**5. Synthesis of 3,4-epoxy-1-butene in liquid phase**

Two competitive methods for direct epoxidation of olefins are gas-phase oxidation with oxygen over silver catalyst and liquid-phase reactions with organic hydroperoxides or hydrogen peroxide in the presence of soluble or supported W, Mo, Ti complexes. The gas-phase epoxidation is typical for obtaining light epoxides, whereas epoxidation with peroxide compounds in liquid is applicable for a wide range of substrates containing double bonds. Both type reactions are based on interaction of olefin with electrophilic oxygen species. Under liquid-phase epoxidation, catalytically active metal complexes react with peroxides to attach the reactive oxygen as ligand which attack the double bond of olefin. Hydrogen peroxide is effective oxygen donor and has an advantage of low-temperature reaction giving environmentally benign water as a by-product [61, 62].

diluted aqueous H2

**Catalyst1 H2**

O)2 ]

OH solvent, room temperature.

CN solvent, room temperature.

TBA4[γ-SiW10O34(H2

(3 μmol)3

Catalyst, H2

O2

CN solvent, 60 °C.

CN solvent, 50 °C.

**Table 5.** Epoxidation of BD with H2

1

2 CH3

3 CH3

4 CH3

5 CH3

**O2 1 (mmol)** **BD (bar)**

As a result, the efficiency of H2

dation of olefins [67].

O2

O2

in solvents.

tungstates exhibit equally effective catalysis.

cursor of tungsten-depleted anions [PW4

demanded and valuable chemicals.

in acetonitrile solution. Epoxidation of BD has been shown to pro-

consumption for producing 3,4-epoxy-1-butene is extremely

O2

O2

], which operate as the most effective

[WO(O2 )2 ]4

O2

is minimal or

, thus increasing

consumption.

}3− in epoxi-

ceed with high selectivity for 3,4-epoxy-1-butene. Appearance of small admixtures of furan, 3-butene-1,2-diol, and 2-butene-1,4-oxygenates is associated with isomerization and hydro-

**Time (h) Epoxide (mmol)**

0.3 2.5 9 0.30 99 99 [64]

Reactivity of a Simplest Conjugated Diolefin in Liquid-Phase Oxidation: Mechanisms and Products

TS-1(6 mg)2 0.5 1.5 1 0.25 n.d. 52 [63]

TBA-PW11(10 μmol)4 0.9 1 5.5 0.51 88 88 [65] EMIm-PW11(10 μmol)4 0.9 1 5 0.65 91 90 [65] EMIm-PW11(2.3 μmol)5 1.0 1 5 0.20 97 100 [65]

and epoxide produced were normalized to 2 mL of the reaction mixture.

**Sel.BD (%) H2**

**O2**

**(%)**

 **efficiency** 

http://dx.doi.org/10.5772/intechopen.71259

**Reference**

111

absent when the reaction is carried out at a low temperature and at a low concentration of hydrogen peroxide. This is favorable for maintaining high selectivity for 3,4-epoxy-1-butene, because the secondary oxidation of 3,4-epoxy-1-butene by radical intermediates is prevented. As a result, only negligible amount of acrolein appears in the product. Moreover, small addi-

high, it approaches to 100% under favorable conditions. Both Si- and P-centered heteropoly-

Under reaction conditions, the catalytically active anions are generated from starting lacunary polyoxotungstate anion. It has been shown by NMR that [HPW11O39]6− anion is a pre-

] and [PW2

activators of hydrogen peroxide and are responsible for epoxidation (**Scheme 9**) [65]. This is

Despite the limited use of 3,4-epoxy-1-butene itself, it is nevertheless a raw material for the synthesis of various C4-oxygenates such as 1,4-butanediol [68], 3-butene-1,2-diol and 2-butene-1,4-diol [69–71], and 2,5-dihydrofuran [72]. Therefore, low-temperature and selective epoxidation of BD can be considered as a principal stage of alternative synthesis of

lysis of 3,4-epoxy-1-butene. The unproductive radical decomposition of H2

tives of EMImBr have been found to inhibit radical decomposition of H2

confirmed by the high reactivity of a specially synthesized anion {PO4

O2

the selectivity of BD to 3,4-epoxy-1-butene conversion and efficiency of H2

The liquid-phase epoxidation of BD with H2 O2 is known to occur over titanium silicates in CH3 OH [63] and in CH3 CN solution of heteropoly compounds [64, 65]. The data for these reactions are given in **Table 5**.

Both catalysts are activators of hydrogen peroxide, capable of forming peroxide complexes. Thoroughly investigated for various olefins, the mechanism of epoxidation is realized for the conversion of BD to 3,4-epoxy-1-butene. Coordinated on metal ion, the electrophilic oxygen interacts with one of the equivalent double bonds of BD leaving intact the second C═C bond. Oxygen transfer from peroxide ligand to double bond of olefin has been proved using isotopic reagents [64]. The addition of oxygen to the second bond of BD is more difficult; therefore, the formation of a diepoxide is not detected in reactions with hydrogen peroxide.

Lacunary polyoxotungstates are effective catalysts for epoxidation of olefins with H2 O2 [66]. Besides olefins, [HPW11O39]6−and [γ-SiW10O34(H2 O)2 ]4− anions catalyze epoxidation of BD with

Reactivity of a Simplest Conjugated Diolefin in Liquid-Phase Oxidation: Mechanisms and Products http://dx.doi.org/10.5772/intechopen.71259 111


1 Catalyst, H2 O2 and epoxide produced were normalized to 2 mL of the reaction mixture.

2 CH3 OH solvent, room temperature.

3 CH3 CN solvent, room temperature.

4 CH3 CN solvent, 60 °C.

**5. Synthesis of 3,4-epoxy-1-butene in liquid phase**

**Catalyst, conditions Products (mmol)**

The liquid-phase epoxidation of BD with H2

Besides olefins, [HPW11O39]6−and [γ-SiW10O34(H2

OH [63] and in CH3

reactions are given in **Table 5**.

CH3

5%Pd0.5%Te/C, H2

110 Alkenes

5%Pd2.7Te/C, H2

5%Pd2.7Te/C, H2

SO4

SO4

SO4

**Table 4.** Products of BD oxidation in solvent CH3

Two competitive methods for direct epoxidation of olefins are gas-phase oxidation with oxygen over silver catalyst and liquid-phase reactions with organic hydroperoxides or hydrogen peroxide in the presence of soluble or supported W, Mo, Ti complexes. The gas-phase epoxidation is typical for obtaining light epoxides, whereas epoxidation with peroxide compounds in liquid is applicable for a wide range of substrates containing double bonds. Both type reactions are based on interaction of olefin with electrophilic oxygen species. Under liquid-phase epoxidation, catalytically active metal complexes react with peroxides to attach the reactive oxygen as ligand which attack the double bond of olefin. Hydrogen peroxide is effective oxygen donor and has an advantage of low-temperature reaction giving environmentally benign water as a by-product [61, 62].

5%Pd0.5%Te/C, 10 mmol BD, 100°C, 3 h 0.54 1.16 0.35 1.58 0.17 1.48 0 0.73

OH (10% H2

, 10 mmol BD, 100°C, 3 h 0.45 2.02 0.08 0.12 1.42 2.30 0 1.81

, 10 mmol BD, 120°C, 2 h 0.24 0.06 0 0.06 0.66 2.80 2.0 0

, 40 mmol BD, 120°C, 2 h 0.23 0.06 0 0.07 0.78 6.70 3.90 0

O) (30 mL), H2

SO4

O2

Both catalysts are activators of hydrogen peroxide, capable of forming peroxide complexes. Thoroughly investigated for various olefins, the mechanism of epoxidation is realized for the conversion of BD to 3,4-epoxy-1-butene. Coordinated on metal ion, the electrophilic oxygen interacts with one of the equivalent double bonds of BD leaving intact the second C═C bond. Oxygen transfer from peroxide ligand to double bond of olefin has been proved using isotopic reagents [64]. The addition of oxygen to the second bond of BD is more difficult; therefore,

the formation of a diepoxide is not detected in reactions with hydrogen peroxide.

Lacunary polyoxotungstates are effective catalysts for epoxidation of olefins with H2

O)2

is known to occur over titanium silicates in

(0.1 mmol where indicated).

**1 2 3 4 5 6 7 8**

]4− anions catalyze epoxidation of BD with

O2 [66].

CN solution of heteropoly compounds [64, 65]. The data for these

5 CH3 CN solvent, 50 °C.

**Table 5.** Epoxidation of BD with H2 O2 in solvents.

diluted aqueous H2 O2 in acetonitrile solution. Epoxidation of BD has been shown to proceed with high selectivity for 3,4-epoxy-1-butene. Appearance of small admixtures of furan, 3-butene-1,2-diol, and 2-butene-1,4-oxygenates is associated with isomerization and hydrolysis of 3,4-epoxy-1-butene. The unproductive radical decomposition of H2 O2 is minimal or absent when the reaction is carried out at a low temperature and at a low concentration of hydrogen peroxide. This is favorable for maintaining high selectivity for 3,4-epoxy-1-butene, because the secondary oxidation of 3,4-epoxy-1-butene by radical intermediates is prevented. As a result, only negligible amount of acrolein appears in the product. Moreover, small additives of EMImBr have been found to inhibit radical decomposition of H2 O2 , thus increasing the selectivity of BD to 3,4-epoxy-1-butene conversion and efficiency of H2 O2 consumption. As a result, the efficiency of H2 O2 consumption for producing 3,4-epoxy-1-butene is extremely high, it approaches to 100% under favorable conditions. Both Si- and P-centered heteropolytungstates exhibit equally effective catalysis.

Under reaction conditions, the catalytically active anions are generated from starting lacunary polyoxotungstate anion. It has been shown by NMR that [HPW11O39]6− anion is a precursor of tungsten-depleted anions [PW4 ] and [PW2 ], which operate as the most effective activators of hydrogen peroxide and are responsible for epoxidation (**Scheme 9**) [65]. This is confirmed by the high reactivity of a specially synthesized anion {PO4 [WO(O2 )2 ]4 }3− in epoxidation of olefins [67].

Despite the limited use of 3,4-epoxy-1-butene itself, it is nevertheless a raw material for the synthesis of various C4-oxygenates such as 1,4-butanediol [68], 3-butene-1,2-diol and 2-butene-1,4-diol [69–71], and 2,5-dihydrofuran [72]. Therefore, low-temperature and selective epoxidation of BD can be considered as a principal stage of alternative synthesis of demanded and valuable chemicals.

**Acknowledgements**

**Author details**

**References**

Boreskov Institute of Catalysis.

\*Address all correspondence to: kuznina@catalysis.ru

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Reactivity of a Simplest Conjugated Diolefin in Liquid-Phase Oxidation: Mechanisms and Products

http://dx.doi.org/10.5772/intechopen.71259

113

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**Scheme 9.** Transformations of heteropolytungstates in oxidation of BD to 3,4-epoxy-1-butene (EpB) [65].
