An oxidovanadium(IV) complex having a perrhenato ligand: An efficient catalyst for aerobic oxidation reactions of benzylic and propargylic alcohols

Article abstract of DOI:10.1016/j.tetlet.2017.07.034

An oxidovanadium(IV) complex having a perrhenato ligand [VO(ReO₄)(4,4′-^tBubpy)₂][0.25SO₄·0.5ReO₄] (4,4′-^tBubpy?=?4,4′-di-tert-butyl-2,2′-bipyridine) efficiently catalyzes not only dehydrogenative oxidation of benzylic and propargylic mono-alcohols but also oxidative C–C bond cleavage of meso-1,2-diaryl-1,2-ethanediols under atmospheric molecular oxygen, affording the corresponding carbonyl compounds in good yield.

Full text of DOI:10.1016/j.tetlet.2017.07.034

Accepted Manuscript
An oxidovanadium(IV) complex having a perrhenato ligand: An efficient cat-
alyst for aerobic oxidation reactions of benzylic and propargylic alcohols
Daiki Kobayashi, Shintaro Kodama, Youichi Ishii
PII:
S0040-4039(17)30881-X
DOI:
http://dx.doi.org/10.1016/j.tetlet.2017.07.034
TETL 49116
Reference:
Tetrahedron Letters
To appear in:
Received Date:
Revised Date:
Accepted Date:
25 April 2017
30 June 2017
10 July 2017
Please cite this article as: Kobayashi, D., Kodama, S., Ishii, Y., An oxidovanadium(IV) complex having a perrhenato
ligand: An efficient catalyst for aerobic oxidation reactions of benzylic and propargylic alcohols, Tetrahedron
Letters (2017), doi: http://dx.doi.org/10.1016/j.tetlet.2017.07.034
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Graphical Abstract
To create your abstract, type over the instructions in the template box below.
Fonts or abstract dimensions should not be changed or altered.
An oxidovanadium(IV) complex having a
perrhenato ligand: An efficient catalyst for
aerobic oxidation reactions of benzylic and
propargylic alcohols
Leave this area blank for abstract info.
Daiki Kobayashi, Shintaro Kodama,∗ and Youichi Ishii∗

1
Tetrahedron Letters
journal homepage: www.els evier.com
An oxidovanadium(IV) complex having a perrhenato ligand: An efficient catalyst for
aerobic oxidation reactions of benzylic and propargylic alcohols
Daiki Kobayashi, Shintaro Kodama,∗ and Youichi Ishii∗
Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan
ARTICLE INFO
ABSTRACT
Article history:
Received
An oxidovanadium(IV) complex having a perrhenato ligand [VO(ReO4)(4,4’-
tBubpy)2][0.25SO4·0.5ReO4] (4,4’-tBubpy = 4,4’-di-tert-butyl-2,2’-bipyridine) efficiently
catalyzes not only dehydrogenative oxidation of benzylic and propargylic mono-alcohols but
also oxidative C−C bond cleavage of meso-1,2-diaryl-1,2-ethanediols under atmospheric
molecular oxygen, affording the corresponding carbonyl compounds in good yield.
Received in revised form
Accepted
Available online
2009 Elsevier Ltd. All rights reserved.
Keywords:
Oxidation reactions
Oxidovanadium complexes
Perrhenate ions
Benzylic alcohols
Molecular oxygen
Oxidation reactions of alcohols to the corresponding carbonyl
compounds are among the most important transformations in
synthetic organic chemistry. In particular, increasing attentions
have been paid towards the transition-metal-catalyzed aerobic
oxidation reactions due to both economic and environmental
reasons.1 Oxidovanadium complexes are known to act as
catalysts for various aerobic alcohol oxidation reactions,
including not only dehydrogenative oxidation of mono-alcohols
but also oxidative C−C bond cleavage of 1,2-diols.2 However,
oxidovanadium complexes with the ability to effectively catalyze
both dehydrogenative oxidation and oxidative cleavage reactions
are still limited so far.
Table 1. Effects of the solvents on oxidation of 1a catalyzed
by V1 under O2
Entry Solvent
Conv.
(%)a
Yield of 2a
(%)a
Select.
(%)b
1
2
3
4
5
6
7
MeCN
48
100
56
96
96
64
52
30
63
94
75
41
19
61
69
MeCN/THF (1:1)
THF
94 (97)c
42
Herein, we report the synthesis and catalytic activities of an
oxidovanadium(IV) complex having a perrhenato ligand
[VO(ReO4)(4,4’-tBubpy)2][0.25SO4·0.5ReO4] (V1; 4,4’-tBubpy =
4,4’-di-tert-butyl-2,2’-bipyridine). It is interesting to note that
V1 catalyzes dehydrogenative oxidation of secondary benzylic
mono-alcohols to the corresponding ketones under O2 (balloon)
or atmospheric air more effectively than the structurally related
oxidovanadium(IV) complex [VO(OH)(4,4’-tBubpy)2][BF4]
(V2)3 and other commercially available vanadium compounds
(vide infra). In addition, oxidative cleavage of meso-1,2-diaryl-
1,2-ethanediols proceeded selectively to afford the corresponding
benzaldehydes under similar reaction conditions with V1 as a
catalyst.
MeOH/THF (1:1)
EtOH/THF (1:1)
MeCN/2-MeTHF (1:1)
MeCN/1,4-dioxane (1:1)
39
18
39
36
a Determined by 1H NMR using 1,2-diphenylethane as an
internal standard. b Select. = (2a (mol)/1a consumed (mol))×100.
c Isolated yield.
/MeOH at room temperature, the reaction mixture turned into a
green suspension. The precipitates were collected, washed with
H2O and Et2O, and dried in vacuo to afford V1 as a green powder
(29% yield). Positive fast atom bombardment mass spectrometry
(FAB-MS) analysis of V1 showed m/z (relative intensity) 854.6
(100, M+) and 852.6 (68, M+) attributable to the cationic complex
When oxidovanadium(IV) sulfate (VOSO4) was allowed to
react with potassium perrhenate (KReO4) and 4,4’-tBubpy in H2O
———
∗ Corresponding author. Tel.: +81-3-3817-1923; fax: +81-3-3817-1895; e-mail: s-kodama@kc.chuo-u.ac.jp
∗ Corresponding author. Tel.: +81-3-3817-1901; fax: +81-3-3817-1895; e-mail: yo-ishii@kc.chuo-u.ac.jp

2
Tetrahedron
Table 2. Effects of catalysts on oxidation of 1a under O2
Table 3. Oxidation of various benzylic mono-alcohols
a
catalyzed by V1 under O2
Entry
Substrate
Product
Time Yield
(%)b
(h)
Entry Catalyst
Conv.
(%)a
Yield of 2a Select.
(%)a
(%)b
94
24
47
0
94 (97)c
1
2
3
4
10
10
10
10
94 (97)c
88 (83)c
88 (90)c
48
1
V1
100
21
68
8
R = C6H5 (1a)
2a
2b
2c
2d
2
3
4
5
6
7
8
9
V2
5
R = 4-MeOC6H4 (1b)
R = 4-ClC6H4 (1c)
R = 4-NO2C6H4 (1d)
VOSO4
32
0
d
KReO4
[VO(acac)2]
[VOCl3]
[VO(OiPr)3]
V2O5
29
84
44
12
2
14
18
trace
0
48
21
−
5
10
93d
0
NH4ReO4
0
0
a Determined by 1H NMR using 1,2-diphenylethane as an
internal standard. b Select. = (2a (mol)/1a consumed (mol))×100.
c Isolated yield. d 10 mol%.
6
7
8
96
96
96
76d
62d
80d
R = C6H5 (1f)
2f
[VO(ReO4)(4,4’-tBubpy)2]+ (calcd m/z: 854.3 (100%), 852.3
(59.7%)), the peak pattern of which is in good agreement with
the isotopic distribution of this cation.4,5
R = 4-MeOC6H4 (1g)
R = 4-ClC6H4 (1h)
2g
2h
To investigate the catalytic activity of V1 in an alcohol
oxidation with O2, diphenylmethanol (1a) was chosen as a model
substrate. Oxidation of 1a was performed in a glass vessel
equipped with an O2 balloon in the presence of 5.6 mol% of V1
at 60 °C for 10 h in various solvents, and the results are
summarized in Table 1. In MeCN as the solvent, benzophenone
(2a) was formed in 30% yield (entry 1), whereas the yield of 2a
dramatically increased to 94% by using a mixed MeCN/THF
(1:1) solvent (entry 2).6 In THF (entry 3) and other mixed
solvents (entries 4−7), 2a was obtained in low to moderate
9
R = iPr(1i)
R = cHex(1j)
OH
2i
2j
O
96
96
55
68
10
Ph
Ph
Ph
11
1
83d
Ph
O
O
1k
2k
−42%) yield.
(18
Under similar reaction conditions shown in Table 1, entry 2,
oxidation of 1a was examined using different catalysts (Table 2).
When the oxidovanadium(IV) complex V23 which is structurally
related to V1 was employed as the catalyst, 2a was formed in 5%
yield (entry 2). VOSO4 and KReO4, the starting materials of V1,
were not effective as catalysts (entries 3 and 4). Commercially
available vanadium and perrhenate compounds such as
12
13
R = C6H5 (1l)
R = CH3 (1m)
2l
1
88d
88d
2m
30
[VO(acac)2] (acac = acetylacetonato), [VOCl3], [VO(OiPr)3],
V2O5, and NH4ReO4 also failed to exhibit appreciable catalytic
activities and selectivities (entries 5−9).
14
15
16
48
10
24
84
Oxidation of various mono-alcohols catalyzed by V1 was
examined under the optimized reaction conditions (Table 1, entry
2), and the results are summarized in Table 3. Diarylmethanols
1b and 1c bearing methoxy or chloro substituents could be
oxidized efficiently to the corresponding ketones 2b and 2c in
high yield (entries 2 and 3), whereas the reaction with α-phenyl-
4-nitrobenzenemethanol (1d) gave 4-nitrobenzophenone (2d) in
48% yield (entry 4). The oxidation of 9-fluorenol (1e) proceeded
smoothly to afford 9-fluorenone (2e) in 93% yield (entry 5). 1-
Phenylethanol (1f) and its derivatives 1g and 1h were oxidized
slowly to the corresponding acetophenones 2f−2h in moderate to
good (62−80%) yield (entries 6−8). The oxidation of α-
n.d.e
n.d.e
a Oxidation reactions were carried out using substrate (0.5
mmol), V1 (0.028 mmol), and 3.0 mL of MeCN/THF (1:1) in a
glass vessel equipped with O2 balloon (0.1 MPa) at 60 °C for
appropriate times. b Determined by 1H NMR using 1,2-
diphenylethane as an internal standard. c Isolated yield.
Determined by 1H NMR using 1,3,5-trimethoxybenzene as an
internal standard. e n.d. = not detected.
d
isopropylbenzenemethanol (1i) and α-cyclohexylbenzene-
methanol (1j) proceeded more slowly than that of 1f (entries 9
and 10), where steric hindrance of substrates is assumed to
influence the reactivity of V1. In contrast, benzoin (1k) was qui-

3
Table 4. Effects of vanadium catalysts on oxidative
cleavage of 1q under O2
Entry Catalyst
Conv.
(%)a
Yield of 2n
(%)a
Select.
(%)b
1
2
3
4
5
6
7
V1
100
84
78
78
61
40
66
83
69
−
V2
51
VOSO4
[VO(acac)2]
[VOCl3]
[VO(OiPr)3]
V2O5
98
39
88
58
100
81
83
56
14
trace
a Determined by 1H NMR using 1,3,5-trimethoxybenzene as
an internal standard. b Select. = (2n (mol)/1q consumed
(mol))×100.
ckly converted into benzil (2k) in 83% yield (entry 11). The
oxidation of 1,3-diphenylpropargyl alcohol (1l) also proceeded
smoothly to form 1,3-diphenylpropynone (2l) in 88% yield,
whereas the methyl analog of 1l (1m) required a longer reaction
time (30 h) to afford the corresponding propargylic ketone 2m.
Benzyl alcohol (1n) was oxidized selectively to benzaldehyde
(2n) in 84% yield (entry 14). Aliphatic alcohols 1o and 1p were
inert to oxidation (entries 15 and 16), which motivated us to
examine the chemoselective oxidation reactions of two different
alcohols. The reaction with a mixture of 1a and 1p resulted in
the formation of 2a in quantitative yield, while the aliphatic
ketone 2p was not detected (Eq. 1).
Although some oxidovanadium complexes [VO(acac)2],
[VOCl3], and [VO(OiPr)3] were found to exhibit moderate to
good catalytic activities toward the oxidative cleavage, these
complexes were not effective as catalysts for the dehydrogenative
oxidation of mono-alcohol 1a (Tables 2 and 4). It is interesting
to note that the present results with V1 provide a rare example of
the vanadium catalyst that is highly effective in both
dehydrogenative alcohol oxidation and oxidative cleavage of 1,2-
diols with O2.
In addition, we expected that meso-1,2-diphenyl-1,2-
ethanediol (1q) would be oxidized to benzil (2k) in the present
catalytic system. The reaction with 1q, however, afforded
benzaldehyde (2n), the oxidative C−C bond cleavage1b,2p–r
product, selectively in 78% yield (Eq. 2). meso-1,2-Diphenyl-
1,2-ethanediols 1r and 1s bearing methoxy and chloro
substituents were also oxidized to the corresponding aldehydes
2r and 2s in good yield, respectively (Eq. 3). The oxidative
cleavage of benzopinacol (1t) proceeded more slowly than that of
1q−1s to afford benzophenone (2a) in 91% yield, probably due to
the steric congestion (Eq. 4).
Furthermore, the oxidations of 1a and 1q catalyzed by V1
were examined using ambient air as the oxidant. To our delight,
the corresponding oxidation products 2a and 2n were obtained in
93% and 86% yield, respectively, by elongating the reaction time
(Eqs. 5 and 6).
Finally, gram-scale oxidation reaction of 1a with O2 was
carried out by reducing the catalyst loading (1.0 mol% of V1) to
demonstrate the utility of the present catalytic system. As
expected, 2a was isolated in 66% yield (Eq. 7).
In conclusion, we have successfully revealed that the newly
synthesized oxidovanadium(IV) complex having a perrhenato
ligand V18 exhibits efficient catalytic activities towards the
aerobic oxidation reactions of secondary benzylic mono-alcohols
and meso-1,2-diaryl-1,2-ethanediols.9 Further studies to
elucidate the effect of a perrhenato ligand and detailed reaction
mechanisms together with oxidations of other organic substrates
using the present catalytic system are now in progress.
By using 1q as a model substrate, we further investigated the
catalytic activities of several vanadium complexes in the
oxidative cleavage of 1,2-diols as shown in Table 4. In the case
of V2, 2n was obtained in 51% yield (entry 2). Among the
commercially available vanadium compounds employed,
[VOCl3] exhibited similar catalytic activity to that of V1 (entries
3−7).

4
Tetrahedron
Brègeault, J. M.; El Ali, B.; Mercier, J.; Martin, J.; Martin, C. C.
R. Acad. Sci., Ser. II 1989, 309, 459–462.
Acknowledgments
3. (a) Waidmann, C. R.; Zhou, X.; Tsai, E. A.; Kaminsky, W.;
Hrovat, D. A.; Borden, W. T.; Mayer, J. M. J. Am. Chem. Soc.
2009, 131, 4729–4743; (b) Triantafillou, G. D.; Tolis, E. I.; Terzis,
A.; Deligiannakis, Y.; Raptopoulou, C. P.; Sigalas, M. P.;
Kabanos, T. A. Inorg. Chem. 2004, 43, 79–91.
The authors acknowledge Mr. I. Yoshikawa and Prof. H.
Houjou (The Univ. of Tokyo) for mass spectrometry. This work
was supported in part by JST ACT-C Grant Number
JPMJCR12Z1, Japan.
4. Perrhenate coordinated oxidovanadium(V) complexes were
reported by Chaudhury et al., see: Chatterjee, P. B.; Abtab, S. M.
T.; Bhattacharya, K.; Endo, A.; Shotton, E. J.; Teat, S. J.;
Chaudhury, M. Inorg. Chem. 2008, 47, 8830–8838.
References and notes
1. Selected reviews: (a) Parmeggiani, C.; Cardona, F. Green Chem.
2012, 14, 547–564; (b) Kirihara, M. Coord. Chem. Rev. 2011,
255, 2281–2302; (c) Gligorich, K. M.; Sigman, M. S. Chem.
Commun. 2009, 3854–3867; (d) Piera, J.; Bäckvall, J.-E. Angew.
Chem. Int. Ed. 2008, 47, 3506–3523; (e) Schultz, M. J.; Sigman,
M. S. Tetrahedron 2006, 62, 8227–8241; (f) Zhan, B.-Z.;
Thompson, A. Tetrahedron 2004, 60, 2917–2935; (g) Muzart, J.
Tetrahedron 2003, 59, 5789–5816; (h) Sheldon, R. A.; Arends, I.
W. C. E.; Dijksman, A. Catal. Today 2000, 57, 157–166.
2. Selected papers concerning vanadium-catalyzed dehydrogenative
−C bond cleavage of 1,2
5. Selected papers concerning the oxidation of alcohols using a
perrhenate catalyst: (a) Yi, J.; Miller, J. T.; Zemlyanov, D. Y.;
Zhang, R.; Dietrich, P. J.; Ribeiro, F. H.; Suslov, S.; Abu-Omar,
M. M. Angew. Chem. Int. Ed. 2014, 53, 833–836; (b) Lippert, C.
A.; Riener, K.; Soper, J. D. Eur. J. Inorg. Chem. 2012, 554–561;
(c) Shiramizu, M.; Toste, F. D. Angew. Chem. Int. Ed. 2012, 51,
8082–8086.
6. Although we must await further studies to clarify the role of THF
in the present catalytic system, we inferred that THF promotes the
oxidation of the vanadium(IV) complex V1 by O27 to form the
vanadium(V) complex which often acts as active species for the
aerobic oxidation of alcohols.2
oxidation of alcohols2a–o and oxidative C
-
diols2p–r under O2 or air: (a) Elkurtehi, A. I.; Walsh, A. G.; Dawe,
L. N.; Kerton, F. M. Eur. J. Inorg. Chem. 2016, 3123–3130; (b)
Marui, K.; Higashiura, Y.; Kodama, S.; Hashidate, S.; Nomoto,
A.; Yano, S.; Ueshima, M.; Ogawa, A. Tetrahedron 2014, 70,
2431–2438; (c) Zhang, G.; Scott, B. L.; Wu, R.; Silks, L. A.;
Hanson, S. K. Inorg. Chem. 2012, 51, 7354–7361; (d) Kodama,
S.; Hashidate, S.; Nomoto, A.; Yano, S.; Ueshima, M.; Ogawa, A.
Chem. Lett. 2011, 40, 495–497; (e) Hanson, S. K.; Wu, R.; Silks,
L. A. Org. Lett. 2011, 13, 1908–1911; (f) Kodama, S.; Ueta, Y.;
Yoshida, J.; Nomoto, A.; Yano, S.; Ueshima, M.; Ogawa, A.
Dalton Trans. 2009, 9708–9711; (g) Jiang, N.; Ragauskas, A. J. J.
Org. Chem. 2007, 72, 7030–7033; (h) Jiang, N.; Ragauskas, A. J.
Tetrahedron Lett. 2007, 48, 273–276; (i) Radosevich, A. T.;
Musich, C.; Toste, F. D. J. Am. Chem. Soc. 2005, 127, 1090–1091;
(j) Reddy, S. R.; Das, S.; Punniyamurthy, T. Tetrahedron Lett.
2004, 45, 3561–3564; (k) Velusamy, S.; Punniyamurthy, T. Org.
Lett. 2004, 6, 217–219; (l) Figiel, P. J.; Sobczak, J. M.;
7. (a) Waidmann, C. R.; DiPasquale, A. G.; Mayer, J. M. Inorg.
Chem. 2010, 49, 2383–2391; (b) Kelm, H.; Krüger, H.-J. Angew.
Chem. Int. Ed. 2001, 40, 2344–2348.
8. Synthesis of [VO(ReO4)(4,4’-tBubpy)2][0.25SO4·0.5ReO4] (V1):
To an aqueous solution of VOSO4·5H2O (50.7 mg, 0.20 mmol)
and KReO4 (232.0 mg, 0.80 mmol) was added a MeOH solution
of 4,4’-di-tert-butyl-2,2’-bipyridine (107.3 mg, 0.40 mmol), and
the resulting green suspension was stirred at room temperature for
10 min. The green precipitates were collected, washed with H2O
and Et2O, and dried in vacuo to afford V1 as a green powder (57.5
mg, 29% yield). IR (KBr, cm–1) 2964, 1617, 1411, 979, 912;
Anal. Calcd for C36H48N4O8Re1.5S0.25V: C, 43.11; H, 4.82; N, 5.59.
Found: C, 43.05; H, 4.84; N, 5.55%.
9. General procedure: V1 (27.6 mg, 0.028 mmol) and substrate (0.5
mmol) were placed in a 20 mL schlenk flask, and then the mixed
MeCN/THF (1:1) solvent (3 mL) was added. The mixture was
stirred at 60 °C for an appropriate time under O2 (balloon) or
atmospheric air. After the reaction was completed, Et2O was
added to the reaction mixture. The resulting suspension was
filtered and rinsed with Et2O. The combined filtrate was
concentrated in vacuo. The yield of the oxidation products was
confirmed by 1H NMR spectroscopy using 1,2-diphenylethane or
1,3,5-trimethoxybenzene as the internal standard. Purification of
2a–2c was performed by silica gel chromatography using hexane
and EtOAc as the eluent to afford the analytically pure ketones.
The isolated products were identified by comparing their 1H NMR
spectra with those of authentic samples.
Ziółkowski, J. J. Chem. Commun. 2004, 244–245; (m) Maeda, Y.;
Kakiuchi, N.; Matsumura, S.; Nishimura, T.; Kawamura, T.;
Uemura, S. J. Org. Chem. 2002, 67, 6718–6724; (n) Maeda, Y.;
Kakiuchi, N.; Matsumura, S.; Nishimura, T.; Uemura, S.
Tetrahedron Lett. 2001, 42, 8877–8879; (o) Kirihara, M.; Ochiai,
Y.; Takizawa, S.; Takahata, H.; Nemoto, H. Chem. Commun.
1999, 1387–1388; (p) Kirihara, M.; Yoshida, K.; Noguchi, T.;
Naito, S.; Matsumoto, N.; Ema, Y.; Torii, M.; Ishizuka, Y.; Souta,
I. Tetrahedron Lett. 2010, 51, 3619–3622; (q) Khenkin, A. M.;
Neumann, R. J. Am. Chem. Soc. 2008, 130, 14474–14476; (r)

5
An oxidovanadium(IV) complex having
a perrhenato ligand: An efficient catalyst
for aerobic oxidation reactions of
benzylic and propargylic alcohols
Daiki Kobayashi, Shintaro Kodama,∗ and Youichi
Ishii∗
Department of Applied Chemistry, Faculty of Science and
Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku,
Tokyo 112-8551, Japan
Highlights
An oxidovanadium(IV) complex having a
perrhenato ligand (V1) has been synthesized.
V1 exhibits high catalytic activities for alcohol
oxidation reactions with O2.
Dehydrogenative oxidation and oxidative cleavage
reaction of alcohols are described.
———
∗ Corresponding author. Tel.: +81-3-3817-1923; fax: +81-3-3817-
1895; e-mail: s-kodama@kc.chuo-u.ac.jp
∗ Corresponding author. Tel.: +81-3-3817-1901; fax: +81-3-3817-
1895; e-mail: yo-ishii@kc.chuo-u.ac.jp