Molybdenum- and rhenium-catalyzed isomerization of cyclopropanemethanols to tetrahydrofurans

Article abstract of DOI:10.1246/cl.2005.790

Molybdenum- and rhenium-complexes work as affective catalysts for isomerization of a variety of cyclopropanemethanols into the corresponding tetrahydrofurans in good to high yields. The reaction may proceed via 1) [3,3]sigmatropic rear-rangement involving an oxo metal cyclopropanemethanolate accompanied by the C-C bond cleavage and 2) the metal-catalyzed intramolecular hydroalkoxylation of the initially produced homoallylic alcohols. Copyright

Full text of DOI:10.1246/cl.2005.790

790
Chemistry Letters Vol.34, No.6 (2005)
Molybdenum- and Rhenium-catalyzed Isomerization
of Cyclopropanemethanols to Tetrahydrofurans
Yasunari Maeda, Takahiro Nishimura,Ã and Sakae UemuraÃ
Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University,
Nishikyo-ku, Kyoto 615-8510
(Received March 25, 2005; CL-050407)
Table 1. Molybdenum- and rhenium-catalyzed isomerization
of cyclopropanemethanols to tetrahydrofurans
Molybdenum- and rhenium-complexes work as affective
catalysts for isomerization of a variety of cyclopropanemeth-
anols into the corresponding tetrahydrofurans in good to high
yields. The reaction may proceed via 1) [3,3]sigmatropic rear-
rangement involving an oxo metal cyclopropanemethanolate ac-
companied by the C–C bond cleavage and 2) the metal-catalyzed
intramolecular hydroalkoxylation of the initially produced ho-
moallylic alcohols.
5 mol% MoO2(acac)2
or MeReO3
10 mol% BHT
R1 OH
R2
R1
R1
R2
OH
+
PhCl (1 mL)
80 °C, 48 h
O
R2
2
1
3
0.2mmol
Yield
of 2/% of 3/%a
Yield
Entry
Substrate
Catalyst
Transformation of cyclopropanes via C–C bond cleavage
into a variety of organic compounds is a useful reaction in view
of organic synthesis and many reactions have been reported.1
Recently, we disclosed the vanadium-catalyzed isomerization
of cyclopropanemethanols to homoallylic alcohols under
atmospheric condition (Eq 1).2 This reaction may proceed via
[3,3]sigmatropic rearrangement of an oxovanadium cyclopropa-
nemethanolate intermediate, similar to vanadium-catalyzed 1,3-
allylic transposition of allylic alcohols.3
1
2
3
4
1a (R1 = R2 = Ph)
MoO2(acac)2
ReMeO3
17
Trb
12
Tr
51
49
61
20
8
82
98
86
95
45
51
0
1a
1b (R1 = R2 = p-Tol)
MoO2(acac)2
1b
ReMeO3
5c 1c (R1 = R2 = 4-ClC6H4) MoO2(acac)2
6c 1c
ReMeO3
7
8
9
1d (R1 = Ph; R2 = H)
MoO2(acac)2
ReMeO3
1d
1e (R1 = Ph; R2 = Me)
0
MoO2(acac)2
ReMeO3
88
65
91
95
92
93
65
70
70
68
R1 OH
10 1e
11 1f (R1 = Ph; R2 = Et)
Tr
Tr
Tr
Tr
Tr
20
22
10
Tr
X
n-1O
R1
O
cat. VOXn
V
MoO2(acac)2
ReMeO3
R1
OH
R2
(1)
−HX
R2
12 1f
R2
13 1g (R1 = Ph; R2 = n-Bu) MoO2(acac)2
During the course of our further studies on this subject, we
14 1g
15c 1h (R1 = Ph; R2 = Bn)
16c 1h
ReMeO3
MoO2(acac)2
ReMeO3
MoO2(acac)2
ReMeO3
c
have now found that the use of an oxo-complex of either molyb-
denum3d,4 or rhenium5 as a catalyst for the above isomerization
in place of a vanadium complex gave the corresponding 2-sub-
stituted tetrahydrofuran (3a) in good yield together with a slight
amount of homoallylic alcohol (2a) (Scheme 1). We describe
herein the first successful example of molybdenum- and rheni-
um-catalyzed isomerization of cyclopropanemethanols into the
corresponding tetrahydrofurans.
Typical results of either molybdenum- or rhenium-catalyzed
isomerization of cyclopropanemethanols to tetrahydrofurans are
listed in Table 1. Similar to the case of vanadium-catalyzed iso-
merization of cyclopropanemethanols to homoallylic alcohols,2
the presence of 2,6-di-tert-butyl-p-cresol (butylhydroxytoluene:
BHT) as a polymerization inhibitor was essential to improve the
17 1i (R1 = R2 = n-Bu)
18 1i
aIsolated yield based on 1 employed. bTrace. For 96 h.
Ph OH
Et
5 mol% MoO2(acac)2
Ph
Et
(2)
PhCl (1 mL)
O
80 °C, 48 h
1f
3f
0.2 mmol
in the absence of inhibitor
in the presence of BHT (0.02 mmol) 91%
51%
yield of tetrahydrofurans. Thus, treatment of the cyclopropane-
methanol 1f in chlorobenzene in the presence of catalytic
amounts of BHT and MoO2(acac)2 gave 3f in an improved yield
compared with the yield in the absence of BHT (Eq 2).
Cyclopropanemethanol having an electron-donating methyl
moiety on a phenyl ring (1b) was converted to 3b in high yield
(Entries 3 and 4), while treatment of the methanol having an
electron-withdrawing chloro moiety on a phenyl ring (1c) gave
3c in moderate yield even for a longer reaction time together
with a similar yield of the homoallylic alcohol 2c (Entries 5
and 6). The secondary alcohol 1d was not converted to the
tetrahydrofuran 3d at all and only the homoallylic alcohol 2d
5 mol% MoO2(acac)2
or MeReO3
10 mol% BHT
Ph OH
Ph
Ph
Ph
Ph
OH
+
PhCl (1 mL)
80 °C, 48 h
O
Ph
2a
Mo: 17%
Re: trace
1a
0.2 mmol
3a
Mo: 82%
Re: 98%
•
5 mol% VOSO4 nH2O
10 mol% BHT
PhCl (1 mL)
80 °C, 48 h
1a
2a
91%
0.2 mmol
Scheme 1.
Copyright Ó 2005 The Chemical Society of Japan

Chemistry Letters Vol.34, No.6 (2005)
791
Table 2. Effect of radical scavenger
O
O
M
R1
5 mol% MoO2(acac)2
10 mol% radical scavenger
R2
Ph OH
Ph
Et
PhCl (1 mL)
80 °C, 48 h
O
Et
R1 OH
R2
O
MOXn
R1
O
HX
R1 OMXn-1
1f
0.2 mmol
3f
OMXn-1
R2
R2
1
A
B
1
Yield/%a
(M = Mo, Re)
Entry
Radical scavenger
1
2
3
4
5
None
BHT
51
91
55
63
40
Galvinoxyl
R1
Hydro-
alkoxylation
R1
R2
m-Dinitrobenzene
OH
R2
O
1,1-Diphenyl-2-picrylhydrazyl
2
3
aIsolated yield based on 1d employed.
Scheme 2.
was obtained in moderate yield (Entries 7 and 8). On the other
hand, other tertiary cyclopropanemethanols like 1e–1h also gave
the corresponding tetrahydrofurans in good to high yields
(Entries 9–16). The methanol having dialkyl substituent (1i)
gave 3i in good yield (Entries 17 and 18).
References and Notes
1
For reviews, see: a) D. Tunemoto and K. Kondo, J. Synth. Org.
Chem. Jpn., 35, 1070 (1977). b) M. Murakami and S. Nishida,
J. Synth. Org. Chem. Jpn., 41, 22 (1983). c) H. N. C. Wong,
M.-Y. Hon, C.-W. Tse, Y.-C. Yip, J. Tanko, and T. Hudlicky,
Chem. Rev., 89, 165 (1989). d) L. K. Sydnes, Chem. Rev., 103,
1133 (2003). e) H.-U. Reissig and R. Zimmer, Chem. Rev.,
103, 1151 (2003).
Next, the effect of a radical scavenger such as BHT, gal-
vinoxyl, m-dinitrobenzene, and 1,1-diphenyl-2-picrylhydrazyl
was investigated to obtain some information about the reaction
pathway. As summarized in Table 2, the reaction was not pre-
vented in the presence of any radical scavengers, showing that
this catalytic reaction may proceed via an ionic pathway.
When homoallylic alcohol 2a was heated in chlorobenzene
in the presence of either MoO2(acac)2 or ReMeO3 as a catalyst,
3a was formed in 64–67% isolated yield (Eq 3). Further, when
the isomerization of 1a was carried out in the presence of a cat-
alytic amount of K2CO3, 2a was obtained as a major product to-
gether with 3a (Eq 4). These results show that 2a is a precursor
for 3a and also that a simple acid-catalyzed reaction might be
ruled out for the formation of the product 2 from 1.
2
3
Y. Maeda, T. Nishimura, and S. Uemura, Chem. Lett., 34, 380
(2005).
a) H. Pauling, D. A. Andrews, and N. C. Hindley, Helv. Chim.
Acta, 59, 1233 (1976). b) P. Chabardes, E. Kuntz, and J.
Varagnat, Tetrahedron, 33, 1775 (1977). c) T. Hosogai, Y.
Fujita, Y. Ninagawa, and T. Nishida, Chem. Lett., 1982, 357.
d) S. Matsubara, T. Okazoe, K. Oshima, K. Takai, and H.
Nozaki, Bull. Chem. Soc. Jpn., 58, 844 (1985). e) S. Oi and
B. M. Trost, J. Am. Chem. Soc., 123, 1230 (2001). f) B. M.
Trost, C. Jonasson, and M. Wucher, J. Am. Chem. Soc., 123,
12736 (2001). g) B. M. Trost and C. Jonasson, Angew. Chem.,
Int. Ed., 42, 2063 (2003).
5 mol% MoO2(acac)2
or MeReO3
4
5
For transposition of allylic alcohols: a) J. Belgacem, J. Kress,
and J. A. Osborn, J. Am. Chem. Soc., 114, 1501 (1992).
b) F. R. Fronczek, R. L. Luck, and G. Wang, Inorg. Chem.
Commun., 5, 384 (2002).
For transposition of allylic alcohols: a) S. Bellemin-Laponnaz,
H. Gisie, J. P. Le Ny, and J. A. Osborn, Angew. Chem., Int. Ed.
Engl., 36, 976 (1997). b) J. Jacob, J. H. Espenson, J. H. Jensen,
and M. S. Gordon, Organometallics, 17, 1835 (1998). c) S.
Bellemin-Laponnaz, J. P. Le Ny, and J. A. Osborn, Tetrahe-
dron Lett., 41, 1549 (2000). d) B. D. Sherry, A. T. Radosevich,
and F. D. Toste, J. Am. Chem. Soc., 125, 6076 (2003). e) C.
Morrill and R. H. Grubbs, J. Am. Chem. Soc., 127, 2842
(2005).
10 mol% BHT
(3)
2a
0.2 mmol
3a
Mo: 64%
Re: 67%
PhCl (1 mL)
80 °C, 48 h
5 mol% MoO2(acac)2
or MeReO3
5 mol% K2CO3
10 mol% BHT
(4)
+
1a
2a
3a
PhCl (1 mL)
80 °C, 48 h
0.2 mmol
Mo: 72%
Re: 73%
Mo: 26%
Re: 27%
A proposed catalytic cycle for the present isomerization is
shown in Scheme 2: 1) an oxo metal complex reacts with cyclo-
propanemethanol to afford an oxo metal cyclopropanemethano-
late (A), 2) [3,3]sigmatropic rearrangement of this alcoholate
involving the C–C bond cleavage occurs to give an oxo metal
homoallylic alcoholate (B) which reacts with another cyclopro-
panemethanol to give the homoallylic alcohol 2 and the oxo
metal methanolate A, and 3) the hydroalkoxylation6 of the
initially produced homoallylic alcohol occurs intramolecularly
to give the tetrahydrofuran derivative 3.7
In summary, we have found a novel molybdenum- and rhe-
nium-catalyzed isomerization of cyclopropanemethanols into
tetrahydrofurans. The salient features of this catalytic behavior
deserve detailed study of the ring opening reaction as well as
the cyclization reaction of homoallylic alcohols.
6
For recent representative examples of the hydroalkoxylation
of alkenes catalyzed by metal catalysts, see: a) K. J. Miller,
T. T. Kitagawa, and M. M. Abu-Omar, Organometallics, 20,
4403 (2001). b) K. Miura and A. Hosomi, Synlett, 2003, 143.
c) K. Miura, T. Takahashi, and A. Hosomi, Heterocycles, 59,
93 (2003). d) H. Qian, X. Han, and R. A. Widenhoefer,
J. Am. Chem. Soc., 126, 9536 (2004). e) Y. Oe, T. Ohta, and
Y. Ito, Synlett, 2005, 179. f) Y. Matsukawa, J. Mizukado,
H.-D. Quan, M. Tamura, and A. Sekiya, Angew. Chem., Int.
Ed., 44, 1128 (2005).
7
The hydroalkoxylation reaction of homoallylic alcohols might
proceed via a similar pathway as proposed in Ref. 6d. Howev-
er, the direct formation of 3 from the intermediate B could not
be ruled out at the present stage.
Published on the web (Advance View) May 7, 2005; DOI 10.1246/cl.2005.790