The intriguing methoxycarbonylation of trimethylsilylacetylene in the presence of Drent's catalytic system

The alkoxycarbonylation of trimethylsilylacetylene has been studied in order to develop an atom economic sustainable synthesis of 2-(trimethylsilyl)acrylates, a family of valuable intermediates. Pd(OAc)2 in combination with CH3SO3H and diphenyl-(pyridin-2-yl)phosphine or diphenyl-(6-methyl-pyridin-2-yl)phosphine is an active catalyst for the reaction affording mixtures of the sought 2-(trimethylsilyl)acrylate and the isomeric 3-(trimethylsilyl)acrylate. The phosphine ligand has a dramatic effect on the reaction. When employing diphenyl-(pyridin-2-yl)phosphine, it is necessary to carry out the reaction at 80°C in order to observe a modest catalytic activity, and the product is an almost equimolecular mixture of the two isomeric esters. On the contrary, when employing diphenyl-(6-methyl-pyridin-2-yl)phosphine, the reaction proceeds under much milder conditions affording with high rate (turnover frequency [TOF] up to 1200 h−1) and selectivity (>95%) of the sought 2-(trimethylsilyl)acrylate. The reaction conditions have been optimized, and the effects of phosphine/palladium, acid/palladium, reaction time, temperature, and CO pressure have been investigated. © 2021 The Authors. Applied Organometallic Chemistry published by John Wiley & Sons Ltd

Mechanism of the fluxional behaviour in (1–5-η-cycloheptadienyl)-(1–5-η-cycloheptatrienyl)iron

Evidence for a 1.2-shift mechanism of the 1-5-η-cycloheptatrienyl moiety with respect to the central iron atom of the title compound is presented together with absolute assignments of the ^(13)C n.m.r. chemical shifts of the C_(7)H_(7) ring. A low-temperature rocking motion of both rings can be frozen out at -70 °C

Polyamidoamide Dendrimers and Cross-Linking Agents for Stabilized Bioenzymatic Resistant Metal-Free Bovine Collagen

The work reports the use of polyamidoamine dendrimers (PAMAM) and a cross-linking agent, 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide/N-hydroxysuccinimide (EDC/NHS) or 4-(4,6-dimethoxy[1,3,5]triazin-2-yl)-4-methyl-morpholinium chloride (DMTMM), for the thermal stabilization of dermal bovine collagen. The efficiency of EDC/NHS/PAMAM and DMTMM/PAMAM in the cross-linking of collagen is correlated to the increase of the collagen shrinkage temperature (Ts), measured by differential scanning calorimetry (DSC). An alternative enzymatic protocol was adopted to measure the degradability of EDC/NHS/PAMAM tanned hides; these data are correlated to the thermal stability values measured by DSC. In the presence of PAMAMs, EDC/NHS provides very high stabilization of bovine dermal collagen, giving Ts of up to 95 °C, while DMTMM achieves lower stabilization. Preliminary tanning tests carried out in best reaction conditions show that EDC/NHS/PAMAM could be an interesting, environmentally-sustainable tanning system which is completely free of metals, formaldehyde, and phenols. Two new unreported dendrimeric species were synthesized and employed

Synthesis of the Chiral Fragrance Methyl Chamomile by Asymmetric Hydrogenation

An alternative synthesis of enantiomerically enriched 2-methylpentanoic butyl ester (Methyl Chamomile) is proposed. The process entails three different steps: the key one is the asymmetric hydrogenation of 2-methylenpentanoic acid catalysed by a Ru(II) complex and a chiral diphosphine

The Leather Industry: A Chemistry Insight Part I: an Overview of the Industrial Process

A panoramic overview of the leather world market is given. The industrial tanning process is schematically explained giving a general outline of how an animal skin is transformed into a durable material having many different characteristics according to its specific future use. All the tanning industrial steps are overviewed starting from soaking, liming and after various steps ending up with finishing. An insight of collagen chemistry is also given

A pyridyl-triazole ligand for ruthenium and iridium catalyzed C=C and C=O hydrogenations in water/organic solvent biphasic systems

The water soluble pyridyl-triazole ligand sodium 2-(1-((pyridin-2-yl)methyl)-1H-1,2,3-triazol-4-yl) ethyl sulfate (Nal) has been successfully employed in combination with ruthenium and iridium for catalytic hydrogenation of C=C and C=O double bonds in water/toluene biphasic systems. Reaction of the ligand with [RuCl2(eta(6)-p-cymene)](2) affords the new water soluble complex [RuCl(eta(6)-p-cymene)(1)] (2) which has been found to be catalytically active in the water/organic solvent biphasic hydrogenation using styrene and 2-cyclohexen-1-one as model substrates. Very conveniently, the iridium based catalytic system is prepared by simply stirring in water [Ir(eta(4)-COD)C1]2 with Nal (Ir:Nal molar ratio-1:4), the resulting solution is catalytically active and appears more efficient than 2. With both the Ru- and Ir-based systems the catalytically active aqueous phases can be used at least three times without loss of activity. (C) 2014 Elsevier B.V. All rights reserved

Delimiting species boundaries within the Bothriochloa saccharoides complex (Poaceae) through morphometric analysis

The Bothriochloa saccharoides complex is one of the most interesting groups within the genus Bothriochloa (Poaceae). The plants inhabit grasslands of tropical and subtropical regions from the Americas. Principal components analysis (PCA) and discriminant analysis (DA) were employed to evaluate the morphological variation among 60 herbarium specimens tentatively identified as B. imperatoides, B. laguroides, B. longipaniculata, B. saccharoides and B. torreyana. Twenty-three morphological characters were included in the analysis in order to clarify problematic species boundaries. Chemical data was incorporated to improve the resolution on delimitation of the species complex. Taxa were delimited according to the observed clustering of specimens in the PCA plots and discriminant analysis, and diagnostic characters were identified. The results showed that five taxa could be distinguished on the basis of morphological characters and chemical data. Two new subspecies are described: B. saccharoides subsp. americana and B. saccharoides subsp. australis. An identification key and a taxonomic synopsis are provided.Fil: Scrivanti, Lidia Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Instituto Multidisciplinario de Biología Vegetal (p); ArgentinaFil: Norrmann, Guillermo Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); ArgentinaFil: Anton, Ana Maria Ramona. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Instituto Multidisciplinario de Biología Vegetal (p); Argentin

A NEW PLATINUM-BASED CATALYST SYSTEM FOR OLEFIN ASYMMETRIC HOMOGENEOUS HYDROFORMYLATION

The complex [Pt(C2H4)((+)-DIOP)] interacts with [PtCl2((+)-DIOP)] to give catalysts active in hydroformylation of styrene and 1-hexene. The activities of these systems depend upon the molar ratio of the two platinum complexes and the nature of the substrate. The systems display good chemioselectivity and induce asymmetry in the branched aldehydes formed. 2-Phenylpropanal can be isolated in ∼ 27% optical purity from hydroformylation of styrene. © 1990