Rhenium-catalyzed deoxydehydration of glycols by sulfite

Article abstract of DOI:10.1021/ic100467p

Methyltrioxorhenium and sodium perrhenate catalyze the deoxydehydration of glycols and deoxygenation of epoxides to olefins in moderate yields with sulfite as the reductant.

Full text of DOI:10.1021/ic100467p

4744 Inorg. Chem. 2010, 49, 4744–4746
DOI: 10.1021/ic100467p
Rhenium-Catalyzed Deoxydehydration of Glycols by Sulfite
Saidi Vkuturi, Garry Chapman, Irshad Ahmad, and Kenneth M. Nicholas*
Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019
Received March 12, 2010
Methyltrioxorhenium and sodium perrhenate catalyze the deox-
ydehydration of glycols and deoxygenation of epoxides to olefins in
moderate yields with sulfite as the reductant.
epoxides and DODH of glycols to alkenes and alkanes with
the more practical reductant H2 is catalyzed by MeReO3.8
The drive to develop new and efficient processes for the
conversion of abundant renewable resources to chemicals
and fuels has spurred new interest in the discovery of selective
chemical transformations of biomass-derived carbohydrates
and polyols. To access many chemicals and most potential
fuels from these resources, partial or complete hydroxyl
group removal via dehydration and/or reduction (deoxy-
genation) is needed.1 Selective monodehydroxylation of
glycols has recently been achieved by hydrogenolysis, cata-
lyzed heterogeneously by Ru-C2 and homogeneously by
Cp*Ru(CO)LH.3 Reactions that effect bothofthese changes,
i.e., deoxydehydration (DODH, eq 1), are attractive for
generating synthetically versatile unsaturated products. Fol-
lowing early studies of stepwise DODH reactions by various
reagents,4 Bergman and co-workers recently reported the
efficient high temperature conversion of polyols to olefins by
formic acid.5 The potential of catalyzing DODH reactions by
oxo-metal complexes was first demonstratedby Andrews and
Cook6 using PPh3 as the reductant with Cp*ReO3 as the
catalyst. Subsequent reports by Gable have shed light on the
catalytic pathway of these reactions and have provided more
robust rhenium-tris(pyrazolyl)borate catalysts.7 Most re-
cently, Abu-Omar et al. reported that the deoxygenation of
We have initiated a project seeking the development of new
DODH systems that would employ inexpensive reductants
and catalysts and the elucidation of their mechanistic path-
ways. We considered sulfite and bisulfite salts to be attractive
reductants for polyol DODH reactions because of their
strong reducing potentials,9 low cost, convenience of use,
low toxicity, and recyclability of the byproduct sulfate.10
Although O-atom transfer reduction of oxo-metal complexes
by sulfite/bisulfite is illustrated by the molybdoenzyme sulfite
oxidase11 and model LMoVIO2 complexes,12 such reactions
are rare among other oxo-metal complexes.13 We disclose
here the first examples of catalytic glycol DODH driven by
sulfite.
During exploratory experiments, 1-phenyl-1,2-ethanediol
(styrenediol) and 1,2-octanediol were tested for reactivity
with NaHSO3 and Na2SO3 in the presence of selected Mo-
and Re-oxo complexes, e.g., (dedtc)2MoO2, Cp*ReO3, and
MeReO3 (150-200 °C, organic solvents and biphasic with
H2O).14 From these experiments, Na2SO3 as a reductant and
(8) Ziegler, J. E.; Zdilla, M. J.; Evans, A. J.; Abu-Omar, M. M. Inorg.
Chem. 2009, 48, 9998.
(9) ΔG0 values for the oxo-transfer couple, X þ O f XO, for SO32- are
-70 to -60 kcal/mol and for HSO3- are -60 to -50 kcal/mol, comparable
to H2. (a) Holm, R. H.; Donahue, J. P. Polyhedron 1993, 12, 571. (b) Lee, S. C;
Holm, R. H. Inorg. Chim. Acta 2008, 361, 1166–1176. (c) Holm, R. H. Chem.
Rev. 1987, 87, 1401–1449.
*To whom correspondence should be addressed. E-mail: knicholas@
ou.edu.
(1) Chheda, J. N.; Huber, G. W.; Dumesic, J. A. Angew. Chem., Int. Ed.
2007, 46, 7164.
(10) (a) Stams, A. J. M.; Lens, P.N. L.; Buisman, C. J. N.; Janssen, A. J.
H.; Muyzer, G. Microbes Environ. 2008, 97. (b) Kaksonen, A. H.; Puhakka, J.
A. Eng. Life Sci. 2007, 7, 541. (c) van Houten, R. T.; Lettinga, G. Prog.
Biotechnol. 1996, 11, 793. (d) Bulk Na2SO3 costs ca. $ 0.92/kg. http://www.
risiinfo.com/technologyarchives/Solvay (accessed Apr 2010).
(11) Feng, C.; Tollin, G.; Enemark, J. H. Biochim. Biophys. Acta 2007,
1774, 527.
(12) (a) Nagarajan, K.; Chaudhury, P. K.; Srinivasan, B. R.; Sarkar, S.
Chem. Commun. 2001, 1786. (b) Das, S. K.; Chaudhury, P. K.; Biswas, D.;
Sarkar, S. J. Am. Chem. Soc. 1994, 116, 9061.
(13) (a) Ernst, T.; Cyfert, M.; Wilgocki, M. Int. J. Chem. Kinet. 1992, 24,
903. (b) Sen Gupta, K. K.; Das, S.; Sen Gupta, S. J. Chem. Res., Synop. 1989, 4,
112.
(14) Modest yields (10-30%) of styrene were also produced in some
reactions of styrene diol with NaHSO3 or Na2SO3 promoted by Cp*ReO3,
MeReO3, or (dedtc)2MoO2 at 150-200 °C.
(2) Deng, W.; Tan, X.; Fang, W.; Zhang, Q.; Wang, Y. Catal. Lett. 2009,
133, 167.
(3) Schlaf, M.; Ghosh, P.; Fagan, P. J.; Hauptman, E.; Bullock, R. M.
Adv. Synth. Catal. 2009, 351, 789.
(4) Block, E. Organic Reactions; W. G. Dauben, Ed.; John Wiley and Sons:
New York, 1984; Chapter 2, Vol. 30, pp 458. Ando, M.; Ohhara, H.; Takase, K.
Chem. Lett. 1986, 879.
(5) Arceo, E.; Marsden, P.; Bergman, R. G.; Ellman, J. A. Chem.
Commun. 2009, 3357.
(6) Cook, G. K.; Andrews, M. A. J. Am. Chem. Soc. 1996, 118, 9448.
(7) (a) Gable, K. P.; Phan, T. N. J. Am. Chem. Soc. 1994, 116, 833.
(b) Gable, K. P. Organometallics 1994, 13, 2486. (c) Gable, K. P.; Juliette, J. J.
J. Am. Chem. Soc. 1996, 118, 2625. (d) Gable, K. P.; Zhuravlev, F. A. J. Am.
Chem. Soc. 2002, 124, 3970. (e) Gable, K. P.; AbuBaker, A.; Zientara, K.;
Wainwright, A. M. Organometallics 1999, 18, 173. (f) Gable, K. P.; Ross, B.
ACS Symp. Ser. 2006, 921 (Feedstocks for the Future), 143.
r
pubs.acs.org/IC
Published on Web 05/04/2010
2010 American Chemical Society

Communication
Inorganic Chemistry, Vol. 49, No. 11, 2010 4745
a
Table 1. Glycol and Epoxide Deoxydehydration by Na2SO3/MeReO3 or NaReO4
a Reactions conducted at 150 °C (oil bath) with 0.2 M glycol or epoxide in the indicated solvent, 1.0-1.5 equiv of Na2SO3, and the indicated mol %
catalyst. determined by gas chromatography with naphthalene as internal standard with glycol as the limiting reagent b Determined by gas
chromatography with naphthalene as the internal standard with glycol as the limiting reagent.
MeReO3 as a catalyst appeared most promising and were
selected for more thorough study in nonaqueous solvents.
Heating a stirred mixture of styrene diol (0.15 mmol),
Na2SO3 (1.0-1.5 equiv), and MeReO3 (10 mol %) in 5 mL
of benzene at 150 °C (sealed tube) resulted in a series of rapid
color changes to produce a red brown reaction mixture; GC
and GC-MS analysis indicated consumption of the glycol
with theformation of styrene in 44% yield and smallamounts
of dimeric ethers derived from dehydration,15 possibly pro-
moted by the Lewis acidic MeReO3 (entry 1, Table 1).16
Increasing the glycol concentration to 0.2 M shortened the
reaction time considerably and improved the yield as well
(entry 2, Table 1). Since Na2SO3 has poor solubility in
nonpolar organic solvents, more polar ones, e.g., THF,
CH3CN, and H2O, were tested in an effort to increase the
reaction rate. In the first two solvents, the conversion of
styrenediol to styrene proceeded more slowly, perhaps a
result of retarding solvent coordination to MeReO3 (entries
3 and 4, Table 1). No appreciable conversion was observed in
water. The inclusion of 10 mol % OPPh3, a potential phase
transfer catalyst,17 had minimal effect on the conversion rate
(entry 5, Table 1).
Aliphatic diols, such as 1,2-octanediol, better models for
carbohydrate-derived polyols, proved less reactive, requiring
longer reaction times under comparable conditions in ben-
zene (7 days, entry 6, Table 1) or chlorobenzene (40 h, entry 7,
Table 1) to produce moderate yields of 1-octene (no isomers
detected by GC/MS), accompanied by small amounts of
volatile byproducts (e.g., 2-octanone and dimeric ethers).
Seeking to enhance the sulfite solubility and conversion rate,
inclusion of 10 mol % of the Naþ-complexing agent
15-crown-518 was found to significantly shorten the reaction
time (entry 8, Table 1). An initial substrate survey suggests
that glycol to olefin DODH by Na2SO3/MeReO3 will have a
broad scope; e.g., cis-1,2-cyclohexanediol was converted to
cyclohexene in moderate yield (entry 13, Table 1).19
(15) (a) Gravimetric and NMR/GC-MS analysis of the benzene-soluble
material from the styrene diol reaction showed ca. 20-30% by mass of a
complex mixture of Ph-containing products, including dimeric ethers
(ref 15b); the non-volatile, MeOH-soluble fraction (ca. 10% by mass)
appears to be largely PhCHOHCH2(OSO2-) by NMR. (b) Zhu, Z.;
Espenson, J. H. J. Org. Chem. 1996, 61, 324–8.
(16) (a) Nabavizadeh, S. M.; Rashidi, M. J. Am. Chem. Soc. 2006, 128,
351. (b) Koestlmeier, S.; Nasluzov, V. A.; Herrmann, W. A.; Roesch, N.
Organometallics 1997, 16, 1786.
(17) Kondo, S.; Furukawa, K.; Tsuda, K. J. Polym. Sci., Part A 1992, 30,
1503.
(18) (a) Kudo, Y.; Fujihara, R.; Ohtake, T.; Katsuta, S.; Takeda, Y. Anal.
Sci. 2008, 24, 999. (b) Rounaghi, G. H.; Masroornia, M.; Ghaemi, A.;
Rahchamani, H. A. Asian J. Chem. 2007, 19, 1679.
(19) Other glycols producing olefins as major products (unoptimized)
include pinacol (2,3-dimethylbutane-2,3-diol) and diethyl tartrate.

4746 Inorganic Chemistry, Vol. 49, No. 11, 2010
Vkuturi et al.
Although not yet optimized, practically attractive solvent-
less reactions are also viable. Thus, heating a stirred mixture
of 1,2-octanediol (1.2 mmol), Na2SO3 (1.5 mmol), and
MeReO3 (0.02 mmol) at 150 °C for 20 h in a sealed tube
produced a 60% yield of 1-octene at 75% diol conversion
(entry 9, Table 1).
Finally, the more economical NaReO4, previously un-
tested for DODH activity, was also found to catalyze
sulfite-driven DODH. Heating 1,2-octanediol, Na2SO3, and
10 mol % NaReO4 together at 150 °C slowly produced
1-octene with minimal formation of a GC-detectable bypro-
duct; entry 10, Table 1). With this sparingly soluble catalyst
and reductant, significant improvements in the conversion
rate were achieved by the addition of 10 mol % 15-crown-5
(entry 11, Table 1) and Na2SO4 as a dehydrating agent (entry
12, Table 1).
Epoxides are also deoxygenated by the sulfite/MeReO3
system. Styrene oxide and cyclohexene oxide were converted
to the corresponding olefins with Na2SO3 (1.2 equiv)/MeR-
eO3 (8 mol %) in moderate yield (entries 14 and 15, Table 1)
under typical conditions. It is noteworthy that significant
quantities of styrene oxide were detected in early stages of the
reactions of styrene diol, possibly indicating its intermediacy in
DODH. However, the reduction of styrene oxide by Na2SO3/
MeReO3 under the same conditions as for the glycol reaction
(entries 14 and 2, Table 1) actually proceeded considerably
slower, 30 h versus 4 h, suggesting that the epoxide is not a
primary intermediate in the diol DODH reaction.
Although the mechanistic details of the catalytic cycle are
under investigation, existing precedents and our initial ob-
servations suggest that two pathways (A and B) are viable, as
outlined in Figure 1. In path A, MeReO3 condenses with the
glycol to generate ReVII-glycolate 2; then, 2 is reduced by sul-
fite to ReV-glycolate 3. In path B, 1 is first reduced by
sulfite; then the resulting MeReO2 (4) condenses with the
glycol to form glycolate 3. Finally, fragmentation of 3
produces the olefin with regeneration of MeReO3. The
viability of path A is supported by the known reversible
condensation of 1 with glycols,20 which in the case of 1 þ
styrene diol (1:1, benzene, rt) produced a 3:1 mixture of 1:2
(R = Ph). Heating the 1/2 mixture or 2 alone (generated from
1 þ styrene oxide)21 with Na2SO3 (150 °C, 2-3 h) produced
styrene (ca. 50%) and regenerated 1. The viability of path B is
supported by known O-transfer reductions of 122 and our
finding that heating 1 with Na2SO3 (benzene, 150 °C, 2 h)
Figure 1. Possible catalytic cycle for sulfite-driven deoxydehydration of
glycols.
produces a dark precipitate (presumably a reduced Re
species), which, upon the addition of styrene diol to the
mixture and continued heating (150 °C, 2 h), also yielded
styrene (ca. 60%) and 1.
In conclusion, we have reported here a new method for
glycol and epoxide reduction to olefins employing commer-
cial rhenium catalysts and Na2SO3 as a reductant that
achieves moderate to good efficiency. Studies of the catalytic
mechanism and the application of DODH to carbohydrate
substrates will be reported in due course.
Acknowledgment. We are grateful for financial support
for this project from the Oklahoma Biofuels Center (OBC).
Note Added after ASAP Publication. This paper was
published on the Web on May 4, 2010, with incorrect
values given in reference 9. The corrected version was
reposted on May 7, 2010.
Supporting Information Available: Experimental procedures,
NMR spectra of reaction mixtures, and representative gas
chromatograms. This material is available free of charge via
the Internet at http://pubs.acs.org.
(22) (a) Espenson, J. H.; Yiu, D. T. Y. Inorg. Chem. 2000, 39, 4113.
(b) Abu-Omar, M. M.; Appelman, E. H.; Espenson, J. H. Inorg. Chem. 1996, 35,
7751. (c) Zhu, Z.; Espenson, J. H. J. Mol. Catal. A 1995, 103, 87–94.
(d) Felixberger, J. K.; Kuchler, J. G.; Herdtweck, E.; Paciello, R. A.; Herrmann,
W. A. Angew. Chem. 1988, 100, 975.
(20) (a) Herrmann, W. A.; Watzlowik, P. J. Organomet. Chem. 1992, 441,
265. (b) Haider, J. J.; Kratzer, R. M.; Herrmann, W. A.; Zhao, J.; Kuhn, F. E.
J. Organomet. Chem. 2004, 689, 3735.
(21) Zhu, Z.; Al-Ajlouni, A. M.; Espenson, J. H. Inorg. Chem. 1996, 35,
1408.