Substrate-Selective Olefin Hydrogenation with a Cavitand-Based Bis(N-anisyl iminophosphorane)

Article abstract of DOI:10.1002/ejoc.201601125

A distally-substituted resorcin[4]arene cavitand equipped with two remote N-anisyl-imino-phosphoranyl (AIP) units has been synthesised and assessed in the competitive hydrogenation of α-olefins (rhodium catalyst). A substrate-selectivity factor of 39.2 in

Full text of DOI:10.1002/ejoc.201601125

DOI: 10.1002/ejoc.201601125
Full Paper
Olefin Hydrogenation
Substrate-Selective Olefin Hydrogenation with a Cavitand-Based
Bis(N-anisyl iminophosphorane)
[a]
[a]
[a]
[a]
Thierry Chavagnan, Claude Bauder, David Sémeril* Dominique Matt* and
[
b]
Loïc Toupet
Abstract: A distally-substituted resorcin[4]arene cavitand that has two double bonds in different steric environments. The
equipped with two remote N-anisyl-imino-phosphoranyl (AIP) remarkable olefin discrimination probably arises from the ability
units has been synthesised and assessed in the competitive of the ligand to generate a cavity-capping N,O-chelator involv-
hydrogenation of α-olefins (rhodium catalyst). A substrate- ing both AIP groups. Chelate formation positions the reactive
selectivity factor of 39.2 in favour of the linear olefin was ob- metal sites inside the receptor moiety, the restricted size of
served after 1 h in the reduction of stoichiometric amounts of which may retard the coordination of larger α-olefins. The re-
hex-1-ene and 3-ethyl-pent-1-ene. The catalyst was also shown sults of this study encourage the further development of cavi-
to be suitable for the regioselective reduction of a compound tands as shape-selective catalysts.
Introduction
molecular interactions, notably π–π-stacking interactions be-
tween the aromatic unit of an olefinic substrate and the inner
part of a catalytic cleft (e.g., based on a diphenylglycoluril
Substrate-selective catalysis[1] is an elegant way to selectively
convert a specific compound from a mixture of substrates, often
a mixture that is difficult to separate. If we exclude the kinetic
resolution of racemic mixtures, only a few examples of sub-
strate-competing experiments involving homogeneous cata-
lysts have been reported. In such experiments, the competing
substrates usually have quite different structures, which facili-
tate the selectivity. The structures distinguish themselves, for
example, by the presence or absence of aromatic subunits, or of
additional polar functional groups. Thus, palladium-containing
dendrimers functionalised with amide groups were found to be
suitable for substrate-specific hydrogenations of polar olefins in
the presence of nonpolar analogues; the observed selectivity
arise from strong interactions between the polar substrates and
[4]
[5]
unit ) or a cavity (ꢀ-cyclodextrin ). An approach based on the
use of a bulky counteranion revealed that a combination of
4–
Wilkinson's catalyst with the Keggin SiW O
anion led to
1
2 40
the preferential hydrogenation of monosubstituted olefins over
[6]
disubstituted ones.
In this paper, we describe the synthesis of the cavitand-
based bis(N-anisyl iminophosphorane) 4 (Figure 1) and its use
in α-olefin-competing hydrogenations. This study was under-
taken with the anticipation that the presence of a hollow space
close to the coordinating centres would be helpful in the dis-
crimination process. It is worth mentioning that to date only
one resorcinarene-derived metal complex has been used in
substrate-competitive reactions (namely in Pd-catalysed allylic
[
2]
the NH groups of the catalyst. Similarly, allylic ethers tethered
to pyridyl groups reacted faster than the corresponding alkenes
[7]
alkylation). Nonmetallated resorcinarenes have also been
used in substrate-selective catalysis; they were used as auxilia-
ries that were able to form self-assembled cavities under cata-
linked to
a phenyl group in transition-metal-catalysed
hydrogenations. The rate acceleration observed for the former
compounds was attributed to the formation of efficient chelate
complexes involving the pyridyl–nitrogen atom. In some
other examples, substrate discrimination resulted from supra-
[
3]
[
[
a] Laboratoire de Chimie Inorganique Moléculaire et Catalyse, UMR 7177
CNRS,
Université de Strasbourg,
4
rue Blaise Pascal, 67070 Strasbourg Cedex, France
E-mail: dsemeril@unistra.fr
dmatt@unistra.fr
http://lcimc.u-strasbg.fr
b] Institut de Physique, UMR 6251 CNRS, Université de Rennes 1,
Campus de Beaulieu, 35042 Rennes Cedex, France
Supporting information and ORCID(s) from the author(s) for this article are
available on the WWW under http://dx.doi.org/10.1002/ejoc.201601125.
Figure 1. Resorcin[4]arene-based bis(iminophosphorane) 4 used in this study.
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lytic conditions. The resulting capsules were shown to function
as containers hosting catalytic reactions that could occur either
[
8]
[9]
with or without an organometallic catalyst.
Results and Discussion
The synthesis of bis(iminophosphorane) 4 began with that of
diphosphine 2. The latter was obtained in two steps from the
bromo-substituted cavitand 1 by a lithium–halogen exchange
[
10]
followed by reaction with ClPPh (Scheme 1).
The product
2
3
1
was purified by column chromatography (70 % yield). The
P
NMR spectrum of 2 shows a singlet at δ = –16.1 ppm. The
double phosphination was confirmed by X-ray diffraction analy-
sis (Figure 2). The cavitand adopts the usual bowl-shaped struc-
2 2
Figure 2. Molecular structure of phosphine 2·3CH Cl . Only the embedded
solvent molecule is shown. Top-rim diameters 7.89 and 8.14 Å. Separation
between the two phosphorus atoms: 10.26 Å.
ture of resorcin[4]arene-derived cavitands containing OCH O
2
[
10a,11]
linkers,
with top-rim diameters (i.e., the segments linking
the C-2 aromatic carbon atoms of opposite resorcinolic rings)
of 7.89 and 8.14 Å. A dichloromethane molecule is poised
above the cavity entrance. In the solid state, the two phos-
phorus lone pairs of 2 are tangential to the cone defined by
the cavity core. This contrasts somewhat with the P=O vectors,
skewed towards the cavitand axis, of the corresponding
di(phosphine oxide) 3 (Scheme 1), which was obtained by treat-
ment of 2 with H O , and which was also structurally character-
2
2
ised (Figure 3).
2
Figure 3. Molecular structure of 3·2MeOH·H O. Only the embedded solvent
molecule is shown. Top-rim diameters 7.89 and 8.14 Å. Separation between
the two phosphorus atoms: 9.98 Å.
(Scheme 1). The compound was characterised by elemental
analysis, mass spectrometry (ESI-TOF) and NMR spectroscopy.
The mass spectrum shows a strong peak at m/z = 1427.68,
which corresponds to the expected [M + H]+ ion. In the
31
P
NMR spectrum, the phosphorus atoms appear as a singlet at
δ = –6.6 ppm. Consistent with a C symmetrical cavitand, the
2
v
1
H NMR spectrum shows an AB pattern for the four methylenic
OCH O groups, and a single methine signal. Compound 4 is
2
only moderately air-stable, and therefore needs to be stored
under argon. Its reaction with water led quantitatively to 3.
Bis(iminophosphorane) 4 was then assessed in α-olefin-com-
peting hydrogenations (Scheme 2). The catalytically active spe-
cies was generated in situ by mixing [Rh(cod) ]BF (1 mol-%,
2
4
[
13]
cod = 1,5-cyclooctadiene) and 4 (1 mol-%).
The runs were
carried out in THF under H (5 bar). Under these conditions, a
2
Scheme 1. Synthesis of diphosphine 2, bis(phosphine oxide) 3 and bis(imino-
phosphorane) 4.
1
:1 mixture of hex-1-ene and 3-ethylpent-1-ene produced hex-
ane and 3-ethylpentane in 19.6 and 0.5 % yields, respectively,
after 1 h (Table 1, entry 1). This corresponds to a substrate-
Iminophosphorane 4 was then obtained through the Staud- selectivity factor of 39.2. After 8 h, the hexene conversion had
[
12]
inger condensation
of bisphosphine 2 and 4-anisyl azide reached 84.6 %, and the hexane/3-ethylpentane ratio was still
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2 4
Table 1. Competitive hydrogenation of α-olefins catalysed by the [Rh(cod) ]BF
/4 system.[a]
[
a] Conditions: [Rh(cod)
2 4 2
]BF (1 mol-%), 4 (1 mol-%), olefins (1.0 mmol of each), H (P = 5 bar), THF (5 mL), room temp. The conversions were determined by
GC.
as high as 4.1:1 (Table 1, entry 3). Tests with two linear α-olefins, with a mixture of [Rh(cod) ]BF and 2 equiv. of PPh was much
2
4
3
namely hex-1-ene and dec-1-ene, resulted in the preferential less selective. With this catalyst, 25 % of the allylic and 20 % of
hydrogenation of the shorter hex-1-ene, with conversions of the vinylic double bonds had undergone hydrogenation after
1
3.5 and 2.5 % after 1 h for the C and C olefins, respectively 1 h.
6 10
(
hexane/decane ratio = 5.4; Table 1, entry 4). When the
In order to get some insight into the possible role played
by the resorcinarene subunit in the above reactions, additional
hydrogenation tests were carried out (Table 2) with 1:1 mixtures
of hex-1-ene and dec-1-ene {THF, H (5 bar), [Rh(cod) ]BF }. The
results obtained were compared to that shown in Table 1, en-
try 4, an experiment carried out with a 4/Rh ratio of 1:1, which
led to a hexane/decane ratio of 5.4 (hexene conversion: 13.5 %)
after a reaction time of 1 h. Lowering the 4/Rh ratio to 1:2
increased the rate of hydrogenation, but selectivity for one of
the two substrates was not observed in this case; full conver-
sion of both olefins was observed after 1 h (Table 2, entry 2).
Increasing the 4/Rh ratio to 2:1 resulted in a hex-1-ene conver-
sion of 33.6 % after 1 h, with a hexane/decane ratio of only 1.5
hydrogenation of this mixture was continued for 4 h, the prefer-
ential hydrogenation of hex-1-ene was maintained, but the hex-
ane/decane ratio dropped to 4.7 (hexene conversion after 5 h:
2
2
4
4
8.1 %; Table 1, entry 5). A lower substrate selectivity was ob-
served after a reaction time of 5 h when styrene was hydrogen-
ated together with 3-ethyl-pent-1-ene; the corresponding ethyl-
benzene/3-ethylpentane ratio was 2.4 for a styrene conversion
of 36.2 % (Table 1, entry 8).
(
Table 2, entry 3). A comparably low substrate selectivity was
Scheme 2. α-Olefin-competing hydrogenations.
observed when the reaction was carried out with 2 equiv. of
mono(iminophosphorane) 5 (Figure 4; Table 2, entry 4), as well
as with the cavity-free ligand 6 (hexane/decane ratio = 1.3;
Table 2, entry 5). Repeating the hydrogenation runs with bis-
We wondered whether the Rh/4 system could also discrimi-
nate between different C=C double in the same compound. To
answer this question, glucosidic substrate 9, which features a
vinyl and an allyl substituent, was hydrogenated in the pres-
ence of 4 (Scheme 3). Remarkably, when the reaction was con-
(
iminophosphorane) 7, which has nBu groups instead of meth-
oxy substituents, also resulted in poor substrate selectivity (hex-
ane/decane ratio of 1.6, Table 2 entry 6). These observations
show that substrate discrimination is only observed if: a) two
iminophosphorane units are available per Rh centre; b) the
nitrogen atoms are substituted with an aryl ring that bears a
methoxy group; and c) the two iminophosphorane units are
tethered to the same resorcinarene platform. Finally, we found
that in the absence of any ligand, the hydrogenation rates were
high, and the substrate selectivity was close to zero (hexane/
decane ratio = 1.1 after 1 h; Table 2 entry 7). Similar observa-
tions were made when the hydrogenation experiments were
carried out in the presence of phosphine oxide 3 or 4-anisyl-
amine (8), which are the typical decomposition products of 4
in the presence of water (Table 2, entries 8 and 9).
ducted with a H pressure of 5 bar and with 2 mol-% of the
2
catalyst, product 10, in which only the allylic double bond had
been hydrogenated, was exclusively formed in 84 % yield after
1
4 h. Complete reduction of both double bonds was observed
when the hydrogenation conditions were maintained for ca.
4 h. For comparison, we found that the hydrogenation of 9
2
Overall, the above described results unambiguously indicate
that both iminophosphorane moieties of 4 are involved in the
catalytic process. Owing to the large N···N separation, this can-
not occur via catalytic intermediates containing an N,N-chelated
Scheme 3. Competitive α-olefin hydrogenation within 9.
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Figure 4. Iminophosphoranes 5–7 used for comparison with bis(iminophosphoranyl)resorcin[4]arene 4.
Table 2. Competitive hydrogenation of hex-1-ene and dec-1-ene (1:1), influ-
ence of the ligand.
planation remains hypothetical at this stage. Note that a 2D
DOSY (Diffusion-Ordered SpectrocopY) experiment carried out
[
a]
on a stoichiometric mixture of ligand 4 and [Rh(cod) ]BF re-
Entry
Ligand (L/Rh ratio)
Hydrogenated products [%]
hexane / decane
2
4
vealed the formation of a species with a diffusion coefficient of
2
–1
4
60 μm s in THF. This value is close to that obtained for the
1
2
3
4
4 (1:1)
4 (1:2)
4 (2:1)
5 (2:1)
6 (2:1)
7 (1:1)
–
13.5 / 2.5 = 5.4
100 / 100 = 1.0
33.6 / 22.0 = 1.5
35.3 / 19.5 = 1.8
26.2 / 20.3 = 1.3
36.4 / 22.6 = 1.6
94.8 / 83.6 = 1.1
94.0 / 85.2 = 1.1
92.7 / 87.7 = 1.1
free ligand (i.e., 4), so the formation of an oligomeric complex
31
appears unlikely. The P NMR spectrum of the reaction mixture
showed a very broad signal at δ ≈ –6 ppm (cf. δ = –6.6 ppm
for 4); this is indicative of a fluxional complex.
[
b]
c]
5
6
7
8
9
[
3 (1:1)
8 (2:1)
Conclusions
[
(
a] Conditions: [Rh(cod)
P = 5 bar), THF (5 mL), room temp., 1 h. The conversions were determined
]BF (0.1 mol-%), 7 (0.2 mol-%), olefins (each
0.0 mmol), 0.1 h. [c] Conditions: [Rh(cod) ]BF (0.1 mol-%), 7 (0.1 mol-%),
olefins (each 10.0 mmol), 0.25 h.
2 4 2
]BF (1 mol-%), ligand, olefins (1.0 mmol of each), H
In summary, we have described the synthesis of a resorcinarene
cavitand substituted with two remote N-anisyl-iminophosphor-
anyl units. Mixing this compound with 1 equiv. of [Rh(cod) ]BF4
by GC. [b] Conditions: [Rh(cod)
1
2
4
2
4
2
resulted in a hydrogenation catalyst suitable for the shape- and
size-selective transformation of binary mixtures of α-olefins. A
high substrate discrimination was observed in the reduction of
a 1:1 mixture of hex-1-ene and 3-ethyl-pent-1-ene; this reaction
gave a substrate-selectivity factor of 39.2 in favour of the linear
olefin after a reaction time of 1 h. The observed selectivity
probably arises from the formation of a N,O-chelate complex,
which fixes the metal at the cavity entrance, and forces incom-
ing olefins to enter a restricted space, ensuring the discrimina-
tion process. The catalyst also regioselectively reduced a com-
pound containing two double bonds in different steric environ-
ments. This study illustrates the potential of cavity-shaped sub-
units in catalysis.
rhodium centre. Instead, it is possible to envisage that one of
the two nitrogen atoms and a methoxy group of the other
anisyl-iminophosphorane moiety form a chelating N,O unit that
spans the wider rim of the cavitand. This would locate the rho-
dium centre at the cavity entrance and orientate two free coor-
dination sites towards the cavity interior (Figure 5). The ob-
served substrate selectivity should then result from a shape se-
lective process controlled by the cavity size. However, this ex-
Experimental Section
General Remarks: All manipulations involving phosphorus deriva-
tives were carried out in Schlenk-type flasks under dry argon. Sol-
vents were dried by conventional methods and were distilled imme-
diately before use. CDCl was passed down a 5 cm-thick alumina
3
column, and stored under nitrogen over molecular sieves (4 Å). Rou-
1
13
1
31
1
tine H, C{ H}, and P{ H} spectra were recorded with Bruker FT
1
instruments (AC 400). H NMR spectra were referenced to residual
protiated solvents (δ = 7.16 ppm for C D , and δ = 7.26 ppm for
6
6
CDCl3). 13C NMR chemical shifts are reported relative to deuterated
Figure 5. Proposed N,O-chelated rhodium intermediate.
solvents (δ = 128.00 ppm for C D , and δ = 77.16 ppm for CDCl ).
6
6
3
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31
P NMR spectroscopic data are given relative to external H PO . 5,17-Bis(diphenylphosphinoyl)-4(24),6(10),12(16),18(22)-tetra-
3
4
Chemical shifts and coupling constants are reported in ppm and
Hz, respectively. Infrared spectra were recorded with a Bruker
FTIR Alpha-P spectrometer. Elemental analyses were carried
out by the Service de Microanalyse, Institut de Chimie, Université
de Strasbourg. The catalytic solutions were analysed with a Varian
methylenedioxy-2,8,14,20-tetrapentylresorcin[4]arene (3): H O
(30 % aq.; 0.5 mL, 0.62 mmol) was added to a solution of 2 (0.060 g,
2 2
0.05 mmol) in CH Cl (10 mL). The resulting solution was stirred at
2
2
room temperature for 2 h. A mixture of CH Cl (10 mL) and water
2
2
(20 mL) was then added. The two phases were separated, and the
3
900 gas chromatograph fitted with a WCOT fused silica column
aqueous phase was washed twice with CH Cl2 (2 × 10 mL). The
2
(
25 m × 0.25 mm, 0.25 μm film thickness). 5,17-Dibromo-
organic solutions were combined, dried with Na SO and filtered.
2
4
4
(24),6(10),12(16),18(22)-tetramethylenedioxy-2,8,14,20-tetra-
The solution was evaporated to dryness to give bis(phosphine ox-
[
11b]
1
pentylresorcin[4]arene (1)
and 5-(diphenylphosphanyl)-
ide) 3 (0.061 g, 99 %) as a white solid. H NMR (400 MHz, CDCl ):
3
4
(24),6(10),12(16),18(22)-tetramethylenedioxy-2,8,14,20-tetra pentyl δ = 7.72–7.67 (m, 8 H, arom. CH, PPh ), 7.48–7.40 (m, 12 H, arom.
2
[
10a]
resorcin[4]arene
were prepared by literature procedures. The
CH, PPh ), 7.35 (s, 2 H, arom. CH, resorcinarene), 7.04 (s, 2 H, arom.
2
synthesis of diolefin 9 is described in the Supporting Information.
-Methoxyphenyl azide and 4-butylphenyl azide were synthesised
CH, resorcinarene), 6.38 (s, 2 H, arom. CH, resorcinarene), 4.64 (t,
3
2
4
J = 8.0 Hz, 4 H, CHCH ), 4.61 and 4.32 (AB spin system, J = 7.6 Hz,
2
by using TfN according to a procedure developed by Liu and
8 H, OCH O), 2.33–2.24 (m, 4 H, CHCH ), 2.16–2.07 (m, 4 H, CHCH ),
2 2 2
3
Tor.[ Although we did not experience any difficulty in handling TfN3, 1.41–1.24 (m, 24 H CH CH CH CH ), 0.90 (t, J = 6.6 Hz, 12 H,
14]
3
2
2
2
3
13
1
care should be taken owing to the potentially explosive nature of CH CH ) ppm. C{ H} NMR (100 MHz, CDCl ): δ = 156.68–117.05
2
3
3
some azides. The reagent should be kept in solution and used immedi- (arom. C's), 100.08 (s, OCH O), 36.46 (s, CHCH ), 32.11 (s,
2
2
ately after its synthesis.
CH CH CH ), 30.18 (s, CHCH ), 27.63 (s, CHCH CH ), 22.80 (s,
2 2 3 2 2 2
31
1
CH CH ), 14.21 (s, CH CH ) ppm. P{ H} NMR (162 MHz, CDCl ): δ =
2
3
2
3
3
5
4
,17-Bis(4-methoxyphenyliminodiphenylphosphoranyl)-
(24),6(10),12(16),18(22)-tetramethylenedioxy-2,8,14,20-tetra-
2
2.3 [s, P(O)Ph ] ppm. C H O P (1217.41): calcd. C 74.98, H 6.79;
2 76 82 10 2
found C 75.09, H 6.87.
pentylresorcin[4]arene (4): A solution of 4-methoxyphenyl azide
0.134 g, 0.90 mmol) in toluene (10 mL) was added to a solution of
(
5-(4-Methox yphenyliminodiphenylphosphoranyl)-
4(24),6(10),12(16),18(22)-tetramethylenedioxy-2,8,14,20-tetra-
pentylresorcin[4]arene (5): A solution of 4-methoxyphenyl azide
(0.067 g, 0.45 mmol) in toluene (10 mL) was added to a solution of
5-(diphenylphosphanyl)-4(24),6(10),12(16),18(22)-tetramethylenedi-
diphosphine 2 (0.533 g, 0.45 mmol) in toluene (10 mL). The solution
was stirred at 60 °C for 16 h, then the reaction mixture was evapo-
rated to dryness under vacuum to give bis(iminophosphorane) 4
1
(0.642 g, quantitative). H NMR (400 MHz, C D ): δ = 7.96–7.91 (m,
6
6
8
2
6
4
5
7
2
H, arom. CH, PPh ), 7.77 (s, 2 H, arom. CH, resorcinarene), 7.45 (s, oxy-2,8,14,20-tetrapentylresorcin[4]arene (0.450 g, 0.45 mmol) in
2
H, arom. CH, resorcinarene), 7.05–6.98 (m, 12 H, arom. CH, PPh ),
toluene (10 mL). The solution was stirred at 60 °C for 16 h, then the
reaction mixture was concentrated to dryness under vacuum to
give iminophosphorane 5 (0.505 g, quantitative). H NMR (400 MHz,
2
3
3
.75 (d, J = 8.2 Hz, 4 H, arom. CH, C H OCH ), 6.53 (d, J = 8.2 Hz,
6
4
3
1
H, arom. CH, C H OCH ), 6.28 (s, 2 H, arom. CH, resorcinarene),
6
4
3
3
2
.05 (t, J = 8.0 Hz, 4 H, CHCH ), 4.98 and 4.49 (AB spin system, J =
C D ): δ = 8.01–7.97 (m, 4 H, arom. CH, PPh ), 7.79 (s, 1 H, arom.
2
6
6
2
.6 Hz, 8 H, OCH O), 3.40 (s, 6 H, OCH ), 2.37–2.29 (m, 4 H, CHCH ),
CH, resorcinarene), 7.53 (s, 1 H, arom. CH, resorcinarene), 7.46 (s, 2
2
3
2
.20–2.13 (m, 4 H, CHCH ), 1.34–1.19 (m, 24 H, CH CH CH CH ), 0.81 H, arom. CH, resorcinarene), 7.03–6.95 (m, 6 H, arom. CH, PPh ), 6.91
2
2
2
2
3
2
3
13
(t, J = 7.0 Hz, 12 H, CH CH ) ppm. C NMR (125 MHz, C D ): δ = (s, 1 H, arom. CH, resorcinarene), 6.27 (s, 2 H, arom. CH, resorcinar-
2 3 6 6
3
3
1
57.52–114.63 (arom. C's), 100.40 (s, OCH O), 55.08 (s, OCH ), 37.07 ene), 6.18 (d, J = 8.0 Hz, 2 H, arom. CH, C H OCH ), 5.85 (d, J =
2 3 6 4 3
(
s, CHCH ), 32.26 (s, CH CH CH ), 30.74 (s, CHCH ), 27.95 (s,
8.0 Hz, 2 H, arom. CH, C H OCH ), 5.73 and 4.58 (AB spin system,
2
2
2
3
2
6
4
3
3
1
2
3
3
CHCH CH ), 23.07 (s, CH CH ), 14.29 (s, CH CH ) ppm. P NMR
(
MS (ESI-TOF): m/z = 1427.68 [M + H], expected isotopic profile.
C H N O P (1427.68): calcd. C 75.71, H 6.78, N 1.96; found C
J = 7.5 Hz, 4 H, OCH O), 5.18 (t, J = 8.0 Hz, 2 H, CHCH ), 5.06 (t,
2
2
2
3
2
3
2
2
–
1
2
162 MHz, C D ): δ = –6.6 (s, PPh ) ppm. IR: ν˜ = 1439 (P = N) cm .
J = 8.0 Hz, 2 H, CHCH ), 4.83 and 4.50 (AB spin system, J = 7.5 Hz,
2
6
6
2
4 H, OCH O), 3.27 (s, 6 H, OCH ), 2.35–2.22 (m, 8 H, CHCH ), 1.40–
2 3 2
3
1.18 (m, 24 H, CH CH CH CH ), 0.81 (t, J = 7.5 Hz, 6 H, CH CH ),
2 2 2 3 2 3
90
96
2
10
2
3
13
7
5.58, H 6.59, N 2.07.
,17-Bis(diphenylphosphanyl)-4(24),6(10),12(16),18(22)-tetra-
methylenedioxy-2,8,14,20-tetrapentylresorcin[4]arene (2): n-
Butyllithium (1.6 in hexane; 0.68 mL, 1.08 mmol) was slowly
0.80 (t, J = 7.5 Hz, 6 H, CH CH ) ppm. C NMR (125 MHz, C D ):
2 3 6 6
δ = 156.96–114.13 (arom. C's), 99.71 (s, OCH O), 99.48 (s, OCH O),
2
2
5
5
4.62 (s, OCH ), 36.77 (s, CHCH ), 36.61 (s, CHCH ), 32.00 (s,
3 2 2
CH CH CH ), 31.93 (s, CH CH CH ), 30.27 (s, CHCH ), 30.16 (s,
2
2
3
2
2
3
2
M
CHCH ), 27.72 (s, CHCH CH ), 27.67 (s, CHCH CH ), 22.73 (s, CH CH ),
2
2
2
2
2
2
3
added to a solution of dibromo-cavitand 1 (0.500 g, 0.51 mmol) in
THF (50 mL) at –78 °C. After 0.5 h, the resulting dianion was
quenched with chlorodiphenylphosphine (0.24 mL, 1.10 mmol), and
the mixture was stirred at 40 °C for 16 h. The solvent was evapo-
rated under reduced pressure, and the crude product was purified
3
1
2
(
2.70 (s, CH CH ), 13.96 (s, CH CH ), 13.92 (s, CH CH ) ppm. P NMR
2 3 2 3 2 3
–1
162 MHz, C D ): δ = –9.7 (s, PPh ) ppm. IR: ν˜ = 1436 (P = N) cm .
6
6
2
MS (ESI-TOF): m/z = 1122.56 [M + H], expected isotopic profile.
C H NO P (1122.37): calcd. C 75.98, H 7.18, N 1.25; found C 76.05,
71
80
9
H 7.22, N 1.15.
by column chromatography (Et O/petroleum ether, 20:80) to give 2
(
2
1
0.424 g, 70 %). H NMR (400 MHz, CDCl ): δ = 7.38–7.31 (m, 20 H, 4-Methoxyphenyliminotriphenylphosphorane (6): A solution of
3
arom. CH, PPh ), 7.22 (s, 2 H, arom. CH, resorcinarene), 7.09 (s, 2 H, 4-methoxyphenyl azide (0.149 g, 1.00 mmol) in toluene (10 mL) was
2
arom. CH, resorcinarene), 6.36 (s, 2 H, arom. CH, resorcinarene), 4.77 added to a solution of triphenylphosphine (0.262 g, 1.00 mmol) in
2
3
and 4.13 (AB spin system, J = 7.2 Hz, 8 H, OCH O), 4.70 (t, J =
toluene (10 mL). The solution was stirred for 16 h at 60 °C, then the
reaction mixture was evaporated to dryness under vacuum to give
2
8
.0 Hz, 4 H, CHCH ), 2.33–2.24 (m, 4 H, CHCH ), 2.20–2.11 (m, 4 H,
2
2
3
1
CHCH ), 1.44–1.30 (m, 24 H CH CH CH CH ), 0.91 (t, J = 7.2 Hz, 12
H, CH CH ) ppm. C{ H} NMR (100 MHz, CDCl ): δ = 157.13–116.79
arom. C's), 99.35 (s, OCH O), 36.75 (s, CHCH ), 32.10 (s, CH CH CH ),
0.19 (s, CHCH ), 27.65 (s, CHCH CH ), 22.84 (s, CH CH ), 14.23 (s,
CH CH ) ppm. P{ H} NMR (162 MHz, CDCl ): δ = –16.1 (s, PPh ) pm
ppm. C H O P (1185.41): calcd. C 77.00, H 6.97; found C 76.91, H
6 (0.383 g, quantitative). H NMR (1400 MHz, C D ): δ = 7.88–7.83
2
2
2
2
3
6 6
13
1
3
(6 H, arom. CH, PPh ), 7.19 (d, J = 7.8 Hz, 2 H, arom. CH, CH OC H ),
2
3
3
3 3 6 4
3
(
7.11–7.04 (9 H, arom. CH, PPh ), 6.81 (d, J = 7.8 Hz, 2 H, arom. CH,
3
2
2
2
2
3
13
1
3
CH OC H ), 3.41 (s, 3 H, CH O) ppm. C{ H} NMR (100 MHz, C D ):
2
2
2
2
3
3 6 4 3 6 6
3
1
1
δ = 152.82 (s, arom. Cquat.-OCH ), 145.41 (s, arom. C -N), 132.91
3 quat
2
3
3
2
2
1
(d, arom., J = 9.2 Hz, CH, ortho to P), 132.64 (d, arom., J
=
76
82
8
2
C,P
C,P
7
.05.
97.9 Hz, Cquat-P), 131.46 (s, arom. CH, C H OCH ), 128.66 (d, arom.,
6 4 3
Eur. J. Org. Chem. 0000, 0–0
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Full Paper
3JC,P = 11.5 Hz, CH, meta to P), 124.30 (d, arom., 4JC,P = 16.9 Hz, CH,
para to P), 115.00 (s, arom. CH, C H OCH ), 55.30 (s, CH O) ppm.
calcd. w = 1/[σ (F ) + (0.0995P) ] in which P = (F + 2 F )/3
2
2
2
2
2
o
o
c
with the resulting R = 0.0531, RW = 0.1482 and SW = 0.961,
P{ H} NMR (162 MHz, C D ): δ = 0.0 (s, PPh ) ppm. IR: ν = 1436 (P= Δρ<0.983 e Å }.
6
4
3
3
31
1
–3
6
6
3
˜
–1
N) cm . C H NOP (383.42): calcd. C 78.31, H 5.78, N 3.65; found
25 22
Colourless single crystals of 3 suitable for X-ray diffraction were
obtained by slow diffusion of non-anhydrous methanol into a
C 78.42, H 5.64, N 3.74.
5
4
,17-Bis(4-butylphenyliminodiphenylphosphoranyl)-
(24),6(10),12(16),18(22)-tetramethylenedioxy-2,8,14,20-tetra-
CH
2
Cl
2
solution of 3 at room temperature. The sample
(0.242 × 0.182 × 0.128 mm) was mounted on an Oxford Diffraction
Xcalibur Saphir 3 diffractometer with graphite-monochromatised
pentylresorcin[4]arene (7): A solution of 4-butylphenyl azide
(
diphosphine 2 (0.533 g, 0.45 mmol) in toluene (10 mL). The solution
was stirred at 60 °C for 16 h, then the reaction mixture was concen-
0.157 g, 0.90 mmol) in toluene (10 mL) was added to a solution of Mo-K
radiation. Formula of the crystals: C76
= 1299.51, monoclinic, space group P2 /c, a = 23.5303(4), b =
16.7471(2), c = 19.4323(3) Å, ꢀ = 114.371(2)°, V = 6975.23(18) Å ,
H O P ·2CH OH·H O,
α
82 10 2 3 2
M
r
1
3
–
3
–1
trated to dryness under vacuum to give iminophosphorane 7
Z = 4, D
x
= 1.236 mg m , λ(Mo-K ) = 0.71073 Å, μ = 0.126 mm ,
α
1
(0.666 g, quantitative). H NMR (400 MHz, C D ): δ = 7.83–7.78 (m,
F(000) = 2772, T = 150(2) K. Data collection (2θmax = 27.0°, ω scan
6
6
8
2
H, arom. CH, PPh ), 7.77 (s, 2 H, arom. CH, resorcinarene), 7.45 (s, frames via 0.7° ω rotation and 30 s per frame, range hkl: h –29 to
2
H, arom. CH, resorcinarene), 7.04–6.99 (m, 20 H, arom. CH, PPh2
30, k –21 to 21, l –24 to 24) gave 52330 reflections. The data re-
vealed 15160 independent reflections of which 9117 were observed
with I > 2.0 σ(I). The structure was solved using SIR-97,
revealed the non-hydrogen atoms of the molecule. After anisotropic
refinement, all the hydrogen atoms were found by Fourier differ-
ence. The whole structure was refined with SHELXL97
and C H nBu), 6.23 (s, 2 H, arom. CH, resorcinarene), 5.14 and 4.69
6
4
2
3
[15]
(AB spin system, J = 7.5 Hz, 8 H, OCH O), 5.04 (t, J = 8.0 Hz, 4 H,
which
2
3
CHCH ), 2.78 (t, J = 8.0 Hz, 4 H, C H CH ), 2.38–2.31 (m, 4 H,
CHCH ), 2.16–2.09 (m, 4 H, CHCH ), 1.60 (quint, J = 7.7 Hz, 4 H,
C H CH CH ), 1.32 (hex, J = 7.7 Hz, 4 H, CH CH , nBu), 1.33–1.18
(
2
6
4
2
3
2
2
3
[16]
using the
6
4
2
2
2
3
3
2
m, 24 H, CH CH CH CH , resorcinarene), 0.87 (t, J = 7.2 Hz, 6 H, full-matrix least-squares technique {use of F ; x, y, z, ꢀij for C, O, and
CH CH , nBu), 0.81 (t, J = 6.7 Hz, 12 H, CH CH , resorcinarene) ppm. P atoms, x, y, z in the riding mode for H atoms; 817 variables and
2 2 2 3
3
2
3
2
3
13
2
2
2
C NMR (125 MHz, C D ): δ = 157.42–117.39 (arom. C's), 100.72 (s,
9117 observations with I > 2.0 σ(I); calcd. w = 1/[σ (F
in which P = (F
0.1553 and S = 0.859, Δρ < 1.532 e Å }.
o
) + (0.1177P) ]
6
6
2
2
OCH O), 37.04 (s, CHCH ), 35.53 (s, C H CH ), 34.61 (s, C H CH CH ),
o
+ 2 F
c
)/3 with the resulting R = 0.0570, R
=
W
2
2
6
4
2
6
4
2
2
3
3
2.21 (s, CH CH CH , resorcinarene), 30.70 (s, CHCH ), 27.88 (s,
W
2
2
3
2
CHCH CH ), 23.06 (s, CH CH , resorcinarene), 22.88 (s, CH CH , nBu),
2
2
2
3
2
3
CCDC 931124 (for 2), and 964375 (for 3) contain the supplementary
crystallographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre.
31
1
4.30 (s, CH CH , nBu), 13.92 (s, CH CH , resorcinarene) ppm.
P
2
3
2
3
NMR (162 MHz, C D ): δ = –5.6 (s, PPh ) ppm. IR: ν˜ = 1329 (P=N)
6
6
2
–1
cm . MS (ESI-TOF): m/z = 1480.76 [M + H], expected isotopic profile.
C H N O P (1479.84): calcd. C 77.92, H 7.36, N 1.89; found C
96 108 2 8 2
7
7.98, H 7.38, N 1.87.
Acknowledgments
General Procedure for the Catalytic Hydrogenation: The
hydrogenation experiments were carried out in a glass-lined stain- This work was supported by the (French) Agence Nationale de
less steel autoclave (100 mL) containing a magnetic stirrer bar. In
a typical run, [Rh(cod) ]BF (0.004 g, 1 mol-%) and a solution of
diiminophosphorane 4 (0.014 g, 1 mol-%) in THF (5 mL) was added
successively to the autoclave under nitrogen. The mixture was
stirred for 30 min, then the two olefins (1.0 mmol of each) were
la Recherche (RESICAT Programme, ANR-12-BS07-0001-01).
D. M. thanks the Institut d'Études Avancées de l'Université de
Strasbourg (USIAS) for financial support.
2
4
added. The autoclave was closed, flushed twice with hydrogen, then Keywords: Cavitands · Ligand design · N,O-ligands ·
pressurised to 5 bar. At the end of the catalytic run, the autoclave
was depressurised, and the resulting solution was passed through
a Millipore filter and analysed by GC.
Rhodium · Substrate-selective catalysis · Hydrogenation
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8
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440.21, triclinic, space group P1¯, a = 14.1288(4), b = 16.0216(5), c =
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Eur. J. Org. Chem. 0000, 0–0
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Published Online: ■
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Full Paper
Olefin Hydrogenation
T. Chavagnan, C. Bauder,
D. Sémeril,* D. Matt,* L. Toupet ..... 1–8
Substrate-Selective Olefin Hydrogen-
ation with a Cavitand-Based Bis(N-
anisyl iminophosphorane)
A resorcin[4]arene cavitand with two preferential conversion of hex-1-ene
N-anisyl iminophosphoranyl (AIP) units vs. that of 3-ethylpent-1-ene, as well as
has been synthesized and applied in the regioselective reduction of a com-
the rhodium-catalysed competitive pound with two double bonds in
hydrogenation of α-olefins. The sys- different steric environments.
tem was shown to be suitable for the
DOI: 10.1002/ejoc.201601125
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© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim