Metal‐Free and Copper‐Promoted Single‐Pot Hydrocarboxylation of Cycloalkanes to Carboxylic Acids in Aqueous Medium

Abstract

A simple and effective method for the transformation, under mild conditions and in aqueous medium, of various cycloalkanes (cyclopentane, cyclohexane, methylcyclohexane, cis-and trans-1,2-dimethylcyclohexane, cycloheptane, cyclooctane and adamantane) into the corresponding cycloalkanecarboxylic acids bearing one more carbon atom, is achieved. This method is characterized by a singlepot, low-temperature hydrocarboxylation reaction of the cycloalkane with carbon monoxide, water and potassium peroxodisulfate in water/acetonitrile medium, proceeding either in the absence or in the presence of a metal promoter. The influence of various reaction parameters, such as type and amount of metal promoter, solvent composition, temperature, time, carbon monoxide pressure, oxidant and cycloalkane, is investigated, leading to an optimization of the cyclohexane and cyclopentane carboxylations. The highest efficiency is observed in the systems promoted by a tetracopper(II) triethanolaminate-derived complex, which also shows different bond and stereoselectivity parameters (compared to the metalfree systems) in the carboxylations of methylcyclohexane and stereoisomeric 1,2-dimethylcyclohexanes. A free radical mechanism is proposed for the carboxylation of cyclohexane as a model substrate, involving the formation of an acyl radical, its oxidation and consequent hydroxylation by water. Relevant features of the present hydrocarboxylation method, besides the operation in aqueous medium, include the exceptional metal-free and acid-solvent-free reaction conditions, a rare hydroxylating role of water, substrate versatility, low temperatures (ca. 50 8C) and a rather high efficiency (up to 72% carboxylic acid yields based on cycloalkane).

Synthesis, Structural Features, and Catalytic Activity of an Iron(II) 3D Coordination Polymer Driven by an Ether-Bridged Pyridine-Dicarboxylate

“…It should be highlighted that the product yield of up to 22% (based on propane) obtained herein is remarkable, especially if taking into account a very high inertness of this gaseous hydrocarbon along with rather mild conditions applied for running the oxidation reaction [37][38][39][40][41]. In addition, compound 1 was evaluated as catalyst precursor in the carboxylation of cyclic C n (n = 5−8) alkanes and propane in the presence of CO (carbonyl source), H 2 O (hydroxyl source) and K 2 S 2 O 8 (oxidant and radical initiator) [42][43][44]. These carboxylations undergo in H 2 O/CH 3 CN at 60 • C and result in generation of the respective C n+1 carboxylic acids (main products, Table 3).…”

“…The use of CH 3 CN as a solvent is important for solubilization of an alkane and catalyst since the oxidation reactions practically do not undergo in only H 2 O as a solvent. Selection of acetonitrile can be justified by the following factors: (i) miscibility of CH 3 CN with H 2 O and aqueous H 2 O 2 , (ii) sufficient solubility of alkanes in CH 3 CN, (iii) good stability of acetonitrile in the reaction medium, and (iv) good prior results for oxidative functionalization of alkanes obtained when using CH 3 CN as a solvent of choice [37][38][39][40][41][42][43][44].…”

“…In addition, compound 1 was evaluated as catalyst precursor in the carboxylation of cyclic Cn (n = 5−8) alkanes and propane in the presence of CO (carbonyl source), H2O (hydroxyl source) and K2S2O8 (oxidant and radical initiator) [42][43][44]. These carboxylations undergo in H2O/CH3CN at 60 °C and result in generation of the respective Cn + 1 carboxylic acids (main products, Table 3).…”

Redox activation of hydrogen sulfide in reaction with cycloheptane

“…Metal-complex analysis is used of oxida tive activation of the C-H bond in cycloalkanes. Thus, the authors of [10,11] successfully performed the reactions of cycloheptane carboxylation and hydroxy lation at the room temperature in the presence of bi , tetra , and polynuclear complexes of Cu(II). This approach is undoubtedly promising, but the choice of metal-complex catalysts stable towards the effect of hydrogen sulfide is sufficiently complex.…”

Structural and Hirshfeld Surface Analyses of a Novel Hetero-Tetranuclear CuII-NaI Bis(Salamo)-Based Coordination Compound

“…Salen-type ligands and their coordination compounds have been extensively investigated [1][2][3][4][5][6][7][8][9][10] for their catalytic activities [11][12][13][14][15], biological activities [16][17][18][19][20][21][22], supramolecular architectures [23][24][25][26][27][28][29][30][31][32], and fluorescence properties [33][34][35][36][37][38]. To improve the properties of Salen-type ligands, in recent years, Nabeshima and our group's researches mostly concentrated on the syntheses of Salamo-type ligands, which are a class of novel Salen-type analogues [39][40][41][42][43][44][45][46][47][48]…”