University of Groningen Selective Catalytic Oxidation of Alcohols, Aldehydes, Alkanes and Alkenes Employing Manganese Catalysts and Hydrogen Peroxide Saisaha, Pattama; Buettner, Lea; van der Meer, Margarethe; Hage, Ronald; Feringa, Ben L.; Browne, Wesley R.; de Boer, Johannes W. Published in: Advanced Synthesis & Catalysis DOI: 10.1002/adsc.201300275 IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Please check the document version below. Document Version Publisher's PDF, also known as Version of record Publication date: 2013 Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Saisaha, P., Buettner, L., van der Meer, M., Hage, R., Feringa, B. L., Browne, W. R., & de Boer, J. W. (2013). Selective Catalytic Oxidation of Alcohols, Aldehydes, Alkanes and Alkenes Employing Manganese Catalysts and Hydrogen Peroxide. 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Download date: 27-09-2021 FULL PAPERS DOI: 10.1002/adsc.201300275 Selective Catalytic Oxidation of Alcohols, Aldehydes, Alkanes and Alkenes Employing Manganese Catalysts and Hydrogen Peroxide Pattama Saisaha,a Lea Buettner,a Margarethe van der Meer,a Ronald Hage,b Ben L. Feringa,a Wesley R. Browne,a,* and Johannes W. de Boerb,* a Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands Fax : (+31)-50-363-4290; phone: (+ 31)-50-363-4428; e-mail: [email protected] b Catexel BV, BioPartner Centre Leiden, Galileiweg 8, 2333 BD Leiden, The Netherlands Fax : (+31)-71-332-2222; phone: (+ 31)-71-332-2221; e-mail: [email protected] Received: April 3, 2013; Revised: July 15, 2013; Published online: September 9, 2013 Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201300275. Abstract: The manganese-containing catalytic system lytic system and to explore which functional groups IV,IV ACHTUNGRE 2+ [Mn 2O3(tmtacn)2] (1)/carboxylic acid (where are oxidised preferentially. This catalytic system, of tmtacn = N,N’,N’’-trimethyl-1,4,7-triazacyclononane), which the reactivity can be tuned by variation of the initially identified for the cis-dihydroxylation and ep- carboxylato ligands of the in situ formed III,III ACHTUNGRE ACHTUNGRE 2+ oxidation of alkenes, is applied for a wide range of [Mn 2(O)(RCO2)2(tmtacn)2] dimers, employs oxidative transformations, including oxidation of al- H2O2 in a highly atom efficient manner. In addition, kanes, alcohols and aldehydes employing H2O2 as ox- several substrates containing more than one oxida- idant. The substrate classes examined include pri- tion sensitive group could be oxidised selectively, in mary and secondary aliphatic and aromatic alcohols, certain cases even in the absence of protecting aldehydes, and alkenes. The emphasis is not primari- groups. ly on identifying optimum conditions for each indi- vidual substrate, but understanding the various fac- Keywords: homogeneous catalysis; manganese; oxi- tors that affect the reactivity of the Mn-tmtacn cata- dation; peroxides; triazacyclononane [7,8,9,10] IV,IV Introduction zymes. The first report on the use of [Mn 2O3 ACHTUNGRE 2+ (tmtacn)2] (1) (Figure 1) as a catalyst was by Hage Oxidative transformations, in particular the oxidation et al. in 1994, where it was employed in an aqueous [1,2] of alkenes to their corresponding diols or epoxides, carbonate buffer (pH 8–9) with H2O2 as terminal oxi- alcohols to aldehydes, ketones or carboxylic acids and dant for clean and efficient low-temperature laundry oxidation of alkanes are central processes in biology, bleaching as well as the epoxidation of alkenes (albeit [3] synthetic organic chemistry and industrial chemistry. typically with 100 equiv. of H2O2 with respect to In recent years, the development of atom-efficient alkene).[11] Since then, several research groups have and environmentally benign catalytic systems has focused on applying this catalyst in oxidative transfor- been a major challenge.[4] A primary goal is to devel- mations with initial efforts directed towards the use of op systems that show high atom efficiency and mini- mal formation of by-products, with molecular oxygen (O2) and hydrogen peroxide (H2O2) being the most atom economic oxidants.[5,6] Over the last two decades several groups have fo- cused on the use of manganese catalysts based on the ligand N,N’,N’’-trimethyl-1,4,7-triazacyclononane (tmtacn) originally developed by Wieghardt and co- workers in the late 1980s as model systems for the IV,IV ACHTUNGRE ACHTUNGRE water splitting component of photosystem II (PS II) Figure 1. Complexes [Mn 2O3(tmtacn)](PF6)2 1 and III,III ACHTUNGRE ACHTUNGRE ACHTUNGRE and dinuclear manganese-based catalase en- [Mn 2O(CCl3CO2)2(tmtacn)2](PF6)2 2. Adv. Synth. Catal. 2013, 355, 2591 – 2603 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 2591 FULL PAPERS Pattama Saisaha et al. additives to suppress the catalase-type activity (i.e., portant challenge examined is whether compounds wasteful decomposition of H2O2)of1 and to enhance containing multiple oxidation sensitive groups can be its activity towards the oxidation of alkenes.[12,13,14,15] oxidised selectively without the need of protecting De Vos et al. reported the efficient epoxidation of groups. Finally, the tolerance of common protecting a range of alkenes using this catalyst in oxalate-buf- groups to the present system is examined. fered aqueous acetonitrile. Under these conditions the catalase-type activity was suppressed effectively [16] (typically 1.5–3 equiv. H2O2 were required). Subse- Results and Discussion quently, Berkessel and co-workers showed that a mix- ture of l-ascorbic acid and sodium l-ascorbate in Oxidation of Secondary Alcohols to Ketones combination with tmtacn and MnII could be used in the epoxidation of alkenes and the oxidation of alco- Treatment of aromatic secondary alcohols (Table 1, hols, albeit with excess H2O2 (typically 2– entries 1–3) by a slow addition of 1.45 equiv. of H2O2 2.6 equiv.).[17] The range of substrate classes that have in the presence of 0.1 mol% 1 and 1 mol% trichloro- been examined with Mn-tmtacn-based catalysts now acetic acid in acetonitrile afforded the corresponding includes alkanes, alkenes, primary and secondary al- ketones in excellent conversions and moderate to cohols and allylic alcohols.[14,18] Later reports showed good isolated yields. Trichloroacetic acid was chosen that the catalytic activity of the Mn-tmtacn system to- as co-catalyst since our earlier studies had identified wards oxidation of alkanes and epoxidation of alkenes this carboxylic acid to provide the most active catalyst could be enhanced dramatically in the presence of system in general.[22,23] Side reactions or side products a large excess of acid, e.g., acetic acid (typically 40 to were not observed. Aliphatic secondary alcohols (en- >100 mol%),[19] or aldehydes such as choral (typically tries 4–7) were oxidised to the corresponding ketones 25 mol%),[20] respectively. Importantly, in the latter case, and in the earlier example by De Vos et al.[21] with a heterogeneous version of this catalyst, Mn-cat- Table 1. Oxidation of secondary alcohols to ketones using H O catalysed by 1.[a] alysed cis-dihydroxylation was observed also. Subse- 2 2 quently, it was shown by our group that carboxylic acids at co-catalytic levels (typically 1 mol%) were the key to controlling the activity of 1 and enabled Entry Substrate Conversion Product Isolated the efficient use of H O for the oxidation of al- 2 2 [%][a] yield [%] kenes.[22,23] The recognition of the role of carboxylic acids and other factors (e.g., solvent composition) in controlling 1[b] full 77 the reactivity of catalyst 1 in the oxidation of al- [23] kenes raises the question as to how conversion of [b] other substrate classes besides alkenes can be con- 2 full 63 trolled and, importantly, how primary and secondary oxidation products can affect the reactivity of the 3[b] full 93 active species formed from 1, in particular the bis-car- III,III boxylato bridged Mn 2 dimers such as 2 [22,23] (Figure 1). In this contribution the focus is on the 4[b] > 90 31[c] catalytic system employing Mn-tmtacn, carboxylic acids (as co-catalyst) and H2O2 (typically 1.05– 1.5 equiv.) as terminal oxidant for the selective and 5[b] > 95 86 atom efficient oxidation of a range of organic sub- strate classes. 6[b] full 92 The substrate classes examined in detail are pri- mary and secondary aliphatic and aromatic alcohols, 7[b] full 99 aldehydes, alkenes and alkanes. In all cases, the condi- tions used for alkene oxidation in our earlier re- [a] 1 ports[22] are applied initially, followed by optimisation. Conversion was determined by H NMR spectroscopy. [b] Reaction conditions: The goal, however, was not primarily to identify opti- 0.1 mol% 1, 1.0 mol% Cl3CCO2H, 1.45 equiv. H2O2,CH3CN ([substrate]=1M), room tem- mum conditions for each individual substrate but to perature. understand the various factors that affect the reactivi- [c] The isolated yield of cyclohexanone is low, however, this ty of the Mn-tmtacn catalytic system in each case and is due to its relatively high volatility (and accompanying to explore which functional groups are oxidised pref- loss during work-up) and not due to poor performance of erentially by the catalytic system.