Eva Csuhai

The functionalisation of saturated hydrocarbons. Part XXI. The Fe(III)-catalyzed and the Cu(II)-catalyzed oxidation of saturated hydrocarbons by hydrogen peroxide: a comparative study☆

Abstract The selective functionalisation of saturated hydrocarbons catalyzed by copper or iron salts are compared. In addition to further studies on the homogeneous oxidation by Cu(II)-H2O2 is pyridine-acetic acid (GoChAgg system), we introduce a heterogeneous GifIII-analog based on Cu0 and dioxygen in pyridine-acetic acid. Both Cu-based systems display Gif-type reactivity. The intermediacy of alkyl hydroperoxides in the Cu(II)-catalyzed reaction has been proven spectroscopically (following the reaction on [1-13C]-cyclohexane by 13C-N.M.R. spectroscopy) and chemically (quenching the reaction with triphenylphosphine to reduce the hydroperoxide to alcohol). The same holds for Cu0/O2 system, as shown by the effect of triphenylphosphine added to the reaction mixture. Thus, both reactions follow the pathway alkane → alkyl hydroperoxide → alcohol or ketone. Experiments running the GoChAgg reaction (H2O2-based) under an 18O2-atmosphere showed the incorporation of 18O2 into the hydroperoxide and the alcohol (which derives itself from the alkyl hydroperoxide). The relative reactivity of this Cu(II) system was studied for a series of cycloalkanes. The participation of another reaction intermediate (A) has also been demonstrated. However, some important differences are presented, that show that the chemical properties of the Cu-A and the Fe-A intermediates are different. Thus, Gif-type reactivity is metal-dependent and involves two chemically different non-radical species.

Effect of ligand variation on the rate of cyclododecane oxidation under modified Go AggII conditions

Abstract The effect of various ligands on the GoAgg II oxidation of cyclododecane to cyclododecanone has been investigated. The addition of picolinic acid and a number of its congeners increases the rate of oxidation up to fiftyfold. On the other hand, the addition of pyridine-2-phosphonic acid stops oxidation completely.

Functionalisation of saturated hydrocarbons. Part xvi. Chemoselective oxidation

Abstract cyclododecane is efficiently oxidised under GifIV and GoAggII conditions to give over 25% of cyclododecanone with some cyclododecanol. The addition in equimolar amounts of ethanol, isopropanol, ethylene glycol, diisopropyl ether, biphenyl, anisole, diphenyl sulfide, methyl benzoate and dimethyl-acetamide have little effect on the oxidation. Thiophenols have a minor effect, but t-butyl thiol and dimethylaniline reduce oxidation to a major extent. In all cases, the mass balances are satisfactory. Overoxidation of cyclododecanone affords cyclododecane-1, 3-, 1,4-, 1,5- and 1,6-diones. The major dione is 1,4-followed by 1,6-.

The functionalization of saturated hydrocarbons. Part XIX. Oxidation of alkanes by H2O2 in pyridine catalyzed by copper(II) Complexes. A Gif-Type Reaction.☆

Abstract The Cu II -catalyzed oxidation of saturated hydrocarbons by hydrogen peroxide proceeds in pyridine-acetic acid solutions affording mainly ketones as the reaction product. The conversion of hydrocarbon is about 20–30 %. This system (called GoChAgg) shares with the Fe III -catalyzed system (GoAgg II ) its unusual chemical characteristics.

Comparison of gif-type reactivity towards alkanes with standard radical reaction selectivity. Gif oxidation of n-butane and propane

Abstract A precise comparison has been made between radical bromination of a series of saturated hydrocarbons using BrCCl 3 and the bromination of the same series with the same reagent under Gif-type (GoAgg III ) conditions. The relative reactivities in the two series are completely different and confirm a difference in mechanism. Experiments with n -butane and with propane have shown that these gases react with the usual Gif selectivity to furnish 2-butanone and acetone respectively.

The functionalization of saturated hydrocarbons. Part 23. Gif-type bromination and chlorination of saturated hydrocarbons: a non-radical reaction☆

Abstract The bromination of saturated hydrocarbons was studied in the GoAgg III system using CBrCl 3 and other polyhaloalkanes. This bromination reaction was compared to free radical processes by (i) evaluating the rates of reactions for a series of polyhaloalkanes, by (ii) measuring the selectivity of the different systems towards various saturated hydrocarbons and by (iii) analyzing the product distribution arising from the bromination of cyclohexyl bromide under both the GoAgg III type conditions and from known processes for alkyl radical generation. Some chlorine containing reagents were also examined for CCl bond formation in the GoAgg III system. All the experimental findings support a mechanism for the reaction that is different from one involving free radicals. This non-radical pathway is common in all Gif-type systems, as seen in common patterns of selectivity. conditions is in agreement with a non-radical reaction pathway for the Gif-type bromination and chlorination reactions.

Studies on the bromination of saturated hydrocarbons Under GoAggIII conditions

Abstract The bromination reaction of saturated hydrocarbons under GoAggIII conditons (FeCl3.6H2O picolinic acid, H2O2 in pyridine/acetic acid) and under radical chain conditions (dibenzoyl peroxide in pyridine/acetic acid or initiation by UV light) are compared. Differences in the selectivity and kinetic behavior for a series of polyhaloalkanes are in agreement with a non-radical mechanism for GoAggIII bromination. Comparison of the kinetic order of reactivity for a series of polyhaloalkanes under chain radical conditions and under GoAggIII conditions is in agreement with a non-radical reaction pathway for the Gif-type bromination reaction.

Gif-type oxidation systems. Evidence for a second intermediate between saturated hydrocarbon and ketone

The addition of dianisyl telluride to a GifIV oxidation of adamantane has a marked effect on the ratio of ketone to secondary alcohol formed. This is interpreted as an indication of a second intermediate in the conversion of saturated hydrocarbons into ketones. This second intermediate is probably an FeIII alkoxide.

Car☐ylation of saturated hydrocarbons by gif systems (Fe0/CO/O2, and CU0/CO/O2 in pyridine-acetic acid)

Abstract Saturated hydrocarbons are transformed into the corresponding homologous car☐ylic acid by treatment with Fe 0 /CO/O 2 or Cu 0 /CO/O 2 in pyridine/acetic acid. Mechanistic studies support a reaction pathway involving the insertion of CO into a carbon-iron or carbon-copper bond.

Detection of cyclohexyl hydroperoxide as an intermediate in Gif type oxidation of cyclohexane to cyclohexanone using 13C NMR spectroscopy

The oxidation of [1-13C]cyclohexane to cyclohexanone under GoAggII conditions is followed using 13C NMR spectroscopy; cyclohexyl hydroperoxide is an intermediate which is transformed quantitatively into cyclohexanone.