Tertiary-Amine-Initiated Synthesis of Acyl Fluorides from Carboxylic Acids and CF3SO2OCF3

A convenient method for deoxyfluorination of aromatic and aliphatic carboxylic acids with CF₃SO₂OCF₃ in the presence of a suitable base at room temperature has been developed. The reaction allows a straightforward access to a variety of acyl fluorides and proves that CF₃SO₂OCF₃ is an effective deoxyfluorination reagent for carboxylic acids. The method features simplicity, expeditiousness, high efficiency, ease of handling, good functional group tolerance, a wide range of substrates, excellent yields of products, compatibility of many amine initiators, use of environmentally friendly reagents, and effortless removal of byproducts. This reaction represents the first utilization of trifluoromethyl trifluoromethanesulfonate as a fluorination reagent.     

Catalytic and Asymmetric Fluorolactonisations of Carboxylic Acids through Anion Phase Transfer

Catalytic fluorolactonisations of aromatic carboxylic acids have been developed. The reactions proceed under mild conditions using the commercially available reagent Selectfluor. A weak phase transfer of the reagent mediated by Na₂CO₃ allows the reaction to be conducted in non‐polar solvents. Furthermore, by the use of a catalytic amount of (DHQ)₂PHAL (hydroquinine 1,4‐phthalazinediyl diether), the first asymmetric fluorolactonisation has been achieved. The corresponding isobenzofuran core can be found in many biologically active molecules.     

Selective Esterification of Aliphatic Carboxylic Acids in the Presence of Aromatic Carboxylic Acids Over Monoammonium Salt of 12‐Tungstophosphoric Acid

Monoammonium salt of 12‐tungstophosphoric acid [(NH₄)H₂PW₁₂O₄₀] was found to be a practical and useful heterogeneous catalyst for an efficient and selective esterification of aliphatic carboxylic acids with alcohols in the presence of aromatic carboxylic acids. The heteropoly acid–based heterogeneous catalyst has the advantages of a simple workup procedure, water insolubility, and good activity.     

Simple and Efficient Procedure for the Friedel–Crafts Acylation of Aromatic Compounds with Carboxylic Acids in the Presence of P2O5/AL2O3 Under Heterogeneous Conditions

An efficient and chemoselective method for the Friedel–Crafts acylation of aromatic compounds using P₂O₅/Al₂O₃ and carboxylic acids. Both aromatic and aliphatic carboxylic acids reacted easily to afford the corresponding aromatic ketones in good yields.     

Selective Hydrogenation and Hydrodeoxygenation of Aromatic Ketones to Cyclohexane Derivatives Using a Rh@SILP Catalyst

Rhodium nanoparticles immobilized on an acid‐free triphenylphosphonium‐based supported ionic liquid phase (Rh@SILP(Ph₃‐P‐NTf₂)) enabled the selective hydrogenation and hydrodeoxygenation of aromatic ketones. The flexible molecular approach used to assemble the individual catalyst components (SiO₂, ionic liquid, nanoparticles) led to outstanding catalytic properties. In particular, intimate contact between the nanoparticles and the phosphonium ionic liquid is required for the deoxygenation reactivity. The Rh@SILP(Ph₃‐P‐NTf₂) catalyst was active for the hydrodeoxygenation of benzylic ketones under mild conditions, and the product distribution for non‐benzylic ketones was controlled with high selectivity between the hydrogenated (alcohol) and hydrodeoxygenated (alkane) products by adjusting the reaction temperature. The versatile Rh@SILP(Ph₃‐P‐NTf₂) catalyst opens the way to the production of a wide range of high‐value cyclohexane derivatives by the hydrogenation and/or hydrodeoxygenation of Friedel–Crafts acylation products and lignin‐derived aromatic ketones.     

High-load, soluble oligomeric carbodiimide: synthesis and application in coupling reactions

A facile preparation of a high-load, soluble oligomeric alkyl cyclohexylcarbodiimide (OACC) reagent via ROM polymerization from commercially available starting materials is described. This reagent is exploited as a coupling reagent for esterification, amidation, and dehydration of carboxylic acids (aliphatic and aromatic) with an assortment of alcohols (aliphatic primary, secondary, and benzylic), thiols, phenols, and amines (aliphatic primary, secondary, benzylic, and aromatic/anilines), respectively. Following the coupling event, precipitation with an appropriate solvent (Et(2)O, MeOH, or EtOAc), followed by filtration through a SPE provides the products in good to excellent yield and purity.     

Ceric Ammonium Nitrate Catalyzed Oxidation of Aldehydes and Alcohols

A variety of aromatic, aliphatic and conjugated aldehydes and alcohols were transformed to the corresponding carboxylic acids and ketones with a quantitative conversion in high yields with 70% t‐BuOOH solution in water in the presence of catalytic amounts of ceric ammonium nitrate [Ce(NH₄)₂(NO₃)₆] (CAN) under room temperature conditions. The scope of our catalytic system is applicable for a wide range of aromatic, conjugated and aliphatic substrates. These aldehydes were converted to the corresponding carboxylic acids in good isolated yields in reasonable times. This method possesses a wide range of capabilities since it can be used with other functional groups which may not tolerate oxidative conditions, involves fairly simple method for work‐up, exhibits chemoselectivity and proceeds under ambient conditions. The resulting products are obtained in good yields within reasonable time.     

O‐Arylation of Carboxylic Acids using (Phenyl)[2‐(trimethylsilyl)phenyl]iodonium Triflate as a Precursor of Arynes

Using (phenyl)[2‐(trimethylsilyl)phenyl]iodonium triflate as a precursor of arynes, Larock's method for O‐arylation of carboxylic acids and arynes was developed. A variety of acids including simple aliphatic carboxylic acids, aromatic carboxylic acids, allenoic acids, and p‐toluenesulfonic acid under mild reaction conditions could generate the aryl esters.     

Friedel-Crafts acylation of aromatic compounds with carboxylic acids in the presence of P2O5/SiO2 under heterogeneous conditions

A convenient and efficient procedure for the Friedel-Crafts acylation of aromatic compounds with carboxylic acids in the presence of P₂O₅/SiO₂ is described. Both aromatic and aliphatic carboxylic acids reacted easily to afford the corresponding aromatic ketones. The use of non-toxic and inexpensive materials, simple and clean work-up, short reaction times and good yields of the products are the advantages of this method.     

Di-tert-butyl dicarbonate as an efficient coupling reagent for the immobilization of carboxylic acid moieties

We describe an efficient methodology for anchoring diverse carboxylic acids to hydroxymethylated resins using di-tert-butyl dicarbonate as coupling reagent. The reaction is equally effective for aromatic and aliphatic acids, and Fmoc-protected amino acids.     

A novel tert-butoxycarbonylation reagent: 1-tert-butoxy-2-tert-butoxycarbonyl-1,2-dihydroisoquinoline (BBDI)

The use of 1-tert-butoxy-2-tert-butoxycarbonyl-1,2-dihydroisoquinoline (BBDI) as a tert-butoxycarbonylation reagent for acidic proton-containing substrates such as phenols, aromatic and aliphatic amines hydrochlorides, and aromatic carboxylic acids in the absence of a base is described. The reactions proceed chemoselectively in high yield under mild conditions.     

Lewis acid-catalyzed Friedel-Crafts acylation reaction using carboxylic acids as acylating agents

Rare-earth metal Lewis acids, in particular Eu(NTf₂)₃, were found to be efficient catalysts for Friedel-Crafts acylation reaction using aliphatic as well as aromatic carboxylic acids as acylating agents at high temperature.     

Syntheses and Crystal Structures of Copper and Silver Complexes with the Ylide Ph3PCHP(O)PPh2 as Ligand

The reactivity of the hydrolysis product of hexaphenylcarbodiphosphorane, PPh₃CHP(O)Ph₂, towards different soft Lewis acids, such as CuI and Ag[BF₄] are reported. While CuI exclusively binds at the ylidic carbon atom, reaction of the silver cation in CH₂Cl₂ leads to proton abstraction from the solvent to give the cation [PPh₃CH₂P(O)Ph₂]⁺. Surprisingly, Ag⁺ replaces the methyl group of [PPh₃CHMeP(O)Ph₂]⁺ to produce a dimeric complex, in which Ag⁺ is coordinated to C and O forming an eight membered ring. The compounds were characterized by spectroscopic methods and X‐ray diffraction.     

NEW APPLICATIONS OF SOLID SILICA CHLORIDE (─SiO2Cl): EFFICIENT OXIDATION OF CYCLIC THIOACETALS,TMS, TBDMS,AND THP ETHERS TO THEIR CARBONYL COMPOUNDS BY SOLID SILICA CHLORIDE/KMnO4 SYSTEM

Solid silica chloride/KMnO₄ system oxidizes effectively aromatic and aliphatic cyclic thioacetals (1,3-dithiolanes, 1,3-dithianes) and silyl and pyranyl ethers into their corresponding carbonyl compounds in dry CH₃CN at room temperature in high yields. Over-oxidation of aldehydes to carboxylic acids has not been observed by this system. In the absence of silica chloride, KMnO₄ in dry CH³CN is an ineffective reagent for these oxidations.     

Reactivity of mixed organozinc and mixed organocopper reagents: 11. Nickel‐catalyzed atom‐economic aryl–allyl coupling of mixed (n‐alkyl)(aryl)zincs

Group selectivity in the allylation of mixed (n‐butyl)(phenyl)zinc reagent can be controlled by changing reaction parameters. CuCN‐catalyzed allylation in tetrahydrofuran (THF)–hexamethylphosphoric triamide is n‐butyl selective and also γ‐selective in the presence of MgCl₂, whereas CuI‐catalyzed allylation in THF in the presence of n‐Bu₃P takes place with a n‐butyl transfer:phenyl transfer ratio of 23:77 and an α:γ transfer ratio of phenyl of 76:24. NiCl₂(Ph₃P)₂‐catalyzed allylation in the presence of LiCl is phenyl selective with an α:γ ratio of 65:35. The reaction of methyl‐ or n‐butyl(aryl)zinc reagents with an allylic electrophile in THF at room temperature in the presence of NiCl₂(Ph₃P)₂ catalyst and LiCl as an additive provides an atom‐economic alternative to aryl–allyl coupling using diarylzincs. Copyright © 2014 John Wiley & Sons, Ltd.     

Rhodium‐Catalyzed Geminal Oxyfluorination and Oxytrifluoro‐Methylation of Diazocarbonyl Compounds

A new reaction for the rhodium‐catalyzed geminal‐difunctionalization‐based fluorination is presented. The substrates are aromatic and aliphatic diazocarbonyl compounds. As the fluorine source a stable and easily accessible benziodoxole reagent was used. A variety of alcohol, phenol, and carboxylic acid reagents were employed to introduce the second functionality. The reaction was extended to trifluoromethylation using a benziodoxolon reagent. The fluorination and trifluoromethylation reactions probably proceed by a rhodium‐containing onium ylide type intermediate, which is trapped by either the F or CF₃ electrophiles.     

A three‐dimensional zinc‐based coordination polymer built from 5‐carboxylato‐1‐carboxylatomethyl‐2‐oxidopyridinium with a 4‐connected sra topology

A novel three‐dimensional Zn^II complex, poly[aqua(μ₄‐5‐carboxylato‐1‐carboxylatomethyl‐2‐oxidopyridinium)zinc(II)], [Zn(C₈H₅NO₄)(H₂O)]_n, has been prepared by hydrothermal assembly of Zn(CH₃COO)₂·2H₂O and 5‐carboxy‐1‐(carboxymethyl)pyridin‐1‐ium‐2‐olate (H₂ccop). The ccop²⁻ anions bridge the Zn^II cations in a head‐to‐tail fashion via monodentate aromatic carboxylate and phenolate O atoms to form an extended zigzag chain which runs parallel to the [011] direction. One O atom of the aliphatic carboxylate group of the ccop²⁻ ligand coordinates to the Zn^II atom of a neighbouring chain thereby producing undulating layers which lie parallel to the (01) plane. A similar parallel undulating planar structure can be obtained if a path involving the other O atom of the aliphatic carboxylate group is considered. Thus, the aliphatic carboxylate group acts in a bridging bidentate mode to give extended –Zn–O–C–O–Zn– sequences running parallel to [001] which link the layers into an overall three‐dimensional framework. The three‐dimensional framework can be simplified as a 4‐connected sra topology with a Schläfli symbol of 4².6³.8 if all the Zn^II centres and ccop²⁻ anions are regarded as tetrahedral 4‐connected nodes. The three‐dimensional luminescence spectrum was measured at room temperature with excitation and emission wavelengths of 344–354 and 360–630 nm, respectively, at intervals of 0.15 and 2 nm, respectively.     

New Method for the Synthesis and Reactivity of (5‐R‐1,3,4‐Oxadiazol‐2‐yl)furoxans

A new, simple and general one‐pot method for the preparation of (5‐R‐1,3,4‐oxadiazol‐2‐yl)furoxans has been developed on the basis of the interaction between accessible 3‐methylfuroxan‐4‐carboxylic acid hydrazide and aliphatic, aromatic and heterocyclic carboxylic acids or their chlorides in the presence of POCl₃. The synthesis and study of (5‐R‐1,3,4‐oxadiazol‐2‐yl)furoxans reactivity resulted in new polyheterocyclic ensembles incorporating furoxan, 1,3,4‐oxadiazole, pyrrole, triazole, furan, thiophene, pyrimidine, and other heterocycles in different combinations.     

Synthesis,Structure and Noncovalent Interactions Palladium（Ⅱ）Complexes with N—Benzoyl—β—phenylalaniate Dianion and Aromatic Diimine

Two palladium(II) complexes, [Pd(bipy)(BzPhe‐N,O)] and [Pd(phen)(BzPhe‐N,O)]·4H₂O were synthesized by reactions between Pd(bipy)Cl₂ and BzPheH₂ (N‐benzoyl‐β‐phenylalanine), Pd(phen) Cl₂ and BzPheH₂ in water at pH‐9, with their structures determined by X‐ray diffraction analysis. The Pd atom is coordinated by two nitrogen atoms of bipy (or phen), the deprotonated amido type nitrogen atom and one of the carboxylic oxygens of BzPhe (BzPhe = N‐benzoyl‐β‐phenylalaninate dianion). In the complex [Pd(phen) (BzFne‐N,O)] · 4H₂O, the side chain of phenylalanine is located above and approximately parallels to the coordination plane. Both the aromatic‐aromatic stacking interaction between the phenyl ring of phenylalanine and phen, and the metal ion‐aromatic interaction between the phenyl ring of phenylalanine and Pd(II) were observed. [Pd(bipy)(BzPhe‐N,O)] has the phenylalanyl side chain oriented outwards from the coordination plane, which is mainly due to the interaction between the carbonyl oxygen atom of the amido group and the phenyl ring of phenylalanine. The reason for the different orientation of phenylalanyl side chain in the complexes was suggested.     

On the Role of Pre‐ and Post‐Electron‐Transfer Steps in the SmI2/Amine/H2O‐Mediated Reduction of Esters: New Mechanistic Insights and Kinetic Studies

The mechanism of the SmI₂‐mediated reduction of unactivated esters has been studied using a combination of kinetic, radical clocks and reactivity experiments. The kinetic data indicate that all reaction components (SmI₂, amine, H₂O) are involved in the rate equation and that electron transfer is facilitated by Brønsted base assisted deprotonation of water in the transition state. The use of validated cyclopropyl‐containing radical clocks demonstrates that the reaction occurs via fast, reversible first electron transfer, and that the electron transfer from simple Sm(II) complexes to aliphatic esters is rapid. Notably, the mechanistic details presented herein indicate that complexation between SmI₂, H₂O and amines affords a new class of structurally diverse, thermodynamically powerful reductants for efficient electron transfer to carboxylic acid derivatives as an attractive alternative to the classical hydride‐mediated reductions and as a source of acyl‐radical equivalents for C?C bond forming processes.