Highly effective peroxidic epoxidation of olefins using hexathiocyanatorhenate(IV) as catalyst and bicarbonate as co-catalyst

Article abstract of DOI:10.1016/j.tetlet.2004.10.163

In the presence of bicarbonate as co-catalyst hexathiocyanatorhenate(IV) functions as an extremely effective catalyst in the epoxidation of olefins using aqueous hydrogen peroxide as the terminal oxidant.

Full text of DOI:10.1016/j.tetlet.2004.10.163

Tetrahedron
Letters
Tetrahedron Letters 46 (2005) 339–341
Highly effective peroxidic epoxidation of olefins using
hexathiocyanatorhenate(IV) as catalyst and bicarbonate as
co-catalyst
a
Subhajit Dinda, Sujoy Roy Chowdhury, K. M. Abdul Malik and
a
b
a,
*
Ramgopal Bhattacharyya
a
Department of Chemistry, Jadavpur University, Kolkata 700032, India
Department of Chemistry, University of Cardiff, PO Box 912, Park Place, Cardiff CF10 3TB, UK
b
Received 21 June 2004; revised 19 October 2004; accepted 28 October 2004
Available online 25 November 2004
Abstract—In the presence of bicarbonate as co-catalyst hexathiocyanatorhenate(IV) functions as an extremely effective catalyst in
the epoxidation of olefins using aqueous hydrogen peroxide as the terminal oxidant.
Ó 2004 Elsevier Ltd. All rights reserved.
Homogeneous epoxidation of olefins using hydrogen
1
In addition, the low cost (compared to MTO) and the
environmentally benign nature of the described method
lead us to claim that this method along with another
method using a Mn(III)–porphyrin system as catalyst
displays excellent efficiency in the catalytic epoxidation
11
of olefinic compounds.
–5
peroxide as terminal oxidant
in conjunction with a
trace amount of a metal complex as catalyst in the pres-
ence of a suitable additive is potentially viable for large-
scale production. Much work has already been done in
1
0
6
this area, but still the % yield and turnover number
7
are far from efficient. Methyltrioxorhenium (MTO) in
the presence of amine derivatives as additives, as intro-
The experimental conditions for the epoxidation involv-
ing a wide variety of olefins are as follows: substrate (be-
tween 400 and 2000 and the co-catalyst between 100 and
500Mequiv per molar equivalent of catalyst), were dis-
solved with stirring in acetonitrile (ꢀ20–25 Mequiv per
molar equivalent of substrate) in a two-neck, flat-bot-
tomed flask (one neck fitted with a reflux condenser).
Reaction solutions were stirred at room temperature
and after every 15min, 0.1mL of the solution was with-
drawn, quenched at ꢁ10°C and extracted with ether
(several extractions were necessary in most cases). The
ether extract was concentrated and analyzed by GC
The retention times were compared with those of com-
mercial standards and for quantitative estimation of
the products, nitrobenzene was used as an internal
standard. Control experiments indicated that the desired
epoxidation failed to occur even after 24h when both the
8
duced by Sharpless and co-workers, may be regarded
as the best olefin epoxidation method available to date
for fairly unreactive substrates with H O as terminal
2
2
oxidant. However, MTO is difficult to prepare, which
makes it highly expensive and in-house synthesis takes
a long time. This motivated us to examine whether an
easily and readily synthesizable Re complex as catalyst
could be used instead of MTO. In this communication
9
we describe the one-pot, single-step synthesis of the rhe-
nium compound, (Ph P) [Re(NCS) ] 1, which when
4
2
6
used in tandem with NaHCO3 as a co-catalyst and
H O as the terminal oxidant results in excellent cata-
2
2
lytic efficiency towards the epoxidation of olefins with
respect to selectivity, % yield, time required, amount
of catalyst loading and catalyst turnover (TON = ratio
of moles of product obtained to moles of catalyst used).
catalyst 1 and NaHCO were omitted. Interestingly, the
3
epoxidation reaction occurred if catalyst 1 was omitted
but NaHCO was present. The results are shown in
Table 1. It was observed that under the above conditions
a stoichiometric (but not catalytic, when the % conver-
sion was found to be negligible) amount of NaHCO3
3
Keywords: Hexathiocyanatorhenate(IV); Catalyst; Co-catalyst; Effi-
cient epoxidation; Sodium bicarbonate.
*
Corresponding author. Tel.: +91 33 2414 6193; fax: +91 33 2414
584; e-mail: argibhatta@yahoo.co.in
6
0
040-4039/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2004.10.163

3
40
Table 1. Details of the catalytic epoxidation of olefinic compounds
.25/0.05 mol% (PPh
-8 eq. H , 25 mol% NaHCO
Time (h)
S. Dinda et al. / Tetrahedron Letters 46 (2005) 339–341
0
4
)
2
6
[Re(NCS) ], acetonitrile
Alkene
Epoxide
7
O
2 2
3
, Room temp.
a
Yield (%)
b
Yield (%)
c
Entry
Substrate
Product
Conversion (%)
TON (TOF)
Chromatographic
Isolated
Molar ratio of substrate:catalyst = 400:1 (0.25mol%)
1
1.5
99
88
99
88
—
80
50
25
396 (264)
352 (704)
O
O
2
0.5
3
4
1
4
96
80
96
80
—
—
24
36
384 (384)
320 (80)
O
O
O
5
1
99
99
88
37
396 (396)
O
6
7
HO
HO
4
99
93
99
93
—
—
45
48
396 (99)
HO
HO
2.5
372 (149)
O
8
9
4.5
3
90
80
90
80
70
—
53
38
360 (80)
O
O
320 (107)
Molar ratio of substrate:catalyst = 2000:1 (0.05mol%)
1
3
99
57
99
51
—
—
75
41
1980 (660)
1140 (285)
O
O
O
2
4
3
4
2
3
77
95
77
95
—
—
52
64
1540 (770)
1900 (633)
O
The methods for the determination of isolated yield and for calculation of the GC yield are enclosed as Supplementary material.
a
%
%
3
Yield of the control experiment without using the catalyst and NaHCO is zero.
b
c
Yield of the control experiments excluding the catalyst only but in the presence of NaHCO
ꢁ1
3
(25mol%).
Figures in the parentheses indicate TOF (turnover frequency; TON h ).
V
was necessary for the reactions to provide the products.
Also, in the absence of the co-catalyst, 1 functions less
efficiently, with % yield and TON being much lower
and the conversion time much higher.
gested that here also the Fe @O (oxoferryl) moiety is
the active species for catalysis. Furthermore, in the case
of MTO and subsequent to their first report, Hermann
1
5
et al. were able to isolate and structurally characterize
ReO(O ) (CH )(H O)] 3 by conducting the synthetic
reaction (MTO+H O ) at 0°C and crystallization at
ꢁ30°C and claimed that 3 was the active catalyst. Since
the rhenium oxo diperoxo system is very unstable at rt,
one cannot be confident in concluding that this is the
active form of the catalyst. We also suggested an active
catalyst system for the oxidation of methyl benzenes
using [MoO(O )(QO)] (QO = 8-quinolinol) as catalyst
[
2
2
3
2
1
2
Richardson has shown that hydrogen peroxide and
3
2
2
1
bicarbonate react to give peroxymonocarbonate,
(
ꢁ
HCO ) and this was considered to be the oxidizing spe-
4
cies present. Interestingly, the catalyst functions poorly
on its own and the co-catalyst much more poorly, but
both together (with the former even in microamounts)
make the reaction extremely facile. It is quite interesting
1
6
2
IV
to note that a catalyst, which contains Re is more
effective than MTO, which contains Re . This can be
and H O as oxidant. However, it is very difficult to
2
2
VII
prove the composition of the catalyst at the moment
of reaction with the substrate and all suggestions are
tentative. In the present case we were not able to iso-
late any peroxorhenium compound by conducting a pre-
parative reaction at ꢁ20°C. Hence at this moment we
cannot suggest a mechanism for this epoxidation reac-
easily rationalized on the basis that H O as oxidant eas-
2
2
IV
ily oxidizes Re to Re
[
VII
(to the putative compound
14
VII
Re O NCS] 2). Evidently 2 is a more efficient catal-
3
yst precursor than MTO for epoxidation when using
H O as a terminal oxidant. An oxo bridged di-iron(II)
compound has recently been found to be an epoxidation
2
2
2
ꢁ ꢁ
tion involving [Re(NCS)6] , HCO , HCO , H O
3
2 2
ꢁ
4
6
k
catalyst in the presence of H O and it has been sug-
2
and olefins.
2

S. Dinda et al. / Tetrahedron Letters 46 (2005) 339–341
341
Cl
Acknowledgements
for 3h when a deep red solution was obtained. PPh
0.78g; 2.11mmol), dissolved in a minimum volume of
4
(
water was added to the red solution with stirring leading
to an orange-red solid precipitate. The solid was filtered
off, washed with water and ethanol and dried over fused
We thank the University Grants Commission, New
Delhi, for funding this project and the Department of
Science and Technology, Government of India, for
funding the Agilent 6890N gas chromatograph.
CaCl
was crystallized from acetone to give fine orange red
crystals. Calcd for, C54 Re, C, 53.5, H, 3.3;
2
in vacuo. The crude compound (yield = 0.70g; 46%)
41 6 0.50 2 6
H N O P S
N, 6.9, S, 15.8. Found C, 53.1, H, 3.4, N, 7.2, S, 15.4%. IR
(KBr disc): m (CN), 2080 (s), 2060 (m); m (CS), 760 (sh),
Supplementary data
ꢁ
1
d(NCS), 480 (w) and m (MꢁN) at 445cm . UV–vis
(
1
acetonitrile solution): 345 (sh) and 452 (e =
230M cm )nm. Besides the physico-chemical charac-
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.tetlet.
ꢁ ꢁ1
1
terization the compound was also structurally character-
ized and found to consist of discrete monomeric anions,
2
004.10.163.
2
]
ꢁ
þ
[Re(NCS)
6
and PPh4 cations, the anion (the catalyst
precursor) having an octahedral geometry.
10. Banfi, S.; Legramandi, F.; Montanari, P.; Possi, G.; Quici,
S. Chem. Commun. 1991, 1285–1287.
References and notes
. Grigoropoulou, G.; Clark, J. H.; Elings, J. A. Green
Chem. 2003, 5, 1–7.
. Rebelo, S. L. H.; Sim o˜ es, M. M. Q.; Neves, M. G. P. M.
S.; Silva, A. M. S.; Cavaleiro, J. A. S. Chem. Commun.
III
1
11. Besides the Mn –porphyrin work, which shows a TOF
ꢁ
1
ꢁ1
(turnover frequency = h ) of 20,000h with cyclooctene
as the only substrate, all other work, to the best of our
knowledge, shows much lower TOFs than we obtained
with 1. The next best TOFs are: (i) Thiel et al. (Thiel, W.
R.; Eppinger, J. Chem. Eur. J. 1997, 3, 696–705) who
observed that cyclooctene could be epoxidized with
2
2
004, 608–609.
3
. Peroxide Chemistry—Mechanistic and Preparative Aspects
of Oxygen Transfer; Adam, W., Ed.; Wiley–VCH: Wein-
heim, FRG, 2000.
ꢁ
1
TOF = 6470h with the Mo-complex used as catalyst
only when t-butyl hydroperoxide (but not H O , which
failed to effect oxidation) was used as oxidant. (ii) W:
4
5
. Sato, K.; Aoki, M.; Noyori, R. Science 1998, 281, 1646–
647.
2
2
1
ꢁ
ꢁ
1
. (a) Jorgensen, K. A. Chem. Rev. 1989, 89, 431–458; (b)
Jones, C. W. Applications of Hydrogen Peroxide and
Derivatives; MPG Books Ltd: Cornwall, UK, 1999.
TOF = 100h
TOF = 38h
,
see Ref. 3,
(for styrene); this catalyst exhibited the
p 355; (iii) Re(MTO):
1
ꢁ1
highest TOF (190h ) for the epoxidation of 1-phenyl
cyclohexene.
6
. For examples of catalytic systems for olefin epoxidation
using aqueous H
2
O
2
see: methyltrioxorhenium: (a) Rud-
12. Richardson, D. E.; Yao, H.; Frank, K. M.; Bannett, D. A.
J. Am. Chem. Soc. 2000, 122, 1729–1739.
13. Lane, B. S.; Vogt, M.; de Rose, V. J.; Burgess, K. J.
Am.Chem. Soc. 2002, 124, 11946–11954.
14. Complex 2 was obtained by treating 1 (0.1g, 0.082mmol)
olph, J.; Reddy, K. L.; Chiang, J. P.; Sharpless, K. B. J.
Am. Chem. Soc. 1997, 119, 6189–6190; (b) Hermann, W.
A.; Fischer, R. W.; Marz, D. W. Angew. Chem., Int. Ed.
Engl. 1991, 30, 1638–1641; Tungsten complexes including
heteropolyoxo tungstates: (c) Zuwei, X.; Ning, Z.; Yu, S.;
Kunlan, L. Science 2001, 292, 1139–1141; (d) Sato, K.;
Aoki, M.; Ogawa, M.; Hashimoto, T.; Noyori, R. J. Org.
Chem. 1996, 61, 8310–8311; (e) Venturello, C.; Alneri, E.;
Ricci, M. J. Org. Chem. 1983, 68, 3831–3833; (f) Ventu-
rello, C.; Aloiso, R. D.; Bart, J. C.; Ricci, M. J. Mol.
Catal. 1985, 32, 107–110; Mn-complexes: (g) Berkessel, A.;
Sklorz, C. A. Tetrahedron Lett. 1999, 40, 7965–7968; (h)
de Vos, D.; Bein, T. Chem. Commun. 1996, 917–918; (i)
Lane, B. S.; Burgess, K. Chem. Rev. 2003, 103, 2457–2473,
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L.; van Vliet, G.; Boaron, R.; Hage, R.; de Vos, D. E.;
Alsters, P. L.; Feringa, B. L. Tetrahedron Lett. 2002, 43,
2 2
with excess H O (10mL, 98mmol) in acetonitrile (20mL)
and stirring for 30min upon which an orange powder
precipitated (yield = 0.09g, 79%). The powder was dis-
solved in acetonitrile and concentrated, when 75% of the
product precipitated as powdery material. Complex 2 was
characterized by elemental analysis [C (found, 3.56; calcd,
4.11), N (found, 4.01; calcd, 4.79), S (found, 9.86; calcd,
10.96) and Re (found, 65.17; calcd, 63.70)]. The elements
C and N were analyzed using a Perkin Elmer 240C
elemental analyzer, for S and Re, about 0.1g of the
respective compounds were separated by fusion with alkali
peroxide and the former was estimated as BaSO
4
(Vogel,
A. I. A Textbook of Quantitative Inorganic Analysis, 3rd
ed.; ELBS and Longmans, Green and Co.: London, 1964)
and the latter as Nitron perrhenate (Geilmann, W.;
Voight, A. Z. Anorg. Allgem. Chem. 1930, 193, 311). IR
2
619–2622; Fe-complexes: (k) White, M. C.; Doyle, A. G.;
Jacobsen, E. N. J. Am. Chem. Soc. 2001, 123, 7194–7195;
Mo-complex: (l) see p 354 of Ref. 3; (m) Mimoun, H.;
Seree de Roch, I.; Sajus, L. Tetrahedron 1970, 26, 37–50;
Ru-complexes: (n) Goldstein, A. S.; Beer, R. H.; Drago,
R. S. J. Am. Chem. Soc. 1994, 116, 2424–2429.
. (a) See Ref. 6b; (b) Hermann, W. A.; K u¨ hn, F. E. Acc.
Chem. Res. 1997, 30, 169–180.
ꢁ
1
(KBr disc) [m(CN) at 2080cm (w), m(Re@O) at 896 (s),
912 (m) and 932cm (sh)]; UV–vis in acetonitrile [472
ꢁ
1
ꢁ1
ꢁ1
ꢁ1
ꢁ1
(e = 880M cm ) and 321 (e = 2120M cm )nm]. The
band at 472nm may be assigned as the
7
8
9
ꢁ
SCN (pp*)!Re(5dp) LMCT transition.
. Adolfson, H.; Converso, A.; Sharpless, K. B. Tetrahedron
Lett. 1999, 40, 3991–3994.
. KReO (0.21g; 0.74mmol) was dissolved in 25mL of 4M
15. Hermann, W. A.; Fischer, R. W.; Scherer, W.; Rauch, M.
U. Angew. Chem., Int. Ed. Engl. 1993, 32, 1157–
1160.
4
HCl and then 0.50g (6.60mmol) of solid NH
4
SCN was
added to the solution with stirring and the temperature
16. Bandyopadhyay, R.; Biswas, S.; Guha, S.; Mukherjee, A.
K.; Bhattacharyya, R. Chem. Commun. 1999, 1627–
1628.
was maintained at 60°C. The resulting solution was stirred