Calcium-Mediated Catalytic Synthesis of 1-(Diorganylamino)-1,4-diphenyl-4-(diphenylphosphanyl)buta-1,3-dienes

Article abstract of DOI:10.1021/acs.inorgchem.6b00586

The hydroamination of diphenylbutadiyne with 1 equiv of the secondary amines HNRR' (R/R' = Ph/Ph, Ph/Me, and pTol/Me) in the presence of catalytic amounts of the tetrakis(amino)calciate K₂[Ca{N(H)Dipp}₄] (Dipp = 2,6-diisopropylphenyl) yields the corresponding 1-(diorganylamino)-1,4-diphenylbut-1-ene-3-ynes as a mixture of E/Z isomers. These tertiary alkenylamines react with diphenylphosphane to form RR'N-C(Ph)=CH-CH=C(Ph)-PPh₂ [R/R' = Ph/Ph (1), Ph/Me (2), and pTol/Me (3)] in the presence of catalytic amounts of [(THF)₄Ca(PPh₂)₂] or of the same calciate K₂[Ca{N(H)Dipp}₄]. Whereas the hydroamination is regio- (amino group in 1-position) but not stereoselective (formation of E and Z isomers), this second hydrofunctionalization step is regio- (phosphanyl group in 4-position) and stereoselective (only E isomers are formed), finally leading to mixtures of (E,E)- and (Z,E)-1-(diorganylamino)-1,4-diphenyl-4-(diphenylphosphanyl)buta-1,3-dienes.

Full text of DOI:10.1021/acs.inorgchem.6b00586

Article
pubs.acs.org/IC
Calcium-Mediated Catalytic Synthesis of 1‑(Diorganylamino)-1,4-
diphenyl-4-(diphenylphosphanyl)buta-1,3-dienes
Fadi M. Younis, Sven Krieck, Tareq M. A. Al-Shboul,+ Helmar Gorls, and Matthias Westerhausen*
̈
Institute of Inorganic and Analytical Chemistry, Friedrich Schiller University (FSU), Humboldstraße 8, D-07743 Jena, Germany
S
* Supporting Information
ABSTRACT: The hydroamination of diphenylbutadiyne with 1
equiv of the secondary amines HNRR′ (R/R′ = Ph/Ph, Ph/Me,
and pTol/Me) in the presence of catalytic amounts of the
tetrakis(amino)calciate K2[Ca{N(H)Dipp}4] (Dipp = 2,6-
diisopropylphenyl) yields the corresponding 1-(diorganylami-
no)-1,4-diphenylbut-1-ene-3-ynes as a mixture of E/Z isomers.
These tertiary alkenylamines react with diphenylphosphane to
form RR′N−C(Ph)CH−CHC(Ph)−PPh2 [R/R′ = Ph/Ph
(1), Ph/Me (2), and pTol/Me (3)] in the presence of catalytic
amounts of [(THF)4Ca(PPh2)2] or of the same calciate
K2[Ca{N(H)Dipp}4]. Whereas the hydroamination is regio-
(amino group in 1-position) but not stereoselective (formation
of E and Z isomers), this second hydrofunctionalization step is regio- (phosphanyl group in 4-position) and stereoselective (only
E isomers are formed), finally leading to mixtures of (E,E)- and (Z,E)-1-(diorganylamino)-1,4-diphenyl-4-(diphenylphosphanyl)-
buta-1,3-dienes.
tetracoordinate calcium atom fulfills these requirements and
hence represents an approved catalytically active calciate
because this ether-free complex is soluble in ethereal solvents.7
The reaction pathway of primary amines H2NR with
butadiynes strongly depends on the reaction conditions and
the N-bound substituent. Nevertheless, both N−H bonds are
able to add to alkyne moieties, yielding either 2,5-substituted
pyrroles at high reaction temperatures8 or multicyclic imines at
room temperature and prolonged reaction times.7,8 Secondary
amines can add only once; hence, cyclic products are
avoided.6,9 Thus, N-alkyl anilines add to one or both CC
bonds of the butadiyne backbone, depending on the reaction
time, the stoichiometry of the substrates, and the amount of
calcium catalyst, yielding 1-aminobut-1-ene-3-yne or 1,4-
diaminobuta-1,3-dienes, respectively. In contrast to this
observation, secondary diphenylphosphane always adds twice
to both CC bonds of the butadiyne unit in the presence of
catalytic amounts of [(THF)4Ca(PPh2)2] (THF = tetrahy-
drofuran, Scheme 1).10 Even a large excess of butadiyne leads
to the formation of bis-phosphanylated compounds, and
unreacted alkyne remains in the reaction mixture. The
hydrophosphanylation of substituted butadiynes with diphe-
nylphosphane yields primarily 1,4-bis(diphenylphosphanyl)-
buta-1,3-dienes; however, other regioisomers such as 1,2-
bis(diphenylphosphanyl)buta-1,3-dienes have also been ob-
served. Neither the hydroamination nor the hydrophosphany-
INTRODUCTION
■
Hydrofunctionalization (hydroelementation, hydropentelation)
resembles an atom-economic addition of H−E bonds [E being
the penteles N (hydroamination) and P (hydrophosphanyla-
tion)] to alkenes and alkynes; however, several challenges must
be solved. Hydroamination and hydrophosphanylation repre-
sent only slightly exothermic reactions that are entropically
disfavored. In addition, the approach of a Lewis base (primary
or secondary amine and phosphane) to an electron-rich CC
and CC multiple bond is disadvantageous and requires an
effective catalyst to overcome the electrostatic repulsion.
Several strategies have been developed, and recently, alkaline
earth metal-mediated hydropentelation catalysis has gained
significant interest.1−3 Calcium-based catalysts are especially
attractive because these alkaline earth metals are globally
abundant, inexpensive, easily available, and nontoxic.
Intramolecular hydroamination of alkenes eliminates the
entropic disadvantage and eases the addition of H−N bonds to
CC bonds. Calcium-based catalysts are able to catalyze this
reaction, yielding azacycloalkanes.4 Intermolecular hydroami-
nation is achieved only with activated alkenes5 and is much
easier with CC bonds, requiring more reactive calcium-based
catalysts correlated with the risk of also promoting undesired
side reactions.6 The reactivity of a calcium amide can be
enhanced by the formation of a calciate. The catalyst should be
coligand-free in order to avoid desolvation of the isolated
crystalline compound due to uncontrolled loss of ligated Lewis
bases such as ethers. This fact is important to allow an accurate
ratio of catalyst to substrate. The heterobimetallic compound
K2[Ca{N(H)Dipp}4] (Dipp = 2,6-diisopropylphenyl) with a
Received: March 8, 2016
© XXXX American Chemical Society
A
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Scheme 1. Calcium-Mediated Hydrophosphanylation of Diphenylbutadiyne with Diphenylphosphane Yielding Isomeric
Mixtures of 1,4-Bis(diphenylphosphanyl)buta-1,3-dienes
lation is stereoselective, but mixtures of E and Z isomers are
formed.
catalyst was destroyed with methanol. The hydropentelation
product 1 was recrystallized from methylene chloride/pentane,
giving yellow crystals of E/E-1 and Z/E-1.
These findings suggest that the synthesis of substituted 1-
amino-4-phosphanylbuta-1,3-dienes requires hydroamination as
the initial step and hydrophosphanylation as a subsequent
reaction. A further objective was the elucidation of the necessity
to change the calcium-based catalyst from K2[Ca{N(H)Dipp}4]
for hydroamination to [(THF)4Ca(PPh2)2] for the following
hydrophosphanylation. On the basis of the pKa values of
arylamines (approximately 31, depending on the substitution
pattern), N-methyl-aniline (29.5), diphenylamine (25.0), and
diphenylphosphane (22.9),11 the calciate K2[Ca{N(H)Dipp}4]
is able to deprotonate secondary amines and diphenylphos-
phane, which is a precondition for the suitability of this calciate
as a catalyst for hydropentelation reactions.
In another trial, the catalytic hydrophosphanylation of 1-
diphenylamino-1,4-diphenylbut-1-ene-3-yne was repeated with
catalytic amounts of K2[Ca{N(H)Dipp}4]. After complete
conversion, the solvent was removed, and the residue was
dissolved in methanol to inactivate the calcium catalyst. After
removal of the methanol, the residue was dissolved in
methylene chloride and filtered to remove the calcium-
containing compounds. Thereafter, recrystallization from
methylene chloride/pentane again provided yellow crystals of
E/E-1 and Z/E-1 (Scheme 3). This result suggests that the two
Scheme 3. Hydroamination and Hydrophosphanylation of
Diphenylbutadiyne with the Same Catalyst
K2[Ca{N(H)Dipp}4]
RESULTS AND DISCUSSION
■
Synthesis and Catalysis. The singly hydroaminated E and
Z isomers of 1-diphenylamino-1,4-diphenylbut-1-ene-3-yne9
were hydrophosphanylated with diphenylphosphane in THF
in the presence of 5 mol % [(THF)4Ca(PPh2)2], quantitatively
yielding 1-diphenylamino-1,4-diphenyl-4-diphenylphosphanyl-
buta-1,3-diene (1) (Scheme 2). The conversion of the
substrates was monitored by 31P{1H} NMR spectroscopy.
The E/Z isomerism at the amino functionality was maintained,
whereas only the E-isomeric hydrophosphanylation was
observed. After complete reaction, the volume of the reaction
mixture was reduced to half of the original volume, and the
Scheme 2. Two-Step Synthesis of 1-Diphenylamino-1,4-
diphenyl-4-(diphenylphosphanyl)buta-1,3-diene (1) Using
Different Calcium-Based Catalysts for the Hydropentelation
Reactions
different hydroelementation reactions can be performed
without a change in the catalyst system and without the need
to isolate the hydroamination product prior to the hydro-
phosphanylation reaction.
Because of the promising finding that K2[Ca{N(H)Dipp}4]
can promote hydroamination and hydrophosphanylation of
diphenylbutadiyne, the hydroamination of diphenylbutadiyne
was also performed with N-methyl-aniline and N-methyl-
tolylamine as previously published with the catalyst K2[Ca{N-
(H)Dipp}4].9 Diphenylphosphane was added to this reaction
mixture, yielding the appropriate hydrofunctionalization
products 1-(N-methyl-anilino)-1, 4-diphenyl-4-
(diphenylphosphanyl)buta-1,3-diene (2) and 1-(N-methyl-
tolylamino)-1,4-diphenyl-4-diphenylphosphanylbuta-1,3-diene
(3) according to Scheme 4. Again, the initial hydroamination
reaction gave an E/Z-isomeric mixture, whereas the hydro-
phosphanylation occurred regio- and stereoselectively to the E-
isomeric hydrophosphanylation products.
B
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Scheme 4. Calcium-Mediated Synthesis of 1-(N-
Methylanilino)-1,4-diphenyl-4-(diphenylphosphanyl)buta-
a
1,3-dienes
Figure 1. Molecular structure and numbering scheme of (E,E)-1-
diphenylamino-1,4-diphenyl-4-(diphenylphosphanyl)buta-1,3-diene
(E,E-1). The ellipsoids represent a probability of 30%; H atoms are
shown with arbitrary radii.
a
Aryl = phenyl (2) or p-tolyl (3).
Isolation of the intermediate hydroamination product 1-
amino-1,4-diphenylbut-1-ene-3-yne proved to be advantageous
to prevent impurities such as bis-hydroaminated compounds.
Unreacted butadiyne also had to be removed prior to the
hydrophosphanylation procedures because otherwise the
product would also contain bis-hydrophosphanylated deriva-
tives. These side products hamper the isolation of analytically
pure 1-amino-1,4-diphenyl-4-(diphenylphosphanyl)buta-1,3-
diene and hence lower the yields. Therefore, the preferred
method involves an initial hydroamination reaction catalyzed by
K2[Ca{N(H)Dipp}4], followed by isolation and purification of
1-amino-1,4-diphenylbut-1-ene-3-yne. Thereafter, the hydro-
phosphanylation of this amine can be performed using catalytic
amounts of either [(THF)4Ca(PPh2)2] or K2[Ca{N(H)-
Dipp}4]. In neither case were E,Z- and Z,Z-isomeric 1-amino-
1,4-diphenyl-4-(diphenylphosphanyl)buta-1,3-dienes observed.
This finding is most probably the consequence of steric strain,
but electronic effects may also play a minor role.
Molecular Structures. The molecular structures of (E,E)-
1-diphenylamino-1,4-diphenyl-4-(diphenylphosphanyl)buta-
1,3-diene (E,E-1) and (Z,E)-1-(N-methyl-anilino)-1,4-diphen-
yl-4-(diphenylphosphanyl)buta-1,3-diene (Z,E-2) are depicted
in Figures 1 and 2, respectively, and the structures of Z,E-1 and
Z,E-3 are represented in the Supporting Information. Selected
structural parameters are compared in Table 1. Regardless of
the isomerism, the structural parameters of these compounds
are very similar. The butadiene fragment shows no delocaliza-
tion, and typical CC and C−C bond lengths of
approximately 135 and 145 pm, respectively, are observed.
For steric reasons, the planar amino group is twisted toward the
planar butadiene plane; therefore, the electron pair at N cannot
interact with the π-system of the butadiene moiety. In contrast
to the amino group, the phosphorus atom is in a trigonal
pyramidal environment with C−P−C bond angles of about
102°. Steric strain between the substituted end groups leads to
a distortion of the C−C−C bond angles of the butadiene
fragment. The C1−C2−C3 and C2−C3−C4 bond angles of
E,E-1 are significantly widened, whereas for all Z,E isomers, the
enlargement of these bond angles is smaller. This finding
verifies an intramolecular steric strain of the Z,E isomers smaller
than that of the E,E derivatives. The lack of interaction between
the phosphanyl end groups and the butadiene units leads to
very similar P−C bonds of approximately 183 pm to the phenyl
Figure 2. Molecular structure and numbering scheme of (Z,E)-1-(N-
methyl-anilino)-1,4-diphenyl-4-(diphenylphosphanyl)buta-1,3-diene
(Z,E-2). The ellipsoids represent a probability of 30%; H atoms are
drawn with arbitrary radii.
and butadiene moieties in all of these compounds, representing
a characteristic P−C single-bond value.
NMR Spectroscopy. Selected NMR parameters of the 1-
amino-1,4-diphenyl-4-(diphenylphosphanyl)buta-1,3-dienes are
compared in Table 2. The E/Z isomerism of the amino group
has a small influence on the chemical shifts of the 31P nuclei.
Thus, the 31P resonances of the E,E isomers are observed at
nearly 5 ppm, whereas the Z,E isomers show chemical shifts of
about 2.5 ppm. The carbon atoms of the butadiene backbone
show low-field shifted signals between 135 and 156 ppm. Here,
the amino-substituted C4 atoms lie at a field lower than that of
n
the P-bound C1 atoms. The absolute values of the JC−P
coupling constants decrease with increasing n from approx-
imately 22 Hz (n = 1) over 12 Hz (n = 2) to 2 Hz (n = 3). The
3
3
vicinal JH−H and JH−P couplings of the hydrogen atoms at C2
and C3 also depend on the isomerism of the amino group with
larger values for the E,E isomers.
In agreement with the structural data, the Z,E-isomeric forms
are the major components, whereas the amount of E,E isomers
is always significantly smaller. Therefore, we were able to isolate
and crystallize the Z,E isomers of all reported derivatives,
C
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alkenylcalcium complex A either deprotonates an amine
(formation of the E-isomeric alkenylamine) or rearranges via
intermediates B and C to the finally formed Z-alkenylamine.
The necessity of obtaining the monohydroaminated products D
and E limits the substitution pattern of the secondary amine
substrates. For more reactive amines, the second calcium-
mediated hydroamination of the other CC bond overlaps
with the first hydroamination step, yielding mixtures of starting
butadiyne and singly and doubly hydroaminated butadienes. In
our hands, the above-utilized aniline derivatives represent the
preferred substrates.9 After complete conversion and preferably
isolation of the alkenylamines, diphenylphosphane is added,
immediately yielding the catalytically active calcium phospha-
nide species (L represents Lewis bases such as anionic amides
and phosphanides or neutral amines, phosphanes, or ethers).
The addition of the newly formed Ca−P bond to the remaining
CC bond yields the intermediates F and G that immediately
deprotonate the still-present diphenylphosphane. This hydro-
phosphanylation always leads to the formation of E-isomeric
alkenylphosphanes, as shown in Scheme 5. In contrast to the
calcium-mediated hydroamination, the catalytic hydrophospha-
nylation represents a very fast addition of a phosphane to an
alkyne moiety. Under these reaction conditions, neither the
amines nor the phosphanes react with the CC bonds. The
sequence of the catalytic steps (first hydroamination, then
hydrophosphanylation) must be maintained because the
phosphanes always add quantitatively to both CC bonds,
invariably yielding doubly hydrophosphanylated derivatives.10
Table 1. Selected Structural Parameters of 1-Diphenylamino-
1,4-diphenyl-4-(diphenylphosphanyl)buta-1,3-diene (1), 1-
(N-Methyl-anilino)-1,4-diphenyl-4-
(diphenylphosphanyl)buta-1,3-diene (2), and 1-(N-Methyl-
tolylamino)-1,4-diphenyl-4-(diphenylphosphanyl)buta-1,3-
diene (3)
E,E-1
Z,E-1
Z,E-2
Z,E-3
P1−C1
C1−C2
C2−C3
C3−C4
N1−C4
P1−C5
P1−C11
C1−C17
182.9(2)
135.5(3)
144.6(3)
134.9(3)
143.3(3)
182.0(3)
182.3(3)
148.4(3)
148.7(4)
143.5(3)
142.9(3)
102.1(1)
102.7(1)
103.9(1)
122.1(2)
125.2(2)
127.1(2)
118.8(2)
117.3(2)
117.7(2)
118.8(2)
183.6(2)
134.6(2)
145.0(2)
135.3(2)
142.3(2)
183.6(2)
182.9(2)
148.4(2)
147.6(2)
141.5(2)
142.6(2)
102.10(8)
102.11(8)
102.44(8)
121.7(1)
127.7(2)
122.3(2)
118.8(2)
120.1(1)
119.5(1)
120.1(1)
183.5(3)
135.2(4)
144.7(4)
135.1(4)
142.0(4)
183.4(3)
183.8(2)
149.3(4)
148.7(4)
139.5(4)
146.1(4)
102.2(1)
103.8(1)
102.5(1)
121.8(2)
126.9(3)
122.1(3)
120.7(2)
120.4(2)
119.5(3)
119.9(3)
182.7(4)
134.0(6)
144.8(6)
135.6(6)
141.4(5)
182.9(5)
182.9(4)
149.6(6)
148.0(6)
141.2(6)
145.0(6)
103.6(2)
102.7(2)
103.3(2)
123.0(3)
126.5(4)
124.8(4)
120.0(4)
120.8(3)
119.0(4)
118.8(4)
C4−C23
N1−C29
N1−C35
C1−P1−C5
C1−P1−C11
C5−P1−C11
P1−C1−C2
C1−C2−C3
C2−C3−C4
C3−C4−N1
C4−N1−C29
C4−N1−C35
C29−N1−C35
CONCLUSION
■
Table 2. Selected NMR Data of the E,E and E,Z Isomers of
1-Diphenylamino-1,4-diphenyl-4-
In summary, 1-amino- and 4-phosphanyl-substituted buta-1,3-
dienes can be prepared and isolated in moderate to good yields
from a calcium-mediated stepwise addition of secondary amines
and phosphanes to butadiyne. Both of these hydrofunctional-
ization reactions can be promoted with the coligand-free
calciate K2[Ca{N(H)Dipp}4] that is easily accessible and stable
in the crystalline state as well as in ethereal solvents, allowing
the preparation of stock solutions. After inactivation of the
catalyst with methanol, pure 1-amino-4-phosphanylbuta-1,3-
dienes are obtained by common workup procedures. Even
though the same catalyst is used for both hydroelementation
steps, the isolation of the intermediate 1-amino-1,4-diphenyl-
but-1-ene-3-yne is recommended to ease isolation of the pure
end products.
(diphenylphosphanyl)buta-1,3-diene (1), 1-(N-Methyl-
anilino)-1,4-diphenyl-4-(diphenylphosphanyl)buta-1,3-diene
(2), and 1-(N-Methyl-tolylamino)-1,4-diphenyl-4-
(diphenylphosphanyl)-buta-1,3-diene (3)
E,E-1
Z,E-1
E,E-2
Z,E-2
E,E-3
Z,E-3
1H NMR
δ(C2-H)
δ(C3-H)
3J(H,H)
3J(H,P)
6.39
6.62
8.3
6.29
6.45
5.3
6.27
6.01
6.51
5.9
6.31
6.49
8.5
6.03
6.42
6.0
6.49
8.2
12.1
10.7
11.6
10.9
2.82
11.5
2.96
10.9
2.81
δ(N-CH3)
3.04
13C{1H} NMR
Dipotassium tetrakis(2,6-diisopropylanilino)calciate is an
easy-to-handle and effective catalyst for the hydrofunctionaliza-
tion of CC bonds in diphenylbutadiyne with both secondary
amines and phosphanes, allowing the synthesis of 1-amino-1,4-
diphenyl-4-phosphanylbuta-1,3-dienes. This calciate crystallizes
as a coordination polymer; nevertheless, it is soluble in ethereal
solvents, enabling the preparation of stock solutions. The
crystalline compound and the stock solutions of this complex
are stable and can be stored under anaerobic conditions. Both
hydroelementation steps are regioselective, but only the
catalytic addition of the H−P bond also stereoselectively yields
the E isomer.
δ(C1)
140.6
23.1
140.4
141.8
19.8
141.1
22.1
140.3
22.2
136.1
10.8
146.6
2.8
142.4
22.7
1J(C,P)
23.1
135.0
12.1
145.7
2.1
δ(C2)
136.4
11.7
136.2
12.3
136.2
12.3
135.5
12.4
2J(C,P)
δ(C3)
146.7
2.5
147.5
2.1
147.5
2.1
147.0
2.2
3J(C,P)
δ(C4)
147.5
147.1
151.6
40.9
149.5
38.1
152.0
38
156.0
37.5
δ(N-CH3)
31P{1H} NMR
δ(P1)
4.45
2.54
4.70
2.28
4.96
2.35
whereas the parameters of the E,E-isomeric compounds had to
be elucidated from isomeric mixtures.
EXPERIMENTAL SECTION
■
Proposed Mechanism. On the basis of these findings, the
catalytic cycle had to be formulated as a two-step reaction
sequence, and the proposed mechanism is presented in Scheme
5. The initial catalytic cycle is depicted in the bottom part. After
addition of the Ca−N bond, the intermediately formed
General Considerations. All manipulations were carried out
under nitrogen using standard Schlenk techniques. The solvents were
dried according to standard procedures prior to use. Deuterated
solvents were dried over sodium, degassed, and saturated with
nitrogen. The yields given are not optimized. 1H, 13C{1H}, and
D
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Scheme 5. Proposed Catalytic Cycle Shown as a Two-Step Process of Subsequent Hydroamination and Hydrophosphanylation
a
Reactions
a
The bottom part shows the hydroamination and offers an explanation for the Z/E isomerism. In the second hydrophosphanylation catalysis, the
amido ligand is substituted by the phosphanido group. The thus-formed Ca−P bond adds to the remaining alkyne moiety, followed by a metalation
reaction. L represents a Lewis base such as amido or phosphanido anions or neutral Lewis bases such as ethers, amines, and phosphanes (see text).
31P{1H} NMR spectra were recorded on Bruker Avance 200, Avance
crystals was obtained and isolated. In method B, to a solution of 1-
diphenylamino-1,4-diphenylbut-1-ene-3-yne (0.140 g, 0.376 mmol) in
THF (18 mL) were added diphenylphosphane (0.07g, 0.376 mmol)
and 5 mol % calciate K2[Ca{N(H)Dipp}4]. The reaction mixture was
stirred for 6 h at rt. Afterward, the solvent was removed in vacuo, and
10 mL of anhydrous methanol was added to inactivate the catalyst.
Then, the methanol was removed, and 12 mL of dichloromethane was
added. This solution was filtered over diatomaceous earth.
Crystallization via the diffusion method (dichloromethane/pentane)
at 5 °C yielded yellow crystals suitable for X-ray diffraction studies
(0.14 g, 0.251 mmol, 67%, mixture of isomers). Mp: 138−142 °C. 1H
400, and Avance 600 spectrometers. Chemical shifts are reported in
parts per million. In some cases, 1H,13C{1H}-HSQC, 1H,13C{1H}-
HMBC, and H,H-COSY NMR experiments were performed for the
assignment of the resonances. For mass spectrometric investigations,
the spectrometers ThermoFinnigan MAT95XL and Finnigan SSQ710
were used. IR spectra were recorded with a Bruker ALPHA FT-IR
spectrometer. The starting amines and calcium-based catalysts
[(THF)4Ca(PPh2)2] and K2[Ca{N(H)Dipp}4] were prepared accord-
ing to the literature protocols.
Synthesis of 1-Diphenylamino-1,4-diphenyl-4-
(diphenylphosphanyl)buta-1,3-diene (1). In method A, 1-
diphenylamino-1,4-diphenylbut-1-ene-3-yne (0.2 g, 0.54 mmol) was
dissolved in 8 mL of THF. Diphenylphosphane (0.094 mL, 0.54
mmol) and 5 mol % [(THF)4Ca(PPh2)2] were added. The reaction
mixture turned yellow immediately. After being stirred at rt for 2 h and
under reflux for an additional 6 h, the volume was reduced to half of
the original volume. A few milliliters of methanol were added, and the
reaction mixture was stored at −15 °C. Yellow crystals of 3 (0.11 g, 0.2
mmol, 37%, mixture of isomers) precipitated and were collected. After
a reduction of the volume of the mother liquor, another crop of
NMR (600 MHz, THF): δ 7.36 (d, JH−H = 7.2 Hz, 2H), 7.31 (JH−H
=
7.7 Hz, 2H), 7.21−7.07 (m, 16H), 7.06−7.01 (m, 4H), 6.88 (m, 6H),
6.66 (d, 3JH−H = 7.5 Hz, 1H, E,E), 6.45 (d, 3JH−H = 10.7 Hz, 1H, Z,E),
6.39 (dd, 3JH−P = 12.1, 8.3 Hz, 1H, C2-H E,E), 6.29 (dd, 3JH−P = 10.7,
5.3 Hz, 1H, C2-H Z,E). 13C{1H} NMR (101 MHz, CD2Cl2): δ 147.5
(C4 E,E), 147.3 (C4 Z,E), 146.7 (d, 3JC−P = 2.5 Hz, C3 E,E), 145.9 (d,
3JC−P = 2.4 Hz, C3 Z,E), 144 (d, JC−P = 16.5 Hz, C11,5), 143.4 (d,
2JC−P = 6.4 Hz), 140.6 (d, JC−P = 23.1 Hz, C1 E,E), 139.8 (d, JC−P
=
=
2
2
23.1 Hz, C1 Z,E), 139.5, 139 (d, JC−P = 3.5 Hz), 136.4 (d, JC−P
2
11.7 Hz, C2 E,E), 135 (d, JC−P = 11.6 Hz, C2 Z,E), 134.8, 134.6,
E
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Inorganic Chemistry
Article
2
134.18 (d, JC−P = 7.5 Hz), 133.5, 133.3, 129.8, 129.7, 129.4, 129.3,
128.2, 128.1, 127, 127.8, 126.9, 126.5, 125.8, 120, 113.7, 37.5 (C35),
19.6 (C36). 13C{1H} NMR (101 MHz, [D8]THF, isomeric mixture):
3
2
129.2 (d, J = 2.8 Hz), 129.1, 128.6 (d, JC−P = 7.3 Hz), 128.4, 127.8,
3
3
127.7, 127.7, 127.6, 126.8, 125.5, 125.1, 122.6 (d, JC−P = 2.0 Hz),
δ 156 (C4 Z,E), 152.8 (C4 E,E), 147.8 (d, JC−P = 2.2 Hz, C3 Z,E),
146.6 (d, 3JC−P = 2.8 Hz, C3 E,E), 142.4 (d, JC−P = 22.7 Hz, C1 Z,E),
140.3 (d, JC−P = 22.0 Hz, C1 E,E), 139.1 (d, 2JC−P = 12.4 Hz, C2 Z,E),
122.3, 122.2, 122.1, 122, 121.9, 121.78. 13C NMR (151 MHz,
3
[D8]THF, Z,E isomer): δ 147.1 (C4), 145.7 (d, JC−P = 2.1 Hz, C3),
3
138.2, 136.9 (d, JC−P = 2.3 Hz), 136.1 (2JC−P = 10.8 Hz, C2 E,E),
143.9 (d, JC−P = 17.6 Hz, C11,5), 140.4 (d, JC−P = 23.1 Hz, C1), 138.5,
2
135 (d, JC−P = 12.1 Hz, C2), 134.3, 134.2, 133.8 (d, 2JC−P = 7.9 Hz),
2
135.5 (d, JC−P = 12.4 Hz, C2 Z,E) 135.4, 135.2, 135.1, 134.3, 134.2,
134.1, 133.3, 132.3, 131.9 (d, 2JC−P = 9.1 Hz), 131.4, 131.5 (d, 2JC−P
5.1 Hz), 130.8 (d, JC−P = 2.7 Hz), 130.5, 130.3 (d, JC−P = 4.8 Hz),
=
129.3 (d, 2JC−P = 9.3 Hz), 128.8, 128.5, 128.1, 128.1, 128, 127.8, 127.1,
127, 122 (d, 2JC−P = 1.7 Hz), 121.8, 121.5. 31P{1H} NMR (243 MHz,
[D8]THF): δ 2.54 (s, Z,E isomer), 4.49 (s, E,E isomer). Elemental
analysis (C40H32NP, 557.21): Calcd C, 86.15; H, 5.78; N, 2.51; P, 5.55.
Found: C, 83.79; H, 5.74; N, 2.51. MS (EI, m/z): 557 (60) [M], 389
(100) [M − C12H11N], 370 (10), 180 (100), 77 (25) [Ph]. IR: 3049
w, 3959 w, 2920 w, 1656 m, 1630 m, 1484 s, 1432 m, 1288 m, 1258 m,
1223 s, 1174 m, 1074 s, 1024 s, 859 m, 797 s, 761 s, 740 s, 690 vs, 602
m, 548 m, 496 s, 479 m.
3
2
130.1, 129.4, 129.2, 129.1, 129, 128.8, 128.5, 128.5, 128.4, 128.3, 128.2,
3
128.1 (d, JC−P = 2.7 Hz), 128.2, 127.9, 127.8, 127.7, 127.6, 127.5,
3
127.4, 127.2, 127, 126.5, 125.8, 125, 120 (d, JC−P = 2.3 Hz), 119.7,
117.7, 117.6, 114.5, 113.6, 38 (C35 Z,E), 37.4 (C35 E,E), 19.7 (C36
Z,E), 19.6 (C36 E,E). 31P{1H} NMR (162 MHz, [D8]THF): δ 4.96 (s,
E,E isomer), 2.35 (s, P Z,E isomer). Elemental analysis (C36H32NP,
509.60): Calcd C, 84.84; H, 6.33; N, 2.75; P, 6.08. Found: C, 84.31; H,
6.18; N, 2.75. MS (EI, m/z): 525 (10) [M + O], 509 (50) [M], 389
(60) [M − C8H11N], 370 (100), 322 (30) [M − L], 183 (100), 118
(60) [PhNC2H3], 77 (25) [Ph]. IR: 3051 w, 3025 w, 2914 w, 1587 m,
1570 m, 1510 s, 1477 m, 1361 m, 1317 m, 1281 m, 1186 m, 1104 s,
1027 m, 911 m, 806 s, 767 s, 742 vs, 692 vs, 596 m, 557 m, 499 s, 461
m.
Synthesis of 1-(N-Methyl-anilino)-1,4-diphenyl-4-
(diphenylphosphanyl)buta-1,3-diene (2). To a solution of 1-(N-
methyl-anilino)-1,4-diphenylbut-1-ene-3-yne (0.100 g, 0.323 mmol) in
THF (17 mL) were added diphenylphosphane (0.06 g, 0.323 mmol)
and 5 mol % calciate K2[Ca{N(H)Dipp}4]. The reaction mixture was
stirred for 4 h at rt. After the consumption of all starting materials, all
volatile materials were removed in vacuo, and 10 mL of anhydrous
methanol was added to destroy the remaining catalyst. Afterward, the
methanol was removed, and 12 mL of dichloromethane was added.
Then, the solution was filtered over diatomaceous earth. Crystal-
lization via the diffusion method (dichloromethane/pentane) at 5 °C
gave single crystals in a yellow mother liquor (0.11 g, 0.222 mmol,
69%). Mp: 146−149 °C. 1H NMR (600 MHz, [D8]THF): δ 7.40 (m,
2H, Ar-H), 7.34 (d, J = 8.2 Hz, 1H, Ar-H), 7.31−7.13 (m, 24H, Ar-H),
6.70 (t, 3JH−H = 7.3 Hz, 1H, Ar-H), 6.62 (m, 2H, Ar-H), 6.51 (d, 3JH−H
= 10.9 Hz, 1H,C3-H, Z,E), 6.27 (dd, 3JH−P = 11.6, 8.2 Hz, C2-H, E,E),
Crystal Structure Determinations. The intensity data for the
compounds were collected on a Nonius KappaCCD diffractometer
using graphite-monochromated Mo Kα radiation. The data were
corrected for Lorentz and polarization effects; absorption was taken
into account on a semiempirical basis using multiple scans.12−14 The
structures were solved by Direct Methods (SHELXS15) and refined by
full-matrix least-squares techniques against Fo (SHELXL-97).15 All
2
hydrogen atoms (with the exception of the methyl groups of C35 and
C36 of compound Z,E-3) were located by difference Fourier synthesis
and refined isotropically. All non-hydrogen atoms were refined
anisotropically.15 Crystallographic data as well as structure solution
and refinement details are summarized in the Supporting Information.
XP (SIEMENS Analytical X-ray Instruments, Inc.) was used for
structure representations.
3
6.05−5.97 (dd, JH−P = 10.9, 5.9 Hz, 1H, C2-H, Z,E), 3.04 (s, 1H,
C35-H, Z,E), 2.82 (s, 3H, C35-H, Z,E). 13C{1H} NMR (151 MHz,
3
[D8]THF): δ 151.6 (C4 E,E), 149.5 (C4 Z,E), 147.5 (d, JC−P = 2.1
Hz, C3 Z,E, E,E), 143.9 (d, 3JC−P = 7.6 Hz), 141.8 (d, 1JC−P = 19.8 Hz,
1
2
C1 E,E), 141.1 (d, JC−P = 22.1 Hz, C1 Z,E), 139, 136.2 (d, JC−P
=
12.3 Hz, C3 Z,E, E,E), 135.08 (d, 2JC−P = 20.6 Hz, C5,11), 134, 134.7,
ASSOCIATED CONTENT
* Supporting Information
■
134.6, 130.7, 130.3 (d, 2JC−P = 7.8 Hz, C17), 130.1 (d, 2JC−P = 8.7 Hz),
S
2
129.5, 129.4, 129.2, 129.1, 129.1, 129 (d, JC−P = 4.0 Hz), 129, 128.8,
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.6b00586. Crystallographic data (excluding structure
factors) have been deposited with the Cambridge Crystallo-
graphic Data Centre as supplementary publication CCDC-
1457771 for E,E-1, CCDC-1457772 for Z,E-1, CCDC-1457773
for Z,E-2, and CCDC-1457774 for Z,E-3.
128.8, 128.7, 128.5, 128.5, 128.3, 127.9, 127.3, 127, 123.1, 122.3, 121.5,
117.9, 114.2, 111.4, 40.9 (C35 E,E isomer), 38.1 (C35 Z,E isomer).
31P{1H} NMR (243 MHz, [D8]THF): δ 4.70 (s, E,E isomer), 2.28 (s,
Z,E isomer). Elemental analysis (C35H30NP, 495.57): Calcd C, 84.82;
H, 6.10; N, 2.83; P, 6.25. Found: C, 84.54; H, 6.10; N, 2.86. MS (EI,
m/z): 434 (90) [M], 389 (100) [M − C7H9N], 370 (50), 309 (30)
[M − L], 183 (90), 118 (70) [PhNC2H3], 77 (25) [Ph]. IR: 3052 w,
2961 w, 2815 w, 2800 w, 1950 w, 1595 m, 1541 m, 1484 s, 1432 m,
1350 m, 1321 m, 1260 m, 1199 m, 1106 s, 1009 m, 885 m, 775 s, 746
vs, 688 vs, 598 m, 505 m, 498 m, 478 s.
Synthesis of 1-(N-Methyl-tolylamino)-1,4-diphenyl-4-
(diphenylphosphanyl)buta-1,3-diene (3). To a solution of (N-
methyl)-(N-4-tolyl)-1,4-diphenylbut-1-ene-3-yne-1-ylamine (0.270 g,
0.834 mmol) in THF (17 mL) were added diphenylphosphane (0.156
g, 0.834 mmol) and 5 mol % calciate catalyst K2[Ca{N(H)Dipp}4],
and the reaction mixture was stirred for 8 h at rt. After the reaction
solvent was removed, 10 mL of dry methanol was added to deactivate
the catalyst. Afterward, the methanol was removed; 12 mL of
dichloromethane was added, and the solution was filtered over Celite.
Recrystallization via the diffusion method (dichloromethane/pentane)
at 5 °C yielded crystals in a yellow solution (0.3 g, 0.588 mmol, 71%).
NMR spectra and details for the quantum chemical
studies (PDF)
Crystallographic data of the crystal structure determi-
nations (CIF)
AUTHOR INFORMATION
Corresponding Author
*E-mail: m.we@uni-jena.de.
■
Present Address
+T.M.A.A.: Department of Chemistry and Chemical Technol-
ogy, Faculty of Science, Tafila Technical University (TTU),
P.O. Box 179, Tafila 66110, Jordan.
1
Mp: 147−152 °C. H NMR (400 MHz, [D8]THF): δ 7.43−7.34 (m,
2H), 7.30−7.10 (m, 18H), 6.99 (d, JH−H = 8.2 Hz, 2H), 6.60−6.50 (m,
Notes
2H), 6.49 (d, 3JH‑H = 7.6 Hz, 1H, C3-H E,E), 6.42 (d, 3JH‑H = 10.9 Hz,
The authors declare no competing financial interest.
3
1H, C3-H Z,E), 6.31 (dd, JH−P = 11.5, 8.5 Hz, 1H, C2-H E,E), 6.03
(dd, JH−P = 10.9, 6.0 Hz, 1H, C2-H Z,E), 2.96 (s, 3H, C35-H E,E),
3
ACKNOWLEDGMENTS
■
2.81 (s, 3H, C35-H Z,E), 2.27 (s, 3H, C36-H E,E), 2.25 (s, 3H, C36-H
Z,E). 13C{1H} NMR (101 MHz, [D8]THF, Z,E isomer): δ 156.2 (C4),
We appreciate the financial support of the Fonds der
Chemischen Industrie im Verband der Chemischen Industrie
e.V. (FCI/VCI, Frankfurt/Main, Germany). F.M.Y. thanks the
3
147 (d, JC−P = 2.2 Hz, C3), 142.4 (d, JC−P = 22.3 Hz, C1), 138.4,
135.5 (d, 2JC−P = 12.4 Hz, C2), 134.5, 134, 129.3, 129.2, 128.5, 128.3,
F
DOI: 10.1021/acs.inorgchem.6b00586
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Inorganic Chemistry
Article
German Academic Exchange Service (DAAD, Bonn, Germany)
for a generous Ph.D. stipend. The infrastructure of our institute
was partially provided by the EU (European Regional
Development Fund, EFRE).
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