Pipe flow of a dense emulsion: Homogeneous shear‐thinning or shear‐induced migration?

The flow field of a 70% concentrated noncolloidal o/w emulsion in a pipe has been investigated by means of Particle Image Velocimetry in a matched refractive index medium. At steady state and in laminar regime, the shape of axial velocity profiles is not parabolic and exhibits a shear‐thinning behavior of the dense emulsion, with a flow index of 0.5 and a negligible yield stress (less than 1 Pa). However, instead of a square root law, the pressure drop increases linearly with U_m. To explain this apparent inconsistency, two mechanisms of different nature are considered. The first originates from a possible relation between the consistency factor and the drop mean diameter. The second mechanism is shear‐induced migration and leads to the development of a concentration gradient in the pipe cross section. Both mechanisms considered reconcile the experimental data, the apparent local shear‐thinning behavior and the linear evolution of the pressure drop with the flow rate. © 2017 American Institute of Chemical Engineers AIChE J, 2017     

The trans‐10,cis‐15 18:2: a Missing Intermediate of trans‐10 Shifted Rumen Biohydrogenation Pathway?

The “trans-10 shifted” biohydrogenation pathway is frequently established in the rumen when high starch diets are fed to ruminants, resulting in the accumulation of trans-10 18:1 in ruminant products. It has been proposed that the “trans-10 shifted” biohydrogenation pathway of α-linolenic acid generates two intermediates, the trans-10,cis-15 18:2 and trans-10,cis-12,cis-15 18:3, although none of these have been found in the rumen. We analyzed digestive contents and meat samples from two trials, where animals were fed: a compound feed diet supplemented with 8 % oil blend containing linseed oil (samples A); and a forage based diet supplemented with 6 % linseed oil (samples B). The use of the new SLB-IL111 chromatographic column allowed the detection of two different 18:2 isomers in each sample trial, which could not be resolved when the CP-Sil 88 column is used. The two 18:2 isomers were characterized by mass spectrometry using 4,4-dimethyloxazoline derivatives. However, because they were subject to higher temperatures and present different chromatographic properties compared with the fatty acid methyl esters, we also used the “covalent adduct chemical ionization” technique to confirm the identity of both 18:2 isomers. We detected and identified the 10,15-18:2 in samples A and the 11,15-18:2 in samples B. The geometry of both isomers was tentatively assigned as trans,cis taking in account their elution order and biologic plausibility. As far as we know, this is the first time that the trans-10,cis-15 18:2 has been found in ruminant digestive contents and meat samples associated with the “trans-10 shifted” biohydrogenation pathway of α-linolenic acid.     

Nano‐Iron Oxide as a Recyclable Catalyst for Intramolecular C?N Cross‐Coupling Reactions under Ligand‐Free Conditions: One‐Pot Synthesis of 1,4‐Dihydroquinoline Derivatives

The ligand‐free nanoparticle ferroferric oxide catalytic system has been developed to promote the intramolecular C N cross‐coupling reaction. With this protocol, various 1,4‐dihydroquinoline derivatives were synthesized from o‐halobenzaldehydes and β‐enaminones in moderate to good yields.     

Copper‐Catalyzed C?NH2 Arylation of 2‐Aminobenzimidazoles and Related C‐Amino‐NH‐azoles

A copper(II)‐catalyzed selective C NH₂ arylation of 2‐aminobenzimidazoles and related C‐amino‐NH‐azoles was achieved in presence of 2,2′‐bipyridine and cesium carbonate at 60 °C under open air conditions and this is first method for the copper‐catalyzed selective C NH₂ arylation in the presence of other reactive nucleophilic sites. Previously unexplored heteroaromatics possessing multiple nucleophilic sites that are selectively arylated at the C NH₂ position are obtained, providing an exceptional tool for rapid delivery of a diverse array of medicinally important C NH(aryl) derivatives of aminoazoles without any protection/deprotection of ring N H bonds. It is first example for the selective C NH₂ arylation of 5‐aminoindazole, 4‐aminopyrazole, 5‐aminopyrazole, 9H‐purine‐6‐amine, and 1H‐pyrazolo[3,4‐d]pyrimidin‐4‐amine derivatives.

     

Design and Synthesis of 2‐Methyl‐7‐aminobenzoxazole as Auxiliary in the Palladium(II)‐Catalyzed Arylation of a beta‐Positioned C(sp3)?H Bond

A palladium(II)‐catalyzed direct arylation of methylene C(sp³) H bonds by 2‐methyl‐7‐aminobenzoxazole as an effective auxiliary is reported. This process exhibited high beta‐site selectivity, broad substrate scope, and compatibility with different functional groups with moderate to high yields up to 89%.

     

Aerobic Oxidative Coupling of o‐Xylene: Discovery of 2‐Fluoropyridine as a Ligand to Support Selective Pd‐Catalyzed C?H Functionalization

An improved method for the direct oxidative coupling of o‐xylene could provide streamlined access to an important monomer used in polyimide resins. The use of 2‐fluoropyridine as a ligand has been found to enable unprecedented levels of chemo‐ and regioselectivity in this palladium‐catalyzed aerobic oxidative coupling reaction. Preliminary insights have been obtained into the origin of the effectiveness of 2‐fluoropyridine as a ligand.     

Grignard‐Type Arylation of Aldehydes via a Rhodium‐Catalyzed C?H Activation under Mild Conditions

An efficient Grignard‐type arylation of aldehydes via aryl C H activation was achieved under mild conditions catalyzed by rhodium. The reaction provides an easy access to a wide variety of benzyl alcohols and can tolerate various functional groups as well as air and water.     

Rhodium‐Catalyzed Direct Oxidative C?H Acylation of 2‐Arylpyridines with Terminal Alkynes: A Synthesis of Pyrido[2,1‐a]isoindoles

A synthesis of pyrido[2,1‐a]isoindoles is reported by the rhodium‐catalyzed direct oxidative C H acylation of 2‐aryl pyridines with terminal alkynes. The desired products were obtained in moderate to excellent yields. This is an efficient and clean method to construct C C/C N bonds in one step. In addition, the effective rhodium(III) catalyst was isolated and characterized by X‐ray crystallography.

     

An Indium(III)‐Catalyzed Synthesis of 4,4‐Dichloro‐1‐aryl‐N‐alkyl‐1‐yn‐3‐amines via an Intermolecular C(sp2)?C(sp) Bond Formation

This paper demonstrates an indium(III) triflate‐catalyzed reaction of electron‐deficient α,α‐dichloroaldimines with terminal alkynes leading to a rapid and selective access to highly functionalized propargylic amines in good to excellent yields. The dichloromethylene moiety of the aldimine acts as an activating group to accomplish this transformation under very mild conditions.     

iso‐OPDA: An Early Precursor of cis‐Jasmone in Plants?

Cis-jasmone is a highly appreciated fragrance and plant-derived signal molecule that controls pollination, attracts parasitoids of attacking herbivores, and serves as an intra- and interspecific signal that controls gene expression. cis-Jasmone is produced from linolenic acid along the jasmonic acid cascade. In addition to the conversion of jasmonic acid into cis-jasmone, a novel pathway might exist that converts cis-oxophytodienoic acid (OPDA), an early precursor of jasmonic acid, into iso-OPDA. The planar iso-OPDA is degraded by beta-oxidation to 3,7-didehydrojasmonic acid, which yields cis-jasmone by spontaneous decarboxylation. The degradation of iso-OPDA to cis-jasmone is demonstrated for many plant species and the yeast Saccharomyces cerevisiae.     

Iridium(III)‐Catalyzed Direct C?H Sulfonamidation of 2‐Aryl‐1,2,3‐triazole N‐Oxides with Sulfonyl Azides

We have developed a method for the direct sulfonamidation of 2‐aryl‐1,2,3‐triazole N‐oxides using sulfonyl azides as the amino source to release molecular nitrogen as the sole by‐product. This protocol exhibits excellent functional group tolerance and proceeds efficiently under external oxidant‐free conditions. Various 2‐(2‐sulfonamidoaryl)‐1,2,3‐triazoles were prepared in up to 97% yields for 25 examples with excellent regioselectivity.

     

A First Example of Cobalt‐Catalyzed Remote C?H Functionalization of 8‐Aminoquinolines Operating through a Single Electron Transfer Mechanism

The development of new C H functionalization protocols based on inexpensive cobalt catalysts is currently attracting significant interest. Functionalized 8‐aminoquinoline compounds are high‐potential building blocks in organic chemistry and pharmaceutical compounds and new facile routes for their preparation would be highly valuable. Recently, copper has been applied as catalyst for the functionalization of 8‐aminoquinoline compounds and found to operate through a single electron transfer (SET) mechanism, although requiring elevated reaction temperatures. Herein, we described the first example of a cobalt‐catalyzed remote C H functionalization of 8‐aminoquinoline compounds operating through a SET mechanism, exemplified using a practical and mild nitration protocol. The reaction uses inexpensive cobalt nitrate hexahydrate [Co(NO₃)₂⋅6 H₂O] as catalyst and tert‐butyl nitrite (TBN) as nitro source. This methodology offers the basis for the facile preparation of many new functionalized 8‐aminoquinoline derivatives.

     

Palladium‐Catalyzed C?N Cross‐Coupling of N′‐Monosubstituted Sulfondiimines with Aryl Bromides

A general method for the N‐arylation of sulfondiimines with aryl bromides using tris(dibenzylideneacetone)dipalladium(0) [Pd₂(dba)₃] and 2‐dicyclohexylphosphino‐2′,6′‐diisopropoxybiphenyl (RuPhos) as catalyst system was developed. A new benzothiazine was obtained, and a protocol for the cleavage of para‐methoxyphenyl (PMP) groups in PMP‐protected sulfondiimines has been found, which provides access to synthetically useful NH‐derivatives, that are difficult to prepare by other means.     

Nickel‐Catalyzed Cross‐Coupling of Arene‐ or Heteroarenecarbonitriles with Aryl‐ or Heteroarylmanganese Reagents through C?CN Bond Activation

The nickel‐catalyzed cross‐coupling reaction of arene‐ or heteroarenecarbonitriles with aryl‐ or heteroarylmanganese reagents via C CN bond activation has been developed. Both electron‐rich and electron‐deficient nitriles can be employed as the electrophilic substrates. The reaction tolerates a range of functional groups and aromatic heterocycles.     

Copper‐Catalyzed Direct C?H Arylation of Thieno[3,4‐c]pyrrole‐4,6‐dione (TPD): Toward Efficient and Low‐Cost Synthesis of π‐Functional Small Molecules

A series of thieno[3,4‐c]pyrrole‐4,6‐dione (TPD)‐based functional small molecules were efficiently synthesized through direct C H arylations using inexpensive copper salts. In this study, we examined all required reaction parameters including various copper complexes, ligands, bases, and (co)solvents. Under the optimum reaction conditions, the C H arylation proceeded smoothly and a variety of functional groups such as ester, nitrile, fluoride, chloride, triazene, and amine were tolerated. This method provides a step‐economical and relatively low‐cost synthetic alternative to presently used coupling reactions for the preparation of TPD‐containing π‐functional materials.

     

Palladium‐Catalyzed C?H Functionalization of Ferrocenecarboxylic Acid by using 8‐Aminoquinoline as a Removable Directing Group

A mild and efficient palladium‐catalyzed synthetic method for the C H functionalization of N‐(quinolin‐8‐yl)ferrocenecarboxamide has been developed. Various aryl iodides containing I, NO₂, CN, COMe, CO₂Et, and NH functionalities and also alkyl iodides underwent the Pd‐catalyzed intermolecular carbon‐carbon bond forming reaction with ferrocenecarboxamide successfully which led to a diverse array of bis(aryl/alkyl)ferrocenecarboxamides in 34–92% yields. Cross‐coupling of the ferrocenyl C H bond with aryl iodides can also be achieved utilizing an economical Ni catalyst. Additionally, selective monoalkylation of ferrocenecarboxamide was studied using sodium bicarbonate as base and dibenzylphosphoric acid as additive under Pd‐catalyzed reaction conditions. Subsequently, removal of the directing group, 8‐aminoquinoline, from bis(aryl)ferrocenecarboxamides led to bis(aryl)ferrocenes bearing versatile methyl ester and carboxaldehyde functional groups.

     

Tetrabutylammonium Iodide‐Catalyzed Phosphorylation of Benzyl C?H Bonds via a Cross‐Dehydrogenative Coupling (CDC) Reaction

Phosphate esters play important roles as biological active principles and synthons in chemistry. An efficient metal‐free approach for the synthesis of phosphate esters through sp³ C H activation is described. By using tetrabutylammonium iodide (Bu₄NI) as a catalyst and tert‐butyl hydroperoxide (TBHP) as an oxidant, various toluene derivatives and phosphorus nucleophiles are tolerated in this transformation, affording the corresponding products in moderate to good yields.

     

One‐Step Synthesis of Substituted Benzofurans from ortho‐ Alkenylphenols via Palladium‐Catalyzed C?H Functionalization

A dehydrogenative oxygenation of C(sp²) H bonds with intramolecular phenolic hydroxy groups has been developed, which provides a straightforward and concise access to structurally diversely benzofurans from ortho‐alkenylphenols. The reaction is catalyzed by palladium on carbon (Pd/C) without any oxidants and sacrificing hydrogen acceptors.

     

Enantioselective Fluorination of β‐Ketoamides Catalyzed by Ar‐BINMOL‐derived Salan?Copper Complex

A facile and powerful enantioselective construction of C F containing molecules was successfully developed through asymmetric fluorination of β‐ketoamides catalyzed by Ar‐BINMOL‐derived salan–Cu^II system (Ar‐BINMOL=1,1′‐Binaphthalene‐2‐α‐arylmethanol‐2′‐ol, Cu = copper). The present catalytic system exhibited excellent enantioselectivity and a broad substrate scope for indanone‐derived β‐ketoamides under mild conditions (up to 99 % ee and 99 % yields). Notably, the biomimetic salan‐copper complex was demonstrated for the first time to be a highly efficient catalyst in the fluorination of β‐ketoamides. Experimental results and mechanistic studies indicated that both excess amount of copper salt and electrophilic attack of cationic fluorine to activated methylene assisted by amide group on the β‐ketoamides were key factors for high yield and excellent enantioselectivity, respectively, in this enantioselective fluorination, which was controlled by the two‐point binding between the salan–copper complex with cyclic β‐ketoamides and hydrogen‐bonding activation of the electrophilic fluorinating reagent.