Selective mixed coupling of carboxylic acids via unsymmetrical diacyl peroxides by electrolysis,thermolysis and photolysis

Unsymmetrical diacyl peroxides are prepared in 85–92 % yields. Their square pulse electrolysis affords unsymmetrical dimers in poor yield and selectivity. Whilst thermolysis or photolysis in solution produces high portions of disproportionation products, the photolysis of the neat peroxides at ?78° C yields selectively 50–75 % of the mixed dimers.     

Selective mixed coupling of carboxylic acids (II). — photolysis of unsymmetrical diacylperoxides with alkenyl-, halo-, keto-, carboxyl-groups and a chiral α-carbon. Comparison with the mixed kolbe electrolysis

Alkenoyl and functionalized alkanoyl dodecanoyl peroxides are prepared in 70 to 97 % yield and photolyzed at ?78° C. Thereby 4- to 10-alkenoyl and 4-alkanoyl peroxides afford good yields (56 – 68 %) of unsymmetrical coupling products. Similarly α- to σ-haloalkanoyl, cholanoyl or 3- and 4-carboxyalkanoyl peroxides can be coupled (40 – 70 %). The α-chiral diacyl peroxide ls undergoes the photochemical coupling reaction with 80 % retention of its configuration. The photolysis of diacyl peroxides at ?78° C proves to be a favorable supplement of the Kolbe-electrolysis in cases, where the electrolysis fails or produces low yields.     

Rearrangement of epoxynitriles: a convenient homologation of acyclic and cyclic ketones to carboxylic acids

A convenient two-step homologation of both aliphatic and aromatic ketones to the corresponding carboxylic acid has been developed. First ketones were converted to epoxynitriles with the Darzens reaction. Second, a Lewis acid mediated rearrangement of these epoxynitriles with lithium bromide was achieved to give homologated secondary alkanoic acids (as well as aryl-alkanoic) in good yields. The mechanism and the scope of the rearrangement reaction were investigated. This strategy constitutes a two-step homologation of ketones to secondary carboxylic acids.     

Photochemistry of carboxylic acids containing the phenyl and thioether groups: Steady-state and laser flash photolysis studies

The mechanisms for the direct photolysis of phenylthioacetic acid (PTAA) and S-benzylthioglycolic acid (SBTGA) in acetonitrile were investigated using steady-state and laser flash photolysis. For both compounds, a variety of stable photoproducts were found under steady-state, 254 nm irradiation of acetonitrile solutions. The products from the direct photolysis of PTAA included carbon dioxide (photodecarboxylation), acetic acid, diphenyl disulfide, diphenyl sulfide, thiophenol, thioanisole, di(phenylthio) methane, and S-phenyl benzenethiosulfate. The products from the direct photolysis of SBTGA included carbon dioxide, toluene, dibenzyl, dibenzyl sulfide, dibenzyl disulfide, thioglycolic acid, benzyl mercaptan, benzyl alcohol, and benzaldehyde. These stable photoproducts were identified and characterized using HPLC, GC, GC–MS, and UV–vis methods. Quantum yields were determined for the formation of the various stable products following steady-state irradiations in the absence and in the presence of oxygen. In laser flash photolysis (266 nm Nd:YAG laser) experiments, a variety of transients (e.g., phenylthiyl radical, benzyl radical, etc.) was found. For both substrates (PTAA and SBTGA), photoinduced CS bond cleavage was the main primary process. It was also found that for both acids, photoinduced CC bond cleavage occurred, but as a minor process relative to CS bond cleavage. Detailed mechanisms of the primary and secondary processes are proposed and discussed. The validity of these proposed mechanisms was supported by an analysis of the quantum yields of stable products and their transient precursors. Supplementary observations on reactions between the radicals (e.g., C₆H₅–S, C₆H₅–CH₂) and oxygen are also consistent with the proposed mechanisms.     

Reaction of 2,3-epoxypropyl alkyl sulfides with carboxylic acids and phenol

Russian Chemical Bulletin -     

Chemical alteration of nucleic acids and their components—XIII: Reaction of nucleosides with diacyl peroxides

Diacyl peroxides reacted at room tempt with cytidine and adenosine. The former gave 4-acyl and 3-oxido derivatives and the latter gave 6-acyl and 1-oxido derivatives. At 90°, diacetyl peroxide reacted with guanosine, adenosine, cytidine, and uridine by a homolytic process to give their C-methylated derivatives. The latter reaction was accelerated by the presence of a ferrous ion.     

Thermochemical kinetics of bromine nitrate,bromine nitrite,halogen hydroperoxides,dichlorine pentoxide,peroxycarboxylic acids,and diacyl peroxides

Heats of formation of BrONO₂, BrONO, BrOOH, FOOH, FOOCl, CF₃C(O)OOH, HC(O)OOH, CH₃C(O)OOH, and [CH₃C(O)O]₂ are estimated from bond contributions taken from J. Phys. Chem., 100, 10150 (1996). They agree within ±2 kcal/mol with recent experimental or ab initio data. The resulting BDE(O(SINGLEBOND)O)=36 kcal/mol value in diacetyl peroxide requires the concerted assistance of exothermic C(SINGLEBOND)C(O) weakening in the transition state of its decomposition into free radicals. It also implies the existence of a previously unrecognized 12 kcal/mol nonbonded repulsion in acyl anhydrides. The formation of chloryl chlorate with ΔH_f(O₂ClOClO₂)=50 kcal/mol, a marginally stable species toward dissociation into (ClO₃+OClO), may account for observations made in the [O(³P+OClO] system at low temperatures. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 41–45, 1998.     

Ring-opening reactions of N-methyl cyclic ketene-N,O-acetals with carboxylic acids, nitrophenol, and arylthiols

Ring-opening reactions of N-methyl cyclic ketene-N,O-acetals with carboxylic acids, 4-nitrophenol, and arylthiols afforded amidoesters, amidoaryl ether, and amidothioethers, respectively, in good yields via an acid-catalyzed S(N)2 mechanism.     

The chemistry of diacyl peroxides - VIII. The reactions between polyfluorodiacyl peroxides and 2-nitro-2-nitrosopropane--Generation of bis(polyfluoroalkyl) nitroxides

Thermal decomposition of 2-nitro-2-nitrosopropane (4) in F113 (CCl₂F-CClF₂) solution involves C-NO bond fission and forms acetone as the major product. In the presence of polyfluorodiacyl peroxide (3), the oxidation of 4 by 3 to 2,2-dinitropropane (5) is the predominant reaction and bis(polyfluoroalkyl) nitroxide(1) is generated as one of the by-products.     

Mass spectral studies of unsaturated carboxylic acids—I: Some cyclic and acyclic βγ-unsaturated acids

The mass spectra of a series of βγ-unsaturated cyclic and acyclic carboxylic acids are reported. Metastable ion studies and precise mass measurements have been employed in demonstrating that the ten compounds studied conform to one or other of two generalised fragmentation pathways.     

Palladium-catalyzed decarboxylative coupling of quinolinone-3-carboxylic acids and related heterocyclic carboxylic acids with (hetero)aryl halides

An efficient and practical decarboxylative cross-coupling reaction of quinolin-4(1H)-one 3-carboxylic acids with (hetero)aryl halides has been established. Under a bimetallic system of PdBr(2) and silver carbonate, the protocol proved to be general, and a variety of 3-(hetero)aryl 4-quinolinones and related heterocycles, such as 3-aryl-1,8-naphthyridin-4(1H)-ones, 3-arylcoumarins, 3-arylquinolin-2(1H)-ones, and 2-arylchromones, can be prepared in good to excellent yields.     

Oxidative addition in the coupling of alkylgold(I) with alkyl halides

MeAu(PPh₃) reacts with MeI to afford C₂H₆ and I(PPh₃)Au by a multi-step mechanism involving: (i) oxidative addition to form an intermediate Me₂AuI(PPh₃) species, which (ii), undergoes iodide-methyl exchange with another MeAu(PPh₃) species to afford Me₃Au(PPh₃), followed by (iii), reductive elimination of C₂H₆ and reformation of MeAu(PPh₃). The more reactive trime thylphosphine derivative also readily undergoes (i) oxidative addition and (ii) methyl exchange. However, Me₃Au(PMe₃) is more stable than the PPh₃ analog and does not undergo (iii) reductive elimination. Instead, it is involved in (iv), a further very slow reaction with IAu(PMe₃) and MeI to afford Me₂ AuI(PMe₃) in high yields. C₂H₅Au(PPh₃) specifically affords n-C₄H₁₀ at 0° in MeI. Reactions of other alkylgold(I) complexes with alkyl halides are also reported, and fit into a general mechanistic pattern desribed by reactions (i) – (iv).     

Synthesis of unsymmetrical biaryl ethers through nickel-promoted coupling of polyfluoroarenes with arylboronic acids and oxygen

Polyfluoro-substituted unsymmetrical biaryl ethers were synthesized via a novel Ni-catalyzed cross-coupling reaction of polyfluoroarenes with arylboronic acids and oxygen. The polyfluorinated arenes presumably captured the phenoxide intermediate efficiently, which made the oxygen-insertion proceed smoothly via the S(N)Ar protocol. The (18)O labeling experiment demonstrated that the oxygen introduced into unsymmetrical diaryl ether originated from very trace amounts of oxygen in the reaction system. A plausible mechanism was also suggested.     

Au(I) complexes-catalyzed transfer vinylation of alcohols and carboxylic acids

Au(I) complexes-catalyzed transfer vinylation of alcohols and carboxylic acids has been achieved. The catalyst system consists of 2 mol % AuClPPh₃ and 2 mol % AgOAc. Primary alcohols and secondary alcohols were converted into corresponding vinyl ethers in good yield (64-93%); however, tertiary alcohols showed poor reactivities. Carboxylic acids were also transformed into corresponding vinyl esters in good yield (78-96%).     

An unexpected coupling reaction between isocyanides and carboxylic acids: a method for the synthesis of highly stable symmetrical and unsymmetrical alkylamidine and arylamidine carbocations

An unexpected coupling reaction between isocyanides and carboxylic acids which led to the synthesis of highly stable symmetrical and unsymmetrical alkylamidine and arylamidine carbocations under mild reaction conditions is described. The structures of these compounds were confirmed by IR, mass, ¹H NMR, ¹³C NMR, and single-crystal X-ray diffraction studies and a plausible mechanism is proposed.     

Reactions on polymers with amine groups. I. Reactions of vinylpridine polymers and of their model compounds with unsaturated carboxylic acids

The reactions of vinylpyridine polymers with α,β-unsaturated carboxylic acids such as acrylic, methacrylic, crotonic, itaconic, cinnamic, fumaric, and maleic acids were studied. It was found that, when reacted with acrylic, itaconic and fumaric acids. poly(4-vinylpyridine) gave macromolecular betaine products while with maleic acid, betaine as well as the corresponding salt was obtained. Poly(2-vinylpyridine) reacted with the same acids as poly(4-vinylpyridine) gave only the salts. No significant changes were observed with the two polymers when reacted with methacrylic, crotonic, and cinnamic acids. To attempt to rationalize these observations with the two macromolecular tertiary amines, the reactions of 4-methyl and 2-methylpyridines with the same carboxylic acids were investigated. The ¹H-NMR methodology was generally applied to elucidate the chemical structure obtained. © 1995 John Wiley & Sons, Inc.     

Reactivity of mixed organozinc and mixed organocopper reagents: 6. Nickel-catalyzed coupling of methylarylzincs with primary alkyl halides; an atom-economic aryl-alkyl coupling

A nickel-catalyzed process for the cross-coupling of mixed arylzincs and primary alkyl halides has been developed. The reaction of a methylarylzinc with a primary alkyl halide in THF in the presence of NiCl₂/PPh₃ takes place with selective aryl transfer at room temperature in moderate yields. This protocol provides an atom-economic alternative to aryl-primary alkyl coupling using diarylzincs.