Chemoselective Oxidation of Alcohols to Aldehydes and Ketones by tert-Butyl Hydroperoxide Catalyzed by a Ruthenium Complex of N,N‘,N‘‘-Trimethyl-1,4,7-triazacyclononane

Abstract

An operationally simple method based on [Cn*RuIII(CF3CO2)3·H2O] (Cn* = N,N‘,N‘‘-trimethyl-1,4,7-triazacyclononane) catalyst and 1−1.2 equiv of tert-butyl hydroperoxide as terminal oxidant is effective for selective transformation of alcohols to aldehydes and ketones in methylene chloride. The reaction proceeds in high yield and selectivity. Preparation of benzaldehyde (98% yield) from benzyl alcohol on a 200 mmol scale can be performed without modification of the procedure such as slow addition of the oxidant or cooling to 0 °C, and catalyst turnovers of 700 are achieved. Oxidation of geraniol which contains an isolated trisubstituted CC bond leads to geranial selectively without oxidation of the CC bond. Results from Hammett correlation studies (ρ = −0.47) and primary kinetic isotope effect (k H/k D = 4.8) for the catalytic benzyl alcohol oxidations are inconsistent with an oxoruthenium (ORu) based mechanism. A mechanism involving reactive tBuO•/tBuOO• radicals is also excluded based on results from previous works: Cheng, W.-C.; Fung, W.-H.; Che, C.-M. J. Mol. Catal. (A) 1996, 113, 311; absence of di-tert-butyl peroxide; and using cumyl hydroperoxide as a radical probe. A tert-butylperoxoruthenium complex is postulated to be the active intermediate.

Molecular Structure–Activity Relationships for the Oxidation of Organic Compounds Using Mesoporous Silica Catalysts Derivatised with Bis(halogeno)dioxomolybdenum(VI) Complexes

“…[27] Species of this nature are also formed by the reaction of TBHP with molybdenum complexes [MoO 2 X 2 L 2 ] (X Cl, Br, CH 3 ), where L 2 is a Lewis base ligand. [18] Hence, we studied the catalytic potential of the derivatised MCM-41 materials in the liquid-phase oxidation of a range of primary and secondary benzylic and aliphatic alcohols, namely benzyl alcohol, sec-phenethyl alcohol, cyclohexanol, cyclooctanol, cyclohexylmethanol, 1-cyclohexylethanol, 1-octanol and (1R,2S,5R)-(À)-menthol.…”

Dinuclear iron, ruthenium and cobalt complexes containing 1,4-dimethyl-1,4,7-triazacyclononane ligands as well as carboxylato and oxo or hydroxo bridges

“…We showed that the presence of pyrazine-2-carboxylic acid strongly increases the catalytic oxidation potential of the dinuclear Fe(III)- [14], so that even alkanes, including ethane and methane, could be oxidised with hydrogen peroxide in acetonitrile. The mononuclear ruthenium(III) complex [(L-Me 3 )Ru(OOCCF 3 ) 3 ] has been reported as an effective catalyst for the epoxidation of alkenes [15] and for the oxidation of alcohols with t-butylhydroperoxide, under mild conditions [16].…”

Ruthenium complexes of 1,4,7-trimethyl-1,4,7-triazacyclononane for atom and group transfer reactions

“…Not only active for alkene epoxidation and alkane oxidation, [Ru III (Me 3 tacn)(OH 2 )(CF 3 CO 2 ) 2 ] + is also an efficient catalyst for oxidation of alcohols with t-BuOOH [50]. A variety of primary alcohols were oxidized to aldehydes with high selectivity in 83-90% yields (Scheme 16, substrate conversions: 67-97%).…”

“…In this review, we focus on the Me 3 tacn complexes of ruthenium bearing terminal ruthenium-ligand multiple bonds including ruthenium-oxo and -imido species and their oxygen [16,17,33,34,[45][46][47] and nitrogen atom/group transfer reactions, together with related reactions catalyzed by ruthenium Me 3 tacn complexes, including epoxidation of alkenes [17,48,49], oxidation of alkanes [17,48], alcohols [50,51], aldehydes [51], and arenes [52], oxidative cleavage of C C, C C, and C-C bonds [51], cisdihydroxylation of alkenes [53], and amination of saturated C-H bonds [54]. Also included here are some of our unpublished results on the DFT calculations on reactive Ru O and Ru NTs (Ts = ptoluenesulfonyl) complexes supported by Me 3 tacn, and on C-N bond formation reactions catalyzed by [Ru(Me 3 tacn)(NH 3 ) 3 ] 2+ , and electrochemical oxidation of Ru(III)-NH 2 R to the putative [Ru V NR] 2+ from the [Ru(Me 3 tacn)(H 2 L)] 2+ (H 3 L = ␣-(1-amino-1-methylethyl)-2-pyridinemethanol) complex [55].…”