Open access peer-reviewed chapter

Metal Catalyzed Oxidation Reactions of Alkenes Using Eco-Friendly Oxidants

By Jay Soni, Pankaj Teli, Nusrat Sahiba, Ayushi Sethiya and Shikha Agarwal

Submitted: April 15th 2021Reviewed: July 6th 2021Published: September 8th 2021

DOI: 10.5772/intechopen.99267

Downloaded: 74

Abstract

Oxidation of alkenes is an important reaction in academia, industry and science as it is used to develop epoxides, carbonyls, allylic compounds, 1,2-diols, etc. Metal catalyzed oxidation of alkenes has aroused as a significant tool in modern organic synthesis. Several techniques are available; however some of them suffer from few shortcomings viz. high cost, toxic nature, harsh reaction condition, solid waste generation, etc. In view of these drawbacks, green oxidants i.e. O2, H2O2, TBHP, etc. have shown noteworthy prospects due to their nature, low cost, high atom economy and high sustainability in metal catalyzed reactions. This chapter highlights the metal catalyzed green oxidation of alkenes and shall provide new strategies for the functionalization and transformation of alkenes.

Keywords

  • Oxidation
  • alkenes
  • green oxidants
  • metal based catalysts
  • organic synthesis

1. Introduction

The carbon–carbon (C-C) bond is the fundamental unit of valuable organic molecules and possesses significant and diversified applications in nature. Alkenes are the copious portion of organic compounds that are produced abundantly from renewable resources and petrochemical feedstocks [1]. The unique reactivity profile of alkenes is responsible for the diversification and modification in the skeleton that makes them essential in organic synthesis. As a consequence, they have been implemented as starting materials in the synthesis of a wide range of organic chemical building blocks. Various types of molecules such as ethers, halo-ether, alcohol, diol, alkane, and halo compounds have been produced from alkenes via different chemical transformations like addition, substitution, oxidation, polymerization and so on.

Oxidation of alkenes is recognized as a powerful and straightforward tool for the construction of carbon–oxygen (C-O) bonds to develop epoxides, carbonyls, 1,2-diols, and allylic compounds, etc [2, 3, 4]. During the past decades, researchers paid much attention on this subject and several methodologies have been proposed to achieve the selective oxidation of alkenes. Several strong oxidizing agents like OsO4, RuO4, NaIO4, CrO2Cl2 are used in stoichiometric amount for this purpose [5, 6, 7, 8, 9]. These protocols suffer from one or more drawbacks like expensive and toxic reagents, waste generation, low yields, harsh reaction conditions and many more. The designing of mild, straightforward, and environmentally friendly methods of alkene oxidation has attracted continuous interest in organic chemistry. Because of these drawbacks, green oxidants i.e. O2, H2O2, TBHP, and, even air have been used as green oxidants for sustainable and eco-friendly synthesis [10, 11, 12, 13, 14, 15]. Recently, metal-catalyzed oxidation of alkenes has aroused as an important tool in modern organic synthesis [16, 17, 18]. Metal organic frameworks (MOFs) have porous and heterogeneous nature and are applied for the efficient catalytic synthesis in various reactions like condensations reactions, coupling reactions, Friedel–Crafts reactions, oxidations and so on [19, 20, 21, 22]. Since this pioneering process was developed, the field has grown considerably and a range of metal-catalyzed oxidation reactions are routinely used in synthetic chemistry laboratories all over the world. In past years, scientists utilized various metals such as Pd, Mn, Mo, Se, Fe, etc. for the effective oxidation of alkenes [23, 24, 25, 26, 27, 28]. The aforementioned results showed that new protocols and mechanisms of these transformations have been developed in past decades. The present chapter systematically summarizes the metal catalyzed green oxidation of alkenes and shall provide new strategies for the functionalization and transformation of alkenes along with their advantages and disadvantages.

Advertisement

2. Metal catalyzed oxidation of alkene

2.1 Copper catalyzed

An easy and practical strategy has been developed for the synthesis of allylic esters by the allylic oxidation of cyclic alkenes with several carboxylic acids in the presence of tert-butyl hydroperoxide as an oxidant and copper−aluminum mixed oxide as a catalyst (Figure 1) [29].

Figure 1.

Allylic oxidation of alkenes catalyzed by copper−aluminum mixed oxide

A copper(I)-catalyzed oxidation of alkenes into α-oxygenated ketones was introduced using molecular oxygen and N-hydroxyphthalimide (NHPI) or N-hydroxybenzotriazole (HOBt) at room temperature (Figure 2). The oxidation proceeded via radical forming process and the molecular oxygen got incorporated into the product, ketone [30]. The reaction worked well for both enynes and styrenes.

Figure 2.

Copper catalyzed oxidation of alkenes

An effective strategy for esterification of unactivated C-H bonds (allylic and non-benzylic) of hydrocarbons using CuBr2 with different carboxylic acids was developed by Zhou et al. Selectfluor (electrophilic fluorinating agent) was used as an oxidant for the reaction. The products were obtained in 17–80% yields via cross dehydrogenative coupling (Figure 3) [31].

Figure 3.

Oxidation of cyclohexene using selectfluor

The allylic oxidation of cyclohexene was catalyzed by copper–bisoxazoline employing copper complexes Cu(MeCN)4PF6, (CuOTf)2·PhH, and Cu(OTf)2 in acetonitrile or acetone as the solvents to obtain benzoic esters. Tert-butyl peroxybenzoate was used as an oxidant. The products were obtained in high yields with enantiomeric excess (<68% ee) (Figure 4) [32].

Figure 4.

Allylic oxidation of cyclohexene using (CuOTf)2C6H6 palladium-catalyzed

A study has been performed for the effect of acid and base on the oxidation of alkenes using palladium catalyst and O2 as a sole oxidant in water as a solvent. The dihydroxylation occurred upon the oxidation in the presence of base while in the acidic medium, aldehydes and ketones were obtained by oxidative cleavage (Figure 5) [33].

Figure 5.

Palladium-catalyzed direct oxidation of alkenes with molecular oxygen

A bis(sulfoxide) palladium catalyst (White catalyst) was applied to promote an intramolecular oxidative allylic cyclization to form biologically relevant tetracyclic flavonoids in the presence of benzoquinone as an oxidant (Figure 6) [34]. The reaction mechanism involved C-H activation and C-O bond formation. Both electron withdrawing and electron donating substituents provided products in high yields.

Figure 6.

Synthesis of tetracyclic flavonoids by intramolecular oxidation allylic cyclization

Numerous catalytic systems have been developed for the selective formation of either linear or branched allylic oxidation products. The linear-selective allylic oxidation of alkenes was done via thioether ligand (Figure 7, method a). Furthermore, the scope of the reaction was similar to the method given firstly, by White. The reaction time was found slightly lesser in this method [35].

Figure 7.

Catalyst system for liner-selective allylic oxidation.

The simple and inexpensive method was used for the synthesis of tetrahydrothiophenes which was highly active and linear-selective ligand using palladium–sulfide as catalyst (Figure 7, method b) [36].

The palladium–sulfide catalytic system was developed to achieve aerobic turnover with 4,5- diazafluorenone ligand (Figure 7, method c). This system proved to be highly selective for linear allylic acetates with good yields and functional group tolerance [37].

Water, as a nucleophile was used in the allylic oxidation of alkenes to allylic alcohols using palladium chloride as a catalyst. Water and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) was used as a co-oxidant in the reaction (Figure 8) [38]. The obtained products were readily oxidized to (E)-alkenyl aldehydes in excellent yields using a second eq. of DDQ .

Figure 8.

Synthesis of alkenyl aldehydes by allylic oxidation with water.

The allylic oxidation of alkenes with polyfluorobenzenes as nucleophiles was performed. The dehydrogenative coupling was achieved in the presence of silver additives to give the corresponding linear functionalised products in good yields (Figure 9) [39].

Figure 9.

Allyic arylation with polyfluorobenzenes in the presence of silver additives.

The oxidation of unactivated alkenes resulted in a mixture of desired allylic arenes and Heck type products. A wide range of polyhalogenated nucleophiles was exemplified.

2.2 Iron catalyzed

Various iron catalysts were designed and employed for the oxidation of dienones using hydrogen peroxide as an oxidant and ethylhexanoic acid as an additive, necessary for controlling activation of the H2O2 at -30°C for 30 min. To optimize the reaction conditions, various solvents were examined like water, acetonitrile, THF, DMF, and toluene. Acetonitrile with 1–3 mol% of catalyst gave the best results for the reaction (Figure 10) [40].

Figure 10.

Oxidation of alkene using [Fe(OTf)2(Bz,TIPSPDP)].

A bifunctional iron nanocomposite catalyst was prepared and doped with N and P and employed for the direct oxidation of alkenes into ketones or 1,2-diketones viaformation of an epoxide intermediate in the presence of TBHP as an oxidant in aqueous condition at mild temperature (Figure 11) [41].

Figure 11.

Oxidation of alkenes by bifunctional iron nanocomposite catalyst.

2.3 Ruthenium catalyzed

A convenient and effective method was developed for the oxidation of alkenes into α-diketones using ruthenium complex as a catalyst and TBHP as an oxidant. This pathway has several advantages like no requirement of additional ligands, highly functional group tolerance, mild reaction conditions and short reaction time (Figure 12) [42].

Figure 12.

Ruthenium-catalyzed oxidation of alkenes at room temperature

2.4 Chromium-catalyzed

Mesoporous chromium terephthalate MIL- 101 was employed as a heterogeneous catalyst for the selective allylic oxidation of various alkenes in the presence of tert-butyl hydroperoxide as an oxidizing agent and provided α,β- unsaturated ketones. The catalyst MIL-101 was stable to chromium leaching and separated easily through the filtration and reused up to several cycles without any loss of catalytic activity [43].

The catalytic activities of Fe-MIL-101 and Cr-MIL-101 metal–organic frameworks were studied for the solvent-free oxidation of cyclohexene and α-pinene in the presence of molecular oxygen. Both catalysts were found effective for alkene oxidation at moderate temperature (40–60°C) and yielded allylic oxidation products. The Cr-MIL-101 afforded predominantly α,β-unsaturated ketones while Fe-MIL-101 produced mainly 2-cyclohexene-1-ol at 40°C after allylic oxidation of alkenes (Figure 13) [44].

Figure 13.

Oxidation of alkenes using Fe-MIL-101 and Cr-MIL-101

2.5 Nickel catalyzed

An efficient pathway was explored for the synthesis of cyclic sulfamides through the selective oxidation of alkenes catalyzed by NiCl2 or [Ni(acac)2] in the mixture of DMF and sodium acetate at 40°C in inert conditions (Figure 14) [45].

Figure 14.

Nickel catalyzed oxidation of alkenes

2.6 Selenium catalyzed

Selenium can be used as a dopant to increase the surface area and total mesoporous volume of polymeric carbon nitride through its sublimation during the process of calcination. Shi and coworkers synthesized Se-doped polymeric carbon nitride (Se/PCN) from the calcination of melamine with Se powder and used it as a catalyst for the oxidation of β ionones in the presence of visible light (Figure 15) [46]. In place of H2O2 reagent, the authors employed water as the oxidant precursor that could produce the H2O2 oxidant via PCN-catalyzed photolysis of water [47, 48]. Catalyzed by doped Se, β-ionone could be oxidized into epoxide in moderate yield. The use of visible light as sustainable energy to drive the reaction is the advantage of the method.

Figure 15.

Oxidation of β-lonone in the presence of Se/PCN

Recently, selenium based catalysts were applied for the oxidation reactions under relatively mild conditions. The authors employed H2O2 as the green oxidant and the transition metal-free conditions avoided the metal residues in the product. Different from the reported selenium catalyzed oxidation reactions using diaryl diselenide or aryl selenic acid catalyst, 5 mol% of dialkyl diselenide, such as (PhCH2Se)2, (n-C4H9Se)2, or (c-C6H11Se)2 was used as the pre-catalyst, converting the alkene substrates into the related carbonyls in 30–74% yields in EtOH at 80–120°C (Figure 16) [49].

Figure 16.

Oxidation of alkene in the presence (RSe)2 with H2O2

Selenization of dihalohydrocarbon with NaHSe (prepared via reduction of Se powder with NaBH4 in situ) afforded polyselenide in just one step and it was found to be an efficient catalyst for alkene oxidative cracking reactions under mild conditions (Figure 17) [50].

Figure 17.

Oxidation of alkenes using polyselenide as a highly efficient catalyst

The selenization of Fe2O3 afforded another convenient access to heterogeneous Se catalyst [51]. The developed method may be used at the industrial scale due to cheap and abundant nature of the support Fe2O3. The reaction mechanism involved attack of HSe anion on the iron positive centre of Fe = O and uploading of Se to produce Se/Fe2O3. It efficiently catalyzed the oxidative of alkenes in dimethyl carbonate (DMC) under mild reaction conditions (Figure 18). The synergistic effect of Se with Fe in the material, Se/Fe2O3 enhanced its catalytic activity [52].

Figure 18.

Oxidation of alkenes in the presence of Se/Fe2O3

The Se-catalyzed oxidation of methylenecyclopropanes (MCPs) generated oxidative ring expansion products, cyclobutanones instead of epoxides (Figure 19). This reaction may afford a direct access to cyclobutanone intermediates. The driving force for the conversion is the high ring strain of MCPs [53].

Figure 19.

Se-catalyzed oxidation of methylenecyclopropanes

Advertisement

3. Metal based nano-particle catalyzed oxidation of alkenes

An eco-benign pathway was developed for the oxidation of alkenes to ketones using water as an oxidant and catalyst combination of dearomatized acridine-based PNP-Ru complex and indium(III) triflate. The present protocol showed good functional group tolerance. The pathway was highly advantageous over Wacker-type oxidation as no chemical oxidant was used and only hydrogen gas was liberated as the byproduct (Figure 20) [54].

Figure 20.

Oxidation of alkenes by water

A variety of mesoporous nanocomposites comprising of zirconium oxide and Keggin 12-phosphomolybdic acid compounds (ZrO2–PMA) was synthesized through the application of evaporation-induced cooperative assembly method and were employed as an efficient catalyst for the oxidation of alkenes in the presence of hydrogen peroxide as an oxidant. ZrO2 impregnated with nearly 37 wt% PMA exhibited significant activity for the oxidation of alkenes (Figure 21) [55].

Figure 21.

Oxidation of alkenes by mesoporous zirconia-polyoxometalate nanocomposite materials

Cobalt ferrite magnetic nanoparticles (CoFe2O4 NPs) were used as effective catalysts for the selective oxidation of alkenes into related aldehydes or epoxides in the presence of t-BuOOH as an oxidant and 1, 2-dichloroethane as a solvent. The catalyst was easily separated from the reaction medium using a magnet, and reused up to five consecutive cycles without any loss of activity (Figure 22) [56].

Figure 22.

Magnetic cobalt ferrite NPs as an efficient catalyst for oxidation of alkenes

A green method was developed for the oxidation of alkenes using chiral dicationic bisguanidinium in the presence of potassium permanganate at 60°C for 12–36 h. (Figure 23) [57].

Figure 23.

Enantioselective oxidation of alkenes with potassium permanganate catalyzed by chiral Dicationic Bisguanidinium

An eco-friendly and highly efficient protocol was developed for the epoxidation of alkenes with m-chloroperbenzoic acid in the presence of Fe3O4/SiO2 as a heterogeneous catalyst in DCM as solvent at mild reaction conditions in 4 h at RT. In addition, the prepared heterogeneous catalyst has some advantages such as easy preparation, reusability, handling and recovery, long-term stability as well as excellent yields (90–97%) in shorter reaction time (Figure 24) [58].

Figure 24.

Oxidation of alkenes in the presence of Fe3O4/SiO2

Oxidation of styrene was done in the presence of mesoporous Mn3O4 nanoparticle (0.04 mmol) as catalyst and tert butyl hydroperoxide as mild oxidant with CH3CN at 70°C for 3 h. Novel, simple, and high yield (67–91%) of products are the advantages of Mn3O4-MNAs. The catalyst was recycled and reused up to five runs without a significant diminution in the catalytic efficiency (Figure 25) [59].

Figure 25.

Oxidation of styrene in the presence of Mn3O4-MNAs with TBHP

Advertisement

4. Applications

In this section, several cases were found that employed the copper-catalyzed allylic oxidation of olefins as an important step in the syntheses of synthetic products and pharmaceuticals. Some of the examples were exemplified by Nakamura and Nakada in their review on allylic oxidation reactions for the synthesis of natural products [60].

In 2009, Hayashi et al. produced the enantioselective synthesis of an O-protected 2-deoxystreptamine precursor, an amino-glycoside antibiotic, the same copper-catalyzed asymmetric desymmetrization procedure for the preparation of a chiral intermediate in the total synthesis of (−)-oseltamivir phosphate [61, 62].

The synthesis of steroids is one field where copper-catalyzed allylic oxidation has been more successful. The relatively inert steroid framework usually yielded the corresponding enone instead of an allylic alcohol. These types of phytosterol could have vivid applications in the field of medicine owing to their ability of modulating mitochondrial activity and their anti-inflammatory properties. Several examples of Kharasch–Sosnovsky reactions for the synthesis of steroids are available in the literature [63].

Barbacenic acid, a novel bisnorditerpene isolated from Barbacenia flava, was synthesized by a highly stereocontrolled route. The authors reported the allylic oxidation on the silyl ether intermediate using TBHP in the presence of CuBr in benzene at 45°C under mild reaction conditions in 60% yield [64]. Moreover, oxidized alkenes were used in the synthesis of fine chemicals [65], arene reduction [66], and water repellency [67].

Advertisement

5. Conclusion

This chapter summarizes the recent strategies of the oxidation of alkenes viametal-based catalytic system. Various innovations have been implemented from time to time to increase the efficiency and sustainability of the protocols. This literature study demonstrated the potential of metal-based catalysts and nano-particle metal based catalysts in the oxidation of alkenes to produce different chemical entities such as carbonyl, 1,2-diol and allylic compounds. However, some challenges like low commercial applicability, less efficiency, low chemoselectivity control, over-oxidation, lack of knowledge and deeper understanding of mechanistic pathways are still present in this field. In this context, the improvement in industrially viability, efficiency and sustainability of synthetic pathways require innovation in both capability and strategy. The knowledge gained for the oxidation of alkenes from these studies along with their pros and cons will continue to enable advances in this area, which in turn shall lead to the advancement of new approaches.

Advertisement

Acknowledgments

The authors are grateful to Department of Chemistry, MLSU, Udaipur (Raj.), India for providing necessary library facilities. A. Sethiya, N. Sahiba and P. Teli are thankful to UGC-MANF and CSIR for providing the financial support.

Advertisement

Conflict of interest

The authors declare no conflict of interest.

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution 3.0 License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

How to cite and reference

Link to this chapter Copy to clipboard

Cite this chapter Copy to clipboard

Jay Soni, Pankaj Teli, Nusrat Sahiba, Ayushi Sethiya and Shikha Agarwal (September 8th 2021). Metal Catalyzed Oxidation Reactions of Alkenes Using Eco-Friendly Oxidants, Alkenes - Recent Advances, New Perspectives and Applications, Reza Davarnejad, IntechOpen, DOI: 10.5772/intechopen.99267. Available from:

chapter statistics

74total chapter downloads

More statistics for editors and authors

Login to your personal dashboard for more detailed statistics on your publications.

Access personal reporting

Related Content

This Book

Next chapter

Construction of C-N Bond via Visible-Light-Mediated Difunctionalization of Alkenes

By Bhisma K. Patel, Tipu Alam and Amitava Rakshit

Related Book

First chapter

Gas Chromatography Application in Supercritical Fluid Extraction Process

By Reza Davarnejad and Mostafa Keshavarz Moraveji

We are IntechOpen, the world's leading publisher of Open Access books. Built by scientists, for scientists. Our readership spans scientists, professors, researchers, librarians, and students, as well as business professionals. We share our knowledge and peer-reveiwed research papers with libraries, scientific and engineering societies, and also work with corporate R&D departments and government entities.

More About Us