Titanium Catalysts with Linked Indenyl-Amido Ligands for Hydroamination and Hydroaminoalkylation Reactions

Article abstract of DOI:10.1021/acs.organomet.8b00332

Titanium complexes containing a bridging indenylethylamido ligand have been synthesized and used as catalysts for hydroamination and hydroaminoalkylation reactions. All dichloro titanium complexes (η⁵:η¹-Ind-C₂H₄-NR)TiCl₂ (R = i-Pr (2a), t-Bu (2b), Cy (2c), Ph (2d)), which were prepared by reacting TiCl₄(Et₂O)₂ with Li₂[Ind-C₂H₄-NR], were fully characterized by single-crystal X-ray analysis. Reaction of 2a-c with methyllithium gave the thermally sensitive corresponding dimethyl titanium complexes [η⁵:η¹-Ind-C₂H₄-N(alkyl)]TiMe₂ (alkyl = i-Pr (3a), t-Bu (3b), Cy (3c)), while the N-aryl-substituted dimethyl titanium complexes [η⁵:η¹-Ind-C₂H₄-N(aryl)]TiMe₂ (aryl = Ph (3d), p-MeOC₆H₄ (3e)) were directly prepared by reacting Li₂[Ind-C₂H₄-N(aryl)] with in situ generated Cl₂TiMe₂. In the case of complex 3d, the molecular structure could be determined by single-crystal X-ray analysis. All dimethyl titanium complexes (η⁵:η¹-Ind-C₂H₄-NR)TiMe₂ (R = i-Pr (3a), t-Bu (3b), Cy (3c), Ph (3d), p-MeOC₆H₄ (3e)) were finally used as precatalysts for the intermolecular hydroaminoalkylation of 1-octene (4), the intramolecular hydroamination and hydroaminoalkylation reactions of aminoalkenes, and the intermolecular hydroamination of 1-phenylpropyne (12). These experiments showed that the N substituent of the indenylethylamido ligand strongly influences the activity of the catalysts in the individual reactions.

Full text of DOI:10.1021/acs.organomet.8b00332

Article
pubs.acs.org/Organometallics
Cite This: Organometallics XXXX, XXX, XXX−XXX
Titanium Catalysts with Linked Indenyl−Amido Ligands for
Hydroamination and Hydroaminoalkylation Reactions
̈
Stefan H. Rohjans, Jan H. Ross, Lars H. Luhning, Lukas Sklorz, Marc Schmidtmann, and Sven Doye*
̈
Institut fur Chemie, Universitat Oldenburg, Carl-von-Ossietzky-Straße 9-11, 26129 Oldenburg, Germany
̈
*
S Supporting Information
ABSTRACT: Titanium complexes containing a bridging indenylethylamido ligand have
been synthesized and used as catalysts for hydroamination and hydroaminoalkylation
5
1
reactions. All dichloro titanium complexes (η :η -Ind-C H -NR)TiCl (R = i-Pr (2a), t-
2
4
2
Bu (2b), Cy (2c), Ph (2d)), which were prepared by reacting TiCl (Et O) with
4
2
2
Li [Ind-C H -NR], were fully characterized by single-crystal X-ray analysis. Reaction of
2
2
4
2
a−c with methyllithium gave the thermally sensitive corresponding dimethyl titanium
5 1
complexes [η :η -Ind-C H -N(alkyl)]TiMe (alkyl = i-Pr (3a), t-Bu (3b), Cy (3c)),
while the N-aryl-substituted dimethyl titanium complexes [η :η -Ind-C H -N(aryl)]-
2
4
2
5
1
2
4
TiMe (aryl = Ph (3d), p-MeOC H (3e)) were directly prepared by reacting Li [Ind-
2
6
4
2
C H -N(aryl)] with in situ generated Cl TiMe . In the case of complex 3d, the
molecular structure could be determined by single-crystal X-ray analysis. All dimethyl titanium complexes (η :η -Ind-C H -
2
4
2
2
5
1
2
4
NR)TiMe (R = i-Pr (3a), t-Bu (3b), Cy (3c), Ph (3d), p-MeOC H (3e)) were finally used as precatalysts for the
2
6
4
intermolecular hydroaminoalkylation of 1-octene (4), the intramolecular hydroamination and hydroaminoalkylation reactions
of aminoalkenes, and the intermolecular hydroamination of 1-phenylpropyne (12). These experiments showed that the N
substituent of the indenylethylamido ligand strongly influences the activity of the catalysts in the individual reactions.
INTRODUCTION
hydroamination and hydroaminoalkylation reactions of alkynes
and alkenes. On the other hand, we have already described the
synthesis of several indenylethylamines and one example of a
■
During the past decade, indenyl metal catalysts have played a
more and more important role in many transition-metal-
22
1
dichloro indenylethylamido titanium complex. Herein we
catalyzed reactions. For example, taking advantage of the
2
describe the synthesis of new indenylethylamido dichloro and
dimethyl titanium complexes and their catalytic reactivity in
hydroamination and hydroaminoalkylation reactions.
indenyl ligand, titanium-catalyzed hydroamination and hydro-
3
aminoalkylation reactions could be achieved very efficiently.
5
In particular, bis(η -indenyl) dimethyl titanium (Ind TiMe ,
2
2
5
Ind = η -indenyl) was found to be a highly reactive catalyst for
RESULTS AND DISCUSSION
■
these types of reactions between primary or secondary amines
and unsaturated substrates such as alkynes and alkenes.
the case of the structurally similar catalyst bis(η -cyclo-
pentadienyl) dimethyl titanium (Cp TiMe , Cp = η -cyclo-
pentadienyl), studies by Bergman and Johnson showed that
during reactions of primary amines with Cp TiMe two methyl
4
−15
Indenylethylamines 1a−e (Schemes 1 and 3) and the dichloro
titanium complex 2d were synthesized according to previously
In
5
22
published literature procedures. Because the N-phenyl-
5
2
2
substituted complex 2d is easily available from the dilithiated
ligand precursor 1d, which reacts smoothly with titanium
2
2
22
tetrachloride in diethyl ether, the same approach was used to
and one Cp ligand are replaced by corresponding amido
synthesize the additional dichloro titanium complexes 2a−c,
which possess N-alkyl substituents (Scheme 1). In these cases,
the amines 1a−c were initially treated with a 2-fold excess of n-
butyllithium to generate the corresponding dilithium salts,
1
6
ligands. Therefore, it can be assumed that Ind TiMe would
2
2
show a similar behavior in amination reactions. A major
drawback of this ligand exchange is the fact that the reactivity
of the catalytically active titanium center is directly influenced
by the nature of the amine substrate. One way to prevent this
unwanted dependence is to link the indenyl ligand with a
secondary amine to generate a chelating ligand that remains on
the titanium center during the reaction. Chelating indenyl−
amido ligands bridged by a dimethylsilyl group are already
which turned out to be only stable as suspensions in Et O.
2
Removal of the solvent led to decomposition of the dilithium
salts. After addition of titanium tetrachloride in diethyl ether,
all dichloro complexes were formed as a brownish precipitate.
To purify complexes 2a−d, the obtained solids were ground in
a mortar with Na SO and extracted continuously with n-
2
4
1
7,18
known,
but this linkage proved to be too labile for
titanium-catalyzed hydroaminoalkylation reactions. To the best
of our knowledge, only a few titanium complexes containing
C H -bridged indenyl−amido or indenyl−amino ligands can
Special Issue: Organometallic Complexes of Electropositive Ele-
ments for Selective Synthesis
2
4
19−21
be found in the literature,
and these so-called constrained
Received: May 18, 2018
geometry complexes (CGC) are almost unexplored in
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.8b00332
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Article
Scheme 1. Synthesis of Dichloro(indenylethylamido)
Titanium Complexes 2a−d from TiCl4
Table 1. Comparison of the Structural Data of Complexes
2a−c (Bond Lengths in Å and Angles in deg)
2
a
2b
2c
Ti1−N1
1.8691(11)
105.72(3)
103.25(3)
104.078(14)
105.1
1.9230(7)
108.26(2)
108.852(19)
102.597(8)
106.8
1.8663(8)
105.58(2)
105.45(2)
104.721(11)
104.6
N1−Ti1−Cl1
N1−Ti1−Cl2
Cl1−Ti1−Cl2
Ct−Ti1−N1
Ct−Ti1−Cl1
Ct−Ti1−Cl2
118.8
118.2
113.9
116.2
116.6
118.7
N1 bonds (2a, 1.8691(11) Å; 2b, 1.9230(7) Å; 2c, 1.8663(8)
Å; 2d, 1.8935(6) Å) are shortened in comparison to a Ti−N
single bond, indicating p −d electron donor interaction,
π
π
which is further confirmed by the trigonal-planar coordination
environment of the nitrogen atoms (∑∠N1: 2a, 359°; 2b,
3
60°; 2c, 360°; 2d, 359°). Small angles between the planes
pentane. Due to the poor solubility of 2a−d in n-pentane,
acceptable yields could only be achieved when the continuous
extraction was carried out over a relatively long period of 12 h.
Although the solubility of 2a−d in benzene was found to be
much better, extraction experiments with benzene failed
because, in these cases, the isolated complexes were always
contaminated with impurities.
C1−C2−C3 and C1−C9−C4−C3 (Ω) and small differences
in the mean distance of Ti1−C9 and Ti1−C4 in comparison to
5
Ti1−C1, Ti1−C2, and Ti1−C3 (Δ ) strongly support an η
Ti−C
23
coordination of the indenyl ligand in all cases (Table 2).
Table 2. Parameters Ω and ΔTi−C of Complexes 2a−d
As can be seen from Figure 1 and Table 1, the molecular
structures of the new dichloro titanium complexes 2a−c could
be confirmed by single-crystal X-ray diffraction after crystal-
lization from benzene solutions. In this context, it must also be
noted that we have already reported the structure of 2d
a
b
entry
complex
Ω (deg)
ΔTi−C (Å)
1
2
3
4
2a
2b
2c
2d
3.9
4.2
4.5
3.6
0.09
0.13
0.12
0.08
2
2
22
elsewhere. The central titanium atoms of complexes 2a−d
a
Angle between the planes C1−C2−C3 and C1−C9−C4−C3. Ω <
are coordinated in a pseudotetrahedral environment. The Ti1−
5
b
8
° indicates η coordination. Difference Δ
= [(Ti1−C9 + Ti1−
Ti−C
C4)/2] − [(Ti1−C1 + Ti1−C2 + Ti1−C3)/3]. Δ
indicates η coordination.
< 0.3 Å
Ti−C
5
23
With dichloro titanium complexes 2a−d in hand, attempts
to synthesize the corresponding dimethyl complexes by
methylation with 2 equiv of methyllithium in diethyl ether
were carried out (Scheme 2). During the experiments, the
Scheme 2. Synthesis of Dimethyl(indenylethylamido)
Titanium Complexes 3a−c by Methylation of 2a−c
reaction mixtures were kept below −10 °C to prevent α
elimination of methane. While in the case of the N-phenyl-
substituted complex 2d it was not possible to obtain the pure
product 3d, the desired N-alkyl-substituted dimethyl titanium
complexes 3a−c were obtained in modest to excellent yields
between 54% and 97%.
As an alternative synthetic approach toward the synthesis of
d, we also tried to react the dilithium salt of indenylethyl-
Figure 1. Molecular structures of complexes 2a−c. Hydrogen atoms
3
are partially omitted for clarity. Thermal ellipsoids are drawn at the
5
0% probability level. The molecular structure of 2d has already been
amine 1d with in situ generated Cl TiMe (Scheme 3). For
2
2
22
published elsewhere.
that purpose, 1d was first treated with 2 equiv of n-
B
DOI: 10.1021/acs.organomet.8b00332
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Article
Scheme 3. Synthesis of Dimethyl(indenylethylamido)
Titanium Complexes 3d,e from TiCl Me2
2
Figure 2. Molecular structure of complex 3d. Thermal ellipsoids are
drawn at the 50% probability level. Selected bond lengths (Å) and
angles (deg): Ti1−N1 1.9360(25), Ti1−C19 2.0994(32), Ti1−C18
2
.1085(37), C11−N1−C12 114.8(2), T1−N1−C11 122.9(2), Ti1−
N1−C12 119.48(19), N1−Ti1−C18 110.39(12), N1−Ti1−C19
1
03.78(12), C18−Ti1−C19 103.03(13), Ct−Ti1−C18 115.0, Ct−
Ti1-C19 117.1, Ct−Ti1−N1 107.0.
3
α to the nitrogen atom of 5, was studied (Table 3). The
corresponding reactions were performed in toluene in sealed
butyllithium. Then in a separate flask, titanium tetrachloride
was mixed with 2 equiv of methyllithium to generate the labile
complex Cl TiMe . Finally, the combination of both mixtures
Table 3. Intermolecular Hydroaminoalkylation of 1-Octene
2
2
(
4) with N-Methylaniline (5)
gave the crude product. To obtain 3d in pure form, the crude
product was then ground in a mortar with Na SO and filled in
2
4
an extraction apparatus. In this context, it is important to
mention that the continuous extraction was performed with n-
pentane at −5 °C under reduced pressure in order to prevent α
elimination of methane from 3d. Impressed by the fact that 3d
was isolated in 74% yield, we finally applied our optimized
procedure for the synthesis of an additional N-aryl-substituted
dimethyl titanium complex. The fact that in this case the N-(p-
methoxyphenyl)-substituted dimethyl titanium complex 3e was
obtained in 52% yield strongly underlines the notion that the
synthetic procedure used represents a general synthetic
approach toward the corresponding N-aryl-substituted deriv-
atives.
a
b
entry
cat.
T (°C)
yield (%)
6a:6b
1
2
3
4
5
6
7
3a
3b
3c
3d
3d
3e
3e
160
160
160
160
180
160
180
41
77
32
31
41
10
35
94:6
90:10
93:7
97:3
97:3
97:3
96:4
As can be seen from Figure 2, we were able to confirm the
structure of complex 3d by single-crystal X-ray diffraction after
crystallization of 3d from a benzene solution. Not surprisingly,
the pseudotetrahedral coordination environment of the
a
Reaction conditions: 1-octene (4, 337 mg, 3.00 mmol), N-
5
titanium center of 3d and the η coordination of the indenyl
methylaniline (5, 214 mg, 2.00 mmol), catalyst (3a−e, 0.20 mmol,
ligand (Ω = 3.3°, Δ
= 0.11 Å) are similar to those for the
Ti−C
10 mol %), toluene (1 mL), 160 or 180 °C, 96 h. Isolated yields of
22
b
dichloro complex 2d (Ω = 3.6°, Δ
= 0.08 Å). In addition,
Ti−C
6a,b are given. GC analysis prior to flash chromatography.
in both cases, the coordination geometry of the nitrogen atom
is trigonal planar (∑∠N1: 2d, 359°; 3d, 357°). However, the
change from chloro (2d) to methyl (3d) ligands leads to a
significant elongation of the Ti−N bond (Ti1−N1: 2d,
Schlenk tubes at 160 °C for 96 h. Interestingly, the catalysts
3a,c,d which contain N substituents with comparable steric
bulk (i-Pr, Cy, Ph) were found to give similar but only modest
yields between 31% and 41% (Table 3, entries 1, 3, and 4)
while the sterically more demanding N-t-Bu-substituted
catalyst 3b turned out to be significantly more active. As a
result, with this catalyst, the hydroaminoalkylation products
6a,b were obtained in 77% combined yield with a
regioselectivity of 90:10 in favor of the branched product 6a
(Table 3, entry 2). A possible explanation for the improved
catalytic activity of 3b could be the fact that, in the case of the
sterically demanding N-tert-butyl substituent, one methyl
group of the tert-butyl substituent always directs toward the
1
.8935(6) Å; 3d, 1.9360(25) Å).
With dimethyl titanium complexes 3a−e in hand, we then
turned our attention toward an investigation in which we
studied the performance of 3a−e as catalysts in four different
types of amination reactions. In this context, it should be noted
that we did not include the dichloro titanium complexes 2a−d
in this study because, in amination reactions, dichloro titanium
catalysts are generally regarded as being far less active than
24
their dimethyl titanium counterparts. Initially, the benchmark
hydroaminoalkylation of 1-octene (4) with N-methylaniline
(5), which takes place by C−H bond activation in the position
C
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reacting metal center. This could facilitate the formation of a
competing reactions: (i) intramolecular hydroamination to
form a seven-membered azepane product or (ii) intramolecular
hydroaminoalkylation, which delivers a six-membered amino-
cyclohexane product. In addition to the fact that, in this case,
3e turned out to lack any catalytic activity (Table 4, entry 5), it
was interesting to note that all other dimethyl titanium
complexes selectively catalyze the intramolecular hydro-
aminoalkylation of 7 at 140 °C and as a consequence, after
derivatization, only the tosyl amide 9 was always obtained as a
mixture of two diastereoisomers in a cis:trans ratio of
approximately 1:4 (Table 4, entries 1−4). As observed before,
the catalysts 3a,c,d which contain N substituents with similar
steric bulk gave product 9 in comparable yields (43−56%;
Table 4, entries 1, 3, and 4) while on the other hand, in this
case, the sterically more demanding N-t-Bu-substituted catalyst
25
sterically less demanding titanaaziridine, which is expected to
be the key intermediate of the overall hydroaminoalkylation
2
6
reaction, from a sterically more demanding corresponding
diamido titanium precursor by C−H bond activation (Scheme
4
). In contrast, the most stable conformers of the catalysts with
Scheme 4. Influence of Bulky Ligands on the Formation of
Titanaaziridines
3
b was found to be significantly less active. The latter finding
suggests that the intramolecular hydroaminoalkylation of 7,
which requires C−H bond activation in the sterically crowded
neopentyl position, is sensitive to bulky N substituents of the
indenylethylamido ligand while the intermolecular reaction of
n-octene (4) with sterically less hindered N-methylaniline (5,
Table 3) is facilitated by larger N substituents. In this context,
it is also worth mentioning that reactions of 7 performed at
lower temperatures only gave access to 9 in significantly
reduced yields.
less bulky N substituents (3a,c,d) are expected to have the
sterically demanding part of the corresponding N substituent
turned away from the titanium center (compare Figure 1) and,
as a consequence, titanaaziridine formation is not facilitated.
While the almost identical yields obtained with the N-Cy- and
N-Ph-substituted catalysts 3c (32%) and 3d (31%; Table 3,
entries 3 and 4) suggest that N-alkyl and N-aryl substituents
with comparable steric bulk result in similar catalytic activity,
the strongly reduced yield of 10% obtained with the N-(p-
methoxyphenyl)-substituted catalyst 3e (Table 3, entry 6)
leads to the impression that the strongly electron donating N-
In contrast to aminoheptene 7, aminopentene 10 (Table 5)
is only able to undergo intramolecular alkene hydroamination
Table 5. Intramolecular Hydroamination of Aminoalkene
1
0
(
p-methoxyphenyl) substituent causes a decreased Lewis
acidity of the titanium center and a correspondingly reduced
catalytic activity. Overall, it must be noted that, with regard to
catalytic activity and regioselectivity, the investigated inden-
ylethylamido titanium catalysts 3a−e cannot compete with the
established hydroaminoalkylation catalyst Ind TiMe , which
2
2
a
entry
cat.
yield (%)
selectively gives access to the branched product 6a in higher
yields under much milder reaction conditions.
14
1
2
3
4
5
3a
3b
3c
3d
3e
72
68
71
81
88
In an additional study, the new dimethyl titanium complexes
a−e were used as catalysts for cyclization reactions of
aminoheptene 7 (Table 4), which can generally undergo two
3
a
Table 4. Intramolecular Hydroaminoalkylation of
Aminoalkene 7
Reaction conditions: aminoalkene (10, 475 mg, 2.00 mmol), catalyst
(3a-3e, 0.10 mmol, 5 mol %), toluene (1 mL), 105 °C, 8 h. Isolated
yields of product 11 are given.
to give the pyrrolidine product 11 because a competing
hydroaminoalkylation would deliver an unfavored four-
membered ring. Due to a strong Thorpe−Ingold activation
of 10, corresponding reactions could already be achieved at
1
05 °C in the presence of 5 mol % of one of the dimethyl
a
b
titanium catalysts 3a−e and interestingly, in this case, the N-
entry
cat.
yield (%)
selectivity 8:9
cis-9:trans-9
alkyl-substituted catalysts 3a−c give product 11 in lower yields
1
2
3
4
5
3a
3b
3c
3d
3e
56
9
48
43
<5
0:100
0:100
0:100
0:100
-
20:80
21:79
20:80
20:80
-
(
68−72%, Table 5, entries 1−3) in comparison to the N-aryl-
substituted catalysts 3d (81%) and 3e (88%; Table 5, entries 4
and 5).
Finally, this reactivity trend could impressively be confirmed
in hydroamination experiments in which 1-phenylpropyne
(12) was reacted with 4-methylaniline (13, Table 6) in the
presence of 5 mol % of the catalysts 3a−e. The reactions were
performed at 60 °C for 24 h, and the initially formed
regioisomeric imine products were always reduced to the
corresponding amines 14a,b prior to isolation by flash column
a
Reaction conditions: (1) aminoalkene (7, 283 mg, 2.00 mmol),
catalyst (3a−e, 0.10 mmol, 5 mol %), toluene (1 mL), 140 °C, 72 h;
2) TsCl (570 mg, 3.00 mmol), NaOH (2 N, 5 mL), CH Cl (50
mL), 25 °C, 16 h. Isolated yields of product 9 are given. Determined
by NMR spectroscopy.
(
2
2
b
D
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Table 6. Intermolecular Hydroamination of 1-
Phenylpropyne (12) with p-Toluidine (13)
efficiently by 3b. In the latter case, much better results were
obtained with catalysts 3a,c,d, which contain sterically less
demanding N substituents (i-Pr, Cy, Ph). Interestingly, for
both hydroaminoalkyation reactions, no significant differences
in catalytic activity among the catalysts 3a,c,d which contain N
substituents with comparable steric bulk were found. Finally, a
comparison between the N-phenyl- and the N-(p-methox-
yphenyl)-substituted catalysts 3d,e shows that the introduction
of the p-methoxy group leads to a slightly improved catalytic
activity in hydroamination reactions, while a severe loss of
catalytic activity is observed in hydroaminoalkylation reactions.
a
b
Unfortunately, the new catalysts do not offer significant
entry
cat.
yield (%)
14a:14b
6
advantages over the previously used catalyst Ind TiMe and,
1
2
3
4
5
3a
3b
3c
3d
3e
13
<5
8
75
78
97:3
2
2
especially in the case of intermolecular hydroaminoalkylation,
the indenylethylamido titanium catalysts are even far less active
98:2
98:2
98:2
than Ind TiMe . A possible explanation for this disappointing
2
2
result can be given on the basis of the generally accepted fact
5
3
a
that a slip of an η -indenyl ligand into an η -allyl coordination
Reaction conditions: (1) 1-phenylpropyne (12, 232 mg, 2.00 mmol),
mode is responsible for the high activity of indenylmetal
p-toluidine (13, 235 mg, 2.20 mmol), catalyst (3a−3e, 0.10 mmol, 5
1
catalysts. While this process can easily take place with simple
mol %), toluene (1 mL), 60 °C, 24 h; (2) NaBH CN (251 mg, 4.00
3
indenyl ligands, the ethylamido tether of the indenylethylami-
do catalysts probably hampers the desired change in
coordination mode and, as a result, a decreased catalytic
activity is observed.
mmol), ZnCl (273 mg, 2.00 mmol), MeOH (10 mL), 25 °C, 24 h.
2
b
Isolated yields of 14a,b are given. GC analysis prior to flash
chromatography.
chromatography. Although with all catalysts excellent
regioselectivities in favor of the anti-Markovnikov product
EXPERIMENTAL SECTION
■
1
4a were observed, the N-alkyl-substituted catalysts 3a−c
General Remarks. All reactions were carried out under an
atmosphere of nitrogen or argon with exclusion of moisture and
oxygen using standard glovebox and Schlenk techniques. Solvents
were dried by distillation from Na and benzophenone under an
atmosphere of argon. Alkynes were purchased from commercial
sources and used without further purification. Amines and alkenes
were distilled and degassed (freeze, pump, thaw) prior to use.
turned out to be far less active than the corresponding N-aryl
derivatives 3d,e. While in the last two cases 2-phenylethyl-
amine 14a could be isolated in good yields of 75% and 78%,
only disappointing yields of ≤13% were obtained with catalysts
3
a−c. Because in alkyne hydroamination alkyl amines were
6−8
often found to be more reactive than aryl amines,
the
27
22
Aminoalkenes (7 and 10) and indenylethylamines (1a−e) were
reduced activity of the N-alkyl-substituted catalysts 3a−c does
not support the idea that this reactivity trend is caused by the
initially mentioned cyclopentadienyl/amido or indenyl/amido
ligand exchange processes during amination reactions
performed with cyclopentadienyl or indenyl titanium catalysts.
1
synthesized according to appropriate literature procedures. H and
1
3
C NMR spectra were recorded on a Bruker AVANCE III 500 MHz
1
13
or a Bruker Avance DRX 500 MHz spectrometer ( H, 500 MHz; C,
1
126 MHz). The H NMR chemical shifts were referenced to the
1
3
residual protons of C
D (δ 7.16) or CDCl (δ 7.26). The C NMR
6
6
3
chemical shifts were referenced to the solvent signal of C D (δ
6
6
CONCLUSION
128.0) or CDCl (δ 77.0). IR spectra were recorded on a Bruker
3
■
Tensor 27 spectrometer using an attenuated total reflection (ATR)
method. Mass spectra and high-resolution mass spectra were recorded
on a Thermo Scientific DFS spectrometer (CI, ionization potential:
In summary, we have presented the synthesis of three new
dichloro indenylethylamido titanium complexes (2a−c) and
five new dimethyl indenylethylamido titanium complexes (3a−
e). In the cases of three dichloro titanium complexes (2a−c)
and one dimethyl titanium complex (3d), we were able to
confirm the corresponding structures by single-crystal X-ray
diffraction. Furthermore, we have investigated the performance
of the five new dimethyl titanium complexes as catalysts for
four different amination reactions. During these studies, it
became clear that N-aryl-substituted indenylethylamido
titanium complexes are significantly better catalysts for
hydroamination reactions of alkenes and alkynes in compar-
ison to their N-alkyl-substituted counterparts. Interestingly, the
difference in catalytic performance is far more pronounced in
the case of alkyne hydroamination. With regard to
intermolecular and intramolecular hydroaminoalkylation re-
actions of alkenes the catalytic activity seems to be mainly
influenced by steric factors. While a corresponding inter-
molecular reaction with a sterically less demanding substrate
such as N-methylaniline (5) gave the best result with the
sterically demanding N-tert-butyl-substituted indenylethylami-
do titanium catalyst 3b, the intramolecular hydroaminoalkyla-
tion of a sterically demanding aminoheptene was not catalyzed
1
40 eV with methane as carrier gas). Melting points were determined
using a MPM-H2 apparatus by Schorpp-Geratetechnik. Further exact
̈
details of the individually synthesized products, crystallographic data,
and NMR spectra are given in the Supporting Information.
Dichloro Titanium Complexes 2a−d. The appropriate amine
(
1a−d, 12.0 mmol) was dissolved in Et O (100 mL) and cooled to
2
−
78 °C. After n-BuLi (9.6 mL, c = 2.5 M, 24.0 mmol) had been
added, the solution was warmed to room temperature and stirred for
h. In a separate round-bottom flask, TiCl (2.28 g, 12.0 mmol) was
2
4
added to Et O (100 mL) at −78 °C and, afterward, the resulting
2
suspension was stirred for 15 min at room temperature. Both mixtures
were cooled to −30 °C and combined via Teflon cannula. After the
resulting mixture had been stirred at room temperature for 2 h, the
solvent was removed under reduced pressure and the resulting solid
was transferred into a nitrogen-filled glovebox. The solid was mixed
with a 3-fold amount of Na SO (mortar and pestle) and filled into an
2
4
extraction apparatus (for details, see the Supporting Information).
The solid was continuously extracted with n-pentane (150 mL) for 12
h. Finally, the solvent was removed under reduced pressure to give the
corresponding dichloro titanium complex.
5
1
[
{(η -C H )C H (η -N-i-Pr)}TiCl ] (2a). Yield: 1.87 g (5.88 mmol,
9 6 2 4 2
1
49%) as an orange-brown solid. H NMR (C D , 500 MHz): δ 0.77
6
6
(d, 3H, J = 6.4 Hz), 0.89 (d, 3H, J = 6.4 Hz), 2.73 (dt, 1H, J = 13.7,
E
DOI: 10.1021/acs.organomet.8b00332
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
7
8
.6 Hz), 3.00 (ddd, 1H, J = 13.6, 7.8, 4.9 Hz), 3.80 (ddd, 1H, J = 14.5,
.0, 5.0 Hz), 4.08 (dt, 1H, J = 14.8, 7.5 Hz), 5.45 (hept, 1H, J = 6.4
Dimethyl Titanium Complexes 3a−c. The appropriate dichloro
titanium complex (2a−c, 1 equiv) was dissolved in Et O (50 mL) at
2
Hz), 6.09 (d, 1H, J = 3.3 Hz), 6.31 (d, 1H, J = 3.3 Hz), 6.88−6.94 (m,
−78 °C. MeLi (2 equiv, c = 1.6 M) was added, and the mixture was
stirred for 2 h at −30 °C. Then the solvent was removed under
reduced pressure and n-hexane (50 mL) was added. The suspension
was filtered through Na SO , and the solvent was removed under
1
3
1
H), 6.95−7.00 (m, 1H), 7.21−7.25 (m, 2H). C NMR (C D , 126
6
6
MHz): δ 17.5 (CH ), 17.7 (CH ), 27.3 (CH ), 53.7 (CH), 68.5
3
3
2
(
(
CH ), 105.3 (CH), 121.4 (CH), 122.4 (CH), 126.5 (CH), 126.8
C), 127.4 (C), 127.72 (CH), 127.74 (CH), 134.6 (C). IR (ATR):
2
2
4
reduced pressure to give the corresponding dimethyl titanium
complex.
1
/λ 2964, 2693, 2374, 1591, 1462, 1392, 1358, 1340, 1220, 1158,
−
1
+
5
1
1
044, 813, 750 cm . MS (CI): m/z (%) 322 ([M + 4 + H] , 8), 320
[{(η -C H )C H (η -N-i-Pr)}TiMe ] (3a). Yield: 1.38 g (4.98 mmol,
9 6 2 4 2
+
+
+
1
(
[M + 2 + H] , 33), 319 ([M + 1 + H] , 17), 318 ([M + H] , 47),
97%) as a dark yellow solid. H NMR (C D , 500 MHz): δ −0.42 (s,
6
6
3
7
+
35
+
2
84 ([C H ClNTi] , 20), 282 ([C H ClNTi] , 49), 202
3H), 0.56 (s, 3H), 1.00 (d, 3H, J = 6.3 Hz), 1.13 (d, 3H, J = 6.3 Hz),
2.67, (dt, 1H, J = 13.5, 7.3 Hz), 2.91 (ddd, 1H, J = 13.5, 7.4, 5.3 Hz),
3.74 (ddd, 1H, J = 12.8, 7.6, 5.4 Hz), 3.91 (dt, 1H, J = 12.7, 7.2 Hz),
5.69 (hept, 1H, J = 6.3 Hz), 5.89 (d, 1H, J = 3.0 Hz), 6.51 (d, 1H, J =
2.8 Hz), 6.85 (t, 1H, J = 7.6 Hz), 7.02 (t, 1H, J = 7.6 Hz), 7.19 (d,
14
17
14 17
+
+
(
[C H N] , 33), 127 (35), 72 ([C H N] , 100). HRMS: calcd
14 20 4 10
35
+
for [C H Cl NTi] 318.0290; found 318.0291. Mp: 151−152 °C
dec. Crystals suitable for crystallographic analysis were grown by slow
evaporation of a benzene solution of compound 2a.
14
18
2
5
1
13
[
{(η -C H )C H (η -N-t-Bu)}TiCl ] (2b). Yield: 2.39 g (7.20 mmol,
1H, J = 7.6 Hz), 7.49 (d, 1H, J = 7.5 Hz). C NMR (C D , 126
9
6
2
4
2
6
6
1
6
2
4
6
0%) as a dark red solid. H NMR (C D , 500 MHz): δ 1.31 (s, 9H),
MHz): δ 20.1 (CH ), 20.3 (CH ), 27.3 (CH ), 47.0 (CH ), 49.4
6
6
3 3 2 3
.66 (dt, 1H, J = 13.7, 6.4 Hz), 2.94 (dt, 1H, J = 13.7, 7.0 Hz), 3.93−
.04 (m, 2H), 6.17 (d, 1H, J = 3.3 Hz), 6.51 (dd, 1H, J = 3.3, 0.9 Hz),
.94 (ddd, 1H, J = 8.5, 6.7, 1.1 Hz), 7.00 (ddd, 1H, J = 8.5, 6.7, 1.1
(CH), 50.7 (CH ), 61.7 (CH ), 100.1 (CH), 120.4 (CH), 122.4
3 2
(CH), 124.1 (C), 124.56 (CH), 124.56 (C), 124.63 (CH), 126.3
(CH), 126.5 (C). IR (ATR): 1/λ 3065, 2960, 2924, 2858, 1461,
1440, 1381, 1354, 1338, 1261, 1221, 1159, 1094, 1040, 1017, 997,
1
3
Hz), 7.21−7.25 (m, 1H), 7.25−7.28 (m, 1H). C NMR (CDCl , 126
MHz): δ 28.5 (CH ), 28.9 (CH ), 64.4 (C), 70.2 (CH ), 109.5
3
−
1
+
981, 798, 743 cm . MS (CI): m/z (%) 279 ([M + 1 + H] , 12), 278
2
3
2
+
+
+
(
(
1
CH), 121.4 (CH), 123.5 (CH), 126.5 (CH), 127.1 (C), 127.9
CH), 128.3 (CH), 128.6 (C), 134.2 (C). IR (ATR): 1/λ 2962, 2960,
457, 1413, 1360, 1262, 1185, 1069, 1016, 824, 750, 712 cm . MS
([M + H] , 31), 262 ([M−Me] , 100), 246 (49), 202 ([C H N] ,
45). HRMS: calcd for [C H NTi] 278.1383; found 278.1361. Mp:
1
4
20
+
16 24
−
1
84−85 °C dec.
5
+
+
1
(
(
2
CI): m/z (%) 336 ([M + 4 + H] , 2), 334 ([M + 2 + H] , 6), 333
[M + 1 + H] , 4), 332 ([M + H] , 9), 316 ([C H Cl NTi] , 21),
[{(η -C H )C H (η -N-t-Bu)}TiMe ] (3b). Yield: 1.53 g (5.25 mmol,
9 6 2 4 2
+
+
+
1
58%) as a brown sticky solid. H NMR (C D , 500 MHz): δ −0.28 (s,
1
4
16
2
6
6
37
+
35
+
98 ([C H ClNTi] , 17), 296 ([C H ClNTi] , 42), 216
3H), 0.68 (s, 3H), 1.44 (s, 9H), 2.54 (dt, 1H, J = 13.5, 5.6 Hz), 2.76
(ddd, 1H, J = 13.4, 8.1, 6.8 Hz), 3.56 (ddd, 1H, J = 12.8, 6.8, 5.0 Hz),
3.78 (ddd, 1H, J = 12.8, 8.0, 6.1 Hz), 5.94 (d, 1H, J = 3.3 Hz), 6.57
(d, 1H, J = 3.3 Hz), 6.88−6.93 (m, 1H), 7.01−7.07 (m, 1H), 7.20 (d,
1
5
19
15 19
+
+
(
[C H N] , 55), 131 (15), 86 ([C H N] , 100). HRMS: calcd
15 22 5 12
35
+
for [C H Cl NTi] 332.0447; found 332.0445. Mp: 139−140 °C
dec. Crystals suitable for crystallographic analysis were grown by slow
15
20
2
1
3
evaporation of a benzene solution of compound 2b.
1H, J = 8.6 Hz), 7.44 (d, 1H, J = 8.5 Hz). C NMR (C D , 126
6 6
5
1
[
{(η -C H )C H (η -N-Cy)}TiCl ] (2c). Yield: 1.38 g (3.85 mmol,
MHz): δ 27.9 (CH ), 29.8 (CH ), 50.0 (CH ), 54.5 (CH ), 59.4 (C),
2 3 3 3
9
6
2
4
2
1
3
2%) as an orange solid. H NMR (C D , 500 MHz): δ 0.74−0.93
62.0 (CH ), 104.3 (CH), 119.5 (CH), 122.3 (C), 123.6 (CH), 124.7
6
6
2
(
m, 3H), 1.15−1.32 (m, 2H), 1.36−1.43 (m, 1H), 1.52−1.59 (m,
(CH), 125.3 (CH), 125.7 (C), 125.8 (C), 126.3 (CH). IR (ATR): 1/
1H), 1.60−1.67 (m, 1H), 1.67−1.73 (m, 1H), 1.95−2.01 (m, 1H),
2.77 (dt, 1H, J = 13.7, 7.6 Hz), 3.04 (ddd, 1H, J = 13.7, 7.8, 4.9 Hz),
3.89 (ddd, 1H, J = 14.5, 8.1, 4.9 Hz), 4.17 (dt, 1H, J = 14.5, 7.5 Hz),
5.11 (tt, 1H, J = 11.1, 3.4 Hz), 6.12 (d, 1H, J = 3.3 Hz), 6.32 (d, 1H, J
λ 2956, 2931, 2862, 2829, 1459, 1435, 1387, 1356, 1343, 1246, 1220,
−
1
1191, 1068, 1042, 1003, 969, 941, 847, 818, 744 cm . MS (CI): m/z
+
+
+
(%) 293 ([M + 1 + H] , 10), 292 ([M + H] , 33), 276 ([M − Me] ,
+
100), 260 (19), 216 ([C H N] , 14). HRMS: calcd for
[C H NTi] 292.1539; found 292.1528.
1
5
22
+
=
2
2
3.3 Hz), 6.91−6.95 (m, 1H), 6.96−7.01 (m, 1H), 7.23−7.28 (m,
17 26
H). 13C NMR (CDCl , 126 MHz): δ 25.6 (CH ), 26.19 (CH ),
[{(η -C H )C H (η -N-Cy)}TiMe ] (3c). Yield: 967 mg (3.05 mmol,
9 6 2 4 2
1
5
1
3
2
2
6.22 (CH ), 27.7 (CH ), 28.1 (CH ), 28.5 (CH ), 62.1 (CH), 70.5
54%) as a yellow-brown solid. H NMR (C D , 500 MHz): δ −0.40
2
2
2
2
6
6
(
(
CH ), 105.6 (CH), 121.6 (CH), 122.6 (CH), 126.2 (CH), 126.9
C), 127.2 (C), 127.69 (CH), 127.70 (CH), 134.9 (C). IR (ATR):
(s, 3H), 0.59 (s, 3H), 0.97 (qt, 1H, J = 12.8, 3.8 Hz), 1.19−1.44 (m,
4H), 1.51−1.57 (m, 1H), 1.59−1.65 (m, 1H), 1.67−1.73 (m, 1H),
1.75−1.81 (m, 1H), 1.82−1.88 (m, 1H), 2.70 (dt, 1H, J = 13.6, 7.3
Hz), 2.94 (ddd, 1H, J = 13.5, 7.5, 5.1 Hz), 3.80 (ddd, 1H, J = 12.8,
7.7, 5.1 Hz), 3.98 (dt, 1H, J = 12.8, 7.2 Hz), 5.29 (tt, 1H, J = 10.5, 3.5
Hz), 5.91 (d, 1H, J = 3.2 Hz), 6.53 (d, 1H, J = 3.2 Hz), 6.85−6.89 (m,
1H), 7.01−7.05 (m, 1H), 7.21 (d, 1H, J = 8.6 Hz), 7.51 (d, 1H, J =
2
1
/λ 2926, 2853, 1450, 1343, 1260, 1111, 1029, 1016, 893, 817, 760
−
1
+
+
cm . MS (CI): m/z (%) 362 ([M + 4 + H] , 6), 360 ([M + 2 + H] ,
+
+
2
(
3), 359 ([M + 1 + H] , 18), 358 ([M + H] , 36), 324
[C H
3
7
+
35
+
ClNTi] , 7), 322 ([C H
ClNTi] , 18), 242
1
7
21
17 21
+
+
(
[C H N] , 81), 131 (46), 112 ([C H N] , 100). HRMS: calcd
17 24 7 14
3
5
+
13
for [C H Cl NTi] 358.0603; found 358.0604. Mp: 162−163 °C
dec. Crystals suitable for crystallographic analysis were grown by slow
8.6 Hz). C NMR (C D , 126 MHz): δ 26.2 (CH ), 27.05 (CH ),
17
22
2
6
6
2
2
27.12 (CH ), 27.4 (CH ), 31.2 (CH ), 31.3 (CH ), 46.7 (CH ), 50.4
2 2 2 2 3
evaporation of a benzene solution of compound 2c.
(CH ), 58.5 (CH), 63.4 (CH ), 100.1 (CH), 120.5 (CH), 122.4
3 2
(CH), 124.1 (C), 124.5 (CH), 124.56 (C), 124.63 (CH), 126.3
5
1
22
[
{(η -C H )C H (η -N-Ph)}TiCl ] (2d). Yield: 1.39 g (3.93 mmol,
9
6
2
4
2
1
3
1
1
3%) as a red-brown solid. H NMR (CDCl , 500 MHz): δ 3.60 (dt,
H, J = 13.8, 7.3 Hz), 3.81 (ddd, 1H, J = 13.8, 7.2, 5.6 Hz), 4.87 (ddd,
H, J = 14.1, 7.6, 5.6 Hz), 5.13 (dt, 1H, J = 14.1, 7.2 Hz), 6.80 (d, 1H,
(CH), 126.5 (C). IR (ATR): 1/λ 2922, 2850, 1446, 1386, 1340,
3
−
1
1259, 1097, 1029, 890, 879, 798, 745, 706 cm . MS (CI): m/z (%)
+
+
+
319 ([M + 1 + H] , 3), 318 ([M + H] , 7), 316 ([M − 1] , 15), 302
+
+
J = 3.4 Hz), 6.82 (d, 1H, J = 3.4 Hz), 7.12 (t, 1H, J = 7.3 Hz), 7.25 (d,
([M − Me] , 10), 300 (20), 286 (13), 284 (100), 242 ([C H N] ,
38), 240 (26). HRMS: calcd for [C H NTi] 318.1696; found
1
7
24
+
2
1
H, J = 7.6 Hz), 7.31−7.36 (m, 2H), 7.37−7.45 (m, 2H), 7.69 (d,
19 28
1
3
H, J = 8.1 Hz), 7.91 (d, 1H, J = 8.2 Hz). C NMR (CDCl , 126
318.1683. Mp: 80−81 °C dec.
Dimethyl Titanium Complexes 3d,e. The appropriate amine
3
MHz): δ 27.8 (CH ), 78.5 (CH ), 107.6 (CH), 120.9 (CH), 122.7
2
2
(
1
(
1
CH), 123.1 (CH), 126.5 (CH), 126.8 (CH), 127.7 (C), 128.0 (C),
28.4 (CH), 128.5 (CH), 129.2 (CH), 135.8 (C), 152.5 (C). IR
ATR): 1/λ 3053, 2854, 1601, 1587, 1478, 1443, 1330, 1221, 1200,
(1d,e, 12.0 mmol) was dissolved in Et O (100 mL) and cooled to
−78 °C. After n-BuLi (9.6 mL, c = 2.5 M, 24.0 mmol) had been
added, the solution was warmed to room temperature and stirred for
2
−
1
058, 1043, 823, 750, 691 cm . MS (CI): m/z (%) 356 ([M + 4 +
2 h. In a separate round-bottom flask, TiCl (2.28 g, 12.0 mmol) was
4
+
+
+
H] , 15), 354 ([M + 2 + H] , 66), 353 ([M + 1 + H] , 46), 352 ([M
+
(
added to Et O (100 mL) at −78 °C and, afterward, the resulting
2
+
37
+
H] , 96), 334 (56), 318 ([C H ClNTi] , 41), 316
suspension was stirred for 15 min at room temperature. Then MeLi
(15.0 mL, c = 1.6 M, 24.0 mmol) was added at −78 °C and the
resulting mixture was stirred for 1 h at −30 °C. Both mixtures were
cooled to −30 °C and combined via Teflon cannula. After the
resulting mixture had been stirred for 2 h at −30 °C, the solvent was
1
7
15
3
5
+
35
+
[C H ClNTi] , 100). HRMS: calcd for [C H Cl NTi]
17 15 17 16 2
3
52.0134; found 352.0137. Mp: 121−122 °C dec. Crystals suitable
for crystallographic analysis were grown from a saturated benzene-d
solution of compound 2d.
6
F
DOI: 10.1021/acs.organomet.8b00332
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
removed under reduced pressure and the resulting solid was
transferred into a nitrogen-filled glovebox. The solid was mixed
with a 3-fold amount of Na SO (mortar and pestle) and filled into an
Notes
The authors declare no competing financial interest.
2
4
extraction apparatus (for details, see the Supporting Information).
The solid was continuously extracted with n-pentane (150 mL) under
reduced pressure at −5 °C for 12 h. Finally, the solvent was removed
under reduced pressure to give the corresponding dimethyl titanium
complex.
ACKNOWLEDGMENTS
■
We thank the Deutsche Forschungsgemeinschaft (DO 601/7-
2) for financial support of our research.
5
1
[
{(η -C H )C H (η -N-Ph)}TiMe ] (3d). Yield: 2.76 g (8.87 mmol,
9 6 2 4 2
1
REFERENCES
■
7
(
4%) as a yellow-brown solid. H NMR (C D , 500 MHz): δ −0.08
s, 3H), 0.88 (s, 3H), 2.59 (dt, 1H, J = 13.5, 6.7 Hz), 2.84 (dt, 1H, J =
6
6
(
1) Trost, B. M.; Ryan, C. M. Indenylmetallkatalyse in der
organischen Synthese. Angew. Chem. 2017, 129, 2906−2924;
Indenylmetal Catalysis in Organic Synthesis. Angew. Chem., Int. Ed.
13.5, 6.7 Hz), 4.04 (dt, 1H, J = 12.2, 6.7 Hz), 4.15 (dt, 1H, J = 12.2,
6.7 Hz), 6.00 (d, 1H, J = 3.2 Hz), 6.51 (d, 1H, J = 3.2 Hz), 6.90 (ddd,
1H, J = 8.6, 6.7, 1.0 Hz), 6.95 (tt, 1H, J = 7.3, 1.1 Hz), 7.00 (ddd, 1H,
2
(
017, 56, 2862−2879.
2) For a selected review on the hydroamination of alkenes and
alkynes, see: Muller, T. E.; Hultzsch, K. C.; Yus, M.; Foubelo, F.;
J = 8.6, 6.7, 1.0 Hz), 7.22−7.25 (m, 1H), 7.25−7.30 (m, 2H), 7.37−
1
3
̈
7
2
.40 (m, 1H), 7.40−7.43 (m, 2H). C NMR (C D , 126 MHz): δ
6
6
Tada, M. Hydroamination: Direct Addition of Amines to Alkenes and
7.0 (CH ), 57.0 (CH ), 61.1 (CH ), 67.8 (CH ), 102.7 (CH), 118.9
2
3
3
2
Alkynes. Chem. Rev. 2008, 108, 3795−3892.
3) For a selected review on the hydroaminoalkylation of alkenes,
see: Chong, E.; Garcia, P.; Schafer, L. L. Hydroaminoalkylation: Early-
Transition-Metal-Catalyzed α-Alkylation of Amines. Synthesis 2014,
(
(
(
1
7
CH), 121.0 (CH), 123.2 (CH), 123.4 (CH), 123.7 (C), 125.3
CH), 125.42 (C), 125.45 (CH), 126.85 (CH), 126.87 (C), 129.6
CH), 152.9 (C). IR (ATR): 1/λ 3050, 2937, 2870, 2826, 1601,
(
505, 1480, 1434, 1317, 1240, 1220, 1179, 1153, 1101, 1081, 1038,
−
1
+
4
(
6, 2884−2896.
99, 744, 692 cm . MS (CI): m/z (%) 313 ([M + 1 + H] , 24), 312
+
+
4) Pohlki, F.; Heutling, A.; Bytschkov, I.; Hotopp, T.; Doye, S.
(
[M + H] , 87), 296 ([M−Me] , 100), 281 (44), 280 (42). HRMS:
+
Titanium Complexes as Catalysts for the Intermolecular Hydro-
amination of Alkynes. Synlett 2002, 799−801.
(5) Pohlki, F.; Bytschkov, I.; Siebeneicher, H.; Heutling, A.; Konig,
̈
calcd for [C H NTi] 312.1226; found 312.1217. Mp: 66−67 °C
dec. Crystals suitable for crystallographic analysis were grown by slow
19
22
evaporation of a benzene solution of compound 3d.
5
1
[
{(η -C H )C H (η -N-C H -p-OMe)}TiMe ] (3e). Yield: 2.13 g (6.24
W. A.; Doye, S. Enantiomerically Pure Amines as Substrates for the
Ti-Catalyzed Hydroamination of Alkynes. Eur. J. Org. Chem. 2004,
2004, 1967−1972.
9
6
2
4
6
4
2
1
mmol, 52%) as a dark orange solid. H NMR (C D , 500 MHz): δ
6
6
−
0.16 (s, 3H), 0.84 (s, 3H), 2.67 (dt, 1H, J = 13.6, 7.0 Hz), 2.90
ddd, 1H, J = 13.6, 7.1, 5.7 Hz), 3.32 (s, 3H), 4.09 (ddd, 1H, J = 12.5,
(
(6) Heutling, A.; Pohlki, F.; Doye, S. [Ind TiMe ]: A General
2 2
7
6
6
7
.2, 5.6 Hz), 4.28 (dt, 1H, J = 12.2, 6.9 Hz), 6.04 (d, 1H, J = 3.2 Hz),
.55 (d, 1H, J = 3.2 Hz), 6.85−6.89 (m, 2H), 6.93 (ddd, 1H, J = 8.6,
.6, 1.0 Hz), 7.03 (ddd, 1H, J = 8.5, 6.7, 1.0 Hz), 7.27−7.31 (m, 3H),
Catalyst for the Intermolecular Hydroamination of Alkynes. Chem. -
Eur. J. 2004, 10, 3059−3071.
(7) Doye, S. Development of the Ti-Catalyzed Hydroamination of
Alkynes. Synlett 2004, 1653−1672.
13
.43−7.46 (m, 1H). C NMR (C D , 126 MHz): δ 27.1 (CH ), 54.7
6
6
2
(
(
(
(
1
1
CH ), 54.9 (CH ), 58.9 (CH ), 70.4 (CH ), 101.9 (CH), 115.0
(8) Heutling, A.; Severin, R.; Doye, S. Regioselective Preparation of
2-Phenylethylamines from 1-Phenyl-2-alkylalkynes by Hydroamina-
tion/Reduction Sequences. Synthesis 2005, 1200−1204.
3
3
3
2
CH), 120.9 (CH), 122.5 (CH), 122.9 (CH), 123.8 (C), 125.09
CH), 125.13 (C), 125.2 (CH), 126.77 (C), 126.82 (CH), 145.6
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2 2
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178, 1116, 1033, 790, 746, 700 cm . MS (CI): m/z (%) 343 ([M +
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+
+
+
+ H] , 41), 342 ([M + H] , 100), 326 ([M − Me] , 93), 310 (26).
+
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ASSOCIATED CONTENT
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CCDC 1497352, 1497528, and 1560433−1560434 contain the
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can be obtained free of charge via www.ccdc.cam.ac.uk/
data_request/cif, or by emailing data_request@ccdc.cam.ac.
uk, or by contacting The Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44
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AUTHOR INFORMATION
Corresponding Author
E-mail for S.D.: doye@uni-oldenburg.de.
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