High chemo and regioselective formation of alcohols from the hydrocarbonylation of alkenes using cooperative ligand effects

Article abstract of DOI:10.1039/b927236d

The hydrocarbonylation of alkenes, including allyl alcohol, catalysed by rhodium complexes and wide angle bidentate ligands together with PEt ₃, gives alcohols as the primary products with high chemo and regio-selectivity.

Full text of DOI:10.1039/b927236d

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COMMUNICATION
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High chemo and regioselective formation of alcohols from the
hydrocarbonylation of alkenes using cooperative ligand effectsw
a
b
a
Ine I. F. Boogaerts, Daniel F. S. White and David J. Cole-Hamilton*
˜
Received (in Cambridge, UK) 23rd December 2009, Accepted 10th February 2010
First published as an Advance Article on the web 26th February 2010
DOI: 10.1039/b927236d
The hydrocarbonylation of alkenes, including allyl alcohol,
catalysed by rhodium complexes and wide angle bidentate
hydridohydroxymethylation (Scheme 1(ii)) were to occur. In
addition, this would reduce the capital cost of any plant
because it would remove one of the reactors (the one in which
the hydrogenation is carried out). We have described such
3
ligands together with PEt , gives alcohols as the primary
products with high chemo and regio-selectivity.
a
hydrohydroxymethylation scheme based on rhodium
The hydroformylation of alkenes is established as a clean and
selective method for homologation of the carbon skeleton by
introducing the synthetically versatile aldehyde functionality,
which is then typically converted into effect products via
complexes of tris-(primary-alkyl)phosphines in protic media,
which gives the alcohols as primary reaction products
5
–9
(path (ii) in Scheme 1), via a hydroxycarbene intermediate.
However, in terms of synthetic efficiency the reaction suffers
from low linear selectivity (typically, linear : branched ratio
(l : b) E 2/1). High electron density on the metal is essential,
but attempts to increase the linear selectivity by increasing the
1
reduction, oxidation, hydroamination or amidocarbonylation.
The Kuraray process is an important application of this
2
multi-catalytic technology (path (i) in Scheme 1). A PPh or
3
3
diop -modified rhodium complex catalyses the hydroformyl-
i
i
3 3
bulk of the electron donating phosphine (PPr or PBu ) were
ation of allyl alcohol in toluene (65 1C, 2.5 bar, H
after which the hydroxyaldehyde products are removed in an
2
/CO = 4),
thwarted by the formation of monophosphine complexes,
which, being less electron rich than their bisphosphine counter-
1
0,11
aqueous extract and hydrogenated to the corresponding diols
s
parts, gave only aldehydes with poor linear selectivity.
using a RANEY nickel catalyst (80 1C, 15 bar H
2
).
Under similar reaction conditions, the rhodium complexes
n
of bis-(diarylphosphino) chelates with b in the range 108–1261
1
,4-Butanediol in particular is a valuable product, widely used
as a cross-linking agent for urethane polymers and as a
4
precursor to tetrahydrofuran.
confer high linear selectivity in the hydroformylation of allyl
alcohol (Table 1, runs 1, 4, 7 and 10). Some of the alkyl
phosphino analogues of 4 have been studied for the hydro-
carbonylation of 1-decene. Some of them do give alcohols, but
generally the l : b ratios are poor except at low conversions
The intermediate hydroxyaldehydes are reactive molecules
which can undergo inter or intramolecular acetal formation as
well as self- or cross-aldol condensation leading to a potential
loss in selectivity to the desired 1,4-butanediol. Indeed, the
major form of the linear aldehyde is as the cyclic hemiacetal,
1
2
where selectivities as high as 9.2 : 1 were observed. In an
attempt to provide 1,4-butanediol with high linear selectivity
in one step, we have studied the hydrocarbonylation of allyl
alcohol using complexes prepared in situ from a rhodium
precursor and both a wide bite angle chelating phosphine
and PEt . A Japanese patent has shown that C alcohols can
2
-hydroxytrihydrofuran (Scheme 1). This problem would be
averted if the intermediate aldehydes were not on the reaction
pathway and the diols were the primary product, i.e. if
3
4
Table 1 Products from the catalytic hydrocarbonylation of allyl
alcohol
a
b
c
[PEt
mmol dm
3
]/
CQO C–OH
(%) (l : b) (%) (l : b) C (%)
À3
d
3
Run
1
2
3
4
5
6
7
8
9
Xantphos (1)
DIOP (2)
0
4
16
0
4
16
0
4
16
0
4
16
89 (5.1)
89 (5.2)
12 (4.9)
96 (6.3)
81 (6.3)
15 (6.3)
97 (13.2)
85 (13.1)
20 (13.1)
82 (4.5)
80 (4.5)
17 (4.5)
0
11
2 (0.2)
78 (5.2)
3 (0.5)
17 (6.5)
83 (6.5)
0
10 (14.3)
76 (14.3)
0
9
10
2
2
2
3
5
4
Scheme 1 (i) Kuraray process for the production of 1,4-butanediol
from allyl alcohol; and (ii) possible direct route avoiding aldehyde
intermediates.
CBM-DXP (3)
BISBI (4)
a
EaStCHEM, School of Chemistry, University of St. Andrews,
10
11
12
18
17
18
St. Andrews, Fife, KY16 9ST, Scotland, UKE-mail: djc@st-and.ac.uk;
Fax: +44 (0)1334 463808; Tel: +44 (0)1334 463808
Lyondell Chemical Company, 3801 West Chester Pike, Newtown
3 (4.7)
65 (4.5)
b
a
3
Conditions: ethanol (4 cm ), [Rh] (8 mmol dm ), diphosphine/Rh = 2,
À3
Square, PA 19073, USA. E-mail: Daniel.White@lyondellbasell.com;
Fax: +1-610-359-4866; Tel: +1-610-359-2064
w Electronic supplementary information (ESI) available: Figure showing
the effect of CO partial pressure on the reaction chemoselectivity, full
product quantification for all catalytic reactions and experimental
details for catalytic reactions. See DOI: 10.1039/b927236d
b
2
Rh/allyl alcohol = 1/185, 120 1C, 40 bar (CO/H = 1), 4 h. Hydroxy-
c
d
aldehyde derivatives. Diol derivatives. Products of isomerisation and
hydrogenation, also includes g-butyrolactone. For a full breakdown of
the products, see ESIw, Table S1.
2
194 | Chem. Commun., 2010, 46, 2194–2196
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be formed from propene with good chemoselectivity
o86.5%) and l : b ratio (6.9) using rhodium complexes of
bidentate phosphines, 1 (best) and 4 together with P(octyl) .
The selectivity to alcohol products maximises at [PEt
3
] =
À3
(
16 mmol dm with selectivities to 1,4-butanediol up to 67%
(using 2). At higher PEt3 loadings, the l : b ratio drops
significantly and there is also a slight rise in the amount of
aldehyde formed (Fig. 1 and ESIw Table S1). Substrate
hydrogenation becomes less significant. For simple alkenes,
3
high selectivity to alcohols is observed at lower PEt
3
loading
À3
(
(
4 mmol dm ) and the linear selectivities are even higher
l : b > 30 : 1), but substrate hydrogenation can still be
In the absence of added PEt
3
, ligands 1–4 (16 mmol) give
significant, although less so for longer chain alkenes. (Table 2).
Deuterium labelling studies using 1-hexene as the substrate
confirm that heptanol is the primary product and that it is
not formed by sequential formation and hydrogenation of
heptanal. 1-Heptanol recovered from 1-heptanal hydrogenation
using D2 in ethanol occurred as the two isotopomers,
C H CH CH CH OH/D (59%) and C H CH CH CHDOH/D
high l : b ratios (up to 13 in the case of 3) for the hydro-
formylation of allyl alcohol in the presence of [Rh(acac)(CO) ]
2
À3
(
8 mmol dm , acacH = 2,4-pentane dione) in ethanol (65 1C,
4
0 bar CO/H = 1) (Table 1, runs 1, 4, 7 and 10, Scheme 1(ia)
2
and ESIw, Table S1). The products are almost exclusively
hydroxyaldehydes or their derivatives—predominantly
4
9
2
2
2
4
9
2
2
2
-hydroxytrihydrofuran (l) and 2-methyl-2-propenal (b).
(
41%) so that 59% of the 1-heptanol obtained from
reaction of 1-hexene with D and CO would be expected to
be CHDCH CHDOH/D if sequential reaction
occurred. The observed product was, however, mainly
Propanal from isomerisation of the substrate is also formed,
2
especially when using 1. Little change in the product distri-
C
4
H
9
2
a
bution is observed on adding PEt
and 11, ESIw, Table S1) but, on further increasing [PEt
Table 1, runs 3, 6, 9 and 12), 1,4-butanediol becomes a
3
(4 mmol, Table 1, runs 2, 5,
8
3
]
C
C
4
H
H
9
CHDCH
CHDCH
2
CD
CHDOH/D. We have previously shown that
–C CH CH CH OH/D comes
2
OH/D (84%) with only 14% of
(
4
9
2
significant product whilst the branched product is 2-methyl
the unexpected H in CH
2
H
4 9
2
2
2
7
propanol, which we previously have shown comes via
8
dehydration of the branched hydroxycarbene.
from the hydroxyl group of ethanol. The above observations
,13
The main
suggest that PEt must be present in the coordination sphere at
3
C3 product is propanol and g-butyrolactone becomes a
significant product.
some point in the catalytic cycle.
The complexation behaviour of the PEt /1 system with
3
[Rh(acac)(CO) ] was studied by high-pressure NMR spectro-
2
scopy in d
4
-methanol under CO/H
2
(40 bar). Formation of
1
(1)] as the only hydride species was indicated by a
4
[Rh(HCO)
2
1
triplet of doublets in the H NMR spectrum at d = À8.9 ppm
1
2
(
J
H–Rh = 6.6 Hz, JP–H = 14.7 Hz) and by a doublet in the
3
1
1
P NMR spectrum at d = 20.7 ppm ( JRh–P = 124 Hz),
together with free PEt
1
3
which gave a sharp singlet in the
3
1
P{ H} NMR spectrum at d = À17.1 ppm. There was no
evidence for exchange between the chelated rhodium complex
and free PEt3 over the temperature range 0–1001. These
observations suggest that the alkene must coordinate to
[RhH(CO)(1)] and that subsequent hydride migration will give
predominantly the linear alkyl complex (Scheme 2).
We have shown that alcohols are the primary products of
the hydrocarbonylation reactions only if there is a high
electron density on the acyl intermediate. This suggests that
Fig. 1 Major products from the hydrocarbonylation of allyl alcohol
as a function of added phosphine. ’ yield, & l : b ratio of aldehydes;
K yield, J l : b of alcohols (conditions as in Table 1).
3 6
[Rh(C(O)C H OH)(1)CO], formed from migration of the
linear alkyl group derived from allyl alcohol onto CO, must
a
Table 2 Products from the hydrocarbonylation of simple alkenes using Rh complexes of 1 and PEt
3
Selectivity C–OH Selectivity CQO
À3
b
Isom (%)
c
Hyd (%)
Substrate
[PEt
3
]/mol dm
Yield (%)
l : b
Yield (%)
l : b
1
-Hexene
0
4
1.2
83.2
89.3
1.1
86.8
0.9
1 : 0
33.1
31.7
1 : 0
40.5
95.9
11.3
3.0
98.1
10.8
83.7
0.7
35.2
34.8
30.6
38.6
38.1
34.1
1 : 0
1.1
0.6
0.3
0.2
0.0
1.8
4.9
6.4
0.7
2.4
1.1
2.7
1
0
0
4
0
4
1
1
-Octene
-Decene
d
1 : 0
31.8
14.4
7.5
89.0
a
À3
À3
À3
À3
b
= 1), 2 h. Internal
[
alkenes. Alkane. Significant amounts of isomerised alkene are present in the starting 1-decene.
Rh(acac)(CO)
c
2
] (8 mol dm ), 1 (16 mmol dm ), [alkene] (2.94 mol dm ), ethanol (4 cm ), 120 1C, 40 bar (CO : H
2
d
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Table 3 Comparison of the effect of benzyl dimethyl amine and
a
3
excess PEt on the hydrocarbonylation of allyl alcohol
Allyl alcohol-based selectivity (mol%)
b
c
d
–OH (l/b)
e
f
L–L
Base
CQO (l/b)
Isom
Hyd
1
2
4
PEt
PhCH
PEt
PhCH
PEt
PhCH
3
13 (4.8)
13 (4.9)
17 (6.2)
16 (6.2)
20 (4.4)
20 (4.6)
75 (2.9)
77 (5.2)
82 (4.3)
81 (6.4)
63 (2.2)
63 (4.5)
9
8
1
2
15
14
3
2
2
2
NMe
NMe
NMe
2
2
2
2
0
1
2
3
3
3
a
3
Conditions: ethanol (4 cm ), [Rh] (8 mmol dm ); L–L (16 mmol dm
À3
À3
)
À3
PEt
3
(8 mmol dm ); Rh/allyl alcohol = 1/185, 120 1C, 40 bar,
b
= 1, 3 h. 8 mmol dm
À3
c
CO/H
d
2
.
Diol derivatives. Propanal. Propanol.
Hydroxyaldehyde derivatives.
e
f
Scheme 2 Proposed mechanism for formation of butanediol from the
hydrocarbonylation of allyl alcohol using a catalyst prepared in situ
À3
(
over 8 mmol dm ) PEt (pK = 9.11) with N,N-dimethyl-
3
a
from [Rh(acac)(CO)
species shown in the centre of the diagram represent the mechanism
occurring in the absence of PEt
2 3
], one of ligands 1–4 and excess PEt . The grey
a
benzylamine (pK = 9.08) (Table 3).
In conclusion, we have demonstrated that high selectivity to
alcoholic products, including 1,4-butanediol from allyl
alcohol, can be obtained from the hydrocarbonylation of
3
.
react with PEt
3
to form [Rh((O)C
3
H
6
OH)(1)(PEt
3
)(CO)] in
alkenes by using wide angle bidentate ligands and PEt
operating in a cooperative manner (Tables 1 and 2). PEt does
3
order to place sufficient electron density onto the acyl oxygen
for protonation to form the hydroxycarbene intermediate on
loss of CO. The presence of three phosphine ligands, one of
them PEt , in [Rh((O)C H OH)(1)(PEt )] must allow enough
3
not coordinate during the regioselectivity controlling
steps, but enters the coordination sphere at the crucial chemo-
selectivity controlling step.
3
3
6
3
electron density to be transmitted to the acyl O atom to allow
protonation by the solvent to form the hydroxycarbene and
thence lead directly to the observed alcohol product.
We thank Lyondell Chemical Company for a studentship
and other support (I. I. F. B).
Notes and references
Since we propose that CO is displaced by PEt
key electron rich acyl intermediate, high [PEt ] should favour
diol formation, but increased CO pressure at a constant [PEt
3
to form the
3
1 Rhodium Catalysed Hydroformylation, ed. P. W. N. M. Van
Leeuwen and C. Claver, Kluwer, Dordrecht, 2000.
3
]
2
M. Matsumoto, S. Miura, K. Kikuchi, M. Tamaru, H. Kojima,
K. Koga and S. Yamashita, US Pat. 4567305, 1986.
should reduce the selectivity to alcohols. Experiments were
performed over a range of ppCO, maintaining constant ppH2
3 W. S. Dubner and W. P.-S. Shum, US Pat. 6225509, 2001.
4 L. Karas and W. J. Piel, Kirk-Othmer Encyclopaedia of Chemical
Technologies, Wiley, New York, 2004.
(20 bar) and total pressure (40 bar) by addition of Ar (ESIw,
Fig. S1). The drop in selectivity to diol with increasing CO
5
J. K. MacDougall and D. J. Cole-Hamilton, J. Chem. Soc., Chem.
Commun., 1990, 165.
6 J. K. MacDougall, M. C. Simpson and D. J. Cole-Hamilton,
partial pressure is consistent with the suggested displacement
of CO in [Rh(C(O)C H OH)(1)(CO) ] by PEt in the pathway
3
3
6
2
to alcohols. Below ppCO of 15 bar, the selectivity diminishes
Polyhedron, 1993, 12, 2877.
J. K. MacDougall, M. C. Simpson, M. J. Green and D. J.
Cole-Hamilton, J. Chem. Soc., Dalton Trans., 1996, 1161.
M. C. Simpson, A. W. S. Currie, J. A. M. Andersen, D. J.
Cole-Hamilton and M. J. Green, J. Chem. Soc., Dalton Trans.,
7
8
because substrate hydrogenation starts to dominate.
À3
At [PEt
3
] > 16 mmol dm , there was a significant decline
in linear selectivity for the diol fraction, but not so for
the hydroxyaldehyde fraction. This suggests that some
1
M. C. Simpson, K. Porteous, J. K. Macdougall and D. J.
996, 1793.
9
[
RhH(CO)
xantphos complex, favours the production of alcohols with
low linear selectivity. At still higher [PEt ], the chemo-
2 3 2
(PEt ) ] forms and, being more active than the
Cole-Hamilton, Polyhedron, 1993, 12, 2883.
0 P. Cheliatsidou, D. F. S. White and D. J. Cole-Hamilton, Dalton
Trans., 2004, 3425.
1 P. Cheliatsidou, D. F. S. White, B. de Bruin, J. N. H. Reek and
D. J. Cole-Hamilton, Organometallics, 2007, 26, 3265.
2 T. Ichihara, K. Nakano, M. Katayama and K. Nozaki, Chem.–Asian
J., 2008, 3, 1722.
13 J. K. MacDougall, M. C. Simpson and D. J. Cole-Hamilton,
J. Chem. Soc., Dalton Trans., 1994, 3061.
4 M. Kranenburg, Y. E. M. Vanderburgt, P. C. J. Kamer,
P. W. N. M. van Leeuwen, K. Goubitz and J. Fraanje,
Organometallics, 1995, 14, 3081.
1
1
1
3
selectivity reverted towards aldehyde. This may be because
PEt3 is a base and reduces the acidity of the solution
sufficiently to prevent formation of the hydroxycarbene inter-
mediate, which is key to the direct formation of diols, as has
i
3
11
been suggested before when using PBu
.
Support for
1
this suggestion comes from the observation that very
similar results were obtained when replacing the excess
2
196 | Chem. Commun., 2010, 46, 2194–2196
This journal is ꢀc The Royal Society of Chemistry 2010