N-alkylation of amines by homogeneous ruthenium complexes in the presence of free diphosphines

Article abstract of DOI:10.1080/00958972.2013.844340

Chemoselective N-alkylation of amines by ruthenium complexes in the presence of free diphosphine ligands under mild conditions is described. Octyl amine and aniline were chosen as aliphatic and aromatic amines to investigate the effect of different phosphines, reaction times, and temperature on conversion, as well as selectivity towards related secondary and tertiary amines. After optimization of the reaction conditions, this catalytic system was used for N-alkylation of other amines and has shown moderate to very good yields. The reaction products were monitored by GC-MS. The crystal structure of [Ru(NO3)2CO(PPh3)2] with a monodentate and a bidentate nitrate was determined by X-ray crystallographic analysis.

Full text of DOI:10.1080/00958972.2013.844340

This article was downloaded by: [Monash University Library]
On: 07 October 2014, At: 11:55
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered
office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Journal of Coordination Chemistry
Publication details, including instructions for authors and
subscription information:
http://www.tandfonline.com/loi/gcoo20
N-alkylation of amines by homogeneous
ruthenium complexes in the presence
of free diphosphines
Bahareh Tamaddoni Jahromia & Ali Nemati Kharata
a School of Chemistry, University College of Science, University of
Tehran, Tehran, Iran
Accepted author version posted online: 16 Sep 2013.Published
online: 18 Oct 2013.
To cite this article: Bahareh Tamaddoni Jahromi & Ali Nemati Kharat (2013) N-alkylation of
amines by homogeneous ruthenium complexes in the presence of free diphosphines, Journal of
Coordination Chemistry, 66:19, 3498-3508, DOI: 10.1080/00958972.2013.844340
To link to this article: http://dx.doi.org/10.1080/00958972.2013.844340
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the
“Content”) contained in the publications on our platform. However, Taylor & Francis,
our agents, and our licensors make no representations or warranties whatsoever as to
the accuracy, completeness, or suitability for any purpose of the Content. Any opinions
and views expressed in this publication are the opinions and views of the authors,
and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content
should not be relied upon and should be independently verified with primary sources
of information. Taylor and Francis shall not be liable for any losses, actions, claims,
proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or
howsoever caused arising directly or indirectly in connection with, in relation to or arising
out of the use of the Content.
This article may be used for research, teaching, and private study purposes. Any
substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing,
systematic supply, or distribution in any form to anyone is expressly forbidden. Terms &
Conditions of access and use can be found at http://www.tandfonline.com/page/terms-
and-conditions

Journal of Coordination Chemistry, 2013
Vol. 66, No. 19, 3498–3508, http://dx.doi.org/10.1080/00958972.2013.844340
N-alkylation of amines by homogeneous ruthenium complexes
in the presence of free diphosphines
BAHAREH TAMADDONI JAHROMI and ALI NEMATI KHARAT*
School of Chemistry, University College of Science, University of Tehran, Tehran, Iran
(Received 13 April 2013; accepted 7 August 2013)
Chemoselective N-alkylation of amines by ruthenium complexes in the presence of free diphosphine
ligands under mild conditions is described. Octyl amine and aniline were chosen as aliphatic and
aromatic amines to investigate the effect of different phosphines, reaction times, and temperature on
conversion, as well as selectivity towards related secondary and tertiary amines. After optimization
of the reaction conditions, this catalytic system was used for N-alkylation of other amines and has
shown moderate to very good yields. The reaction products were monitored by GC–MS. The crystal
structure of [Ru(NO3)2CO(PPh3)2] with a monodentate and a bidentate nitrate was determined by
X-ray crystallographic analysis.
Keywords: N-alkylation; Homogeneous catalyst; Ruthenium complex; Diphosphines
1. Introduction
Syntheses of amines have received attention in bulk and fine chemical industries [1]. Due
to their interesting physiological activities, amines are extremely important pharmacophores
in numerous biologically active compounds and have been touted in the area of drug dis-
covery [2]. Aromatic secondary amines play a key role in petrochemical, pharmaceutical,
agrochemical, and food additives [3]. Despite widespread interest, methods of amine
preparation are often problematic because of harsh reaction conditions, poor yields, and low
chemical selectivities [4]. Traditionally, the alkylation of amines is performed using conven-
tional alkylating agents, such as alkyl halides. This route has serious selectivity problems
because of multiple alkylations. Catalytic methodologies, such as reductive amination,
hydroamination, and hydroaminomethylation of olefins or alkynes, have been developed
for the synthesis of amines [5–8]. Buchwald and co-workers have made considerable
contributions towards the development of reliable and practical catalysts for the formation
of aromatic carbon nitrogen bonds by cross-coupling of amines and aryl halides [9]. The
disadvantages of these reactions are high temperatures and long reaction times required to
obtain optimum yields. Therefore, the development of a selective N-alkylation method that
is cost effective, salt-free, and environmentally acceptable is of considerable interest. There
is ongoing interest for improving previous methods and developing new efficient synthetic
routes [10]. N-alkylation of amines with alcohols [11] in place of alkyl halides, tosylate,
mesylate, or triflate has attracted interest and is well documented [10, 12]; known since the
*Corresponding author. Email: alnema@khayam.ut.ac.ir
© 2013 Taylor & Francis

N-alkylation of amines
3499
beginning of the twentieth century, yet the reaction conditions are difficult for industrial
applications. Therefore this method was explored using different additives. Alcohol
condensation with aromatic amines in the vapor phase using various catalysts has enjoyed
synthetic utility in the introduction of an alkyl functionality on nitrogen. Numerous catalysts
have been explored in the reaction of an aromatic primary amine with an alcohol to form a
product containing an N-alkyl-substituted amine allowing a wide variety of environmentally
safe heterogeneous catalysts to be developed [13, 14]. Alcohols have been condensed with
amines using transition metal catalysts such as nickel [14, 15], rhodium [16], or ruthenium
[17]. All of these heterogeneous catalysts suffer from low selectivity and harsh conditions.
The first example of a homogenous catalyst in this field was published by Grigg and
Watanabe [18], followed by reports from the Beller group using bulky phosphines and
ruthenium carbonyl complexes [19–21]. Hartwig investigated the addition of anilines to
pseudo-halides and aryl triflates catalyzed by a soluble palladium complex and diphenyl-
phosphino ferrocene [22]. The advantage of this procedure in comparison with the
traditional methods is the high selectivity under mild conditions.
The amination of alcohols involves three well-known steps; the oxidation of an
alcohol into a carbonyl with a transition metal catalyst, imine formation between an amine
and a carbonyl compound, and the reduction of imine to amine. These systems have
disadvantages, for example, the recovery and reuse of expensive catalysts and the need of
co-catalysts, such as bases and stabilizing ligands. Therefore, the search for cheaper cata-
lysts with the same performance is necessary for industrial application. Ruthenium-based
homogeneous catalytic systems are relatively cheaper than other transition metal catalysts,
such as iridium and rhodium and are mostly commercially available.
In this research, we investigate N-alkylation of several aromatic and aliphatic amines
with benzyl alcohol by ruthenium complexes under relatively mild conditions. Under our
experimental conditions, ruthenium catalysts have no activity in the absence of phosphine
ligands. A number of diphosphine ligands were added to the reaction mixture and their
activities and selectivities were compared. The reactions were run in different solvents,
temperatures, and reaction times to find optimum conditions.
2. Experimental
2.1. Materials and instrumentation
All chemicals and reagents were purchased from Aldrich and Strem chemical companies
and used without purification. The solvents were of analytical grade, and purified prior to
use based on standard methods. Amines were distilled under argon and stored in tightly
closed containers. Reactions were carried out under inert atmosphere using standard
Schlenk techniques. Melting points are uncorrected and were obtained with the Electrother-
mal 9200 melting point apparatus. For monitoring of reaction products and their identity, a
gas chromatograph, Agilent Technologies 7890A Instrument (equipped with a HP-1
capillary column, a FID detector, and a mass spectroscope model 5975C with a triple-axis
detector), was used. Dodecane was used as the internal standard.
2.2. Synthesis of complexes
Xantphos derivatives were prepared according to previously published methods [23].
[Ru(p-cymene)Cl2]2, [RuCl(PPh3)2Cp], [RuHCl(CO)(PPh3)3], [RuH2CO(PPh3)3], and

3500
B.Tamaddoni Jahromi and A.Nemati Kharat
[Ru3CO12] were prepared according to literature methods [24–26]. For preparation of
crystals of [Ru(NO3)2CO(PPh3)2] and [Ru(NO3)2(CO)2(PPh3)2], a slightly modified method
was used [27]. Typically 0.1 g [RuH2CO(PPh3)2] was refluxed in 3 M nitric acid (25 mL)
for 3 h. The resultant viscous oil was separated by decantation and dried over sodium
sulfate. The product was filtered off and dissolved in dichloromethane/methanol. After
cooling to 10 °C, yellow cubic crystals of Ru(NO3)2CO(PPh3)2 appeared (yield 60%). mp:
269–271 °C. Elemental Anal. Calcd for C37H30N2O7P2Ru: C, 57.12; H, 3.88; N, 3.60.
Found: C, 57.26; H, 3.91; N, 3.68. For the preparation of [Ru(NO3)2(CO)2(PPh3)2], carbon
monoxide was bubbled through a suspension of 0.2 g [Ru(NO3)2CO(PPh3)2] in boiling eth-
anol (30 mL) for 2 h. After cooling the mixture, white solids were separated and washed
with ethanol (yield 92%). mp: 180–183 °C. Elemental Anal. Calcd for C38H30N2O8P2Ru:
C, 56.65; H, 3.75; N, 3.48; found: C, 56.57; H, 3.78; N, 3.37.
2.3. N-alkylation reaction
Ruthenium complex (0.015 mM), diphosphine ligand (0.07 mM), potassium carbonate
(0.03 mM), and activated molecular sieves 3Å (0.1 g) were added to the reaction flask. The
mixture was exposed to nitrogen for 10 min. Amine (1.0 mM), benzyl alcohol (1.0 mM),
and dry toluene as solvent (1.0 mL) were added and refluxed for 12 h. After filtration, the
reaction mixture was extracted three times with 5% hydrochloric acid solution, then the pH
of the combined aqueous phase was adjusted to nine by the addition of dilute sodium
hydroxide solution. The aqueous phase was extracted with dichloromethane and dried over
MgSO4 prior to the injection to GC.
3. Results and discussion
The N-alkylation of amines by alcohols is a thermodynamically favored process. This reac-
tion has synthetic importance in the preparation of secondary and tertiary amines. Herein,
we report the N-alkylation of several aliphatic and aromatic amines with benzyl alcohol in
the presence of different ruthenium catalysts (scheme 1). Secondary amines, because of
their higher nucleophilicity, are generally more reactive than primary amines, such that fur-
ther reaction favored the formation of tertiary amines. Our primary goal was to find suitable
conditions for chemoselective synthesis of amines.
The mechanism of N-alkylation of amines with alcohols in the presence of transition
metal catalysts are shown in scheme 2. This reaction proceeds stepwise, whereby the ruthe-
nium catalyst dehydrogenates the alcohol to form an aldehyde that is readily attacked by
the amine, then transformed initially into the imine, where concentration remains low and
almost constant throughout the reaction [28]. A successive hydrogenation converts the
imine into the N-alkyl derivative. This third step uses the hydrogen which was removed
Scheme 1. N-alkylation of amines with benzyl alcohol.

N-alkylation of amines
3501
Scheme 2. Mechanism of ruthenium catalyzed N-alkylation of amines with alcohols.
from the alcohol in the first step. Thus, an overall redox reaction is catalyzed with a series
of steps involving both oxidation and reduction.
In the above mechanism, water was formed as the reaction proceeded, which can lead to
increased hydrolysis of the imine to yield the ketone, which can also be hydrogenated by
the catalyst. Thus, in most cases, for the removal of water from the reaction medium
molecular sieves were used, having a beneficial effect on these reactions. Another common
protocol includes the presence of an inorganic base or ammonia to affect the aforemen-
tioned transformation. The most conventional conditions utilize an alkali metal carbonate in
a polar aprotic solvent at room temperature or under heating, depending on the nature of
the starting materials. As mentioned in the published literature [29], this additive has a cru-
cial effect on both conversion and selectivity. Some work claimed that it can render forma-
tion of tertiary amines [30] in the course of the reaction. According to scheme 2, addition
of an alkali can expedite dehydrogenation of alcohols and formation of related aldehydes.
Another effect of alkali addition should be increasing nucleophilic power of the amines.
In table 1, activities of various ruthenium complexes in N-alkylation of amines are
shown. Catalyst loading was 3 M% based on the ruthenium complex. The combination of
diphenyl-phosphinopropane (dppp) with different ruthenium complexes under mild condi-
tions was chosen as the model reaction to find the active ruthenium complexes.
As shown in table 1, among the synthesized complexes, [(Ru(Cymene)Cl2)2], [Ru3CO12]
and [RuCl(PPh3)2Cp] show good activity and [(Ru(p-cymene)Cl2)2] appeared to be the
most effective catalyst. Under the experimental conditions of this study, [RuHClCO(PPh3)3]
and [RuH2CO(PPh3)3] show less reactivity. It was proposed that a free coordination site on
ruthenium is necessary for activation in this type of reaction. In these saturated metal
hydride complexes, an energy consuming preliminary ligand dissociation is the reason for
low or even no reactivity. Normally, 16-electron complexes are active in dehydrogenation
and the 18-electron complexes are active in hydrogenation reactions [31]. Unexpectedly,
[Ru(NO3)2CO(PPh3)2] showed better activity than other 18-electron complexes studied in
this paper.

3502
B.Tamaddoni Jahromi and A.Nemati Kharat
Table 1. Conversions of ruthenium complexes in N-alkylation of amines.
Catalyst
n-Butylamine
96
Hexylamine
93
Octylamine
94
Cyclohexylamine
89
Aniline
89
80
63
34
77
56
28
74
50
25
80
61
15
82
51
10
29
77
30
68
25
75
12
62
14
65
41
38
38
31
30
Notes: Reaction condition: 1 mM amine, 1 mM benzyl alcohol, 3 M% ruthenium catalyst, 0.07 mM dppp, 0.03 mM base, 1 mL tol-
uene, 110 °C, 12 h. Yields were determined by GC.
X-ray crystallography of [Ru(NO3)2CO(PPh3)2] confirmed the six-coordinate geometry
with one monodentate and one bidentate nitrate in the complex. Switching from a bidentate
to a monodentate nitrate should provide a vacant site for the coordination of alcohol or amine.
Crystallographic data and selected bond lengths and angles are listed in tables 2 and 3,
respectively. [Ru(NO3)2CO(PPh3)2] crystallizes as yellow cubes in the monoclinic space
group C2/c with 8 molecules in the unit cell (figure 1).
The ruthenium–oxygen bond distance is 2.133(3) Å for monodentate and 2.149(3) and
2.166(2) Å for bidentate nitrate, comparable with reported bond lengths for a six-coordinate
ruthenium complex [32–34]. Another reason for unusual reactivity is the high tendency of
[Ru(NO3)2CO(PPh3)2] for alcohol dehydrogenation [35]. This reaction, which is accelerated
in the presence of a base, proceeds by a β-elimination mechanism, and is accompanied by
the formation of an aldehyde and a metal hydride, [RuH(NO3)(CO)(PPh3)2], by a nitrate
dissociation; the steps are shown in the catalytic scheme 2. The unit cell-packing diagram
of the complex is presented in figure 2.
Some weak hydrogen bonds exist in the structure, stabilizing the packing of the complex.
One of these hydrogen bonds exists between the C–H bond of phenyl and oxygen of nitrate of
the next molecule (C(4)–H(4)⋯O(7) = 2.30 with an angle of 160.2 and C(29)–H(29)⋯O(2)

N-alkylation of amines
3503
Table 2. Crystallographic and structure refinement data of Ru(NO3)2CO(PPh3)2.
Formula
C37H30N2O7P2Ru
Formula weight
777.64
Crystal system
Monoclinic
Space group
C 2/c
a/Å
19.111(4)
b/Å
10.741(2)
c/Å
34.370(7)
α/°
90
β/°
100.26
γ/°
90
6942(2)
Volume/Å3
Z
8
Density (Calcd)/gm
θ Ranges for data collection
F (0 0 0)
1.488
2.21–29.15°
3168
0.596
Absorption coefficient/mm−1
Index ranges
−26 ≤ h ≤ 26, −12 ≤ k ≤ 14, −47 ≤ l ≤ 47
Data collected
26864
Unique data (Rint
)
9259 (0.0475)
412, 0
0.0611, 0.1257
0.0807, 0.1335
1.064
Parameters, restraints
Final R1, wR2a (obs. data)
Final R1, wR2a (all data)
Goodness of fit on F2(S)
Largest diff. peak and hole/eÅ3
1.622, −1.188
Note:aR1 = Σ||F0| − |Fc||/Σ|F0|; wR2 = [Σ(w(F02−Fc2)2)/Σw(F02)2]1/2
.
Table 3. Selected bond distances (Å)
and angles (°) for [Ru(NO3)2(CO)(PPh3)2].
Ru(1)–C(37)
Ru(1)–O(5)
Ru(1)–O(2)
Ru(1)–O(3)
Ru(1)–P(1)
1.838(4)
2.133(3)
2.149(3)
2.166(2)
2.312(1)
C(37)–Ru(1)–O(5)
O(5)–Ru(1)–O(2)
C(37)–Ru(1)–O(3)
O(2)–Ru(1)–P(1)
100.42
79.98
59.84
160.95
with an angle of 170.6). The other hydrogen bond belongs to C–H⋯π interaction of the phenyl
groups (figure 3).
In this type of reaction, using alkylating agent in a limited amount is not sufficient for
selective synthesis of a given product and only with careful adjustment of reaction parame-
ters, such as the relative proportions of the reactants, reaction temperature, time, and the use
of proper additives [36, 37], can one tune conditions, so that the desired product becomes
predominant. Other constraints such as amine basicity, steric demands, and relative solubili-
ties in the reaction media [38, 39] need to be taken into account if product yields are of
importance.
Using an excess of free ligand is crucial for high conversion. Previous researchers
suggested that phosphine may displace the complexed aldehyde to facilitate its reaction in
solution with amine [40] or that it may accelerate the catalytic hydrogenation of imine to

3504
B.Tamaddoni Jahromi and A.Nemati Kharat
Figure 1. ORTEP of Ru(NO3)2CO(PPh3)2 with atom numbering scheme. The thermal ellipsoids are drawn at the
50% probability level at 298 °K.
Figure 2. Packing view of Ru(NO3)2CO(PPh3)2.

N-alkylation of amines
3505
Figure 3. View of C–H⋯O hydrogen bonding (blue dashed line) and C–H⋯π interactions (black dashed line) in
the packing (see http://dx.doi.org/10.1080/00958972.2013.844340 for color version).
tertiary amine. To further investigate the importance of ligands in the course of this reac-
tion, a series of diphosphine ligands, such as xantphos and their calcogenides, xantphos
oxide, xantphos sulfide, and xantphos selenide, diphenylphosphinomethane (dppm), diphen-
ylphosphinoethane (dppe), diphenylphosphinopropane (dppp), diphenylphosphinobutane
(dppb), and diphenylphosphinopentane (dpppe) were tested in the N-alkylation reaction of
benzyl alcohol. Octyl amine and aniline were chosen as probes of aliphatic and aromatic
amines to investigate the effect of ligands. In the absence of any additional ligand, only low
conversion of the starting material after 12 h at refluxing toluene was obtained for all
catalysts. A high yield of the product with good chemoselectivity was obtained using
diphenylphosphinopropane (dppp), while the structurally similar dppm, dppe, and dpppe
provided only poor yields. As shown in table 4 comparison of different xantphos
derivatives show that replacing the soft donor P in xantphos with hard O in xantphos oxide,
conversions increased significantly. Xantphos oxide showed better conversion than other
calcogenides. In the reaction with xantphos derivatives, better selectivity is observed toward
secondary amines in the reaction with aniline. Because of higher nucleophilicity, secondary
amines are generally more reactive than primary amines, so further reaction favored the
formation of tertiary amines. Under our experimental conditions, using bulky xantphos
derivatives gave higher selectivity for secondary amines.
Some authors [41] have pointed out that the presence of a chloride is a prerequisite for
catalytic activity in N-alkylation reactions. However, this does not apply to our catalytic
systems, because we observe good conversion using catalysts containing no chloride in

3506
B.Tamaddoni Jahromi and A.Nemati Kharat
Table 4. Effect of different ligands on conversion and selectivity of ruthenium complexes in N-alkylation of
amines.
Octyl amine
°2 Amine
Aniline
Entry
Ligand
Conv. %
°3 Amine
Conv. %
°2 Amine
°3 Amine*
1
2
3
4
5
6
7
8
9
No ligand
Xantphos
Xantphos=O
Xantphos=S
Xantphos=Se
dppm
dppe
dppp
dppb
dpppe
8
75
88
80
77
75
83
94
83
79
–
–
5
73
84
80
75
69
78
89
74
70
–
15
18
24
23
28
30
23
27
24
79
81
73
74
70
69
74
72
74
43
55
74
86
39
45
50
43
39
55
40
23
10
61
50
50
55
61
10
Notes: Reaction condition: 1 mM amine, 1 mM benzyl alcohol, 3 M% [Ru(cymene)Cl2]2, 0.07 mM diphosphine ligand, 0.03 mM
K2CO3, 1 mL toluene, 110 °C, 12 h.
*Besides secondary and tertiary amines, small amounts of unknown heavy by-products were formed.
their structure. As shown in table 5 in the alkylation of secondary amines, basicity and size
of amines are important. Secondary amines such as morpholine and diethylamine gave
lower yields compared to the primary amines under the same condition and required higher
catalyst loading to obtain good yields. Aromatic amines showed lower activity with respect
to aliphatic amines and as expected, electron-rich toluidine showed better results than
chloroaniline.
In some catalytic runs, a light-brown ruthenium containing deposit was recovered from
the reaction media after completion of the reaction. Infrared spectra of these residues
showed a strong absorption in the ν(COstretch) at 1944 cm−1, pointing to the formation of
ruthenium–carbonyl complexes during the reaction. Decomposition of ruthenium aldehyde
intermediates has been reported to occur during the N-alkylation reactions of long-chain
aliphatic amines with primary alcohols [40]. Attempts to characterize these ruthenium-
containing deposits failed because of their insolubility in common solvents. Production of
Table 5. Catalytic N-alkylation of amines with benzyl alcohol.
Selectivity
Entry
Starting amine
Conv.%
°2 amine
°3 amine*
1
2
3
4
5
6
7
8
Isopropylamine
n-Butylamine
Sec-butylamine
t-Butylamine
Hexylamine
Octylamine
Cyclohexylamine
Benzylamine
Aniline
95
94
86
98
93
94
89
92
89
86
92
60
81
50
44
28
25
30
23
24
43
50
44
45
–
50
53
70
72
67
74
73
55
50
53
50
86
82
9
10
11
12
13
2-Chloroaniline
Toluidine
aDiethylamine
aMorpholine
–
Notes: Reaction condition: 1 mM amine, 1 mM benzyl alcohol, 3 M% [Ru(cymene)Cl2]2, 0.07 mM dppp,
0.03 mM K2CO3, 1 mL toluene, 110 °C, 12 h.
aWith catalyst loading of 10 M% only dialkylated amine was produced.
*Besides secondary and tertiary amine, small amount of unknown heavy by-products were formed.

N-alkylation of amines
3507
Figure 4. Effect of reaction time on alkylation of benzyl alcohol with octylamine (left) and aniline (right). Cata-
lyst: [Ru(cymene)Cl2]2, a: secondary amine; b: tertiary amine.
such colored ruthenium-containing deposits decreased while performing the experiments at
lower temperatures. Variation of solvent polarity had no significant effect on the amination
reaction. The reactions were run with a molar ratio of 1:5:70:70 for catalyst:ligand:amine:
alcohol in toluene as the solvent. N-alkylation of octylamine in refluxing benzene within
12 h led to 85% benzyl octylamine and 15% dibenzyl octylamine, with a total conversion
of 70%. When using benzene as the solvent, the reaction stopped predominantly at the
monoalkylation stage. Under these conditions, aniline was alkylated with 68% conversion
and 95% selectivity to benzyl aniline. At temperatures over 140 °C by using xylene as the
solvent, conversion of alcohol to alkylated amines increased over 95%, but with poor
selectivity.
The influence of reaction time was examined from 4 to 24 h. Satisfying results were
obtained after 12 h, during which a total conversion of over 90% was observed under our
experimental conditions. As seen in figure 4, over 12 h of reaction gave no significant
change in conversion; however, the selectivity dropped significantly.
After 12 h, the selectivity diminished gradually when compared to a reaction time of 6 h;
using longer reaction times the amount of secondary amines decreased in favor of tertiary
amines.
4. Conclusion
A number of amines with benzyl alcohol were converted into the corresponding secondary
and tertiary amines with good to excellent yields. The effect of different ligands, time, and
temperature were investigated in this reaction to obtain optimum conditions. This process is
potentially attractive to pharmaceuticals and fine chemical industries because low loading of
catalyst is needed; only H2O is formed as the by-product and alcohols are used, which are
more readily available than the potentially harmful alkyl halides or carbonyl compounds.
Proceeding under transfer hydrogenation conditions, no hydrogen gas is needed for the
alkylation, which allows this methodology to be a green and atom-efficient process.
Acknowledgment
The authors gratefully acknowledge the financial support from the University of Tehran.

3508
B.Tamaddoni Jahromi and A.Nemati Kharat
Supplementary material
CCDC number 922503 contains the supplementary crystallographic data for catalysts. These
data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or
from the Cambridge Crystallographic Data Center, 12 Union Road, Cambridge CB2 1EZ,
UK; Fax: +44 1223 336 033; or E-mail: deposit@ccdc.cam.ac.uk.
References
[1] J.F. Hartwig. In Handbook of Organo-palladium Chemistry for Organic Synthesis, Wiley-Interscience, New
York (2002).
[2] S.S. Insaf, D.T. Witiak. Synthesis, 3, 435 (1999).
[3] M.S. Gibson. In the Chemistry of Amino Group, S. Patai, Interscience, New York (1968).
[4] G. Solomons, C. Fryhle. Organic Chemistry, Wiley, New York (2000).
[5] M. Utsunomiya, R. Kuwano, M. Kawatsura, J.F. Hartwig. J. Am. Chem. Soc., 125, 5608 (2003).
[6] J.-S. Ryu, G.Y. Li, T.J. Marks. J. Am. Chem. Soc., 125, 12584 (2003).
[7] A.M. Johns, M. Utsunomiya, C.D. Incarvito, J.F. Hartwig. J. Am. Chem. Soc., 128, 1828 (2006).
[8] T. Mizuta, S. Sakaguchi, Y. Ishii. J. Org. Chem., 70, 2195 (2005).
[9] M.C. Harris, O. Geis, S.L. Buchwald. J. Org. Chem., 64, 6019 (1999).
[10] R.N. Salvatore, C.H. Yoon, K.W. Jung. Tetrahedron, 57, 7785 (2001).
[11] D.M. Roundhill. Chem. Rev., 92, 1 (1992).
[12] J.S. Bradshaw, K.E. Krakowiak, R.M. Izatt. Tetrahedron, 48, 4475 (1992).
[13] K. Yamaguchi, N. Mizuno. Angew. Chem. Int. Ed., 48, 9888 (2009).
[14] C.F. Winans, H. Adkins. J. Am. Chem. Soc., 54, 306 (1932).
[15] R.G. Rice, E.J. Kohn. J. Am. Chem. Soc., 77, 4052 (1955).
[16] Y. Watanabe, Y. Tsuji, Y. Ohusugi. Tetrahedron Lett., 22, 2667 (1981).
[17] A. Baiker, J. Kijenski. Catal. Rev. Sci. Eng., 27, 653 (1985).
[18] R. Grigg, T.R.B. Mitchell, S. Sutthivaiyakit, N. Tongpenyai. J. Chem. Soc, Chem Commun., 611 (1981).
[19] D. Hollmann, A. Tillack, D. Michalik, R. Jackstell, M. Beller. Chem. Asian J., 2, 403 (2007).
[20] A. Tillack, D. Hollmann, D. Michalik, M. Beller. Tetrahedron Lett., 47, 8881 (2006).
[21] A. Del Zotto, W. Baratta, M. Sandri, G. Verardo, P. Rigo. Eur. J. Inorg. Chem., 524, (2004).
[22] J. Louie, M.S. Driver, B.C. Hamann, J.F. Hartwig. J. Org. Chem., 62, 1268 (1997).
[23] B. Tamaddoni Jahromi, A. Nemati Kharat, S. Zamanian, A. Bakhoda, K. Mashayekh, S. Khazaeli. Appl.
Catal. A, 433–434, 188 (2012).
[24] J.P. Fackler. Inorganic Syntheses, Wiley Interscience Publication, New York (1982).
[25] R.J. Angelici. Inorganic Syntheses, Wiley Interscience Publication, New York (1990).
[26] G.W. Parshal. Inorganic Syntheses, Mcgraw-Hill Book Company, New York (1974).
[27] P.B. Critchlow, S.D. Robinson. Inorg. Chem., 17, 1896 (1978).
[28] M.H.S.A. Hamid, P.A. Slatford, M.J. Williams. J. Adv. Synth. Catal., 349, 1555 (2007).
[29] S.K. Srivastava, P.M.S. Chauhan, A.P. Bhaduri. Synth. Commun., 29, 2085 (1999).
[30] M.H.S.A. Hamid, M.J. Williams. Chem. Commun., 725 (2007).
[31] K. Mashima, T. Nakamura, Y. Matsuo, K. Tani. Organomet. Chem., 607, 51 (2000).
[32] T. Hamaguchi, I. Ando. Acta Cryst., E67, m1687 (2011).
[33] A. Muller, W.L. Davis. Acta Cryst., E68, m1446 (2012).
[34] C.M. Kepert, G.B. Deacon, L. Spiccia. Inorg. Chim. Acta, 355, 213 (2003).
[35] P.B. Critchlow, S.D. Robinson. Inorg. Chem., 17, 1902 (1978).
[36] R.O.C. Norman, J.M. Coxon. Principles of Organic Synthesis, 3rd Edn, Blackie Academic, New York (1993).
[37] H. Beyer, W. Walter. Handbook of Organic Chemistry, Prentice Hall, New York (1996).
[38] R.W. Alder. Chem. Rev., 89, 1215 (1989).
[39] H.C. Brown, N.R. Eldred. J. Am. Chem. Soc., 71, 445 (1949).
[40] S. Ganguly, D.M. Roundhill. Polyhedron, 9, 2517 (1990).
[41] Y. Watanabe, Y. Tsuji, H. Ige, Y. Ohsugi, T. Ohta. J. Org. Chem., 9, 3359 (1984).