Shvo's catalyst and [IrCp7z.ast;Cl2(amidine)] effectively catalyze the formation of tertiary amines from the reaction of primary alcohols and ammonium salts

Article abstract of DOI:10.1002/adsc.201100135

The reaction of (pentamethylcyclopentadienyl)iridium dichloride dimer, [IrCp*Cl₂]₂, with bis(2,4,6-trimethylphenyl) formamidine allows the preparation of two new [IrCp*Cl ₂(amidine)] and [IrCp*Cl(amidinate)] complexes, which have been fully characterized. Both complexes have been tested in the β-alkylation of 1-phenylethanol with primary alcohols, and in the formation of tertiary amines from the reaction of ammonium salts with primary alcohols, and the results have been compared with those shown by Shvo's catalyst. Our studies demonstrate that both [IrCp*Cl₂(amidine)] and Shvo's catalyst are very efficient in both catalytic processes. The high activity of the Ir-amidine complex may be attributed to the presence of the NH group in the amidine ligand. Copyright

Full text of DOI:10.1002/adsc.201100135

FULL PAPERS
DOI: 10.1002/adsc.201100135
Shvoꢀs Catalyst and [IrCp*Cl (amidine)] Effectively Catalyze the
2A
Formation of Tertiary Amines from the Reaction of Primary
Alcohols and Ammonium Salts
Candela Segarra,a Elena Mas-Marzꢀ,a,* Josꢁ A. Mata,a and Eduardo Perisa,*
a
Departamento de Quꢂmica Inorgꢀnica y Orgꢀnica, Universitat Jaume I, Avda. Vicente Sos Baynat s/n, E-12071 Castellꢃn,
Spain
Fax : (+34)-964-728-214; e-mail: emas@qio.uji.es or eperis@qio.uji.es
Received: February 22, 2011; Revised: May 4, 2011; Published online: August 4, 2011
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/adcs.201100135.
Abstract: The reaction of (pentamethylcyclopenta- those shown by Shvoꢄs catalyst. Our studies demon-
dienyl)iridium dichloride dimer, [IrCp*Cl2]2, with strate that both [IrCp*Cl
bis(2,4,6-trimethylphenyl)formamidine allows the lyst are very efficient in both catalytic processes. The
preparation of two new [IrCp*Cl2A(amidine)] and high activity of the Ir-amidine complex may be at-
2ACHTUNGERTN(NUNG amidine)] and Shvoꢄs cata-
CTHUNGTRENNUNG
[IrCp*Cl(amidinate)] complexes, which have been tributed to the presence of the NH group in the ami-
fully characterized. Both complexes have been tested dine ligand.
in the b-alkylation of 1-phenylethanol with primary
alcohols, and in the formation of tertiary amines
from the reaction of ammonium salts with primary Keywords: alcohols; b-alkylation; ammonia; homo-
alcohols, and the results have been compared with geneous catalysis; iridium
Introduction
On the other hand, the ubiquitous Shvoꢄs catalyst
[(h5-C5Ph4O)2HRu2H(CO)4] is very active in all kinds
Although ammonia has rarely been used as substrate of transfer hydrogenations to alkenes, alkynes, car-
for homogeneously catalyzed transformations, some bonyl groups and imines from alcohols and other di-
recently developed catalysts have allowed the prepa- hydrogen sources.[6] In general, this catalyst is unique
ration of nitrogen-containing compounds from this in- because the mechanism that explains its activity in-
expensive nitrogen source.[1] The alkylation of ammo- volves simultaneous transfer of separate hydrogen
nia with alcohols is normally catalyzed by heterogene- atoms from (or to) the metal and the ligand, thus pro-
ous catalysts requiring high pressures and tempera- viding one clear example of a metal-ligand bifunction-
tures,[2] although a number of such processes cata- al catalyst.
lyzed by soluble transition metal complexes are now
known.[3] For example, Fujita and co-workers recently C N and C C bond formation processes implying al-
described that [IrCp*Cl2]2 catalyzes the alkylation of cohols and amines, mostly using ꢅIrCp*(NHC)ꢄ
ammonium acetate with benzylic alcohols,[3c] and that (NHC=N-heterocyclic carbene) type complexes.[7] In
[IrCp*
(NH3)3]2+ is able to alkylate aqueous ammonia all these reactions, the oxidation of the alcohol plays
We have recently been interested in the study of
À
À
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG
with primary and secondary alcohols.[4] Additionally, an important role in the initial steps of the reaction,[8]
Milstein described the alkylation of pressurized am- and the presence of cooperating ligands is known to
monia with primary alcohols using a ruthenium PNP improve the catalytic efficiency, through a metal-
pincer complex.[3b] In all these reactions, the selectivi- ligand bifunctional catalysis.[9] Specifically, Fujita and
ty on the product obtained is one of the main goals to co-workers elegantly showed that the acceptorless ox-
achieve, since imines can be obtained together with idation of alcohols by ꢅIrCp*ꢄ complexes may be fa-
primary, secondary or tertiary amines. Nitriles can cilitated by the presence of 2-hydroxipyridine, on a
also be obtained from the homogeneously catalyzed ꢅligand-promoted dehydrogenationꢄ.[10] Based on these
reaction of alcohols and ammonia.[5]
principles, we now report the preparation of two new
ꢅIrCp*ꢄ complexes with a bis(2,4,6-trimethylphenyl)-
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Adv. Synth. Catal. 2011, 353, 2078 – 2084

Shvoꢄs Catalyst and [IrCp*Cl2ACTHNUTRGNEU(GN amidine)] Effectively Catalyze the Formation of Tertiary Amines
Scheme 1. Synthesis of complexes 1 and 2.
Figure 1. Molecular diagram of complex 1. Selected bond
À
À
distances (ꢇ) and angles (8): Ir(1) N(1) 2.126(3), Ir(1)
À
À
Cl(1) 2.4199(10), Ir(1) Cl(2) 2.4113(10), N(1) C(11) 1.290
À
À
À
À
(4), N(2) C(11) 1.334 (5); Cl(1) Ir(1) Cl(2) 89.47(4), N(1)
formamidine ligand, which have been used in several
À
À
À
Ir(1) Cl(1) 84.73(8), N(2) Ir(1) Cl(2) 85.22(8).
À
À
C C and C N bond forming reactions. The complex
with the monocoordinated amidine (1, as will be la-
belled later on) is highly active in the formation of
tertiary amines from the reaction of primary alcohols
with solutions of ammonia.
The molecular structure of compound 2 (Figure 2),
consists of an IrACTHNUTRGNE(NUG III) centre with one Cp*, one chlo-
ride and an amidinate ligand in a chelating form. The
À
two Ir N distances are virtually identical (2.140 and
2.149 ꢇ), and the same happens with the two N C
À
Results and Discussion
bonds (1.292 and 1.332 ꢇ), which gives a highly sym-
The reaction of bis(2,4,6-trimethylphenyl)formami-
dine with [IrCp*Cl2]2 at room temperature affords the
formamidine-IrACHTUNGTRENNUNG(III) complex 1 (Scheme 1). The com-
plex was characterized by the usual spectroscopic
techniques and gave satisfactory elemental analysis.
As a diagnostic of the monodentate coordination of
1
the ligand, the H NMR spectrum shows two doublets
(3JH,H =13 Hz) due to the CH (8.1 ppm) and NH
(5.8 ppm) groups at the imine. This is one of the very
few examples in which an amidine ligand is monoden-
tate,[11] and the only Ir complex with this type of coor-
dination that has been reported to date. When the re-
action between the same two reactants is carried out
in THF in the presence of n-BuLi, the formamidate
complex 2 is obtained.
The molecular structures of complexes 1 and 2
were determined by means of X-ray diffractommetry.
The molecular diagram of 1 is shown in Figure 1. The
molecule consists of an IrACTHNUTRGNEUGN(III) center in a pseudo-
three-legged piano-stool environment, with one Cp*,
two chlorides and one amidine ligand completing the
À
coordination sphere. The Ir N bond distance is
Figure 2. Molecular diagram of complex 2. Selected bond
distances (ꢇ) and angles (8): Ir(1) N(1) 2.140(7), Ir(1) N(2)
2.126 ꢇ, and the mesityl group bound to N(1) is
pointing out of the metal coordination sphere, in a
quasi-parallel orientation with respect to the Cp*
plane.
À
À
À
À
À
2.149(8), Ir(1) Cl(2) 2.391(2), N(1) C(11) 1.292(11), N(2)
À
À
À
À
C(11) 1.332(11); N(1) Ir(1) Cl(2) 89.6(2), N(2) Ir(1) Cl(2)
À
À
89.0(2), N(1) Ir(1) N(2) 60.4(3).
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FULL PAPERS
Table 1. b-Alkylation of 1-phenylethanol with primary alco-
metric chelating coordination form. The chelate bite-
hols.[a]
À
À
angle is 60.48, based on the N(1) Ir(1) N(2) angle.
Compounds 1 and 2 were first tested in the b-alky-
lation of 1-phenylethanol with primary alcohols. We
decided to start by studying this model reaction, be-
cause we wanted to test the capabilities of our two
catalysts in a general borrowing-hydrogen process,
prior to the study of the activation of the more chal-
lenging substrate, ammonia, which we will discuss
later. In both reactions the oxidation of the alcohol to
Entry
Cat.
(mol%)
R
t
Alcohol
[%][b]
Ketone
[%][b]
N
[h]
1
1 (1)
2 (1)
1 (1)
1 (0.1)
1 (1)
2 (1)
1 (1)
1 (0.1)
1 (1)
2 (1)
1 (1)
1 (0.1)
1 (1)
2 (1)
1 (1)
1 (0.1)
1 (1)
Ph
Ph
Ph
Ph
n-Pr
n-Pr
n-Pr
n-Pr
3-ClC6H4
3-ClC6H4
3-ClC6H4
3-ClC6H4
4-ClC6H4
4-ClC6H4
4-ClC6H4
4-ClC6H4
Ph
3
3
8
24
6
6
8
24
6
6
8
24
3
3
3
90
72
75
65
62
61
91
10
93
60
40
40
91
62
80
80
37
9
23
0
À
À
an aldehyde/ketone is needed prior to the C C or C
N bond formation. The b-alkylation of secondary al-
cohols is believed to involve oxidation of both alco-
hols to form a ketone and an aldehyde, which then
undergo an aldol condensation giving an a,b-unsatu-
rated ketone, which is further reduced to give the sa-
turated alcohol.[8a,12] The reactions were carried out in
toluene at 1008C under aerobic conditions, using cata-
lyst loadings of 1 or 0.1 mol%. We performed the re-
actions trying to achieve the maximum atomic effi-
ciency, so we used a molar ratio of 1:1 between the
primary and secondary alcohols, except in the cases
shown in Table 1 (entries 3, 7, 11 and 15). As can be
seen from the data shown in Table 1, 1 is far more ef-
ficient than 2 (compare entries 1/2, 5/6, 9/10 and 13/
14), both in terms of conversions to the final products
and selectivity toward the corresponding b-alkylated
alcohols. Catalyst 1 is also active at a catalyst loading
of 0.1 mol%, especially when benzyl alcohol and 4-
chlorobenzyl alcohol were used, although longer reac-
tion times were needed (24 h). These data compare
well with the catalytic outcomes shown by other pre-
2
3[c]
4
0
5
25
15
8
0
4
7
0
0
8
7
0
0
0
6
7c
8
9
10
11[c]
12
13
14
15[c]
16
17[d]
24
3
[a]
Reaction conditions: 1-phenylethanol (1 mmol), primary
alcohol (1 mmol), KOH (1 mmol), and 1 (or 0.1) mol% of
catalyst in 0.3 mL of toluene at 1008C.
Yields determined by H NMR.
Primary alcohol (2 mmol).
[b]
[c]
[d]
1
In situ preparation of 1 by addition of 0.5 mol% of
[IrCp*Cl2]2 and 1 mol% of dimesitylformamidine.
viously reported catalysts based on ꢅIrCp*
ported by Crabtree[13] and us,[7c,d] and Ru
(NHC)ꢄ[14] complexes. Remarkably, the in situ prepa- and 1 were also tested in the alkylation of NH4Cl, for
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG
ration of 1, resulted in a much lower activity than that which they provided very similar activity. Remarka-
shown by the preformed catalyst (compare entries 1 bly, 1 was moderately active in the alkylation of an
and 17).
aqueous solution of NH3 (entry 14), an observation
In order to test the catalytic versatility of 1 and 2, that will probably deserve further incoming studies.
we decided to test their activities in the alkylation of For the reactions carried out in the absence of an
ammonium salts with primary alcohols. Ammonia is extra amount of base, Shvoꢄs and 1 afforded excellent
one of the most desirable substrates for the formation yields to the final product (entries 6 and 11) while
of nitrogen-containing organic molecules, despite its [IrCp*Cl2]2 and 2 provided moderate-low outcomes
lack of reactivity in most catalytic reactions.[15] We (entries 3 and 8, respectively).
first made a catalyst screening by comparing the activ-
ity of [IrCp*Cl2]2, our newly reported compounds 1 widen the catalytic scope of 1 and Shvoꢄs catalyst by
and 2, and the ubiquitous Shvoꢄs catalyst. studying their activity with a variety of primary alco-
Taking all these data into account, we decided to
As can be seen from the data shown in Table 2, hols. Compound 2 was also tested in some selected re-
both 1 and Shvoꢄs catalyst afford excellent catalytic actions for comparative purposes. The results are
outcomes for the reactions carried out using NH4OAc summarized in Table 3. As can be seen from the data
and NaHCO3, especially when we compare these data shown, both 1 and Shvoꢄs catalyst afford excellent
with those provided by [IrCp*Cl2]2 and 2 under the yields for the coupling of several ammonium salts
same reaction conditions. As previously reported by with a wide set of primary alcohols, including benzylic
Fujita and co-workers,[3c] all catalysts exhibited excel- and alkylic alcohols. Catalyst 2 is less active than the
lent activities when the ammonium/alcohol ratio was other two catalysts under study. In general, catalyst 1
increased from 3 to 3.6, even when the catalyst load- affords excellent yields when benzylic alcohols are
ing was reduced to 0.5 mol%. Both Shvoꢄs catalyst used, but its activity is moderate-high when alkylic
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Shvoꢄs Catalyst and [IrCp*Cl
2ACHTUNGRTEN(NUNG amidine)] Effectively Catalyze the Formation of Tertiary Amines
Table 2. Alkylation of ammonium salts with benzyl alcohol.[a]
+
Entry
Cat.
Load (mol%)
X
Base
Alcohol/NH4
T [8C]
Yield [%]
1
2
3
4
5
6
7
8
N
3
OAc
OAc
OAc
OAc
OAc
OAc
OAc
OAc
OAc
OAc
OAc
Cl
NaHCO3
NaHCO3
–
NaHCO3
NaHCO3
–
NaHCO3
–
NaHCO3
NaHCO3
–
NaHCO3
NaHCO3
–
KOH
KOH
3
110
130
130
110
130
130
110
130
110
130
130
110
110
110
130
130
72
87
44
97
99
97
98
60
97
99
99
51
18
44
99
99
0.5
0.5
3
0.5
0.5
3
0.5
3
0.5
0.5
3
3.6
3.6
3
3.6
3.6
3
3.6
3
3.6
3.6
3
9
10
11
12
13
14[b]
15[c]
16[c]
3
3
5
5
Cl
OH
Cl
3
3
3.6
3.6
Cl
[a]
Reaction conditions: benzylalcohol (3 or 3.6 mmol), ammonium source (1 mmol), NaHCO3 (3 mol%) and 0.5, 3 or
5 mol% of catalyst at 110 or 1308C for 17 h. Yields determined by GC, using anisole as internal standard.
NH4OH, 30% in H2O.
t=39 h; 1 mmol of KOH.
[b]
[c]
primary alcohols are utilized. The activity of the we believe that the amidine ligand may stabilize the
ruthenium catalyst is higher in most of the cases, thus Ir(V) transition states (A and B, Scheme 2) through a
illustrating the wide applicability of this exceptional hydrogen bond between the NH and the oxygen of
À
catalyst. The reactions are very selective to the forma- the alkoxide ligand in A and a NH HIr dihydrogen
tion of the tertiary amines, except those where cyclo- bond[17] in B. As previously proposed by Fujita and
hexanol is used, that selectively renders dicyclohexyl- Yamaguchi,[3c,4] once the aldehyde has been formed,
amine (entries 26–30). Catalyst 1 is more selective its reaction with ammonia would facilitate the forma-
than Shvoꢄs catalyst in the production of the tertiary
amine when 3-chlorobenzyl alcohol is used (compare
entries 9 and 10; Shvoꢄs catalyst produces the secon-
dary and primary amines in a 1/1 ratio).
We believe that the presence of the NH group on
the amidine ligand of the catalyst 1 is increasing the
catalytic activity compared to the activity shown by
[IrCp*Cl2]2. This ꢅNH effectꢄ may facilitate the dehy-
drogenation of the primary alcohol to aldehyde in the
first steps of the catalytic cycle,[3c] in a similar way to
that previously shown by Noyoriꢄs group for the re-
verse reaction implying the hydrogenation of ke-
ACHTUNGTRENNUNG
tones.[9d,16] However, we believe that the NH bond
does not deprotonate during the process, because this
would imply the formation of the chelated species 2,
which – as we have shown – displays a much lower
catalytic activity than 1, so its participation in the pro-
cess can be discarded. In fact, the conversion of 1 into
2, needs the addition of a very strong base, such a n-
BuLi, so the formation of this species under the reac-
tion conditions is rather unlikely. Based on our previ-
ously proposed mechanism for the dehydrogenation
of alcohols performed by ꢅIrCp*ACTHNUTRGNEU(GN NHC)ꢄ complexes, Scheme 2. Dehydrogenation of alcohols catalyzed by 1
Adv. Synth. Catal. 2011, 353, 2078 – 2084
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Table 3. Alkylation of ammonium salts with primary alcohol-
Conclusions
s.[a]
In summary, we have described two effective catalytic
systems for the selective synthesis of tertiary amines
by multialkylation of ammonium salts, in the absence
of solvent. The two catalysts (Shvoꢄs and 1) add to
the list of the very few metal complexes active in this
type of reaction and clearly improve the catalytic out-
comes of previously reported systems.[3c] We have also
added a new extraordinary useful catalytic application
of the ubiquitous Shvoꢄs catalyst.
Entry Cat.
(mol%)
X
R
Base
t
Yield
N
[h] [%]
1
2
1 (1)
2 (1)
OAc 4-Cl-benzyl
OAc 4-Cl-benzyl
–
–
–
17 76
17 73
17 99
3
Shvoꢄs (1) OAc 4-Cl-benzyl
4
1 (5)
Cl
4-Cl-benzyl
4-Cl-benzyl
KOH 39 67
KOH 39 99
–
–
–
5
Shvoꢄs (5) Cl
6
7
1 (1)
2 (1)
OAc 3-Cl-benzyl
OAc 3-Cl-benzyl
17 45[c]
17 20
17 66
Experimental Section
8
Shvoꢄs (1) OAc 3-Cl-benzyl
General Comments
9
10
1 (5)
Shvoꢄs (5) Cl
Cl
3-Cl-benzyl
3-Cl-benzyl
KOH 39 87
KOH 39 90[c]
All manipulations were carried out using standard Schlenk
techniques. Solvents were purified using an MBraun SPS
solvent system (THF, CH2Cl2, hexane). Deuterated solvents
were used as received (Merk and Aldrich) without further
purification. NMR spectra were recorded on Varian Innova
300 and 500 MHz spectrometers, using C6D6 and CDCl3
(Merk). Elemental analyses were carried out in an EA 1108
CHNS-O Carlo Erba analyzer. Electrospray mass spectra
(ESI-MS) were recorded on a Micromass Quatro LC instru-
ment, and nitrogen was employed as drying and nebulizing
gas. A gas chromatograph GC-2020 (Shimadzu) equipped
11
12
13
14
15
16
1 (1)
2 (1)
OAc 4-Me-benzyl
OAc 4-Me-benzyl
–
–
–
17 99
17 70
17 99
Shvoꢄs (1) OAc 4-Me-benzyl
1 (5)
Shvoꢄs (5) Cl
1 (1)
1 (3)
Shvoꢄs (3) OAc n-hexyl
1 (5)
Shvoꢄs (5) Cl
1 (1)
1 (3)
Shvoꢄs (3) OAc n-butyl
1 (5)
Shvoꢄs (5) Cl
1 (1)
1 (3)
Shvoꢄs (3) OAc cyclohexyl
1 (5)
Shvoꢄs (5) Cl
Cl
4-Me-benzyl
4-Me-benzyl
KOH 39 99
KOH 39 99
–
–
–
KOH 39 95
KOH 39 99
–
–
–
OAc n-hexyl
OAc n-hexyl
17 51
17 90
17 99
17[b]
18[b]
19[b]
20[b]
21
Cl
n-hexyl
n-hexyl
OAc n-butyl
OAc n-butyl
17 15
17 37
17 93
with an FID and
a Teknokroma (TRB-5MS, 30 mꢈ
22[b]
23[b]
24[b]
25[b]
26
0.25 mmꢈ0.25 mm) column. Bis(2,4,6-trimethylphenyl)for-
[19]
mamidine[18] and [IrCp*Cl2]2 were prepared according to
Cl
n-butyl
n-butyl
KOH 39 26
KOH 39 99
literature procedures. All other reagents are commercially
available and were used as received.
OAc cyclohexyl
OAc cyclohexyl
–
–
–
17 51[d]
17 78[d]
17 99[d]
27[b]
28[b]
29[b]
30[b]
Synthesis of Compound 1
Cl
cyclohexyl
cyclohexyl
KOH 39 66[d]
KOH 39 99[d]
AHCTUNGTERNGUN[N IrCp*Cl2]2 (100 mg, 0.126 mmol) and bis(2,4,6-trimethyl-
phenyl)formamidine (70 mg, 0.250 mmol) were stirred at
room temperature under nitrogen in dry CH2Cl2 (10 mL) for
2 h. After evaporation of the solvent under vacuum, the re-
maining solid obtained was washed with hexane (3ꢈ5 mL).
Compound 1 was obtained as a crystalline orange solid by
precipitation from CH2Cl2/hexane; yield: 153 mg (90%).
Crystals suitable for X-ray diffraction were obtained by slow
diffusion of hexane into a concentrated solution of 1 in
CHCl3. Analysis for C29H39N2IrCl2 [found (calculated)]: C
[a]
Reaction conditions: alcohol (3.6 mmol), NH4X (1 mmol),
at 1308C. Yields determined by GC, using anisole as in-
ternal standard.
6 mmol of alcohol and 1 mmol of NH4X, at 1408C.
Yield as a mixture in a ratio 1/1 trisalkylamine:bisalkyla-
mine.
[b]
[c]
[d]
Only bisalkylamine is observed.
51.47 (51.32),
H 5.70 (5.79), N
4.22 (4.13); 1H NMR
(300 MHz, CDCl3, 303 K): d=8.08 (d, 3JH,H =13 Hz, 1H,
CH), 7.00 (s, 2H, CHMes), 6.77 (s, 2H, CHMes), 5.75 (d,
3JH,H =12 Hz, 1H, NH) , 2.34 (s, 3H, CH3), 2.31 (s, 6H,
CH3), 2.19 (s, 3H, CH3), 2.16 (s, 6H, CH3), 1.29 [s, 15H, C5-
tion of the corresponding primary imine, which is
then reduced to the corresponding amine by the pri-
mary alcohol, in a metal-mediated transfer hydroge-
nation process. Subsequent alkylations of the resulting
primary amine, afford the final tertiary amine.
In order to prove that catalyst 1 is able to oxidize
primary alcohols under hydrogen-acceptorless condi-
tions, we performed a reaction of benzyl alcohol in re-
fluxing toluene in the presence of 1 (5 mol%) and
Cs2CO3. After 15 h we observed a 65% yield of ben-
zaldehyde, although the conversion of the alcohol was
complete.
AHCTUNGTRENNUNG
(CH3)5]; 13C{1H} NMR (125 MHz, CDCl3, 303 K): d=160.8
(s, CH), 140.4 (s, CMes), 136.8 (s, CMes), 136.4 (s, CMes), 133.9
(s, CMes), 133.2 (s, CMes), 132.7 (s, CMes), 129.6 (s, CHMes),
129.4 (s, CHMes), 85.6 [s, C5ACHTNUGRTNEUNG(CH3)5], 21.0 (s, CH3), 20.9 (s,
CH3), 19.1 (s, CH3), 17.8 (s, CH3), 8.6 [s, C
5ACHTUNGTREN(UNNG CH3)5]; electro-
spray MS: m/z=634.4 [MÀCl]+.
Synthesis of Compound 2
Bis(2,4,6-trimethylphenyl)formamidine (70 mg, 0.250 mmol)
was dissolved in dry THF under nitrogen and cooled to 08C.
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Adv. Synth. Catal. 2011, 353, 2078 – 2084

Shvoꢄs Catalyst and [IrCp*Cl2ACTHNUTRGNEU(GN amidine)] Effectively Catalyze the Formation of Tertiary Amines
n-BuLi (120 mL, 2.5M in hexanes) was added, and the solu-
tion was stirred for 10 min. The resulting yellow solution
was cannuled into a Schlenk tube with ([IrCp*Cl2]2 (100 mg,
0.126 mmol) in dry THF (10 mL). The resulting solution was
stirred for 10 min at 08C and then for 2 h at room tempera-
ture. After evaporation of the solvent under vacuum, the re-
maining solid obtained was extracted with benzene. After
evaporation of the benzene, the solid obtained was washed
with hexanes, affording compound 2 as a yellow solid; yield:
113 mg (70%). Crystals suitable for X-ray diffraction were
obtained by slow diffusion of hexane into a concentrated so-
lution of 2 in benzene. Analysis for C29H38N2IrCl [found
(calculated)]: C 54.11 (54.23), H 6.00 (5.96), N 4.28 (4.36);
1H NMR (300 MHz, C6D6, 303 K): d=9.16 (s, 1H, CH), 6.83
(s, 4H, CHMes), 2.57 (s, 12H, CH3), 2.17 (s, 6H, CH3), 1.26
with the aid of successive difference Fourier maps and re-
fined using SHELXTL 6.1 software package.[22] All non-hy-
drogen atoms were refined anisotropically, and hydrogen
atoms were assigned to ideal positions and refined using a
rigid model. CCDC 804268 (1) and CCDC 813587 (2) con-
tain the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.a-
c.uk/data_request/cif.
Acknowledgements
We gratefully acknowledge financial support from the Minis-
terio de Ciencia e Innovaciꢀn of Spain (CTQ2008-04460),
and Bancaixa (P1.1B2007-04). We also like to thank the Juan
de la Cierva program (E. M.-M.) and the Ministerio de Cien-
cia e Innovaciꢀn for a fellowship (C. S.). The authors are
grateful to the Serveis Centrals d’Instrumentaciꢀ Cientꢁfica
(SCIC) of the Universitat Jaume I for providing us with spec-
troscopic and diffractometric facilities.
[s, 15H, C
d=167.6 (s, CH), 140.4 (s, CMes), 134.2 (s, CMes), 133.1 (s,
CMes), 129.6 (s, CHMes), 83.2 [s, C5A(CH3)5], 21.8 (s, CH3), 20.9
(s, CH3), 9.0 [s, C5A(CH3)5].
5ACHTUNGTRENNUNG
(CH3)5]; 13C{1H} NMR (75 MHz, C6D6, 303 K):
CTHUNGTRENNUNG
CHTUNGTRENNUNG
Dehydrogenation of Benzyl Alcohol
A mixture of benzyl alcohol (0.4 mmol), catalyst 1 (5 mol%)
and Cs2CO3 (20 mol%) was refluxed in toluene (1 mL) for
1
15 h. The reaction mixture was analyzed by H NMR spec-
troscopy using anisole as internal standard.
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2084
asc.wiley-vch.de
ꢆ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2011, 353, 2078 – 2084