Cerium metal- mediated Reformatsky-type reaction with ethyl bromosuccinate for the synthesis of novel paraconic acid analogs

The treatment of cerium metal with ethyl bromosuccinate (1) forms the stabilized organolanthanoid intermediate (2), which reacts with carbonyl compounds in a Reformatsky-type reaction, under mild conditions, to produce functionalized gamma-substituted paraconic acids (4) in good yields. (C) 2012 Elsevier Ltd. All rights reserved.

Intramolecular Reactivity - Keto Participation in the Hydrolysis of N-Methyl-N-(9-Oxobicyclo[3.3.1]Nonan-2-Alpha-YL) Morpholinium Iodide, and A Cannizzaro-Type Reaction of 3-(2-Oxocyclohexyl)Propanal

Mechanistic studies of two intramolecular processes, nucleophilic displacement of N-methylmorpholinium in N-methyl-N-{9-oxobicyclo[3,3,1]nonan-2 alpha-yl}morpholinium iodide, anchimerically assisted by keto carbonyl, and a Cannizzaro-type reaction of 3-(2-oxocyclohexyl)propanal, occurring via axial hydride transfer onto the cyclohexanone, are reported.

Synthesis of bischromones by deformylative Mannich type reaction on chromone-3-carbaldehyde using alpha-aminoacid as the source of amine

Chromone-3-carbaldehyde reacts with N-methylglycine or glycine in the presence of excess formaldehyde to produce N-(chromone-3-ylmethyl)-N-methylglycine or N,N-di(chromone-3-ylmethyl)glycine, respectively, by a deformylative Mannich type reaction. Use of alanine or leucine or methionine in place of glycine produces N-(chromone-3-ylmethyl)alanine/-leucine/-methionine, respectively. (C) 2009 Elsevier Ltd. All rights reserved.

A Facile, Versatile, and Mild Morita-Baylis-Hillman-Type Reaction for the Modular One-Pot Synthesis of Highly Functionalized MBH Adducts

MoritaBaylisHillman derivatives have been extensively investigated as intermediates in the preparation of important classes of compounds. However, there are intrinsic limitations regarding the structure of the Michael electrophile acceptors, the aldehydes, and the catalysts. Therefore, this transformation has several drawbacks, including, for example, its long reaction times. Herein we present a simple, general, fast, and high-yielding protocol for the one-pot synthesis of MoritaBaylisHillman derivatives. Our approach is driven by a lithium selenolate Michael/aldol operation with concomitant O-functionalization/selenoxide elimination cascade sequences.

Sequential alcohol oxidation/putative homo Claisen-Tishchenko-type reaction to give esters: a key process in accessing novel biologically active lactone macrocycles

We report an efficient methodology for the direct oxidative esterification of primary alcohols to diether-esters using pyridinium chlorochromate (PCC). Numerous studies were carried out to probe the reaction mechanism and at the same time optimize the reaction conditions. The reaction could be conducted with 1 equivalent of PCC and 1 equivalent of BF3 center dot OEt2. Indications based on literature precedent were that the reaction may proceed via a sequential alcohol oxidation to the aldehyde followed by a putative Cr or boron catalyzed Claisen-Tishchenko-type reaction. Using this efficient methodology, we synthesized a family of novel diether-esters in very good yields; some of these molecules were subsequently tested against both acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). In addition, we also disclose a new synthetic strategy for the synthesis of lactam macrocycles with potential biological activity. This methodology included the regioselective borylation of the ester substrate and a subsequent Suzuki-Miyaura coupling to obtain the desired lactam macrocycle.

The Reaction of a Nitro-Capped Cobalt(III) Cage Complex With Base: the Crystal Structure of a Contracted Cage Complex, and the Mechanism of Its Formation

The synthesis, properties and crystal structure of the cage complex (1-hydroxy-8-methyl-3,6,10,13,15,18-hexaazabicyclo[6.6.5]nonadecane)cobalt(III) chloride hydrate ([Co(Me,OH-absar)] C13.H2O) are reported. The mechanism of the formation of this contracted cavity cage from a nitro-capped hexaazabicycloicosane type cage has been investigated. Treatment of (1-methyl-8-nitro-3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosane)cobalt(III) chloride ([Co(Me,NO2-sar)] 3+) with excess base in aqueous solution leads initially to rapid (t1/2 < 1 ms) and reversible deprotonation of one coordinated secondary amine. This species undergoes a retro-Mannich type reaction and imine hydrolysis (t1/2 almost-equal-to 90 s). Quenching the reaction with acid gives rise to a pair of isomeric intermediate species which have been isolated and characterized. They have a pendant arm macrocyclic structure, resulting from the loss of a methylene unit from one of the arms of the cap. Heating either isomer in aqueous solution gives the new cage compound with the contracted cap. It is postulated that this occurs through a Nef reaction, resulting in the formation of a ketone which then condenses with the coordinated primary amine. A comparison with the corresponding bicycloicosane analogue indicates a reduced chromophoric cavity size for the contracted cage. The reduction potential of the cobalt(III)/cobalt(II) couple is 170 mV more negative for the smaller cage, and, in the electronic spectrum of the cobalt(III) complex, the d-d transitions are both shifted to higher energy, corresponding to a stronger ligand field.

PEG-supported dipyridyl ligand for palladium-catalyzed Suzuki and Suzuki-type reactions in PEG and aqueous media

An air- and water-stable PEG-supported bidentate nitrogen ligand is prepared and its applications in the palladium-catalyzed Suzuki reaction of aryl halides with arylboronic acids in PEG and Suzuki-type reaction of aryl halides with sodium tetraphenylborate in aqueous media are reported. The homogeneous catalyst system is environmentally friendly and offers the advantages of high activity, reusability and easy separation.

Reaction path for oxidation of ethylene to acetic acid over Pd/WO3-ZrO2 in the presence of water

Pd-supported on WO3-ZrO2 (W/Zr atomic ratio=0.2) calcined at 1073 K was found to be highly active and selective for gas-phase oxidation of ethylene to acetic acid in the presence of water at 423 K and 0.6 MPa. Contact time dependence demonstrated that acetic acid is formed via acetaldehyde formed by a Wacker-type reaction, not through ethanol by hydration of ethylene.

(A) BODIPY as a versatile fluorophore (B) Synthesis of PNAs via Staudinger reaction

(A) In recent years, 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) fluorophores have attracted considerable interest due to their unique photochemical properties. However detailed studies on the stability of BODIPY and analogues under acidic and basic conditions have been lacking. Thus the stability of a series of BODIPY analogues in acidic (di- and trichloroacetic acid) and basic (aqueous ammonium hydroxide) conditions was investigated using 11B NMR spectroscopy. Among the analogues tested, 4,4-diphenyl BODIPY was the most stable under the conditions used in the experiments. It was found that reaction of 4,4-dimethoxy BODIPY with dichloroacetic acid gave mixed anhydride 4,4-bis(dichloroacetoxy) BODIPY in good yields. Treatment of the latter mixed anhydride with alcohols such as methanol and ethanol in the presence of a base afforded corresponding borate esters, whereas treatment with 1,2-diols such as ethylene glycol and catechol in the presence of a base gave corresponding cyclic borate esters. Furthermore treatment of 4,4-difluoro-8-methyl-BODIPY with secondary amines in dihalomethane resulted in carbon–carbon bond formation at the meso-methyl position of BODIPY via Mannich-type reactions. The resulting modified BODIPY fluorophores possess high fluorescent quantum yields. Five BODIPY analogues bearing potential ion-binding moieties were synthesized via this Mannich-type reaction. Among these, the BODIPY bearing an aza-18-crown-5 tether was found to be selective towards copper (II) ion, resulting in a large blue shift in absorption and sharp fluorescent quenching, whereas aza-15-crown-4 analogue was selected towards fluoride ion, leading to effective florescent quenching and blue shift. (B) Peptide nucleic acids (PNA), as mimics of natural nucleic acids, have been widely applied in molecular biology and biotechnology. Currently, the preparation of PNA oligomers is commonly achieved by a coupling reaction between carboxyl and amino groups in the presence of an activator. In this thesis attempts were made towards the synthesis of PNA through the Staudinger ligation reactions between C-terminal diphenylphosphinomethanethiol thioesters and N-terminal α-azido PNA building blocks.

Dba-free palladium intermediates of the Heck-Matsuda reaction

The dba-free Heck-Matsuda reaction was investigated via direct ESI-MS(/MS) monitoring. Palladium species involved in the reduction of Pd(ii) during a Wacker type reaction and several dba-free arylpalladium transient complexes were detected and characterized. Based on these findings, a more comprehensible catalytic cycle for this pivotal reaction is suggested. © 2013 The Royal Society of Chemistry.

Development of Organocatalytic stereoselective SN1 type reactions

The proposal in my thesis has been the study of Stereoselective α-alkylation through SN1 type reaction. SN1 type reaction involves a stabilized and reactive carbocation intermediate By taking advantages of stability of particular carbocations, the use of carbocations in selective reactions has been important. In this work has been necessary to know the stability and reactivity of carbocations. And the work of Mayr group has helped to rationalize the behaviour and reactivity between the carbocations and nucleophiles by the use of Mayr’s scale of reactivity. The use of alcohols to performed the stable and reactive carbocations have been the key in my thesis. The direct nucleophilic substitution of alcohols has been a crucial scope in the field of organic synthesis, because offer a wide range of intermediates for the synthesis of natural products and pharmaceutics synthesis. In particular the catalytic nucleophilic direct substitution of alcohols represents a novel methodology for the preparation of a variety of derivatives, and water only as the sub-product in the reaction. The stereochemical control of the transformation C-H bond into stereogenic C-C bond adjacent to carbonyl functionalized has been studied for asymmetric catalysis. And the field of organocatalysis has introduced the use of small organic molecule as catalyst for stereoselective transformations. Merging these two concepts Organocatalysis and Mayr’s scale, my thesis has developed a new approach for the α-alkylation of aldehydes and ketones through SN1 type reaction.

Multiple pathways for ultrafast transduction of light energy in the photosynthetic reaction center of Rhodobacter sphaeroides

A pathway of electron transfer is described that operates in the wild-type reaction center (RC) of the photosynthetic bacterium Rhodobacter sphaeroides. The pathway does not involve the excited state of the special pair dimer of bacteriochlorophylls (P*), but instead is driven by the excited state of the monomeric bacteriochlorophyll (BA*) present in the active branch of pigments along which electron transfer occurs. Pump-probe experiments were performed at 77 K on membrane-bound RCs by using different excitation wavelengths, to investigate the formation of the charge separated state P+HA−. In experiments in which P or BA was selectively excited at 880 nm or 796 nm, respectively, the formation of P+HA− was associated with similar time constants of 1.5 ps and 1.7 ps. However, the spectral changes associated with the two time constants are very different. Global analysis of the transient spectra shows that a mixture of P+BA− and P* is formed in parallel from BA* on a subpicosecond time scale. In contrast, excitation of the inactive branch monomeric bacteriochlorophyll (BB) and the high exciton component of P (P+) resulted in electron transfer only after relaxation to P*. The multiple pathways for primary electron transfer in the bacterial RC are discussed with regard to the mechanism of charge separation in the RC of photosystem II from higher plants.

Silica Microparticles Supported Gold and Copper Ferrite Nanoparticles: A Magnetically Recyclable Bimetallic Catalyst for Sonogashira Reaction

Novel silica supported gold and copper ferrite nanoparticles (NPs) have been synthesized, characterized and used as a separable dual catalyst in Sonogashira type reaction. These Au.CuFe2O4@Silica NPs show a high efficiency as catalyst in the alkynylation not only of aryl iodides but also aryl bromides. By using only 0.5 mol% loading and t-BuOK as base in N,N-dimethylacetamide as solvent, aryl iodides react at 115 ºC in 1 d, whereas for aryl bromides the cross-coupling takes place at 130 ºC in 2 d. The catalyst can be successfully recycled using an external magnet for four consecutive runs.

Journeys with friends

Journeys with Friends Truna aka J. Turner, Giselle Rosman and Matt Ditton Panel Session description: We are no longer an industry (alone) we are a sector. Where the model once consisted of industry making games, we now see the rise of a cultural sector playing in the game space – industry, indies (for whatever that distinction implies) artists (another odd distinction), individuals and well … everyone and their mums. This evolution has an affect – on audiences and who they are, what they expect and want, and how they understand the purpose and language of these “digital game forms’; how we talk about our worlds and the kinds of issues that are raised; on what we create and how we create it and on our communities and who we are. This evolution has an affect on how these works are understood within the wider social context and how we present this understanding to the next generation of makers and players. We can see the potential of this evolution from industry to sector in the rise of the Australian indie. We can see the potential fractures created by this evolution in the new voices that ask questions about diversity and social justice. And yet, we still see a ‘solution’ type reaction to the current changing state of our sector which announces the monolithic, Fordist model as desirable (albeit in smaller form) – with the subsequent ramifications for ‘training’ and production of local talent. Experts talk about a mismatch of graduate skills and industry needs, insufficient linkages between industry and education providers and the need to explore opportunity for the now passing model in new spaces such as adver-games and serious games. Head counts of Australian industry don’t recognise trans media producers as being part of their purview or opportunity, they don’t count the rise of the cultural playful game inspired creative works as one of thier team. Such perspectives are indeed relevant to the Australian Games Industry, but what about the emerging Australian Games Sector? How do we enable a future in such a space? This emerging sector is perhaps best represented by Melbourne’s Freeplay audience: a heady mix of indie developers, players, artists, critical thinkers and industry. Such audiences are no longer content with an ‘industry’ alone; they are the community who already see themselves as an important, vibrant cultural sector. Part of the discussion presented here seeks to identify and understand the resources, primarily in the context of community and educational opportunities, available to the evolving sector now relying more on the creative processes. This creative process and community building is already visibly growing within the context of smaller development studios, often involving more multiskilling production methodologies where the definition of ‘game’ clearly evolves beyond the traditional one.

Parameters Affecting the Extraction of Polycyclic Aromatic Hydrocarbons with Pressurised Hot Water

Pressurised hot water extraction (PHWE) exploits the unique temperature-dependent solvent properties of water minimising the use of harmful organic solvents. Water is environmentally friendly, cheap and easily available extraction medium. The effects of temperature, pressure and extraction time in PHWE have often been studied, but here the emphasis was on other parameters important for the extraction, most notably the dimensions of the extraction vessel and the stability and solubility of the analytes to be extracted. Non-linear data analysis and self-organising maps were employed in the data analysis to obtain correlations between the parameters studied, recoveries and relative errors. First, pressurised hot water extraction (PHWE) was combined on-line with liquid chromatography-gas chromatography (LC-GC), and the system was applied to the extraction and analysis of polycyclic aromatic hydrocarbons (PAHs) in sediment. The method is of superior sensitivity compared with the traditional methods, and only a small 10 mg sample was required for analysis. The commercial extraction vessels were replaced by laboratory-made stainless steel vessels because of some problems that arose. The performance of the laboratory-made vessels was comparable to that of the commercial ones. In an investigation of the effect of thermal desorption in PHWE, it was found that at lower temperatures (200ºC and 250ºC) the effect of thermal desorption is smaller than the effect of the solvating property of hot water. At 300ºC, however, thermal desorption is the main mechanism. The effect of the geometry of the extraction vessel on recoveries was studied with five specially constructed extraction vessels. In addition to the extraction vessel geometry, the sediment packing style and the direction of water flow through the vessel were investigated. The geometry of the vessel was found to have only minor effect on the recoveries, and the same was true of the sediment packing style and the direction of water flow through the vessel. These are good results because these parameters do not have to be carefully optimised before the start of extractions. Liquid-liquid extraction (LLE) and solid-phase extraction (SPE) were compared as trapping techniques for PHWE. LLE was more robust than SPE and it provided better recoveries and repeatabilities than did SPE. Problems related to blocking of the Tenax trap and unrepeatable trapping of the analytes were encountered in SPE. Thus, although LLE is more labour intensive, it can be recommended over SPE. The stabilities of the PAHs in aqueous solutions were measured using a batch-type reaction vessel. Degradation was observed at 300ºC even with the shortest heating time. Ketones and quinones and other oxidation products were observed. Although the conditions of the stability studies differed considerably from the extraction conditions in PHWE, the results indicate that the risk of analyte degradation must be taken into account in PHWE. The aqueous solubilities of acenaphthene, anthracene and pyrene were measured, first below and then above the melting point of the analytes. Measurements below the melting point were made to check that the equipment was working, and the results were compared with those obtained earlier. Good agreement was found between the measured and literature values. A new saturation cell was constructed for the solubility measurements above the melting point of the analytes because the flow-through saturation cell could not be used above the melting point. An exponential relationship was found between the solubilities measured for pyrene and anthracene and temperature.