Simple salts of abundant metals (Fe, Bi, and Ti) supported on montmorillonite as efficient and recyclable catalysts for regioselective intramolecular and intermolecular hydroalkoxylation reactions of double bonds and tandem processes

Article abstract of DOI:10.1039/c5ra25176a

The transfer of catalytic hydroalkoxylation reactions of olefins from homogeneous to heterogeneous conditions has been studied using two types of solid catalysts, namely montmorillonite (MMT) doped with metal cations and metal nanoparticles supported on oxides. In the case of intramolecular reactions, 38-99% yields of cyclic ethers have been obtained using Fe-MMT and Bi-MMT both in CH₃NO₂ and dimethyl carbonate (DMC) compared with other supported metal salts or metal nanoparticles. In the case of more challenging intermolecular reactions, conversions up to 72% and yields up to 54% were obtained with metal-doped MMT as well, such as Fe-, Bi-, and Ti-MMT. In this paper, we detail the substrate scope and limitations for both classes of reactions and tandem processes, their transposition in flow and some mechanistic insights concerning the active species, in processes identified as truly heterogeneously catalysed. As a general trend, it was observed that trisubstituted double bonds allowed the best results both in intra- and intermolecular reactions. The transfer of homogeneous catalysts onto heterogeneous ones in the case of Fe-MMT and Bi-MMT was successful and even allowed enhanced catalytic activities in the case of Bi-MMT.

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PAPER
Simple salts of abundant metals (Fe, Bi, and Ti) supported on
Montmorillonite as efficient and recyclable catalysts for regioselective
intramolecular and intermolecular hydroalkoxylation reactions of
double bonds and tandem processes
5
Irene Notar Francesco,a Bastien Cacciuttolo,b Oana Pascu,c Cyril Aymonier,c Mathieu Pucheaultb and
Sylvain Antoniottia*
Received (in XXX, XXX) Xth XXXXXXXXX 200X, Accepted Xth XXXXXXXXX 200X
DOI: 10.1039/b000000x
The transfer of catalytic hydroalkoxylation reactions of olefins from homogeneous to heterogeneous
10 conditions has been studied using two types of solid catalysts, namely Montmorillonite (MMT) doped
with metal cations and metal nanoparticles supported on oxides. In the case of intramolecular reactions,
38ꢀ99% yields of cyclic ethers have been obtained using FeꢀMMT and BiꢀMMT both in CH3NO2 and
dimethylcarbonate (DMC) compared with other supported metals salts or metal nanoparticles. In the case
of more challenging intermolecular reactions, conversions up to 72% and yields up to 54% were obtained
15 with metalꢀdoped MMT as well, such as Feꢀ, Biꢀ, and TiꢀMMT. In this paper, we detail the substrate
scope and limitations for both classes of reactions and tandem processes, their transposition in flow and
some mechanistic insights concerning the active species, in processes identified as truly heterogeneously
catalysed. As a general trend, it was observed that trisubstituted double bonds allowed the best results
both in intraꢀ and intermolecular reactions. The transfer of homogeneous catalysts onto heterogeneous in
20 the case of FeꢀMMT and BiꢀMMT was successful and even allowed enhanced catalytic activities in the
case of BiꢀMMT.
45 homogeneous catalysts to inert supports, the latter being either
organic (polymers, dendrimers, polysaccharides, …) or inorganic
(mesoporous silica, metal oxides, aluminosilicates, …).8ꢀ10
Introduction
Metalꢀbased catalysts, and in particular transition metalꢀbased
catalysts, have been successfully used for decades in a myriad of
25 organic transformations.1ꢀ4 Most of the developpements of metal
catalysis in fine chemicals transformations have been designed in
organic solvents which allow, in the same phase, preꢀcatalysts,
catalysts, intermediates, substrates and products solubilisation
(homogeneous catalysis). Despite many assets, homogeneous
30 metalꢀbased catalysis rarelly go beyond the laboratory scale. The
main reasons are related to cost (metal and ligands), tedious
recycling operations, scale up issues, and in the case of ther
synthesis of active pharmaceutical principles, the presence of
residual metal in the final product.5 So, for industrial applications,
35 costꢀeffective solid catalysts are prefered, allowing an easy
recycling, and/or amenability to continuous processes.6 However,
solid catalysts have been so far mostly designed for commodity
chemicals’ synthesis, and do not offer the same degree of
selectivity and efficiency when dealing with sophisticated
40 reactions.
In the context of sustainable chemistry, a stronger stress is placed
to design new catalysts being based on abondant metals and
50 easily recyclable, most of the metals conventionally used in
catalysis being under a threat of depletion within 50 years.11
Metals such as iron, copper, and bismuth have thus attracted the
attention of chemists, these metals being abundant and having
also acceptable (eco)toxicity profiles.12ꢀ16
55 For all these reasons, we have chosen to study simple and salts of
sustainable metals supported on clays such as MMT, a layered
inorganic material with exchangeable cations in the interlamellar
space. MMT is a cheap, natural and abundant inorganic material
with both Lewis and Bronsted acidic site very attractive as a
60 support for catalysts.17 To test these catalysts, we have selected
the hydroalkoxylation of olefins: a very useful reaction widely
studied in homogeneous catalysis, and rarely in heterogeneous
catalysis.18ꢀ36 Zeolites have been the most studied heterogeneous
catalysts for this reaction and generally required elevated
65 temperatures (85ꢀ150 °C) to proceed, sometimes with selectivity
issues.34,37,38 Lanthanide triflates could be used and recycled
efficiently in intramolecular reaction at 120 °C upon their
sequestration in ionic liquids.36 Gold nanoclusters were also
As a result, a significant part of current research in catalytic
methodologies is thus directed towards the transfer of the
reactions from homogenous to heterogeneous conditions.7 The
most straightforward strategy probably consists in attaching
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reported as efficient catalysts in intramolecular reactions,
although limited to monosubstituted olefins.30
In a preliminary communication, we reported our results in the
protonolysis.19 These differences in terms of intermediates
influence the regioselectivity and the ringꢀclosure overall
efficiency. Substrates with trisubstituted double donds, leading to
intramolecular version of the reaction catalysed by Fe(III) and 60 tertiary carbenium ions, are efficiently cyclised under Bronsted
5
Bi(III) salts supported on MMT.39 In the present paper, our
intention is to provide full experimental studies, the scope and
limitations of the intramolecular reaction, as well as new data for
the intermolecular version, introducing TiꢀMMT as catalyst, and
a mechanistic rationale.
acidꢀtype activation while substrates with
a
terminal
monosubstituted double bond are more efficiently cyclised by
transition metalꢀcatalysts. Hybrid mechanisms based on Lewis
acidꢀassisted Bronsted acid catalysis have been invoked in
65 reactions with metal triflates where activation of the hydroxyl
group by the Lewis acid provides an acidified proton further
transferred to the double bond.22
10 Results and discussion
Catalysts preparation and characterisation
"H+"
OH
Metal doped Montmorillonites (MꢀMMT)
- H+
H
MꢀMMT materials were perpared by impregnating solutions of
chlorides salts in MeOH with lyophilized MMT. Namely, BiCl3,
15 FeCl3, CuCl2, and TiCl4 were added to a suspension of NaꢀMMT
in MeOH in a 1 mmol/g of metal salt/MMT ratio. Exchange
reached the thermodynamic equilibrium within few hours as
monitored by conductimetry using a Na+ꢀselective electrode.
After filtration and trituration in degased MeOH, MꢀMMT were
20 dried extensively under reduced pressure for 24 h. ICPꢀMS
titration of metal content in the modified clays showed between
1.8 and 4.9% w/w metal content (CuꢀMMT 2.04%, FeꢀMMT
2.67%, BiꢀMMT 4.87%, TiꢀMMT 1.81%). As witnessed by XPS
analysis, the oxidation state of inserted metal ions remained
25 identical except in the case of Fe where a Fe3+/Fe2+ 53/47 ratio
was shown to be the thermodynamic resulting mixture of the
process. SMAXS analysis clearly showed metal insertion in the
interlayer spacing, although in the case of BiꢀMMT remaining
BiOCl formed upon hydrolysis of BiCl3 was simultaneously
30 observed.
70
OH
O
H
O
MLn
75
- MLn
MLn-1
+ L
Scheme 1. Generic reaction pathways for H+ꢀ and metalꢀcatalysed
intramolecular hydroalkoxylation
80
We initially screened a series of supported catalysts, either MMTꢀ
supported metal salts and metal oxidesꢀsupported transition metal
nanoparticles to possibly observed the abovementionned types of
activation on substrates 1a and 1b. (Table 1).
85 Table 1. Initial screening of catalysts and conditions for the
intramolecular hydroalkoxylation of olefins.a
R1
O
R1
R2
OH
Silica supported Metal Nanoparticles (M NP@SiO2)
Catalyst
For the fabrication of silica supported metal/metal oxide
nanoparticles (Table 1, entries 1ꢀ5), we used supercritical CO2
(scCO2) as the main solvent in a batch mode setup. A detailed
35 description of the setup and experimental conditions can be found
elsewhere.40 In summary, in a stainless steel batch reactor, the
silica support is mixed with a metal hexafluoroacetylacetonate
precursor (5% w/w of metal loading) in the absence of H2 (as
reducing agent) but using EtOH, as coꢀsolvent and reducing
40 agent, together with a surfactant (hexadecylamine) typically used
in wet chemistry for metal reduction. After reaction, a fast
depressurization in parallel with CO2 purging yielded dry clean
powder in the form of metal/metal oxide nanoparticles deposited
on the silica support (catalyst physicochemical properties and
45 TEM images are presented in ESI).
R2
Solvent, T°C
R2
R2
1a
R1=Me, R2=H:
2a
2b
1b
R1=H, R2=Ph:
Entry R1 R2
Catalyst
Pt NPs/SiO2
PtꢀCu NPs/SiO2
Cu NPs/SiO2
CuxO NPs/SiO2
Solventb T°C Conversion Yield
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Me
Me
Me
Me
H
H
H
H
H
A
A
40 °C
40 °C
0%
0%
0%
0%
0%
0%
0%
0%
0%
35%
100%
100%
100%
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
A
A
A
A
A
B
B
40 °C
40 °C
40 °C
60 °C
60 °C
40 °C
40 °C
Me
H
H
H
H
H
H
H
H
H
H
H
H
H
SnO2 NPs/SiO2
Ph Au NPs/TiO2
Ph Au NPs/TiO2
c
c
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
NiꢀLDH
MgꢀLDH
FeꢀMMT
BiꢀMMT
BiꢀMMT
BiꢀMMT
Fe-MMT
CuꢀMMT
CuꢀMMT
FeꢀMMT
None
CH3NO2 40 °C
DMC 80 °C
CH3NO2 80 °C
CH3CN 80 °C
35%
76%
77%
76%
86%
36%
81%
83%
ꢀ
Intramolecular hydroalkoxylation
Intramolecular hydroalkoxylation of olefins is the most direct and
atomꢀeconomical route to cyclic ethers. It is typically achieved
following two disctincts modes of activation and mechanisms
50 (Scheme 1). In the former, the double bond is activated by a
Bronsted or a Lewis acid facilitating the nucleophilic attack of the
pendant hydroxyl group: carbenium intermediates are
involved.41,42 In the latter, transition metals are first coordinated
to the double bond which then undergo the attack of the pendant
55 hydroxyl group resulting in the formation of an organometallic
intermediate featuring a carbonꢀmetal bond eventually cleaved by
DMC 80 °C 100%
DMC 80 °C
CH3NO2 80 °C
CH3NO2 80 °C
DMC 80 °C
39%
100%
100%
0%
a
Reaction conditions: substrate (0.25 mmol), anhydrous and degassed
90 solvent (1 mL) and catalyst (1ꢀ5 mol% metal/substrate ratio). A: Either
CH3NO2 or DCE. B: Either toluene, CH3OH, heptane, CH3CN, dioxane,
b
c
acetone, AcOEt, THF, H2O/THF (9:1), DMF, CH3NO2, or DCE.
Commercially available from Strem.
2
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The metal choice was guided in both cases by the frequency of
densely substituted ones presenting increased steric hindrance but
leading ot more stable carbenium ions.
A series of unsaturated alcohols was thus prepared following
several synthetic routes (see ESI for details). Secondary
appearance of those in homogenous catalysis for
hydroalkoxylation reactions of multiple bonds: Pt, Cu, Au and Sn
for NPs, Fe, Bi, and Cu for supported metal salts.
5
Unfortunately, in our reaction conditions, metal/metal oxides NPs 45 homoallylic alcohols were obtained by Grignard reaction of
of Pt, PtꢀCu, Cu, CuxO, Au and SnO2 supported on SiO2 or TiO2
(entries 1ꢀ7), as well as NiꢀLDH and MgꢀLDH (entries 8,9), were
unreactive. MMT doped with metal cations such Fe(III) (Feꢀ
MMT) exhibited a promising 35% yield in cyclised product 2b at
prenylmagnesium bromide with the corresponding aldehydes.
Methallyl ethers derived from glycerol were obtained in two steps
from solketal (glycerol acetonide) to yield 1f (R4=H). Upon
protection of the primary alcohol, 1g and 1h were obtained
10 40 °C (entry 10). This result was further confirmed at 80 °C with 50 bearing an acetyl or a TBDMS group, respectively. Primary bisꢀ
BiꢀMMT, FeꢀMMT, and CuꢀMMT allowing conversion rates to
reach 100% and 76ꢀ86% isolated yields of 2b (entries 11ꢀ17).
Control reactions were performed with pristine MMT, and in the
absence of catalyst in CH3NO2 at 80 °C. In these conditions, no
15 conversion of the starting material 1b was observed.
Recyclability of the catalysts was tested with FeꢀMMT in DMC
and CH3NO2 in the reaction conditions of entry 14 (Table 1). In
DMC, the yield of 2b could be maintained 5 times without
significant loss, while in CH3NO2, it rapidly decreased down to
20 zero at 4th cycle.
homoallylic alcohols 1iꢀk were formed by a Wittig reaction of γꢀ
butyrolactol with the corresponding phosphonium salts.43
Allylation of phenol was performed with the desired allylbromide
(allyl, prenyl, geranyl) in the presence of NaH.44
55 Our optimised conditions based on FeꢀMMT in DMC at 80 °C
were thus tested firstly on secondary alcohols bearing a
trisubstituted double bond (Table 2).
Intramolecular hydroalkoxylation of trisubstituted double
bonds by secondary alcohols
60 With substrate 1a, the reaction was almost quantitative in 7 hours
in cyclised product 2a, for which the yield was determined by 1Hꢀ
NMR by the method of external calibration to avoid evaporation
during workꢀup (entry 1). Substrates 1c and 1d were cleanly
cyclised to their corresponding products both in 89% yield
65 (entries 2,3). When a tolyl substituent was introduced (substrate
1e), a competition with the dehydration reaction was observed.
The cyclised product 2e was obtained in 38%, together with 12%
of styrene derivative; we assumed that the mass loss was due to
the polymerisation of the latter at 80 °C in this acidic medium
70 (entry 4). A limitation of this reaction was thus identified when
stabilised carbenium ion could be formed upon the loss of HOꢀ as
exemplified by 1e possibly leading to a benzylic cation.
100
90
Cycle 1
Cycle 2
80
Cycle 3
70
60
50
40
30
20
10
0
Cycle 4
Cycle 5
Table 2. Cyclisation of alcohols 1a, 1cꢀe.a
Fe-MMT (5 mol%) R3
DMC, 80 °C
O
R3
OH
75
DMC
CH3NO2
CH3NO2
Entry
R3
Me
nꢀC5H11
PhꢀCH2ꢀCH2
pꢀCH3C6H4
Substrate Time (h) Conversion Isolated yield
1
2
3
4
1a
1c
1d
1e
7
7
7
7
100%
100%
100%
100%
98%b
89%
89%
38%c
Figure 1. Recycling studies of FeꢀMMT in DMC and CH3NO2.
This significant difference of results only depending on the
25 solvent used suggested that the metal could be washed out of
MMT in polar CH3NO2 (ꢁ=3.46 D), while in DMC (ꢁ=0.91 D)
leaching was avoided. As a result, we selected DMC for the
transposition of the reaction in continuous flow systems.
Satisfyingly, using a 25 cm long stainless steel column with 10
30 mm of internal diameter charged with FeꢀMMT, 15.3 grams of
cyclised product 2a could be obtained in 1 h at a flow rate of 1
mL.minꢀ1 of a 1a 2M solution in DMC. The key parameter of the
system turned out to be the temperature, all reactions conducted
above 75 °C leading to complete conversions with this system.
35 We further evaluated the scope of the reaction in terms of
substrates. With this type of catalysts, a mechanism involving
carbenium ions was likely to occur. In such case, we expected
a
Reaction conditions: substrate (0.25 mmol), anhydrous and degassed
b
DMC (1 mL) and FeꢀMMT (5 mol% metal/substrate ratio). Due to the
80 high volatility of product 2a, the reaction was performed in DMCꢀd6 and
the yield determined by 1HꢀNMR using benzene as internal standard.
c
Along with 12% of dehydration product.
Intramolecular hydroalkoxylation of 1,1-disubstituted double
85 bonds by secondary alcohols derived from glycerol
We next turned our attention to secondary alcohols bearing a
disubstituted terminal double bond derived from glycerol. These
unsaturated alcohols were obtained from solketal by
methallylation/deprotection (1f, R4=H) and with an additional
that the reaction would be influenced by the class of alcohol, for 90 protection of the primary alcohol by an acetyl or a TBDMS group
the reason of steric hindrance and the competition with acidꢀ
40 catalysed dehydration reaction, and the class of the double bond,
(1g and 1h, respectively). These substrates where tested under
our optimised reaction conditions based on FeꢀMMT in DMC at
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Table 4. Cyclisation of alcohols 1iꢀj.a
OH R5
80 °C (Table 3).
Table 3. Cyclisation of alcohols 1fꢀh.a
O
R5
Fe-MMT (5 mol%)
O
+
R5
solvent, 100 °C
R1
R1
Fe-MMT (5 mol%)
O
O
OH
R1=H,
R5=n-C5H11
R1=H,
R5=n-C5H11
2i-k
R4O
R4O
DMC, 80 °C
O
2i
2i'
Entry
R
H
Substrate Time (h) Conversion
Isolated yield
R5=Ph
2j
1
2
3
1f
1g
1h
24
22
7
100%
100%
100%
51% (2 dias 1:1)b
59% (2 dias 1:1)
Mixture
Ac
TBDMS
Isolated
yield
Entry R1, R5 Substrate Solvent Time (h) Conversion
a
1b H, nꢀC5H11 (Z)ꢀ1i
2b
H, Ph (E,Z)ꢀ1j DMC
3c H, nꢀC5H11 (Z)ꢀ1i CH3NO2
DMC
72
72
48
72
92%
82%
4%
89%
100%
100%
72%
Mixture
Mixture
Trace
5
Reaction conditions: substrate (0.25 mmol), anhydrous and degassed
b
DMC (1 mL) and FeꢀMMT (5 mol% metal/substrate ratio). Together
with 31% of the corresponding dioxane.
4
5
H, nꢀC5H11 (Z)ꢀ1i CH3NO2
62%c
H, Ph
H, Ph
(Z)ꢀ1j CH3NO2 2.5
99%
99%
Mixture
With these substrates featuring an oxygen atom on the tether on
6
(E)ꢀ1j CH3NO2
24
24
7b
Me, Me (E,Z)ꢀ1k DMC
10 the allylic position, the reaction yielded 1,3ꢀdioxolanes. This
reaction could either proceed by isomerisation/cyclisation,
involving the formation of an enol ether intermediate, in a
process already described with αꢀmethallyloxy carboxylic acids
in the presence of Cu(OTf)2 as the catalyst,45 or by formation of a
15 transient oxonium ion (Scheme 2). With unprotected substrate 1f,
a 5:3 mixture of the corresponding 1,3ꢀdioxolane and 1,3ꢀdioxane
was obtained upon the nucleophilic attack of either one or the
other alcohol function. With the primary alcohol function blocked
by an acetyl group (substrate 1g), only the 1,3ꢀdioxolane was
20 formed in 59% isolated yield. With TBDMSꢀprotected substrate
1h however, the silyl protecting group was partially removed in
our reaction conditions and a mixture of protected and nonꢀ
protected 1,3ꢀdioxolanes and 1,3ꢀdioxanes was obtained.
a
45 Reaction conditions: substrate (0.25 mmol), anhydrous and degassed
solvent (1 mL) and FeꢀMMT (5 mol% metal/substrate ratio). T °C=80
b
°C. c T °C=40 °C. d 2i/2i’=95:5.
Substrate 1i was commercially available as the (Z)ꢀstereoisomer.
50 Substrate 1j was prepared by Wittig olefination of γꢀbutyrolactol.
However, since the reaction with benzyltriphenylphosphonium
bromide delivered a mixture of (E)ꢀ and (Z)ꢀ1j, the stereoisomer
(E)ꢀ1j was obtained independently in two steps. Treatment of 1ꢀ
phenylpropꢀ2ꢀenꢀ1ꢀol with triethylorthoacetate furnished ethyl
55 (E)ꢀ5ꢀphenylpentꢀ4ꢀenoate which was then reduced to (E)ꢀ1j
unsing LiAlH4 (see ESI for details).
When (Z)ꢀ1i was put to react with FeꢀMMT at 80 °C in DMC, the
expected cyclisation was observed leading to 2ꢀ
pentyltetrahydrofuran 2i (28% GCꢀMS yield) but the main
60 product was the methylcarbonate formed upon reaction with
DMC. Only trace amount of 2ꢀbutyltetrahydropyran 2i’ was
formed (entry 1). With (E,Z)ꢀ1j under the same reaction
conditions, the (Z)ꢀisomer reacted faster and the formation of the
methycarbonate was again observed (36% GCꢀMS yield) while
65 the cyclic ether 2j was formed in 46% yield (entry 2). By
replacing DMC by CH3NO2, at 40 °C the reaction of 1i was very
slow and only 4% conversion was observed after 48 hours (entry
3). However, at 100 °C the reaction proceeded with 89%
conversion in 72 hours and delivered 2i in 62% yield and 95%
70 regioselectivy compared with 2i’ (entry 4). With (Z)ꢀ and (E)ꢀ1j,
the reaction was completed in shorter reaction times and
quantitatively provided the cyclic ether 2j (entries 5,6). Substrate
1k was partially converted (72%) to a mixture of elimination
products and isomers, as suggested by GCꢀMS analysis (entry 7).
75 The double bond substitution was thus shown to impact
significantly the reaction efficiency. The stabilisation of
positively charged intermediates formed by activation of the
double bond requires substitution by electronꢀdonating groups. In
the case of 1j, the presence of the phenyl group allowed to
80 reached both high conversions and yields.
O
25
cat.
OH
R4O
O
R4O
O
1f-g
2f-g
+ H
30
1,2 H shift
OH
OH
R4O
R4O
O
O
- H
+ H
OH
OH
R4O
R4O
O
O
35 Scheme 2. Possible mechanisms accounting for the formation of
1,3ꢀdioxolanes 2fꢀg.
Intramolecular hydroalkoxylation of 1,2-disubstituted double
bonds by primary alcohols
The catalytic system was then tested on substrates 1iꢀj featuring a
40 combination of primary alcohol function and a 1,2ꢀdisubstituted
double bond (Table 4).
Intramolecular hydroalkoxylation of trisubstituted double
bonds by phenols
We further tested the efficiency of the catalytic system on
phenolic substrates 1lꢀn featuring monoꢀ and trisusbtituted double
4
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bonds (Table 5).
Table 5. Cyclisation of alcohols 1lꢀn.a
Bi-MMT
Bi-MMT (5 mol%)
CH3NO2, 80 °C
O
O
OH
OH
45
OH
R7
2l
M-MMT (5 mol%)
solvant, 80 °C
(R6=R7=H)
or
R6
1n
R6
R7
H
O
1l-n
5
- Bi-MMT
+ H
O
50
2m-n
Time
(h)
Fe DMC 48
Bi DMC 48
Bi DMC 48
Isolated
Entry R6, R7 Substrate
M
Solvent
Conversion
yield of 2lꢀn
1
H, H
H, H
H, H
1l
1l
1l
1m
1m
1m
1m
0%
0%
ꢀb
3n
, 96%
2c
3d
ꢀb
(trans/cis 2:1)
64%
100%
100%
91%
100%
50%
99%
57%
90%
99%
40%e
32%f
21%g
ꢀh
4c Me, Me
5c Me, Me
6c Me, Me
Bi
DCE
24
55 Scheme 3. Tandem reaction of 1n with BiꢀMMT as catalyst and
possible mechanism.
Bi CH3NO2 24
Bi DMC 24
Fe DMC 24
7
Me, Me
Me,
The superiority of BiꢀMMT over FeꢀMMT in this specific
process could be a consequence of the difference of ionic radii
60 between Fe3+ and Bi3+, the larger Bi3+ being most likely to
interact with the remote position of the substrate (Bi: 0.96ꢀ1.17
Å; Fe: 0.49ꢀ0.78 Å). To test our hypothesis, we engaged dienol
substrate 1o, featuring similarly to 1n an internal trisubstituted
double bond, but with a terminal primary hydroxyl group and a
65 tetrasubstituted double bond. In our optimised conditions with
FeꢀMMT, only the intramolecular hydroalkoxylation was
observed and delivered the corresponding cyclic ether 2o in 56%
yield (89% conversion) in DMC and 71% yield in CH3NO2. With
BiꢀMMT in CH3NO2, a mixture of cyclic products was obtained
70 without selectivity (Scheme 4). It is worth noting that in Bronsted
acidꢀpromoted reaction, 1o is the precursor of an industrially
relevant odorant molecule, ambroxide, formed upon a tandem
cyclisation process.47
8
1n
1n
1n
1n
Fe DMC
Bi DMC 24
Fe CH3NO2
Bi CH3NO2 24
5
100%
100%
100%
100%
prenyl
Me,
prenyl
Me,
prenyl
Me,
prenyl
9c
10
5
11c
a
Reaction conditions: substrate (0.25 mmol), anhydrous and degassed
b
solvent (1 mL) and FeꢀMMT (5 mol% metal/substrate ratio).
10 Quantitative recovery of the starting material. BiꢀMMT prepared from
BiCl3 was used as catalyst. BiꢀMMT prepared from Bi(OTf)3 was used
c
d
e
as catalyst. Together with 39% of tricyclic product 3n formed upon
tandem reaction. f Together with 42% of product 3n. g Together with 79%
of product 3n. h Product 3n formed in 96% was the sole product.
15
With substrate 1l featuring a monosubstituted double bond, no
conversion was observed under our optimised conditions either
using FeꢀMMT or BiꢀMMT (entries 1,2). Interestingly, by using a
BiꢀMMT prepared by impregnation of Bi(OTf)3 instead of BiCl3,
20 a conversion of 64% was observed in DMC for an isolated yield
of cyclised product 2l of 50% (entry 3). Substrate 1m, with the
phenol ring orthoꢀsubstituted with a prenyl side chain, cyclised
readily either with FeꢀMMT or BiꢀMMT in DMC or CH3NO2
(entries 4ꢀ7), the best result being obtained in our standard
25 conditions with 100% conversion and a quantitative yield of 2m
(entry 7). Finally, substrate 1n, an orthoꢀgeranylated phenol,
reacted faster than 1l and 1m reaching total conversion in 5 hours
in our optimised conditions but to yield a mixture of the expected
chromane 2n and a tricyclic compound 3n resulting from a
30 tandem reaction involving both double bonds (entries 8ꢀ10).
While with FeꢀMMT, only a mixture was obtained after several
attempts, with BiꢀMMT (exꢀBiCl3) in CH3NO2, tricyclic product
3n was formed in 96% yield as the sole product (entry 11 and
Scheme 3). We hypothetised that the tandem process might start
35 by the activation of the remote double bond by the catalyst
followed by the attack of the internal double bond and
interception of the carbenium ion formed by the phenolic
hydroxyl group. It is worth mentioning that olefins that should be
formed upon proton elimination from these intermediates were
40 not observed,46 suggesting a fast ring closure to 2n.
M-MMT
(5 mol%)
75
OH
O
Solvant, 80 °C
24 h
1o
2o
Fe
Fe
Bi
DMC
CH3NO2
CH3NO2
56%
71%
80
Mixture
Scheme 4. Cyclisation of 1o to 2o.
Intermolecular hydroalkoxylation
85 Having in hand an efficient catalytic system for the
intramolecular hydroalkoxylation of olefins, we next focused on
the more challenging intermolecular version of the reaction. For
this reaction, one has to address several hurdles compared with
the intramolecular version, such as the difficulty to run a
90 bimolecular reaction with two substrates of low affinity, typically
a polar protic alcohol and an apolar hydrophobic olefin, and the
energetic penalties due to an entropically disfavoured process.
Consequently, most of the catalytic systems described in the
literature report modest conversion rates and yields and reactions
95 performed at elevated temperatures. For example, in
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homogeneous catalysis, a combination of Pd(II) complexes and
polar protic nucleophiles with hydrophobic electrophiles, several
Cu(II) salts was used for the hydroalkoxylation of styrene 60 attempts to use ionic liquids or surfactants were performed with
derivatives18 and vinylphenols.20 Metal triflates such as Zr(II),
La(III)48 and Hg(II)49 have been used for styrene and αꢀolefins
hydroalkoxylation, respectively. Styrenes and αꢀolefins could
also be converted into ethers by additon of simple alcohols with
Au(III) chloride as catalyst in the presence of Cu(II) salts.50 In
heterogeneous catalysis, zeolite beta could be used to catalyse the
ethoxylation of αꢀolefins in continuous flow,38 while in batch
MꢀMMT as catalysts but did not allow to improve conversions
and yields (data not shown).
5
Table 6. Hydroalkoxylation of olefins 1pꢀr.a
R9
R9
65
70
75
M-MMT(x mol%)
X
R10
X
R10
R11OH
10 reaction limonene and αꢀpinene could be functionalised with
various C1ꢀC5 alcools.21
solvent, T°C
OR11
R8
R8
R8
1p-r
X=H2, O
R8
In this context, we tested several MMT doped with metal cations
and metal nanoparticles supported on inorganic matrix as possible
catalysts for the reaction. Initial attempts on a typical αꢀolefin (1ꢀ
15 decene) in various alcoholic solvents (MeOH, EtOH, nꢀPrOH, nꢀ
BuOH) or in organic solvents in the presence of alcohols with the
catalysts of Table 1 were unsuccessful, the starting material being
recovered unchanged. Positive control experiments of the
catalysts activity were performed on the cyclisation of 1b to 2b
20 for MMT doped with metals and dipolar cycloaddition reaction
following a recently published procedure for Cu nanoparticles.51
The olefin class could significantly account for the absence of
reactivity in our conditions and we thus moved towards
trisubstituted double bonds such as in 1p and 1q-r obtained by
25 alkylation of citronellol and Wittig olefination, respectively
(Scheme 5) and octꢀ1ꢀenꢀ3ꢀone 1s presenting an activated
terminal double bond. Substrate 1p has been already studied for
intermolecular hydroalkoxylation catalysed by Sn(OTf)4 by some
of us and could be useful to compare with a homogeneous
30 system.23
2(p-r)(a-d)
R11
=
Me: a
R8=H, Me
R9=H, Me
R10=Me, Et, OMe
b
Et:
n-Pr: c
d
n-Bu:
Solvent,
T°C
Product,
yieldb
Entry Substrate M (x)
R11OH Conversionb
1
2
3
4
5
6
7
8
9
1p
1p
1p
1p
1p
1p
1p
1p
1q
1q
1q
Fe (5) MeOHc, reflux
Bi (5) MeOHc, reflux
63%
72%
40%
24%
37%
30%
29%
79%
27%
17%
33%
2pa, 54%
2pa, 45%
2pb, 16%
2pb, 13%
2pc, 26%d
2pc, 17%d
2pd, 19%d
2pd, 8%d
2qa, 9%
Fe (5)
Bi (5)
EtOHc, reflux
EtOHc, reflux
Fe (5) nꢀPrOHc, reflux
Bi (5) nꢀPrOHc, reflux
Fe (5) nꢀBuOHc, reflux
Bi (5) nꢀBuOHc, reflux
Fe (5) MeOHc, reflux
Bi (5) MeOHc, reflux
Ti (5) MeOHc, reflux
10
11
2qa, 14%
2qa, 22%
Cu NPs
(0.25)
12
1s
MeOHc, reflux
100%
Degradation
a
NaH
MeI
Reaction conditions: substrate (0.25 mmol), anhydrous and degassed
solvent (1 mL) and MꢀMMT stirred at the specified temperature for 48 h.
b
1
c
Determined by HꢀNMR or GCꢀTCD by external calibration. Used as
the solvent. d Determined by GCꢀMS.
OH
OMe
35
40
45
80
Finally we tested equimolar amounts of our recyclable TiꢀMMT
for the hydroalkoxylation of 1q-r (Table 7).
1p
BuLi
Table 7. Hydroalkoxylation of olefins 1q-r with equimolar TiꢀMMT.a
PPh3.Br
( )n
n-C7H15
( )n
O
R11
=
( )n
neat, -20 °C to rt
Et: b
n-Pr:
n-Bu: d
( )n
Ti-MMT(1 equiv.)
R11OH, 70 °C
c
1q
n=2
n=1 1r
85
OR11
O
O
Scheme 5. Preparation of 1p, 1q and 1r.
e
2(q-r)(b-e)
1q-r
Entry Substrate R11OH Conversionb Product, yieldb
For these substrates, we focused on the use of MMT doped with
metal cations or nanoparticles, and proceeded to an intial
50 screening (Table 6).
1
2
3
4
1q
1r
1r
1r
Et
nꢀPr
nꢀBu
solketal
36%
45%
42%
23%
2qb, 36%
2rc, 45%
2rd, 42%
2re, 23%
The results showed olefins conversions below 72% and yields of
hydroalkoxylation product up to 54%. Substrate 1s led to
degradation products (entry 12). Interestingly, comparing entries
1ꢀ3 with 9ꢀ11, the presence of the methoxy substituent (R10) of 1p
55 instead of a methyl group allow for better results in terms of both
conversion and yield. This trend could be seen as an effect on the
overall polarity of the electrophile, as well as an improvement of
its coordination ability. In order to favour the contact between the
a
Reaction conditions: substrate (0.25 mmol), anhydrous and degassed
90 solvent (1 mL) and TiꢀMMT stirred at the specified temperature for 48 h.
b Determined by GCꢀTCD by external calibration.
By increasing the molar fraction of TiꢀMMT, improved yields
could thus be obtained for hydrophobic olefins 1q-r at 70 °C
95 even with higher alcohols such as nꢀpropanol and nꢀbutanol or
6
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solketal which are typically leading to low yields.
50 tetrahydronaphtalene derivative formed upon Lewis acidꢀ
catalysed FriedelꢀCrafts type addition of the phenyl ring to the
double bond. With BiCl3, substrate 1b was recovered unchanged
while with BiꢀMMT, 2b was formed in 76% yield, indicating the
presence of active bismuth species within the solid catalyst.
55 Supported catalysts FeꢀMMT and BiꢀMMT were thus superior to
their homogeneous equivalents in terms of activity and
selectivity.
Control reactions with solid catalytic materials such as pristine
NaꢀMMT, MMT K10, Amberlyst and Nafion were performed on
60 various substrates (Table 8). With NaꢀMMT, no conversion of
starting material 1a, 1e, 1f was observed (entries 2ꢀ4). With a
physical mixture of NaꢀMMT and BiCl3 (5 mol%) as catalyst,
conversion was not complete and a complex mixture of products
was obtained (entry 5), as well as with MMT K10 (entry 6). With
65 acidic resins Ambelystꢀ15 and Nafion SACꢀ13, a good reaction
profile was observed in terms of conversion and yields, but the
formation of the undesired hydroarylation product 2b’ was
observed with 17ꢀ18% selectivity (entries 7,8). The reaction
could thus be observed under Bronsted catalysis, but the most
70 efficient conditions and catalyst remained those described above
with FeꢀMMT. These data suggested a truly metalꢀcatalysed
rather than a protonꢀcatalysed process.
Mechanistic studies
A reasonnable question when using supported catalysts is
whether or not the process is truly heterogeneously catalysed. I
our case, metal cations are simply anchored to the MMT support
by electrostatic binding and could be displaced in the reaction
medium. For example, the result presented in Figure 1 with
CH3NO2 as the solvent suggest a loss of a fraction of supported
10 metal at each cycle, solubilised in such a polar solvant, resulting
in an overall decrease of the solid catalyst efficiency. In DMC
however, a solvent in which the activity was maintained, we
hypothetised that most of metal cations remained bound to MMT.
We further performed a hot filtration test to determine whether or
15 not solubilised metal species could be active in solution. The test
consisted of a monitoring of the reaction progress (product
formation) until the conversion reached ca. 50% conversion. The
whole reaction mixture was then filtered over a fritted glass
heated at 80 °C and the filtrate was put to react again at the same
20 temperature under monitoring. The results are presented in Figure
2 for reactions of 1b with FeꢀMMT and BiꢀMMT in DMC.
5
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
Hot filtration
Table 8. Comparison of FeꢀMMT with solid catalysts.
Products,
Entry
Catalyst
Substrate Time (hr) Conversionc
selectivityc
1a
2b
3b
4b
FeꢀMMT
NaꢀMMT
NaꢀMMT
1b
1a
1e
1f
7
100%
0%
0%
2b/2b’ 100/0
24
12
4.5
ꢀ
d
-
Fe-MMT
Bi-MMT
NaꢀMMT
0%
ꢀ
NaꢀMMT +
5 mol% BiCl3
MMT K10
Amberlyst 15
5b
1a
7
Mixture
0
50
100
150
200
250
300
6b
1a
1b
1b
7
24
24
100%
100%
100%
Mixture
2b/2b’ 83/17
2b/2b’ 82/18
Time (min)
7a
Figure 2. Hot filtration tests on reaction of 1b with FeꢀMMT and
25 BiꢀMMT in DMC at 80 °C.
8a Nafion SACꢀ13
a
Reaction conditions: substrate (0.25 mmol), anhydrous and degassed
75 CH3NO2 (1 mL) at 60 °C. FeꢀMMT: 25 mg; Amberlyst: 20 mg; Nafion:
It is clear that upon removal of the solid catalyst, no additional
b
20 mg. Reaction conditions: substrate (0.5 mmol), anhydrous and
product formation was observed, which endorsed
a
truly
c
degassed DMC (2 mL) at 80 °C. NaꢀMMT, MMT K10: 50 mg.
d
heterogeneous process. For the sake of comparison, we tested the
30 activity of FeCl3 and BiCl3 in homogeneous conditions on the
same reaction, these halide salts being the precursors of FeꢀMMT
and BiꢀMMT, respectively (Scheme 6).
Determined by GCꢀTCD by external calibration. Less than 5% yield of
dehydrated product was observed by GCꢀMS.
80
The question of the characterisation of the coordination sphere of
the cations is difficult to address on these solid catalysts. It is
reasonable to imagine mixed species with one or two chlorine
atoms replaced by silicates from the interlamellar surface of
85 MMT (Scheme 7).
Catalyst
(5 mol%)
O
OH
35
+
Ph
Ph
Ph
Ph
DMC, 80°C
7 hr
Ph
HO
1b
2b
2b'
40
Fe-MMT
86%
76%
76%
0%
-
5%
-
MMT
FeCl3
Bi-MMT
BiCl3
90
O
O
O
O
O
O
-
Si
Cl
Si
O
O
45 Scheme 6. Comparison between heterogeneous and homogeneous
version of the reaction
Bi
Na
Bi
95
Cl
Cl
With FeCl3 (5 mol%) after 7 hours, the expected cyclised product
2b was formed in 76% yield, along with 5% of
Scheme 7. Hypothetical metal species within MMT doped with
metal cations.
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In such hypothesis where the binding to a pseudoꢀsurface brings a
large degree of steric hindrance, the metalꢀoxygen bond lenghts
should be longer than expected and cations should therefore
exhibit an enhanced Lewis acid character, as it is the case with
TCD. After completion, the mixture is filtered through a cotton
wool pad. The filter is rinsed with diethyl ether and the solution
concentrated at reduced pressure affording the crude cyclic ether
which is then purified by flash chromatography over silica gel
5
metal salts with bulky anions of low nucleophilicity, e.g. triflates 60 (petroleum ether/Et2O).
or triflimidates.52,53
2,2,6ꢀTrimethyltetrahydroꢀ2Hꢀpyran 2a.22,42 1H NMR (DMCꢀd6,
200 MHz): δ 3.78ꢀ3.54 (m, 1H), 1.75 – 1.53 (m, 2H), 1.52ꢀ1.25
(m, 4H), 1.17 (s, 3H), 1.13(s, 3H), 1.04 (d, J = 6.1 Hz, 3H). 13C
NMR (DMCꢀd6, 50 MHz): δ 71.64, 66.65, 36.43, 33.99, 31.84,
65 22.53, 21.67, 20.59. MS (EI; 70 eV) 128(0) [M]⋅+, 113(47), 95(7),
70(10), 59(100), 56(36), 43(80).
Conclusions
Efficient, costꢀeffective, and sustainable catalysts for
hydroalkoxylation reactions of olefins could be obtained upon
10 impregnation of Fe(III), Bi(III), and Ti(IV) salts on
Montmorillonite. For intramolecular reactions, a large number of
substrates with various substitution patterns could be efficiently
cyclised. For intermolecular reactions, the results were modests in
terms of both conversions and yields but remained in the range of
15 what is typically observed under homogeneous and
heterogeneous catalysis. These catalytic systems were shown to
proceed under truly heterogeneous catalysis and could be
transferred in continuous flow conditions, the first step towards
industrial transfer.
2,2ꢀDimethylꢀ5,5ꢀdiphenyltetrahydroꢀ2Hꢀpyran 2b.19 1H NMR
(CDCl3, 200 MHz): δ 7.37ꢀ7.10 (m, 10H), 4.06 (s, 2H), 2.50ꢀ2.33
(m, 2H), 1.40 (dd, J = 7.3, 5.0 Hz, 1H), 1.23 (s, 6H). 13C NMR
70 (CDCl3, 50 MHz): 146.54, 128.21, 128.02, 126.05, 71.32, 69.06,
45.96, 32.65, 30.91, 26.46. MS (EI; 70 eV) 266(5) [M]⋅+, 236(15),
180(100), 165(36), 152 (4); 129(2), 115(13), 103(4), 91(14),
73(8), 65(3), 43(10), 41(5).
1
2,2ꢀDimethylꢀ6ꢀpentyltetrahydroꢀ2Hꢀpyran 2c. H NMR (CDCl3,
75 200 MHz): δ 3.50ꢀ3.41 (m, 1H), 1.67ꢀ0.94 (m, 14H), 1.19 (s, 3H),
1.17 (s, 3H), 0.87 (t, J = 6.8 Hz, 3H). 13C NMR (CDCl3, 50
MHz): δ 71.57, 70.46, 37.10, 36.45, 32.10, 31.66, 25.39, 22.79,
22.13, 20.28, 14.22. MS (EI; 70 eV) 184(0) [M]⋅+, 169(16), 151
(4), 126(3), 113(63), 99 (15), 95(61), 83(15), 69(38), 59(100),
80 56(72), 43(57). HRMS calculated for C12H23O (MꢀH)+: 183.1749;
found: 183.1743. ׀ꢂ׀= 3.3 ppm.
20 Experimental
1H NMR and 13C NMR spectra were recorded on BRUCKER AC
200 (200 MHz). 1H NMR spectra are reported as follows:
chemical shift in ppm (δ) relative to the chemical shift of CDCl3
at 7.26 ppm, integration, multiplicities (s = singlet, d = doublet, t
25 = triplet, q = quartet, m = multiplet and br = broadened), and
coupling constants (Hz). 13C NMR spectra reported in ppm (δ)
relative to CDCl3 at 77.16 ppm. Column chromatography was
carried out on silica gel (spherical, neutral, 63ꢀ200 um, Geduran
Si 60, Merck KGaA). GCꢀTCD analysis were carried out using a
30 Shimadzu QP2010plus gas chromatograph, under the following
operation conditions: vector gas, He; injector temperature, 250
°C; detector temperature, 210 °C at 60 mA; split ratio, 1/20; total
flow, 22,5 mL/min; Phenomenex Zebron ZB5MS column,
polydimethylsiloxane (10 m, inside diameter 0.10 mm, film
35 thickness 0.10 ꢁm); temperature program, 80ꢀ200 °C at 10
°C/min and 200 °C for 8 min. GC/MS analysis were performed
by using a Shimadzu QP2010 gas chromatograph (conditions:
carrier gas, He; injector and detector temperatures, 250 °C;
injected volume, 0.5 ꢁL; split ratio, 1/100; (pressure, 180 kPa);
40 SLBꢀ5ms capillary column (thickness: 0.25 mm, length: 30 m,
inside diameter: 0.25 mm); temperature program, 60ꢀ250 °C at 2
°C/min, and 250 °C, coupled to a mass selective detector. Mass
spectra were obtained by electron ionisation at 70 eV, m/z 35ꢀ
400, source temperature 250 °C; only the most abundant ions are
45 given. High resolution mass spectrometry (HRMS) was
performed at ERINI platform (Grasse, FRANCE) using a Waters
APGC coupled with a Waters Xevo G2 QTOF spectrometer.
Screening reactions were performed in a Carousel 12 Plus
parallel synthesizer purchased from Radleys.
2,2ꢀDimethylꢀ6ꢀ(2ꢀphenylethyl)ꢀtetrahydroꢀ2Hꢀpyran 2d. 1H
NMR (CDCl3, 200 MHz): δ 7.43ꢀ7.01 (m, 5H), 3.66ꢀ3.30 (m,
1H), 2.89ꢀ2.46 (m, 2H), 1.90ꢀ0.99 (m, 8H), 1.23 (s, 3H), 1.17 (s,
85 3H). 13C NMR (CDCl3, 50 MHz): δ 142.64, 128.62, 128.23,
125.60, 77.80, 77.16, 76.53, 71.62, 69.19, 38.49, 36.39, 32.05,
31.76, 22.07, 20.18. MS (EI; 70 eV) 218(12) [M]⋅+, 185(6), 157
(7), 140(25), 129(14), 113(34), 104(36), 91(100), 69(22), 56(14),
43(29). HRMS calculated for C15H23O (M+H)+: 219.1749; found:
90 203.1751. ׀ꢂ׀ = 0.9 ppm.
2,2ꢀDimethylꢀ6ꢀ(pꢀtolyl)tetrahydroꢀ2Hꢀpyran 2e. 1H NMR
(CDCl3, 200 MHz): δ 7.25 (d, J = 8 Hz, 2H), 7.12 (d, J = 8 Hz,
2H), 4.55 (dd, J = 11.5, 1.9 Hz, 1H), 2.31 (s, 3H), 1.82ꢀ1.41 (m,
6H), 1.30 (s, 3H), 1.29 (s, 3H). 13C NMR (CDCl3, 50 MHz): δ
95 141.33, 136.76, 129.04, 126.15, 72.90, 72.42, 36.19, 34.21,
32.13, 22.07, 21.24, 20.61. MS (EI; 70 eV) 204(14) [M]⋅+, 189(5),
146 (25), 131(15), 121(100), 105 (5), 91(19), 84(4), 77(6), 69(6),
56(31), 43(11). HRMS calculated for C14H19O (MꢀH)+: 203.1436;
found: 203.1436. ׀ꢂ׀= 0.0 ppm.
100 cis/transꢀ(2ꢀIsopropylꢀ1,3ꢀdioxolanꢀ4ꢀyl)methanol
cis,transꢀ2ꢀisopropylꢀ1,3ꢀdioxanꢀ5ꢀol 2f’.54
2f
and
[cis/transꢀ2f] 1H NMR (CDCl3, 200 MHz): δ 4.75 (d, J = 4.7 Hz,
1H), 4.66 (d, J = 4.6 Hz, 1H), 4.32ꢀ4.02 (m, 3H), 4.00ꢀ3.16 (m,
7H), 2.04 (br s, 2H), 1.94ꢀ1.70 (m, 2H), 0.97 (d, J = 5.6 Hz, 6H),
105 0.94 (d, J = 6.6 Hz, 6H). 13C NMR (CDCl3, 50 MHz): δ 108.79,
108.65, 76.52, 76.29, 66.80, 66.55, 63.52, 62.76, 32.30, 31.85,
16.99, 16.95, 16.89, 16.80. MS (EI; 70 eV) 146(0) [M]⋅+, 145(1),
115(3), 103(82), 97(7), 86(2), 71(5), 69(2), 57(100), 55(31),
43(24), 41(15). (I stereoisomer). MS (EI; 70 eV) 146(0) [M]⋅+,
110 145(2), 115(4), 103(80), 97(10), 86(1), 71(6), 69(3), 57(100),
50
General procedure for cyclisation of unsaturated alcohols
In a Schlenk tube, substrate (1 mmol), FeꢀMMT (5 mol% of
metal, 100 mg of material) and DMC (2 ml) are introduced and
the tube closed with a PTFE cap. The mixture is stirred at the
55 desired temperature and the reaction monitored by TLC or GCꢀ
1
55(31), 43(26), 41(16). (II stereoisomer). [cis/transꢀ2f’] H NMR
(CDCl3, 200 MHz): δ 4.27 (d, J = 5 Hz, 1H), 4.20 (d, J = 5 Hz,
1H), 4.13 (t, J = 4.6 Hz, 2H), 4.01 (d, J = 11.2 Hz, 1H), 3.93ꢀ3.76
8
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(m, 3H), 3.86 (d, J = 11.2 Hz, 1H), 3.54ꢀ3.45 (m, 1H), 3.36 (d, J
6.70 (m, 2H), 5.17ꢀ5.06 (m, 1H), 2.82ꢀ2.52 (m, 2H), 2.08ꢀ1.39
= 10.9 Hz, 1H), 3.31 (d, J = 10.2 Hz, 1H), 2.02 (br s, 2H), 1.91ꢀ 60 (m, 6H), 1.72 (s, 3H), 1.64 (s, 3H), 1.34 (s, 3H). 13C NMR
1.66 (m, 2H), 0.94 (d, J = 6.8 Hz, 6H), 0.92 (d, J = 6.8 Hz, 6H).
13C NMR (CDCl3, 50 MHz): δ 106.35, 105.69, 71.88, 71.70,
64.28, 61.61, 32.82, 32.35, 17.31, 16.94. MS (EI; 70 eV) 146(0)
[M]⋅+, 145(1), 116(1), 103(100), 73(53), 57(63), 55(31), 43(42),
(CDCl3, 50 MHz): δ 154.09, 129.50, 127.33, 124.38, 121.22,
119.64 117.41, 76.02, 39.66, 31.06, 25.80, 24.37, 22.40, 22.24,
17.71. MS (EI; 70 eV) 230(52) [M]⋅+, 215(2), 187(20), 174(17),
5
161(27), 147(48), 133(20), 123(59), 107(94), 91(40), 81(40),
1
41(15). (I stereoisomer). MS (EI; 70 eV) 146(0) [M]⋅+, 145(1), 65 69(74), 55(16), 41(100). [cisꢀ3n] H NMR (CDCl3, 200 MHz): δ
116(2), 103(100), 73(54), 57(64), 55(33), 43(46), 41(17). (II
stereoisomer).
7.05 (d, J = 7.1 Hz, 2H), 6.88ꢀ6.69 (m, 2H), 3.05 (dd, J = 17.7,
7.9 Hz, 1H), 2.76 (d, J = 17.7 Hz, 1H), 2.08ꢀ1.20 (m, 7H), 1.21
(s, 3H), 0.97 (s, 3H), 0.65 (s, 3H). 13C NMR (CDCl3, 50 MHz): δ
154.64, 129.04, 126.81, 122.18, 119.94, 117.23, 75.36, 44.58,
10 cis/transꢀ(2ꢀIsopropylꢀ1,3ꢀdioxolanꢀ4ꢀyl)ꢀmethyl acetate 2g. 1H
NMR (CDCl3, 200 MHz): δ 4.73 (d, J = 4.6 Hz, 1H), 4.66 (d, J =
4.4 Hz, 1H), 4.37ꢀ4.18 (m, 2H), 4.17ꢀ3.98 (m, 3H), 3.91 (dd, J= 70 41.80, 39.71, 34.12, 32.41, 27.16, 23.74, 21.54, 18.23. MS (EI;
8.3, 6.9 Hz, 1H), 3.74 (dd, J= 8.3, 4.9 Hz, 1H), 3.58 (dd, J= 8.4,
6.7 Hz, 1H), 2.08 (s, 3H), 2.06 (s, 3H), 1.94ꢀ1.67 (m, 2H), 0.97ꢀ
15 0.88 (m, 12H). 13C NMR (CDCl3, 50 MHz): 170.89, 170.84,
109.02, 108.51, 73.70, 73.53, 67.27, 67.19, 64.72, 64.30, 32.06,
70 eV) 230(31) [M]⋅+, 214(4), 187(2), 173(1), 159(11), 145(17),
123(100), 107(39), 91(10), 81(30), 77(10), 67(12), 55(10), 43(9),
41(18). [transꢀ3n] 1H NMR (CDCl3, 200 MHz): δ 7.09 (d, J = 7.1
Hz, 2H), 6.81ꢀ6.72 (m, 2H), 2.73 (dd, J = 16.2, 6.7 Hz, 1H), 2.57
31.77, 20.89, 20.86, 16.93, 16.87, 16.59, 16.55. MS (EI; 70 eV) 75 (d, J = 16.4 Hz, 1H), 2.17ꢀ1.16 (m, 7H), 1.23 (s, 3H), 1.04 (s,
188(0) [M]⋅+, 187(0), 145(43), 115(1), 97(4), 86(1), 71(3), 61(4),
57(18), 43(100), 41(7). (I stereoisomer). MS (EI; 70 eV) 188(0)
20 [M]⋅+, 187(1), 145(46), 115(2), 97(45), 86(1), 71(4), 69(2),
57(19), 43(100), 41(7). (II stereoisomer). HRMS calculated for
C9H15O4 (MꢀH)+: 187.0970; found: 187.0967. ׀ꢂ׀= 1.6 ppm.
2ꢀHexyltetrahydrofuran 2i and 2ꢀpentyltetrahydroꢀ2Hꢀpyran
3H), 0.94 (s, 3H). 13C NMR (CDCl3, 50 MHz): δ 154.38, 129.75,
127.23, 122.72, 119.74, 117.15, 76.29, 48.19, 41.63, 40.13,
33.49, 32.22, 23.37, 20.80, 19.96, 19.91. MS (EI; 70 eV) 230(54)
[M]⋅+, 215(14), 187(10), 173(3), 159(26), 145(37), 123(100),
80 107(92), 91(21), 81(31), 77(17), 67(13), 55(18), 43(14), 41(32).
2ꢀMethylꢀ2ꢀ(2ꢀ(2,6,6ꢀtrimethylcyclohexꢀ1ꢀenꢀ1ꢀyl)ethyl)tetrahyꢀ
drofuran 2o.60 1H NMR (CDCl3, 200 MHz): δ 3.97ꢀ3.68 (m, 1H),
2.17ꢀ1.33 (m, 14H), 1.59 (s, 1H), 1.21 (s, 1H), 0.98 (s, 1H). 13C
NMR (CDCl3, 50 MHz): δ 137.12, 126.90, 82.88, 67.20, 41.13,
1
2i’.42,55 [THFꢀether/2i] H NMR (CDCl3, 200 MHz): δ 3.97ꢀ3.59
25 (m, 3H), 2.08ꢀ1.69 (m, 3H), 1.69ꢀ1.03 (m, 11H), 0.86 (t, J = 6.8
Hz, 3H). 13C NMR (CDCl3, 50 MHz): δ 79.59, 67.70, 35.89,
31.97, 31.51, 29.55, 26.50, 25.84, 22.73, 14.19. MS (EI; 70 eV) 85 40.05, 36.83, 35.22, 32.92, 28.78, 26.24, 25.48, 23.63, 19.84,
156(1) [M]⋅+, 138 (1), 96 (1), 81(1), 71(100), 55(6), 43(31),
41(31). [THPꢀether/2i’] 1H NMR (CDCl3, 200 MHz): δ 4.01ꢀ3.88
30 (m, 1H), 3.40 (td J= 10.9, 3.6 Hz, 1H), 3.29ꢀ3.08 (m, 1H), 2.17ꢀ
1.04 (m, 14H), 0.87 (t, J = 6.5 Hz, 3H). 13C NMR (CDCl3, 50
19.69. MS (EI; 70 eV) 236(2) [M]+., 221(2), 203(2), 177(4),
161(2), 149(2), 136(18), 123(15), 121(25), 107(15), 95(17),
93(17), 85(100), 81(14), 69(9), 67(10), 55(14), 43(52), 41(24).
1,7ꢀDimethoxyꢀ3,7ꢀdimethyloctane 2pa.23 1H NMR (CDCl3, 200
MHz): δ 78.08, 68.63, 36.78, 32.12, 32.09, 26.40, 25.36, 23.76, 90 MHz): δ 3.39 (t, J=6.7 Hz, 2H), 3.32 (s, 3H), 3.16 (s, 3H), 1.79ꢀ
22.77, 14.19. MS (EI; 70 eV) 156(1) [M]⋅+, 138 (1), 95 (1),
85(100), 67(16), 57(15), 43(21), 41(24).
1.20 (m, 9H), 1.12 (s, 6H), 0.88 (d, J=6.4 Hz, 3H). 13C NMR
(CDCl3, 50 MHz): δ 74.6, 71.2, 58.6, 49.1, 40.1, 37.7, 36.7, 30.2,
21.2, 19.6. MS (EI; 70 eV) 202(0) [M]+., 187(4), 138(11),
123(29), 109(14), 95(50), 81(95), 73(100), 55(94).
35 2ꢀPhenyltetrahydroꢀ2Hꢀpyran 2j.41 1H NMR (CDCl3, 200 MHz):
δ 7.39ꢀ7.15 (m, 5H), 4.36ꢀ4.24 (m, 1H), 4.12 (dd, J = 11.4, 3.5
Hz, 1H), 3.76ꢀ3.46 (m, 1H), 2.01ꢀ1.46 (m, 6H). 13C NMR 95 7ꢀEthoxyꢀ1ꢀmethoxyꢀ3,7ꢀdimethyloctane 2pb.23 1H NMR
(CDCl3, 50 MHz): 143.45, 128.38, 127.38, 125.95, 80.26, 69.11,
34.14, 26.02, 24.14. MS (EI; 70 eV) 162(54) [M]⋅+, 161 (46),
40 144(2), 133(4), 129(4), 115 (6), 105 (100), 91(29), 77(45), 65(8),
55(26), 51(19), 41(31).
(CDCl3, 200 MHz): δ 3.50ꢀ3.25 (m, 7H); 1.70ꢀ1.00 (m, 18H);
0.82 (d, J=6.4 Hz, 3H). MS (EI; 70 eV) 216(0) [M]+., 87(100),
59(59), 55(9), 45(13), 43(13), 41(9).
1ꢀMethoxyꢀ7ꢀpropyloxyꢀ3,7ꢀdimethyloctane 2pc.23 1H NMR
2ꢀMethylꢀ2,3ꢀdihydrobenzofuran 2l.56 1H NMR (CDCl3, 200 100 (CDCl3, 200 MHz): δ 3.39 (t, J=6.7 Hz, 2H), 3.31 (s, 3H), 3.23 (t,
MHz): δ 7.23ꢀ7.05 (m, 2H), 6.85 (dd, J = 7.4, 0.9 Hz, 1H), 6.77
(d, J = 7.9 Hz, 1H), 4.93 (ddq, J = 8.7, 7.7, 6.2 Hz, 1H), 3.32 (dd,
45 J = 15.4, 8.8 Hz, 1H), 2.82 (dd, J = 15.4, 7.7 Hz, 1H), 1.48 (d, J =
6.2 Hz, 3H). 13C NMR (CDCl3, 50 MHz): δ 159.63, 128.07,
J=6.7 Hz, 3H), 1.80ꢀ1.10 (m, 11H), 1.06 (s, 6H), 0.90ꢀ0.75 (m,
6H). MS (EI; 70 eV) 230(0) [M]+., 215(1), 101(74), 83(9), 69(7),
59(100), 55(11), 45(16), 43(21), 41(14).
7ꢀButoxyꢀ1ꢀmethoxyꢀ3,7ꢀdimethyloctane 1pd.23 1H NMR
127.15, 125.08, 120.28, 109.44, 76.52, 37.25, 21.88. MS (EI; 70 105 (CDCl3, 200 MHz): δ 3.40ꢀ3.10 (m, 7H); 1.70ꢀ1.00 (m, 22H);
eV) 134(100) [M]⋅+, 133(42), 119(66), 115(27), 113(34), 119(11),
107(100), 91(22), 77(25), 65(6), 51(13), 41(11).
0.82 (d, J=6.4 Hz, 3H). MS (EI; 70 eV) 244(0) [M]+., 229 (1),
115(55), 83(7), 69(7), 59(100), 55(10), 45(15), 43(10), 41(16).
1
50 2,2ꢀDimethylchromane 2m.57,58 1H NMR (CDCl3, 200 MHz): δ
7.15ꢀ7.05 (m, 2H), 6.90ꢀ6.70 (m, 2H), 2.80 (t, J = 6.7 Hz, 2H),
2ꢀMethoxyꢀ2ꢀmethyldecane 2qa. H NMR (CDCl3, 200 MHz): δ
3.17 (s, 3H), 1.52ꢀ1.37 (m, 2H), 1.37ꢀ1.20 (m, 12H), 1.12 (s, 6H),
1.83 (t, J = 6.7 Hz, 2H), 1.36 (s, 6H). 13C NMR (CDCl3, 50 110 0.88 (d, J=6.4 Hz, 3H). 13C NMR (CDCl3, 50 MHz): δ 74.79,
MHz): δ 153.48, 128.93, 126.73, 120.39, 119.08, 116.72, 73.56,
32.29, 26.37 (2), 21.94. MS (EI; 70 eV) 162(11) [M]⋅+, 147(17),
55 133(17), 119(40), 107(100), 91(5), 77(8), 51(8), 41(9).
49.20, 39.97, 32.06, 30.41, 29.79, 29.47, 25.12 (2), 24.03, 22.82,
14.26. MS (EI; 70 eV) 186(0) [M]+., 171(3), 73(100), 69(4),
55(8), 43(10).
1
2ꢀMethylꢀ2ꢀ(4ꢀmethylpentꢀ3ꢀenyl)chromane 2n and cis/transꢀ
2ꢀEthoxyꢀ2ꢀmethyldecane 2qb. H NMR (CDCl3, 200 MHz): δ
1,1,4aꢀtrimethylꢀ2,3,4,4a,9,9aꢀhexahydroꢀ1Hꢀxanthene 3n.59 [2n] 115 3.29 (q, J=7.0 Hz, 2H), 1.45ꢀ1.30 (m, 2H), 1.30ꢀ1.15 (m, 12H),
1H NMR (CDCl3, 200 MHz): δ 7.06 (d, J = 7.3 Hz, 2H), 6.88ꢀ
1.08 (t, J=7.0 Hz, 3H), 1.07 (s, 6H), 0.81 (d, J=6.4 Hz, 3H). 13C
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NMR (CDCl3, 50 MHz): δ 74.59, 56.38, 40.29, 32.06, 30.40,
9 J. H. Clark, Acc. Chem. Res., 2002, 35, 791.
29.79, 29.47, 25.85 (2), 24.06, 22.82, 16.36, 14.25. MS (EI; 70
eV) 200(0) [M]+., 185(3), 87(100), 59(57), 43(16).
10 D. J. MacQuarrie, in Heterogenized Homogeneous Catalysts for Fine
60 Chemicals Production, eds. P. Barbaro and F. Liguiro, Springer, New
York, 2010, pp. 1.
2ꢀPropyloxyꢀ2ꢀmethylnonane 2rc. 1H NMR (CDCl3, 200 MHz): δ
3.25 (t, J=6.8 Hz, 2H), 1.66ꢀ1.38 (m, 4H), 1.38ꢀ1.19 (m, 10H),
1.13 (s, 6H), 0.90 (t, J=7.3 Hz, 3H), 0.88 (d, J=6.4 Hz, 3H). 13C
NMR (CDCl3, 50 MHz): δ 74.39, 62.93, 40.44, 32.04, 30.38,
29.51, 25.78 (2), 24.05, 23.99, 22.83, 14.26, 10.94. MS (EI; 70
5
11 J. R. Dodson, A. J. Hunt, H. L. Parker, Y. Yang and J. H. Clark, Chem.
Eng. Process. Process Intensif., 2012, 51, 69.
12 W. M. Czaplik, M. Mayer, J. Cvengroš and A. J. von Wangelin,
65 ChemSusChem, 2009, 2, 396.
eV) 200(0) [M]+., 171(4), 87(100), 69(13), 59(64), 43(19).
13 G. K. S. Prakash, T. Mathew and G. A. Olah, Acc. Chem. Res., 2012,
45, 565.
1
10 2ꢀButyloxyꢀ2ꢀmethylnonane 2rd. H NMR (CDCl3, 200 MHz): δ
3.28 (t, J=6.4 Hz, 2H), 1.61ꢀ1.34 (m, 6H), 1.34ꢀ1.18 (m, 10H),
1.12 (s, 6H), 1.01ꢀ0.81 (m, 6H). 13C NMR (CDCl3, 50 MHz): δ
74.37, 60.91, 40.43, 32.96, 32.04, 30.38, 29.50, 25.76 (2), 24.04,
22.83, 19.65, 14.25, 14.13. MS (EI; 70 eV) 214(0) [M]+., 199(1),
15 173(22), 115(95), 101(68), 85(28), 71(31), 57(84), 43(100).
2,2ꢀDimethylꢀ4ꢀ(2ꢀmethylnonanꢀ2ꢀyloxy)methyl)ꢀ1,3ꢀdioxolane
2re. 1H NMR (CDCl3, 200 MHz): δ 4.18ꢀ4.11 (m, 1H), 4.10ꢀ4.01
(m, 1H), 3.80ꢀ3.69 (m, 1H), 3.50ꢀ3.38 (m, 1H), 3.32ꢀ3.19 (m,
1H), 1.52ꢀ1.38 (m, 5H), 1.36 (s, 3H), 1.30ꢀ1.18 (m, 10H), 1.13 (s,
20 6H), 0.88 (t, J=6.4 Hz, 3H). 13C NMR (CDCl3, 50 MHz): δ
109.25, 75.36, 75.14, 67.68, 62.98, 40.35, 32.03, 30.32, 29.49,
26.95, 25.62, 25.56 (2), 24.01, 22.82, 14.25. MS (EI; 70 eV)
272(0) [M]+., 257(8), 173(19), 115(84), 101(65), 85(25), 71(28),
57(77), 43(100).
14 M. Sankar, N. Dimitratos, P. J. Miedziak, P. P. Wells, C. J. Kiely and
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25 Acknowledgements
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This work was supported by the University Nice Sophia
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)ꢀ1o
30 and Baptiste Giroire from ICMCB (Bordeaux, France) for
material analyses.
85 24 M. J. L. Tschan, C. M. Thomas, H. Strub and J.ꢀF. Carpentier, Adv.
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a
Institut de Chimie de Nice, UMR 7272 CNRS ꢀ Université Nice Sophia
Antipolis, Parc Valrose, 06108 Nice, France. Eꢀmail
:
35 sylvain.antoniotti@unice.fr
b
Institut des Sciences Moléculaires, UMR 5255 CNRS ꢀ Université de
Bordeaux, 351 cours de la libération, 33405 Talence cedex, France.
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CNRS ꢀ Université de Bordeaux, 87, Avenue du Docteur Schweitzer,
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† Electronic Supplementary Information (ESI) available: characterisation
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RSC Advances
Page 12 of 12
View Article Online
DOI: 10.1039/C5RA25176A
Simple salts of abundant metals (Fe, Bi, and Ti) supported on
Montmorillonite as efficient and recyclable catalysts for regioselective
intramolecular and intermolecular hydroalkoxylation reactions of double
bonds and tandem processes
5
10
15
Irene Notar Francesco, Bastien Cacciuttolo, Oana Pascu, Cyril Aymonier, Mathieu Pucheault and Sylvain
Antoniotti*
• 17 examples
• Yields up to 99%
• Recyclable catalyst
• Flow chemistry
Montmorillonites doped with metal cations are efficient and recyclable catalysts for hydroalkoxylation reactions
20 and amenable to flow chemistry.
25