Simple metal salts supported on montmorillonite as recyclable catalysts for intramolecular hydroalkoxylation of double bonds in conventional and VOC-exempt solvents

Article abstract of DOI:10.1039/c4gc01990c

We describe herein an efficient and particularly sustainable catalytic system for the intramolecular hydroalkoxylation of double bonds. A heterogeneous catalyst based on the impregnation of benign metals such as iron and bismuth on montmorillonite was used for a highly atom-economic transformation in DMC, a non-VOC solvent. The transformation allowed the formation of a large range of cyclic ethers from the corresponding unsaturated alcohols and the catalyst could be recycled several times.

Full text of DOI:10.1039/c4gc01990c

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Simple metal salts supported on Montmorillonite as recyclable catalysts
for intramolecular hydroalkoxylation of double bonds in conventional
and VOC exempt solvents
Irene Notar Francesco,a Bastien Cacciuttolo,b Mathieu Pucheaultb and Sylvain Antoniottia*
5
Received (in XXX, XXX) Xth XXXXXXXXX 200X, Accepted Xth XXXXXXXXX 200X
DOI: 10.1039/b000000x
We describe herein an efficient and particularly sustainable catalytic system for the intramolecular hydroalkoxylation of double bonds. A
heteregenous catalyst based on the impregnation of benign metals such as iron and bismuth on Montmorillonite was used for a highly
atomꢀeconomical transformation in DMC, a nonꢀVOC solvant. The transformation allowed the formation of a large range of cyclic ethers
10 from the corresponding unsaturated alcohols and the catalyst could be recycled several times.
Intramolecular hydroalkoxylation of olefins is the most
achieve this goal, various stategies have been developped
straightforward and atomꢀeconomical route to cyclic ethers. The 35 including for example the use of solid acid catalysts10 such as
reaction can be promoted or catalysed by a large variety of
15 Bronsted or Lewis acids in homogeneous conditions1,2
heterogeneous catalysts such as zeolites.3,4 The methodology has
proven its utility in the synthesis of fine chemicals including
bioactives5ꢀ7 and fragrant molecules,8,9 for example (Fig. 1).
zeolites11ꢀ14 or acidic resins (Amberlyst, nafion),15,16 attachment
of metal complexes or salts to a solid support such as silica17,18 or
nafion19 by physisorption, or by covalent linkage of one or more
ligand.20 The nonꢀcovalent linkage of catalysts onto solid
40 supports has been developped with success through “catch and
release” strategies.21 Recently, supported metal nanoparticles
(e.g. gold nanoparticles) have appeared in the litterature as
efficient catalysts in various chemical processes.22ꢀ26
O
We have been looking for a cheap and readily available
45 unprocessed solid material to support simple metal salts and use
these supported metals as catalysts for the intramolecular
hydroalkoxylation of double bonds. In this regards,
Montmorillonite (MMT) appeared very appealing to us to provide
supported metal catalysts with limited footprints among other
50 advantages as supporting material.27,28 We previously reported
the use of MMTꢀsupported gallium species as catalyst for 1,6ꢀ
enynes cycloisomerisation.29
20
O
(-)-cis-Doremox
Rose odor
(-)-Ambrox
Ambergris
O
O
MeO
OH
The catalysts were prepared by impregnation of solutions of
sustainable metals salts such as BiCl3, FeCl3, and CuCl2 in
55 MeOH. Under an inert atmosphere, 10 mmol of anhydrous
precursor was added to 10 g of preꢀlyophilised MMT and 50 mL
of MeOH. The mixture was stirred vigorously for 4 hours, filtered
and then triturated in a minimum of methanol. The material was
dried under vacuum for 24 h and stored under inert atmosphere.
60 Characterisation of the catalysts involved ICPꢀMS titration of the
metal contents, indicating 4.87% w/w for Bi@MMT, 2.67% w/w
for Fe@MMT, and 2.04% w/w for Cu@MMT. Small angle XRD
analysis confirmed the insertion of metal cations in the MMT
interlayers. In the case of BiꢀMMT, signals attributed to crystals
65 of BiOCl, presumably formed upon hydrolysis within the MMT,
could be observed. Those cations are under their most stable
oxidation state (Bi3+, Fe3+/Fe2+ (53/47) and Cu2+) as witnessed by
XPS analysis (See Electronic Supplementary Information).
(±)-Centrolobine
Antiparasitic, antibiotic
(-)-cis-Rose oxide
25
Rose odor
OH
O
O
O
O
H
H
H
H
O
O
H
O
HOOC
N
O
H
O
OH
H
O
NMe2
Panamycin 607
Platensimycin
Antibiotic
Antibiotic
Fig. 1. Fine chemicals featuring cyclic ether frameworks obtained by
intramolecular double bonds hydroalkoxylation.
30
To go beyond the laboratory towards largeꢀscale applications, the
ideal catalyst should however not only by efficient in terms of
yields and selectivity, but also offer recycling capabilities. To
We started our study with a screening of the reaction conditions
70 and solvents including conventional and VOC exempt solvents
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DOI: 10.1039/C4GC01990C
such as dimethyl carbonate (DMC) and 2ꢀmethyltetrahydrofuran
not in solution phase after leaching from the support. Thus,
(Table 1). DMC is particularly attractive since it is considered 45 supported catalysts FeꢀMMT and BiꢀMMT were equal or superior
nonꢀVOC thanks to its low vapour pressure (2400 Pa, to be
compared to 2340 for water and 29000 for toluene), and have
good solvent properties (bp=90 °C, δ=3.1, ꢁ=0.91 D).30
to their homogeneous equivalents in terms of both activity and
selectivity.
FeꢀMMT being identified as the most potent catalyst, we further
performed a recycling study in our optimised conditions in DMC
5
DMC and nitromethane appeared as the most suitable solvents for
the model reaction of olefinic alcohol 1a converted with total 50 (Fig. 2). Satisfyingly, the FeꢀMMT catalyst could be recycled 4
Markovnikov regioselectivity to cyclic ether 1b. With BiꢀMMT,
yields beyond 75% in 5 hours at 80 °C were obtained (entries
10 1,2). Reaction in acetonitrile needed prolonged reaction times (24
h, entry 3) to proceed efficiently, while the other tested solvents
times and at the 5th cycle still allowed to reach 80% yield of
cyclised product 1b upon total conversion of 1a. This result
suggested that the possible leaching of iron species was not
significant in DMC at 80 °C. It is interesting to note that the
gave moderate results within the same reaction time (30ꢀ70%, 55 recycling capacities in CH3NO2 were found to be lower (ESI page
entries 4ꢀ7).
S13).
Ph
Ph
Ph
Ph
M-MMT (5% mol)
Solvent, T°C
100
90
80
70
60
50
40
30
20
10
0
15
O
HO
60
1a
Table 1. Solvents and conditions screeninga
1b
Entry
1
2
3
4
5
6
7
8
M
Bi
Bi
Bi
Solvent
DMC
CH3NO2
CH3CN
T (°C) Time (hr) GC Yieldb
80
80
80
80
80
80
80
80
80
80
80
30
30
30
80
80
5
5
76%
77%
76%
70%
20%
45%
60%
86%
83%
36%
81%
77%
80%
7%
65
24
24
24
24
24
7
24
24
24
24
4
Bi CH3(CO)CH3
Bi
Bi
Bi
Fe
Fe
Cu
Cu
Bi
2ꢀMeꢀTHF
AcOEt
DCE
DMC
CH3NO2
70
9
10
11
12
13
14
DMC
Cycle 1
Cycle 2
Cycle 3
Cycle 4
Cycle 5
CH3NO2
CH3NO2
CH3NO2
CH3NO2
CH3NO2
CH3NO2
Fig. 2. Recycling studies. Yields of 1b in % obtained after 7 hrs at 80 °C
Fe
Cu
75
in DMC with recycled FeꢀMMT.
24
7
24
15 MMT
16
0%
0%
To further estimate the possibility of leaching in these systems,
kinetic plots of reactions of FeꢀMMT and BiꢀMMT in DMC were
recorded and a hot filtration test was performed after 75 mins
reaction time.31 After removal of the catalyst, the concentration of
80 cyclised product 1b in the filtrate did not change over a period of
220 mins, ruling out the possibility of hidden homogeneous
catalysis (ESI page S13).
ꢀ
a
Reaction conditions: substrate (0.25 mmol), anhydrous and degassed
20 solvent (1 mL) and catalyst (5 mol% metal/substrate ratio). b Determined
by GCꢀTCD by external calibration. Trace of hydroarylation product 1b’
resulting from the 6ꢀendoꢀtrig addition of one phenyl group across the
double bond could be observed.
We only focused on DMC and nitromethane for further catalysts
25 testing and obtained again very good isolated yields of cyclic
ether with FeꢀMMT (entries 8,9). With CuꢀMMT, the reaction
proceeded poorly in DMC with a low 31% yield, while in
nitromethane 81% yield was obtained (entries 10,11). In a last set
of experiments, the temparature was lowered to 30°C and the
30 reaction conducted in nitromethane. BiꢀMMT yielded 77% of
product after 24 hrs (entry 12), but FeꢀMMT was the most
efficent catalyst in these conditions with 80% isolated yield after
only 4 hrs (entry 13). CuꢀMMT did not allow to reach 10% yield
at this temperature (entry 14 ). Control experiments without metal
35 (MMT alone) and without additives were performed and showed
no background reaction (entries 15,16). The performance of these
supported catalysts was compared with their homogeneous
counterparts. Thus, the reaction of 1a was performed with 5
mol% FeCl3 and BiCl3 in DMC at 80 °C. After 7 hrs, cyclic
40 product 1b was formed in 76% yield with FeCl3, along with 5%
of FriedelꢀCrafts product 1b’. With BiCl3, substrate 1a was
recovered unchanged, indicating the presence of the active Bi
species in the heterogeneous reaction within the solid catalyst and
With this sustainable catalytic system in hand, we next turned our
attention to the reaction substrate scope (Table 2). Unsaturated
85 secondary alcohols such 2a and 3a reacted readily in the presence
of 5 mol% FeꢀMMT in DMC at 80°C to yield regioselectively the
corresponding 6ꢀmembered cyclic ethers 2b and 3b in excellent
yields (entry 1, 2). The introduction of an aryl substituent in
geminal position with the hydroxyl group as in 4a was
90 detrimental to the intramolecular hydroalkoxylation and the
cyclic ether 4b was formed in a modest 38%, together with 12%
of styryl derivative obtained upon the dehydration of 4a (entry 3).
The high mass loss observed was presumably due to
polymerisation reaction. Substrate 5a however, with the phenyl
95 substituent one ethylene away from the alcohol function, could
efficiently cyclise to 5b with 89% yield under the same
conditions (entry 4). With orthoꢀprenylated phenol 6a, the
conversion was 81% in the same conditions, and the expected
cyclic ether 6b was formed in 63% yield (entry 5). Bisꢀ
100 hydroxylated substrate 7a was prepared from biosourced glycerol
and afforded a mixture of 5 and 6ꢀmembered cyclic ketals 7c and
2
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7d in 51 and 31% yield, respectively (entry 6). The reaction
selectively towards the formation of the 5ꢀmembered ring 8c (2
presumably proceeded by isomerisation/cyclisation, involving the
dias 1:1) in 59% yield (entry 7). TBDMS protecting group was
formation of an enol ether intermediate, in a process already 10 not stable in our conditions (not shown). With a linear substrate
described with αꢀmethallyloxy carboxylic acids in the presence of
Cu(OTf)2 as the catalyst.32 Both products were formed as
equimolar mixtures of diastereomers. After conversion of the
primary alcohol function into its acetate, the reaction proceeded
such as 9a, featuring an internal disubstituted double bond, the
reaction required both high temperature and longer reaction time
in CH3NO2 to reach 89% conversion and to deliver
regioselectively the product 9b in 62% yield (entry 8).
5
15 Table 2. Substrate scopea
T Time
(°C) (hr)
Products,
Isolated Yield
Entry
Substrate
M Solvent
1
Fe DMC 80
Fe DMC 80
7
2b, 98%b
2a
2
3
7
O
C5H11
3a
3b, 89%
4b, 38%c
5b, 89%
Fe DMC 80
Fe DMC 80
Fe DMC 80
7
7
7
4a
4
O
5a
5
6
6b, 63%d
6a
Fe DMC 80 24
7a
8a
7c (2 dias 1:1), 51%
7d (2 dias 1:1), 31%
7
8
Fe DMC 80 20
Fe CH3NO2 100 72
8c (2 dias 1:1), 59%
9b, 62%e
(Z)ꢀ9a
9
Fe CH3NO2 100 2.5
Fe CH3NO2 100 24
Fe DMC 80 48
Bi DMC 80 48
(Z)ꢀ10a
(E)ꢀ10a
10b, Quant.
10b, Quant.
10
11
12
ꢀf
ꢀf
11a
11a
13
Fe DMC 80
5
(E)ꢀ12a
12b, 40%
12b’ (trans/cis 2:1), 39%
14
15
16
17
(E)ꢀ12a
(E)ꢀ12a
(E)ꢀ12a
(E)ꢀ12a
Bi DMC 80 24
Fe CH3NO2 80
Bi CH3NO2 80 24
Bi DCE 80 24
12b, 32% + 12b’ (trans/cis 2:1), 42%
12b, 21% + 12b’ (trans/cis 4:1), 79%
12b’ (trans/cis 2:1), 96%
5
12b’ (trans/cis 2:1), 92%
18
Fe DMC 80 24
13b, 56%g
(E)ꢀ13a
19
20
(E)ꢀ13a
(E)ꢀ13a
Fe CH3NO2 80 21
Bi CH3NO2 80 21
13b, 71%
Mixture
a
b
Reaction conditions: substrate (1 mmol), anhydrous and degassed solvent (2 mL) and catalyst (5 mol% metal/substrate ratio). Reaction performed in
DMCꢀd6 using benzene as internal standard. c Along with 12% of dehydration product. d Conversion 81%. e Conversion 89%. Traces of 6ꢀmembered ring
product were observed (~5%). f No conversion, quantitative recovery of the starting material. g Conversion 63%.
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Substrate (Z)-10a afforded an example of internal disubstituted
double bond reacting efficiently towards the formation of the 6ꢀ
membered ring 10b obtained in an excellent 99% yield but
required heating in CH3NO2 at 100 °C (entry 9). The presence of
the phenyl substituent allowed both a perfect regiocontrol of the
nucleophilic attack of the hydroxyl group and a sufficient
stability of the reactive intermediates. Its stereoisomer (E)ꢀ10a
reacted similarly, ableit in longer reaction time (entry 10).
Substrate 11a featuring a monosubstituted double bond did not
10 react neither in the presence of FeꢀMMT or BiꢀMMT at 80 °C in
DMC and was quantitatively recovered unchanged after 48 hrs
(entry 11,12). Homogeneous versions of the reaction with this
substrate and analogs have been previously reported to require
the dual action of an aluminiumꢀbased catalyst and high
15 temperatures (250 °C)33 or the combination of FeCl3 and silver
triflate34 as additive to proceed efficiently.
With this system in hand, we evaluated the possiblity to catalyse
tandem reaction involving the formation of CꢀC and CꢀO bonds
with polyunsaturated alcohols. Firstly, the orthoꢀgeranylated
20 phenol (E)ꢀ12a was reacted in the presence of 5 mol% FeꢀMMT
or BiꢀMMT in DMC at 80°C, and a mixture of the tricyclic
product 12b’ (in the form of a 2:1 diastereomeric mixture in favor
of the transꢀfused ring system), resulting from the double
cyclisation of 12a, and the monocyclic ether 12b were obtained
25 unselectively (entries 13,14). With FeꢀMMT in CH3NO2, the
selectivity in favour of 12b’ was increased to 79% (entry 15).
Interestingly, the tricyclic product 12b’ was the sole product
obtained in 96 and 92% isolated yields when the reaction was run
with BiꢀMMT in CH3NO2 and DCE, respectively (entries 16, 17).
30 In an effort to obtain the commercial odorant Ambrox®, we tested
our system for a tandem reaction with substrate (E)ꢀ13a.
However, in contrast with the case of substrate (E)ꢀ12a, only one
single cyclisation was observed to yield the tetrahydrofuran
derivative 13b in 56ꢀ71% yield (entries 18, 19). The use of Biꢀ
35 MMT resulted in the formation of a mixture of isomerised
products in the same reaction conditions, but no tandem product
(entry 20).
Conclusions
In summary, we have developped and described herein an
55 efficient and particularly sustainable catalytic system based on
the use of benign metals such as iron and bismuth supported on a
natural inorganic material to allow for an highly atomꢀeconomical
transformation in DMC, a nonꢀVOC solvant. The transformation
allowed the formation of a large range of cyclic ethers from the
60 corresponding unsaturated alcohols by intramolecular
hydroalkoxylation and the catalyst could be recycled several
times.
5
Acknowledgements
This work was supported by the University Nice Sophia
65 Antipolis, the CNRS, and the ANR program CD2I (Nanocausys
project, grant number 12ꢀCDIIꢀ0010ꢀ02). We are grateful to Dr
Charles Fehr (Firmenich, CH) for a kind gift of compound (E)ꢀ
13a and Dr Cyril Aymonier and Baptiste Giroire from ICMCB
(Bordeaux, France) for material analyses.
70 Notes and references
a
Institut de Chimie de Nice, UMR 7272 CNRS ꢀ Université Nice Sophia
Antipolis, Parc Valrose, 06108 Nice, France. Eꢀmail
:
sylvain.antoniotti@unice.fr
b
Institut des Sciences Moléculaires, UMR 5255 CNRS ꢀ Université de
75 Bordeaux, 351 cours de la libération, 33405 Talence cedex, France
† Electronic Supplementary Information (ESI) available: Procedures and
full spectral data of products and catalysts. See DOI: 10.1039/b000000x/
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