenium complexes in organic synthesis, including our own studies on the reactions of acetylenes and olefins, 5] led us to envisage the reactivity of rhenium complexes towards allenes. By heating a mixture of b-ketoester 1a and allene 2a in toluene in the presence of rhenium complex [{ReBr(CO)3(thf)}2], the insertion of 2a into either the C H bond at the a-position or the carbon– carbon bond of 1 a was expected. After carrying out the above reaction, C H insertion product 4 a was produced in 27% yield in addition to the unexpected formation of cyclopentene 3a in 32 % yield [Eq. (1)]. The structure of 3a was determined by both NMR spectroscopy and singlecrystal X-ray crystallographic analysis (Figure 1). For structure 3a, both the regiochemistry and the stereochemistry at the three carbon centers was defined. Additional investigation of the catalysts showed that treatment of b-ketoester 1a and allene 2 a with [ReBr(CO)5] (5.0 mol%) furnished the desired product in 35 % yield. The yield of 3a was improved to 76% by using [Re2(CO)10] (2.5 mol%) instead of [ReBr(CO)5]. Gratifyingly, the yield was improved to 85 % by heating 1a and 2 a under solvent free conditions [Eq. (1)]. Notably, we detected another isomer peak in the GC-MS analysis, but it was less than 1% yield. Changing the electronic properties of the rhenium complexes by using phosphine ligands ([ReCl3(PPh3)2(NCMe)], [ReCl3(PMe2Ph)3], and [ReOCl3(PPh3)2]) afforded decomposition products of allenes. Other metal complexes, such as [Mn2(CO)10], [MnBr(CO)5], and [Ru3(CO)12] were also ineffective. Once the optimal catalyst and reaction conditions were identified, we investigated the scope and limitations of this new synthetic method for making cyclopentenes using b-ketoesters and aliphatic allenes. Aliphatic allenes reacted with b-ketoesters in the presence of 2.5 mol% of the [Re2(CO)10] catalyst to furnish the corresponding cyclopentene derivatives in moderate to excellent yields (61–91%) (Table 1). Cyclopentene 3b was isolated in 80 % yield from the reaction of active methylene compound 1a with allene 2b (entry 1). Ester and silyloxy groups are tolerated under the reaction conditions as evidenced by the high yields of products, 3c and 3d, respectively (entries 2 and 3). Active methylene compound 1b also served as a good coupling partner to give cyclopentene 3e in 61% yield. (entry 4). Changing the substituent from the ethyl group of the Figure 1. X-ray crystal structure of 3a. Thermal ellipsoids set at 50% probability.

Antileukemic activity of lignans and phenylpropanoids of Cinnamomum parthenoxylon.

In this study, we evaluated the in vitro cytotoxicity of fractions and isolated constituents from Cinnamomum parthenoxylon woods against human leukemia HL-60 and U937 cells. The n-Hex, EtOAc, and MeOH-H2O fractions of the woods inhibited cell proliferation in both cell lines. Our phytochemical investigation of the n-Hex and EtOAc fractions led to the isolation of lignans and phenylpropanoids, whose chemical structures were confirmed by spectroscopic analyses. All isolated compounds were evaluated for their in vitro antileukemic activity; especially, hinokinin and cubebin exhibited strong inhibition toward U937 cell proliferation. Morphological observation indicated that these cytotoxic actions were mediated by apoptosis. Our findings suggested that an oxygenated functional group at the C-9 position in dibenzylfuran skeleton contributed their potency. In addition, these results enhanced the ethnopharmacological value of C. parthenoxylon.

SILVER-CATALYZED SYNTHESIS OF 1,2-DIHYDROISOQUINOLINES THROUGH DIRECT ADDITION OF CARBON PRONUCLEOPHILES TO ORTHO-ALKYNYLARYL ALDIMINES

AgOTf-catalyzed reaction of ortho-alkynyl-arylaldimines with various kinds of pronucleophiles afforded a variety of 1,2-dihydroisoquinoline derivatives in good to high yields. Treatment of ortho-alkynyl-arylaldimines with a stoichiometric amount of AgOTf, followed by the protonation with TfOH produced isoquinolinium trifluoromethanesulfonate, which suggested the formation of isoquinolinium intermediate in the present direct addition reaction.

Rhenium- and manganese-catalyzed carbon-carbon bond formation using 1,3-dicarbonyl compounds and alkynes*

A rhenium complex, [ReBr(CO)3(thf)]2, catalyzed insertion of terminal alkynes into a C–H bond of active methylene sites of 1,3-dicarbonyl compounds. When a catalytic amount of isocyanide or molecular sieves was added to the reaction mixture, the reaction course changed markedly, and insertion of alkynes into a C–C single bond between α- and β-positions of cyclic and acyclic β-keto esters occurred. The formed acyclic δ-keto esters could be converted to 2-pyranones, which were applied to the synthesis of multisubstituted aromatic compounds via the Diels–Alder reaction and successive elimination of carbon dioxide. In the case of the rhenium-catalyzed reactions between terminal alkynes and β-keto esters without substituent at the α-position, tetrasubstituted benzenes were produced regioselectively by two-to-one reaction of the components. The yields of tetrasubstituted benzenes were improved by using a manganese catalyst.

Fabrication of ZnAl2O4 from corresponding metals nitrate in the co-existence of natural SiO2 and it application as adsorben of mercury nitrate

In situ fabrication of ZnAl2O4 from precursorof zinc nitrate and andaluminium nitrate aqueous solutions was carried out in a rice husk’s SiO2 suspension. The reaction’s mixture was heated at 100 °C in open air under stirring and the solvent was evaporated to form white gel. The gel was cooled to room temperature and a solid material was obtained, subsequently heated at 1100 °C for 5 hours. The obtained material was applied as adsorbent for mercury ions at room temperature

Iron sand - ZnO based materials of natural origin for dye decolorization under sunlight irradiation

A mixed iron sand - ZnO materials was prepared by heating a mixture of natural iron sand and ZnO at 900 °C for 5 hours. XRD study of the sample revealed that, in the mixed iron sand - ZnO present some minor peaks that similar with XRD pattern of γ-Fe2O3 and/or Fe3O4. Observation of the sample using SEM, showed a compact morpholgy and almost homogenenous in particles size. In purpose to evaluate the ability of this materials for textile dying wastewater treatment, a study on rhodamine B decolorization was carried out as a reperesentative.