Hydroxylation of Unactivated C(sp³)–H Bonds with m-Chloroperbenzoic Acid Catalyzed by an Iron(III) Complex Supported by a Trianionic Planar Tetradentate Ligand

Abstract

Hydroxylation of cyclohexane with m-chloroperbenzoic acid was examined in the presence of an iron(III) complex supported by a trianionic planar tetradentate ligand. The present reaction system shows a high turnover number of 2750 with a high product selectivity of alcohol (93%). The turnover frequency was 0.51 s −1 , and the second-order rate constant (k) for the C−H bond activation of cyclohexane was 1.08 M −1 s −1 , which is one of the highest values among the iron complexes in the oxidation of cyclohexane so far reported. The present catalytic system can be adapted to the hydroxylation of substrates having only primary C− H bonds such as 2,2,3,3-tetramethylbutane as well as gaseous alkanes such as butane, propane, and ethane. The involvement of an iron(III) acyl peroxido complex as the reactive species was suggested by spectroscopic measurements of the reaction solution.Article pubs.acs.org/IC

C–H bond chlorination using nickel(ii) complexes of tetradentate amido-quinoline ligands

“…The reaction rate can be expressed as eqn (1), 14 which indicates that the turnover limiting step (TLS) of the catalytic reaction is the substrate oxidation step by a reactive species generated from 1 / 2 and NaOCl. The reaction rate ( V , Mmin −1 ) increased linearly with an increase of the concentration of 1 or 2 added in the reaction mixture (Fig.…”

Mechanistic Study for the Reaction of B12 Complexes with m-Chloroperbenzoic Acid in Catalytic Alkane Oxidations

“…This value could be ranked in the high category of the reported cyclohexane oxidation system using iron complexes though it was measured at 50 °C. 15 The results also indicated that 2 was not involved in the rate-determining step (RDS) of the catalytic reaction. Therefore, the step of the cobalt complex combined with mCPBA to form the Co(III)−mCPBA adduct might be considered as the RDS in the present catalytic system.…”

“…As many research groups have reported oxidation of 2 by the metal complex/mCPBA system under their own conditions, we checked the reaction by Cat Co(II) using some reported conditions to see the effect of the employed conditions on the product yield and selectivity (entries 2−4 in Table 3). High A/K ratios of 3.7 and 1.9 were obtained under Hikichi's 22 and Morimoto and Itoh's 15 conditions, respectively (entries 3 and 4 in Table 3). The low A/K ratio of 0.17 was obtained in N 2 under our standard conditions (entry 1′ in Table 3).…”

“… a The yields of the products (Cy 6 –OH and Cy 6 O) were based on the initial concentration of m CPBA. b Our standard condition: [ 2 ] = 0.54 M, [HNO 3 ] = 6 mM in CH 3 CN. c Our conditions but under N 2 . d Our conditions but under N 2 at 25 °C. Values in parentheses are obtained in 12 h. e Condition in ref : [ 2 ] = 0.9 M in 3/1 (v/v) CH 2 Cl 2 /CH 3 CN. f Condition in ref : [ 2 ] = 2.7 M in 3/1 (v/v) CH 2 Cl 2 /CH 3 CN. g Condition in ref : [ 2 ] = 0.47 M in 3/1 (v/v) CH 2 Cl 2 /CH 3 CN. …”

“…Among the oxidants, m -chloroperbenzoic acid ( m CPBA) has been used as a reagent to form reactive species of a metal complex for C–H bond oxidation . As the metal complex, various metal porphyrins were synthesized as models of the alkane oxygenation enzyme, such as cytochrome P-450, and used for bio-mimetic alkane oxidation. − Non-heme metal complexes were also developed as a catalyst for such reactions with many ligand variations. − In these studies, the central metals are not fixed to iron relevant to the iron enzyme but other transition metals, such as nickel, − cobalt, − and copper, , that are used for the catalyst design. Therefore, many efforts have been made to characterize the reactive species for alkane oxidation in each of the metal complexes with m CPBA to develop a good catalytic system.…”