Oxorhenium-catalyzed deoxydehydration of glycols and epoxides

Article abstract of DOI:10.1016/j.tetlet.2014.05.044

The conversion of renewable cellulosic biomass into hydrocarbons has attracted significant attention with a growing demand of sustainability. MeReO₃ catalyzes the deoxydehydration (DODH) of glycols and epoxides to alkenes by primary and secondary alcohols (5-nonanol, 3-octanol, 1-butanol) in the benzene solvent. The product yield range from moderate to excellent.

Full text of DOI:10.1016/j.tetlet.2014.05.044

Tetrahedron Letters xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Oxorhenium-catalyzed deoxydehydration of glycols and epoxides
⇑
Jacqkis Davis, Radhey S. Srivastava
Department of Chemistry, University of Louisiana at Lafayette, LA 70504, United States
a r t i c l e i n f o
a b s t r a c t
Article history:
The conversion of renewable cellulosic biomass into hydrocarbons has attracted significant attention
with a growing demand of sustainability. MeReO3 catalyzes the deoxydehydration (DODH) of glycols
and epoxides to alkenes by primary and secondary alcohols (5-nonanol, 3-octanol, 1-butanol) in the ben-
zene solvent. The product yield range from moderate to excellent.
Received 15 April 2014
Revised 5 May 2014
Accepted 7 May 2014
Available online xxxx
Ó 2014 Elsevier Ltd. All rights reserved.
Keywords:
Deoxydehydration (DODH)
Oxorhenium (CH3ReO3)
Epoxides
Glycols
Secondary alcohols
Primary alcohol
Introduction
[POCOP = g
3-C6H3-1,3-(OP(tBu)2)2] was employed in the partial
hydrogenolysis of 1,2-propanediol to n-propanol under mild
The growth of effective procedures for the synthesis of reduced
oxygen-content products from cellulosic biomass is an important
step toward the practical utilization of renewable resources to pro-
duce fuels and valuable chemicals.1,2 Discerning homogeneous
(CpÃRu(CC)LH) and heterogeneous (Ru-C) catalyzed monodehydr-
oxylation of glycols has been realized via hydrogenolysis.3,4 The
use of hypervalent oxorhenium complexes for deoxydehydration
conditions in acidic aqueous dioxane.14
We recently reported the [CpÃRu(CO)2]2-catalyzed hydrodeoxy-
genation and hydrocracking and RuCl2(R2SO)4-catalyzed hydrog-
enolysis of diols and epoxides15 (Scheme 1).
In the quest to develop new and cheaper DODH processes, at
least in part, for the conversion of renewable cellulosic biomass
into valuable chemicals we revisited the chemistry of MeReO3
and developed a modified process which requires a small amount
of a primary or secondary alcohol as a reductant compared to
earlier reports.8,11
6
(DODH) employing various reductants such as PPh3,5 H2 and
7
Na2SO3 are well known. The Bergman group established a hydro-
gen-transfer-type DODH reaction catalyzed by [Re2(CO)10] and
[BrRe(CO)5] in conjunction with a secondary alcohol as solvent
and reductant.8 Fernandes et al. have demonstrated oxorhenium-
catalyzed DODH of styrene oxides in the absence of reductant.9
A recent report from the Sen group10 demonstrated the practi-
cability of a one-step rhodium-catalyzed process for the produc-
tion of THF derivatives for liquid fuels from carbohydrates and
cellulosic biomass. Oxorhenium-catalyzed deoxygenation of sug-
ars and sugar alcohols has been reported lately by Toste.11 This
group reported that glycerol, a by-product of biodiesel (fatty
acid esters) was transformed to allyl alcohol in 90% yield.11
Likewise, a C4 alcohol sugar such as erythritol (obtained by
the fermentation of glucose12 or by the decarbonylation of
pentoses)13 was converted into 1,3-butadiene, an industrially
important rubber precursor. The pincer complex, IrH2(POCOP)
Results and discussion
During our experiments, 1-phenyl-1,2-ethanediol (styrenediol),
a prototypical substrate was examined for reactivity with small
amounts of a secondary alcohol such as 5-nonanol, 3-octanol,
and 1-butanol (6.8 Â 10À4 mol) in the presence of MeReO3 (MTO)
R
H2
R
HO
R
OH
[Cp*Ru(CO)2]2
and
[RuCl2(R2SO)4]
+
RCH3
O
(R= methyl, tetramethylene)
Scheme 1. [CpÃRu(CO)2]2-catalyzed hydrodeoxygenation and hydrocracking and
RuCl2(R2SO)4-catalyzed hydrogenolysis of diols and epoxides (R = methyl and
tetramethylene).
⇑
Corresponding author. Tel.: +1 337 482 5677; fax: +1 337 482 5676.
E-mail address: rss1805@louisiana.edu (R.S. Srivastava).
http://dx.doi.org/10.1016/j.tetlet.2014.05.044
0040-4039/Ó 2014 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Davis, J.; Srivastava, R. S. Tetrahedron Lett. (2014), http://dx.doi.org/10.1016/j.tetlet.2014.05.044

2
J. Davis, R. S. Srivastava / Tetrahedron Letters xxx (2014) xxx–xxx
Ph
R'
MeReO3
Ph
R
H
5-Nonanol
HO
OH
CH3
Re
anh. Benzene
OH
R
O
O
R
R'
Scheme 2. Re-catalyzed deoxydehydration of styrenediol to styrene.
O
H2O
+
1
O
CH3
Re
O
1 and benzene solvent. (Scheme 2) The reaction between the glycol
and 5-nonanol was first conducted in benzene with 10 mol % MTO
in a thick-walled sealed glass tube at 90 °C, resulting in the quan-
titative conversion of styrene diol into styrene (97%) (Table 1, entry
1). To understand the mechanism of ruthenium-catalyzed deoxy-
dehydration, we examined the catalyst activity as a function of
dependence on the solvent, temperature, and reductant. Thus in
the presence of toluene and THF, 34% (in toluene) and trace
amount (in THF) of styrene was detected. On the examination of
the reaction rate at 110 and 200 °C, styrene was obtained in 80%
and 56%, respectively (Table 1, entries 2 and 3). Likewise, in the
presence of the reductant 3-octanol styrene was produced in 35%
and 1-butanol produced 22% styrene. We also examined the reac-
tivity of another rhenium catalyst, [Re(CO)10], which only gave
trace amounts of styrene and phenyl ethyl alcohol.
Glycols which may be better models for biomass-derived prod-
ucts were also examined in the Re-catalyzed DODH reaction in
order to determine the products’ selectivity and efficiency (Table 1).
When subjected to the reaction conditions (140 °C, 0.687 mmol 5-
nonanol and 10 mol % 1), 1,2-hexanediol produced hexene in 10%
yield in 48 h (Table 1, entry 4) as the only detected product by
GC–MS. No products were detected at lower temperatures. The
CH3
Re
2
O
O
O
O
R
4
CH3
Re O
O
O
3
Ph
Scheme 3. Plausible mechanistic pathway of Re-catalyzed deoxydehydration of
glycols.
long chain 1,2-tetradecanediol was even less reactive, with no
hydrocarbons being detected at a low temperature. However,
when this reaction was conducted at 150 °C, tetradecene (50%)
and two other isomeric alkenes of same molar mass (5% and 8%)
were produced after 95 h (Table 1, entry 5). In contrast, the cyclic
glycol, cis-1,2-cyclohexanediol was converted into cyclohexene
(15%), with no detectable alkane or cracking products (Table 1,
entry 6). When 1,4-anhydroerythritol (a biomass-derived glycol)
was treated under same reaction conditions, it afforded 3-tetrahy-
drofuranol in low yield (10%) (Table 1, entry 7).
Table 1
Re-catalyzed deoxydehydration of glycols and epoxidesa
entry
1
substrate
major product(s)
time (h)
24
yield (%)
97
temp(°C)
90
Ph
OH
OH
2
110
24
80
3
4
200
140
24
48
56
10
OH
OH
C12H25
50b
15
OH
150
140
95
67
5
6
C12H25
OH
OH
OH
OH
HO
HO
7
140
90
45
24
10
99
O
O
O
O
8
O
150
150
24
45
54
17
9
10
a
0.36 mmol glycol in benzene (2 mL), 0.036 mmol MeReO3, 5-nonanol (0.68 mmol) 90 °C;
yields determined by GC–MS with n-dodecane as internal standard.
b
Other possible isomeric alkenes observed in low yields.
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J. Davis, R. S. Srivastava / Tetrahedron Letters xxx (2014) xxx–xxx
3
The DODH of epoxides catalyzed by 1 was also examined. Thus,
Supplementary data
styrene oxide was converted quantitatively into styrene (99%)
(Table 1, entry 8), the same product (styrene) was formed from
the corresponding glycol. Similarly, cyclohexene oxide afforded
cyclohexene in 54% yield after 24 h at a high temperature (Table 1,
entry 9), again with no alkane detected. 1,2-Hexene oxide (like the
corresponding glycol) was converted into 2-hexene in 17% yield
(Table 1, entry 10).
The catalytic pathways for the DODH reactions promoted by 1
are unclear at present. The similar product profiles in both the gly-
col and epoxide deoxydehydration suggest the involvement of
common intermediates. Based on our observation and literature
reports6,11 we believe that the mechanism for glycols would be
similar to the one proposed by Toste et al.11 We have shown the
mechanism for the epoxides in Scheme 3. MeReO3 (1) reacts with
alcohol to generate Re(V)-dioxide (2) to which epoxide would
coordinate and form Re(V)-glycolate (4) followed by generation
of alkene and MeReO3(1). The validity of Re(VII)-glycolate is sup-
ported by the known reversible condensation of 1 with glycol.6,16,17
Formation of truncated alkenes in the present system can also be
Supplementary data (experimental procedure and spectral data
for compounds) associated with this article can be found, in the
online version, at http://dx.doi.org/10.1016/j.tetlet.2014.05.044.
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explained by the intermediacy of
a metallogycolate species
(Scheme 2).15
In conclusion, we report here a modified system for glycol and
epoxide conversion into alkenes using primary and secondary alco-
hols (1-butanol, 5-nonanol, and 3-octanol) as reductant and
MeReO3 as a pre-catalyst. Future investigations will focus on eluci-
dating the important catalytic species and mechanisms of these
reactions and their application to biomass-derived polyols.
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Financial support from the Louisiana Board of Regents (RSS) is
greatly appreciated.
Please cite this article in press as: Davis, J.; Srivastava, R. S. Tetrahedron Lett. (2014), http://dx.doi.org/10.1016/j.tetlet.2014.05.044