Asymmetric catalytic hydroamination of activated olefins in ionic liquids

Article abstract of DOI:10.1002/hlca.200790048

The addition of a series of both aliphatic and aromatic amines to electron-poor olefins was investigated using [Ni(Pigiphos)(THF)]^2- as catalyst (with different counterions) in various ionic liquids based on imidazolium- and picolinium-salt der

Full text of DOI:10.1002/hlca.200790048

Helvetica Chimica Acta – Vol. 90 (2007)
411
Asymmetric Catalytic Hydroamination of Activated Olefins in Ionic
Liquids
by Luca Fadini*a) and Antonio Tognib)
a
´
) Departamento de Química, Universidad Nacional de Colombia, Sede de Bogota, D.C., Colombia
(e-mail: lfadini@unal.edu.co)
b) Department of Chemistry and Applied Biosciences, ETH Hçnggerberg, HCI, CH-8093 Zurich
The addition of a series of both aliphatic and aromatic amines to electron-poor olefins was
investigated using [Ni(Pigiphos)(THF)]2þ as catalyst (with different counterions) in various ionic liquids
based on imidazolium-and picolinium-salt derivatives. The catalysts gave rise to selectivities comparable
to those obtained when the reaction was conducted in neat organic solvents (ee up to 66%), but
significant higher activities, with a total turnover number (TON) of up to 300.
Introduction. – The use of ionic liquids [1][2] in catalysis has grown recently [3][4],
mainly in the context of exploiting solvent properties for the optimization and/or
recycling of catalysts [5]. For example, ionic liquids with non-coordinating anions
dissolve cationic transition-metal complexes and can have a positive effect on both the
activity and enantioselectivity of catalytic reactions [3][6]. These effects may result
from stabilization of polar complexes or transition states [7]. Additionally, the Lewis
acidity of such solvents might activate the catalyst [8], or the ionic liquids can react to
form carbene-like ligands [9]. The most important feature of ionic liquids, however, is
related to the possibility of catalyst recycling to improve the total turnover number
(TON). Catalyst recycling is especially important in slow catalysis, and it is in this area
where the use of ionic liquids has been most significant [10][11].
There are only few examples of the addition of amines to olefins in ionic liquids.
Brunet and co-workers [12] have shown that molten salts can increase rates and TON
values in RhIII-catalyzed (hydroamination of norbornene with anilines) and PtII-
catalyzed reactions (reaction of aniline with ethylene or hexene), giving rise to TON
values of up to 250. Moreover, Müller and co-workers [13] described the intramolecular
reaction of hex-6-yne-1-amine catalyzed by Lewis acids; conversion and selectivity are
improved when the reaction is carried out in ionic liquids. Also, ZnII catalysts have been
used in biphasic systems for i) the intermolecular addition of aniline derivatives to
cyclohexadiene and ii) for the hydroamination of phenylacetylene with different
primary amines, with respective turnover frequencies (TOFs) of 1.8 hÀ1 and 25 hÀ1 [14].
Recently, the use of Lewis and/or Brønsted acids for the hydroamination/hydro-
arylation of olefins in ionic liquids has been reported, with a positive solvent effect on
the activity [15].
So far, there have been no examples of chiral Pd [16], Ir [17][18], lanthanide [19],
or Zr [20] complexes catalyzing the asymmetric additions of amines to olefins [21] in
ꢀ 2007 Verlag Helvetica Chimica Acta AG, Zürich

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Helvetica Chimica Acta – Vol. 90 (2007)
ionic liquids. Herein, we, thus, report the first asymmetric hydroamination of activated
olefins catalyzed by NiII complexes in various ionic liquids [22].
Recently, we illustrated that complexes of NiII with tridentate phosphorous (PPP)
ligands such as Pigiphos catalyze the addition of aliphatic and aromatic amines to
activated (i.e., electron-poor) olefins, as shown in the Scheme below [22][23]. The good
productivity of the catalyst (up to quantitative yields, TON values up to 71 at room
temperature), the modest activity (TOF up to 2.5 hÀ1), and the low-to-moderate
enantioselectivity (enantiomeric excess (ee) up to 69% for the addition of morpholine
to methacrylonitrile) motivated us to improve this system. The tuning of the ferrocenyl
tridentate ligand of Pigiphos and the possible transformation of the catalysis products
to b-amino acids have recently been reported [22]. Because the active NiII complexes
may be cationic species [24], the next step was to perform the reaction in ionic liquids.
Scheme. Hydroamination of Olefins Catalyzed by [Ni(Pigiphos)(L)]2þ (L ¼ THF)
Results and Discussion. – To better understand the effectiveness of the reported
cationic Ni complexes, different salts containing more-or less-coordinating anions were
added to a model catalytic system: the NiII-catalyzed hydroamination of morpholine
with methacrylonitrile (¼2-methylprop-2-enenitrile). Dicationic NiII complexes were
previously reported to be highly active in such reactions [23]. Thus, cation – anion
interactions may have important effects on the catalytic activity. The effect of different
tested salts on the above hydroamination reaction (Scheme) are illustrated in Fig. 1. As
can be seen, addition of the non-coordinating anions BFÀ4 or PF6À led to almost
unaltered selectivities and activities, giving rise to isolated yields of ca. 80%. However,
when halide salts were added, both lower enantioselectivities (Cl > Br> I) and
moderate activities (I > Cl > Br) were observed. These results indicate that in situ
formed [Ni(PPP)(halide)]þ complexes are less-active catalysts. The addition of a
ꢁnakedꢂ fluoride (FÀ) [17] even caused complete deactivation of the catalytic system,
probably by forming [Ni(PPP)F]þ. Nitrate (NOÀ3 ) and acetate (AcOÀ) gave similar
results as with halides, leading to decreased activities and selectivities.
Having noted significant counterion effects on the enantioselectivity of the
[Ni(Pigiphos)(THF)]2þ-catalyzed hydroamination, with ClO4À being better than BF4À
or PFÀ6 (Fig. 1), we next attempted to improve the catalytic system by using 3-alkyl-1-
methyl-1H-imidazolium (RMIMþ)-and 1-alkylpicolinium (RPIC þ)-based ionic liquids
as solvents (Fig. 2). We anticipated that the hydroamination catalysis would benefit

Helvetica Chimica Acta – Vol. 90 (2007)
413
Fig. 1. Effect of the addition of salt (5 mol-%) on the hydroamination reaction between morpholine and
methacrylonitrile catalyzed by [Ni(Pigiphos)(THF)](ClO4)2 in THF solution
from such a more-polar reaction medium. As catalyst for the hydroamination of
morpholine with methacrylonitrile, [Ni(Pigiphos)(THF)]2þ(ClO4À )2 was used in differ-
ent ionic liquids. Thereby, it was necessary to use THF or acetone as co-solvent, which,
however, were evaporated after complete dissolution of the NiII salts. Some preliminary
results of this reaction are summarized in Table 1.
The use of ionic liquids as solvent, either in a one-phase or two-phase-system1),
gave results comparable to those obtained when working in neat THF or acetone, but
with much higher activities (TON values of up to 300; Table 1, Entry 6). Thus, the
catalyst loading was reduced to 0.1 mol-%, and the reaction still gave 30% yield and
48% ee. However, the enantioselectivities in ionic liquids vs. classical organic solvents
were comparable (up to 66%) for reaction times of 24 h at room temperature using
5 mol-% of catalyst. Catalysis in ionic liquids was less sensitive to air (O2; Entry 8) and
Fig. 2. Imidazole- and picoline-derived ionic liquids used in this study
1
)
Single phase: ionic liquid as solvent for all components. Binary system: catalyst dissolved in ionic
liquid, substrates dissolved in organic solvent (e.g., hexane or Et2O) immiscible with ionic liquid.

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Helvetica Chimica Acta – Vol. 90 (2007)
Table 1. Hydroamination of Methacrylonitrile with Morpholine. All reactions were performed for 24 h at
r.t. in BMIM · BF4/THF 2 : 1 under inert conditions (unless noted otherwise); the catalyst, [Ni(Pigi-
phos)(THF)](ClO4)2, was generated in situ. For abbreviations of ionic liquids, see Fig. 2.
Entry
mol-% catalyst
Recycling
TONa)
Yield [%]b)
ee [%]c)
1
2
3
4
5
6
7
8
5
none
none
from 1
none
from 4
none
none
none
19.2
20
20
95
72
300
18
20
96
> 95e)
> 95e)
> 95e)
72
30
90
> 95e)
62
64
59
61
51
48
57
59
5d)
5
1
1
0.1
5f)
5g)
a) Total turnover number. b) Isolated yield after flash chromatography. c) Enantiomeric excess,
determined by chiral GC on a b-dex column; abs. configuration of the major products: (R) [24].
d) Reaction performed with a different commercial sample of BMIM · BF4. e) Determined by NMR after
f
extraction with Et2O/hexane 1 : 5 and solvent evaporation. ) Reaction performed in ionic liquid/hexane
binary phase. g) Reaction performed under aerobic conditions.
moisture (H2O), allowing the use of non-distilled reagents. These might be due to
stabilization of the cationic species in the ionic liquid. Also, the reaction was fully
reproducible when using different commercial samples of the same ionic liquid (Entries
1 and 2) [25]. Activity and enantioselectivity were similar when the catalytic reaction
was carried out in a binary system of hexane/ionic liquid (Entry 7), but greatly
facilitated the extraction of the organic compounds. On the other hand, the positive
environmental effect of the absence of solvents with low vapor pressure was missing.
Next, the catalytic hydroaminations of methacrylonitrile or crotonitrile with
morpholine, thiomorpholine, piperidine, 1-methylpiperazine, dibenzylamine, and ani-
line, respectively, were examined using different imidazolium salts as solvents. The
results are collected in Table 2. As can be seen, addition of morpholine to
methacrylonitrile always gave the best results in terms of activity and enantioselectivity
(Table 2, Entry 1). As expected, the counterion, XÀ, of the ionic liquid has a significant
effect, in particular on enantioselectivity. However, when ionic salts with dicyano-
amide, [N(CN)2]À, as anion were used, the reaction did not proceed (Entries 2, 7, and
10). Although ionic liquids with this specific counterion are less viscous, both the
catalyst and the substrates were found to be only poorly soluble. This likely explains our
recovery of the starting materials.
The hexyl-substituted imidazolium (HMIMþ) ionic liquids gave rise to comparable
activities but lower asymmetric induction in the addition of morpholine (Table 2,
Entries 5, 13, and 16). When thiomorpholine was used, both lower conversion and
lower selectivity were observed (44% yield, 53% ee).
The ethyl (EMIMþ)-substituted ionic liquids gave rise to an improvement in
enantioselectivity for the hydroamination of methacrylonitrile with thiomorpholine.
Thus, when EMIMþ · CF3SO3À was used as solvent, the ee was 66%, while it was 61% in
THF (Table 2, Entry 12). Aliphatic amines such as dibenzylamine (Bn2NH) reacted in
excellent yield to the corresponding addition product (Entry 18). The addition of

Helvetica Chimica Acta – Vol. 90 (2007)
415
Table 2. Catalytic Hydroamination of Olefins with Different Amines in Various Imidazolium-Based Ionic
Liquids. All reactions were performed in ionic-liquid/THF 2 : 1 at r.t. under inert conditions, with in situ
generated [Ni(Pigiphos)(THF)](ClO4)2 (5 mol-%) as catalyst.
Entry
Amine
Olefin
Ionic liquida)
TON
TOF [hÀ1]b)
Yield [%]c)
ee [%]d)
1
2
3
4
5
BMIM · CF3SO3
BMIM · (CN)2N
EMIM · BF4
EMIM · CF3SO3
HMIM · PF6
20
0
19
19
20
0.83
–
0.79
0.79
0.83
> 95e)
0
95
95
> 95e)
57
–
63
61
46
6
7
8
BMIM · CF3SO3
BMIM · (CN)2N
EMIM · BF4
20
0
20
0.83
–
0.83
> 95e)
0
> 95e)
16
–
14
9
10
11
12
13
BMIM · CF3SO3
BMIM · (CN)2N
EMIM · BF4
EMIM · CF3SO3
HMIM · PF6
10.4
0
20
20
8.8
0.43
–
0.83
0.83
0.37
52
0
> 95e)
> 95e)
44
30
–
61
66
53
14
15
16
BMIM · BF4
EMIM · BF4
HMIM · PF6
20
19
20
0.83
0.79
0.83
> 95e)
95
65
44
42
> 95e)
17
EMIM · BF4
19
0.79
95
55
18
Bn2NH
HMIM · PF6
19
0.79
95
0
a) For abbreviations, see Fig. 2. b) Total turnover frequency. c) Yield of isolated material after flash
chromatography. d) Determined by chiral GC on a b-dex column; abs. configuration of major products:
(R) [24]. e) Yield determined by NMR after extraction with Et2O/hexane 1 : 5 and evaporation of the
solvent.
aniline to either crotonitrile or methacrylonitrile did not proceed at all, except when
performed in EMIMþ · CF3SO3À (10% yield, 8% ee; data not shown). Probably, the
lower nucleophilicity of the aromatic amines and the poor solubility of the substrates in
the chosen ionic liquids are responsible for these results.
Next, the hydroamination reaction of a wide range of substrates were tested with
picolinium (RPICþ) derivatives, and the results are shown in Table 3. The correspond-
ing tetrafluoroborate, hexafluorophosphate, and dicyanoamide salts have the advant-
age of not being soluble in Et2O, THF, and AcOEt, which greatly facilitates the
extraction of organic substrates [1][3][10].

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Helvetica Chimica Acta – Vol. 90 (2007)
As can be seen from Table 3, the catalytic properties of [Ni(Pigiphos)(THF)]2þ in
the presence of picolinium ionic-liquids were similar or better than those in
imidazolium salts, and the binary system was viable also with these solvents. For
example, reaction of morpholine with methacrylonitrile in the octyl-substituted ionic
liquid (OPICþ · BF4À ), proceeded under complete conversion, affording 53% ee after
24 h at room temperature, both in single or binary phases; Table 3, Entries 1 and 2). The
reaction of aniline and methacrylonitrile in a solvent mixture of OPICþ · BF4À/hexane
gave rise to a good yield (71%), but a low enantioselectivity (23% ee; Entry 22), with
similar results (Entry 24) for the addition of aniline to crotonitrile (65% yield, 14% ee).
On the other hand, the enantioselectivities were in general lower than for the catalysis
in THF under the same conditions. Only in the case of thiomorpholine/methacryloni-
trile was the enantioselectivity similar in ionic liquid compared to THF (59% ee; Entry
13). In the case of various aniline derivatives, the reaction performed in OPICþ · BF4À
gave similar results as in THF (Entries 25 – 30) [23][24].
In Fig. 3, the results of the NiII-catalyzed addition of morpholine to methacryloni-
trile in various ionic liquids are summarized.
As shown in Tables 4 – 6, an additional benefit of the use of ionic liquids is that the
catalyst/ionic-liquid mixture can be readily recycled. After the original catalysis (24 h at
room temperature), the catalyst/ionic-liquid mixture was extracted repeatedly with
hexane/Et2O 1 :1 (5 – 10ꢀ). The washed ionic liquid, containing the dicationic Ni –
Pigiphos catalyst, was re-used by addition of an immiscible organic solvent (Et2O or
hexane) containing the organic hydroamination substrates. The resulting binary-phase
was stirred at room temperature for another 24 h, and worked up analogously.
However, the good productivity of the recycled catalyst (TON up to 116 after 6
cycles) in the hydroamination in OPICþ · BF4À solution was not accompanied by
constant enantioselectivity. Unexpectedly, for the addition of morpholine or thiomor-
Fig. 3. Yield and enantiomeric excess (ee) of the hydroamination of methacrylonitrile with morpholine
catalyzed by [Ni(Pigiphos)(THF)](ClO4)2 in various ionic liquids

Helvetica Chimica Acta – Vol. 90 (2007)
417
Table 3. Catalytic Hydroamination of Olefins with Different Amines in Various Picolinium-Based Ionic
Liquids. Reactions were performed either in pure ionic-liquid (neat) or in ionic liquid/hexane 2 : 1
(binary) for 24 h at r.t. under inert conditions, with in situ generated [Ni(Pigiphos)(THF)](ClO4)2
(5 mol-%) as catalyst.
Entry
Amine
Olefin
Ionic liquid
System
Yield [%]a)
ee [%]b)
1
2
3
4
5
6
OPIC · BF4
OPIC · BF4
OPIC · PF4
OPIC · (CN)2N
BPIC · BF4
neat
99
99
53
53
46
35
62
0
binary
binary
binary
binary
binary
> 95c)
25
> 95c)
5
BPIC · (CN)2N
7
8
9
10
11
12
OPIC · BF4
OPIC · BF4
OPIC · PF6
OPIC · (CN)2N
BPIC · BF4
neat
99
99
10
4
18
–
6
–
binary
binary
binary
binary
binary
> 95c)
0
> 95c)
0
BPIC · (CN)2N
13
14
15
16
17
18
OPIC · BF4
OPIC · BF4
OPIC · PF4
OPIC · (CN)2N
BPIC · BF4
neat
99
99
30
0
50
5
59
57
30
–
50
30
binary
binary
binary
binary
binary
BPIC · (CN)2N
19
20
OPIC · BF4
OPIC · BF4
neat
binary
62
50
5
14
21
22
OPIC · BF4
OPIC · BF4
neat
binary
17
71
10
23
23
24
OPIC · BF4
OPIC · BF4
neat
binary
26
65
0
14
25
26
OPIC · BF4
OPIC · BF4
neat
binary
8
14
19
18
27
28
OPIC · BF4
OPIC · BF4
neat
binary
9
13
0
0
29
30
OPIC · BF4
OPIC · BF4
binary
binary
4
5
9
0
a) Isolated yield after flash chromatography. b) Enantiomeric excess, determined by chiral GC or HPLC.
c) Determined by NMR after extraction with Et2O/hexane 1 : 5 and evaporation of the solvent.

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Helvetica Chimica Acta – Vol. 90 (2007)
Table 4. Activity of Recycled Catalyst in the Hydroamination of Olefins in Picolinium-Based Ionic
Liquid. Reactions were performed in OPIC · BF4/hexane 1 : 1 for 24 h at r.t. under inert conditions, with
in situ generated [Ni(Pigiphos)(THF)](ClO4)2 as catalyst. The catalyst was recycled by extractive
removal (hexane/Et2O 1 : 1) of the organic products.
Entry
1
Amine
Olefin
na)
TON (cycles)b)
Yield [%]c)
ee [%]d)
0
20
99
99
95
95
95
95
82
53
1e)
2
40 (2)
59 (3)
78 (4)
97 (5)
116 (6)
–
10.1
6.3
6.2
6.2
0
3f)
4
5
6g)
50
2
3
4
5
6
0
20
99
61
95
95
95
95
59
2.1
4.6
0
0
0
1e)
2
32 (2)
51 (3)
70 (4)
89 (5)
108 (6)
3f)
4
5
0
14
71
40
40
20
18
8
13.5
24.1
23.8
24.3
24.3
23.6
1e)
2
22 (2)
30 (3)
34 (4)
38 (5)
40 (6)
3f)
4
5
0
20
99
95
99
95
95
95
4.2
7.1
8.4
3.6
3.8
2.6
1e)
2
39 (2)
59 (3)
78 (4)
97 (5)
116 (6)
3f)
4
5
0
12
62
28
75
50
50
95
10.1
8.7
8.9
10
9.7
8.5
1e)
2
18 (2)
33 (3)
43 (4)
53 (5)
72 (6)
3f)
4
5
0
13
65
95
99
8
9
10
16.9
16.9
15.1
14.7
14.1
14.9
1e)
2
32 (2)
52 (3)
54 (4)
56 (5)
58 (6)
3f)
4
5
a) Recycling number; n ¼ 0 means that the catalyst was freshly prepared and not used before. b) Total
turnover number (TON) and number of cycles (in parenthesis). c) Isolated yield after extraction.
d) Enantiomeric excess, determined by chiral GC or HPLC. e) Catalyst was exposed to air for 3 d before
f
being re-used. ) Re-used after 3 d. g) Catalyst from Entry 6.

Helvetica Chimica Acta – Vol. 90 (2007)
419
Table 5. Activity of Recycled Catalyst in the Hydroamination of Methacrylonitrile. Reactions were
performed in BMIM · BF4/hexane 1 : 1 for 24 h at r.t. under inert conditions, with in situ generated
[Ni(Pigiphos)(THF)](ClO4)2 as catalyst. The catalyst was recycled by extractive removal (hexane/Et2O
5 : 1) of the organic products.
Entry
1
Amine
na)
TON (cycles)b)
Yield [%]c)
ee [%]d)
0
1
2
3
4
5
20
> 99e)
> 99e)
> 99e)
58
47
32
52.7
53.5
53.4
51.1
51.6
48.2
40 (2)
60 (3)
72 (4)
81 (5)
87 (6)
2
3
4
0
1
2
3
4
5
20
> 99e)
80
60
45
38
53.8
52.4
54.0
54.1
53.2
53.3
36 (2)
48 (3)
57 (4)
65 (5)
71 (6)
30
0
1
2
3
4
5
20
> 99e)
> 99e)
71
27
27
65.5
64.3
57.9
36.8
12.1
1.0
40 (2)
54 (3)
59 (4)
65 (5)
67 (6)
12
0
1
2
3
4
5
20
> 99e)
94
61
25
11
54.5
54.9
50.2
44.5
36.7
27.0
39 (2)
51 (3)
56 (4)
58 (5)
59 (6)
5
a) Recycling number. b) Total turnover number (TON) and number of cycles (in parenthesis). c) Iso-
lated yield after extraction. d) Enantiomeric excess, determined by chiral GC or HPLC. e) No traces of
starting material detected by GC/MS or GC/HPLC analysis.
pholine to methacrylonitrile (Table 4, Entries 1 and 2), the enantioselectivity strongly
decreased after each recycling, the products being racemic after six cycles. In contrast,
for the reaction between methacrylonitrile and aniline, or between crotonitrile and
morpholine, thiomorpholine, or aniline, the enantiomeric excess remained constant
(Table 4, Entries 3 – 6). It is important to note that the less-nucleophilic aniline reacted
more efficiently (TON up to 58 after six cycles; Entry 6). A catalyst mixture that had
been recycled six times in the reaction of aniline and crotonitrile was then used for the
addition of morpholine to methacrylonitrile. Surprisingly, after 24 h at room temper-
ature, the corresponding hydroamination product, 2-methyl-3-morpholin-4-ylpropane-
nitrile, was formed with moderate enantioselectivity (50% ee) in 82% yield. This result
is similar to the hydroamination results with the non-recycled catalyst. Thus, it appears
that aniline does not deactivate the NiII catalyst to the same degree as morpholine does.

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Helvetica Chimica Acta – Vol. 90 (2007)
Table 6. Activity of Recycled Catalyst in the Hydroamination of Crotonitrile. Reactions were performed
in BMIM · BF4/hexane 1 : 1 for 24 h at r.t. under inert conditions, with in situ generated [Ni(Pigi-
phos)(THF)](ClO4)2 as catalyst. The catalyst was recycled by extractive removal (hexane/Et2O 5 : 1) of
the organic products.
Entry
1
Amine
na)
TON (cycles)b)
Yield [%]c)
ee [%]d)
0
1
2
3
4
5
20
99e)
99e)
99e)
90
81
67
6.0
1.8
5.9
6.9
8.0
7.0
40 (2)
60 (3)
78 (4)
94 (5)
107 (6)
2
3
4
0
1
2
3
4
5
20
99e)
50
40
25
32
8.5
8.2
4.4
3.2
3.1
2.1
30 (2)
38 (3)
43 (4)
49 (5)
53 (6)
20
0
1
2
3
4
5
20
99e)
99e)
99e)
99e)
99e)
72
7.3
6.4
–
5.4
7.4
2.4
40 (2)
60 (3)
80 (4)
100 (5)
114 (6)
0
1
2
3
4
5
20
99e)
99e)
99e)
99e)
60
14
40 (2)
60 (3)
80 (4)
92 (5)
104 (6)
–
13.3
12.1
3.7
1.5
60
a) Recycling number. b) Total turnover number (TON) and number of cycles (in parenthesis). c) Iso-
lated yield after extraction. d) Enantiomeric excess, determined by chiral GC or HPLC. e) No traces of
starting material detected by GC/MS or GC/HPLC analysis.
However, at present, it is difficult to identify the specific factors responsible for the loss
of enantioselectivity upon catalyst recycling.
The recycling procedure was next tried with the imidazolium salts, namely with
BMIMþ · BFÀ4 , as shown in Tables 5 and 6. The hydroamination with methacrylonitrile
did not give very high yields. After recycling, the activity decreased, with a total TON of
87 after six cycles (Table 5, Entry 1). Nevertheless, the enantioselectivities remained
constant for the first three cycles, and were comparable to those of the non-recycled
catalysts. The [Ni(Pigiphos)(THF)](ClO4)2 complex in BMIMþ · BF4À did not catalyze
the addition of aniline to methacrylonitrile. Only traces of the products were detected
by GC/MS analysis.
The addition of amines to crotonitrile was more productive, with TON values of up
to 114. The results were comparable to those obtained with the recycled catalyst in the

Helvetica Chimica Acta – Vol. 90 (2007)
421
picolinium salts (Table 6). No significant changes were detected for the rather low
enantioselectivities, and even after five cycles, the asymmetric induction remained in
the same range. Once again, the NiII complexes in imidazolium-based ionic liquids did
not catalyze the addition of aniline to an electron-poor olefin.
Conclusions. – [Ni(Pigiphos)(THF)]2þ complexes catalyze the hydroamination of
aliphatic amines with methacrylonitrile or crotonitrile in different ionic liquids, with
typically higher catalytic activities than in regular organic solvents. Unfortunately, the
enantioselectivity of the reaction in ionic liquids could not be improved. Ionic liquids
seem to stabilize the cationic NiII complexes, allowing to carry out the reaction without
particular protection from O2 and H2O, and to re-use the catalyst/solvent mixture. The
recycling process permits, in fact, an improvement of the total turnover number of the
hydroamination reactions.
Experimental Part
General. All reactions with air-or moisture-sensitive materials were carried out under Ar gas using
standard Schlenk techniques, or in a glove box under N2 atmosphere. Hydroamination reactions
performed with the help of a parallel synthesizer were conducted with a thermostated Argonaut Quest-
210 system (Artisan Scientific) using 20 vials (1 – 10, Part A; 11 – 20, Part B), 5 or 10 ml, with vertical
stirring. HPLC Analyses were performed on a Agilent Series-1100 and HP-1050 using Chiralcel OD-H
(4.6 ꢀ 250 mm; 5 mm), Chiralcel OJ (4.6 ꢀ 250 mm; 10 mm), or Chiralcel OB-H (4.6 ꢀ 250 mm; 5 mm)
columns and a DAD-type UV detector, eluting with hexane/i-PrOH. GC Analyses were performed on a
Fisons Instruments GC-8000 or a ThermoQuest Trace GC-2000 instrument with FID detector and one of
the following columns: a-dex 120 (30 m ꢀ 0.25 mm ꢀ 0.25 mm), b-dex 120 (30 m ꢀ 0.25 mm ꢀ 0.25 mm),
or g-dex 120 (30 m ꢀ 0.25 mm ꢀ 0.25 mm). Routine 31P{1H}-, 13C{1H}-, and 1H-NMR spectra were
recorded on Bruker Avance-200 (13C: 50.32, 1H: 200.13 MHz), Bruker Avance-250 (31P: 101.26, 13C:
1
1
62.90, H: 250.13 MHz), Bruker Avance-300 (31P: 121.49, 19F: 282.40, 13C: 75.47, H: 300.13 MHz), or
Bruker Avance-DPX500 [31P: 202.46, 13C: 125.75, 1H: 500.23 MHz) spectrometers at r.t. Chemical shifts d
in ppm rel. to Me4Si, referenced to solvent signals for H-and 13C{1H}-NMR, or relative to an external
1
reference for 19F{1H}-(CFCl 3: d ¼ 0.0 ppm), and 31P{1H}-NMR (85% H3PO4: d ¼ 0.0 ppm), coupling
constants J in Hz. EI-, FAB-, and MALDI-MS experiments were performed by the MS service of the
ꢁLaboratorium für Organische Chemieꢂ, ETH Zurich; in m/z (rel. %). GC/MS Analyses were performed
on a Thermo Finnigan TraceMS system in the EI mode, with a Zebron ZB-5 (30 m ꢀ 0.25 mm ꢀ 0.25 mm)
column.
Bis{(1R)-1-[(S)-2-(Diphenylphosphino)ferrocenyl]ethyl}cyclohexylphosphine (Pigiphos). (S)-2-
Diphenylphosphino-1-[(1R)-1-(dimethylamino)ethyl]ferrocene (7 g, 15.9 mmol) was dissolved at 408
in degassed AcOH (30 ml), containing TFA (1.2 ml, 15.9 mmol). Then, cyclohexylphosphane (H2PCy;
1.05 ml, 7.9 mmol) was added, and the mixture was stirred at 808 for 4 h. The solvent was removed under
reduced pressure at 608, and AcOEt was added. The resulting precipitate was filtered and washed with
hexane/AcOEt 1:1, yielding the pure product. The solvent of the mother liquor was removed under
reduced pressure, and the residue was further purified by flash chromatography (FC) (hexane/AcOEt
3 :1) and recrystallization (hexane, À 208). Total yield: 6.101 g (85.2%). Microscopic orange crystals.
1H-NMR (250 MHz, CD2Cl2)2): 0.70 – 1.70 (m, 11 H, Cy); 1.59 (dd, J ¼ 6.5, MeCH); 1.65 (dd, J ¼ 7.5,
MeCH); 2.77 – 2.91 (m, MeCH); 3.08 – 3.22 (m, MeCH); 3.80 (s, 5 H of cp’), 3.84 (s, 5 H of cp’); 3.90 (s,
1 H of cp); 3.97 – 4.02 (m, 2 H of cp); 4.04 – 4.12 (m, 1 H of cp); 4.22 – 4.27 (m, 2 H of cp); 7.20 (d, J ¼ 3.5,
5 H of Ph); 7.25 – 7.29 (m, 5 H of Ph); 7.37 – 7.46 (m, 6 H of Ph)); 7.50 – 7.75 (m, 4 H of Ph). 31P{1H}-NMR
2
)
Cy ¼ cyclohexyl; cp ¼ cyclopentadienyl.

422
Helvetica Chimica Acta – Vol. 90 (2007)
(101 MHz, CDCl3): À 25.15 (d, J ¼ 11.8, PAPh2); À 25.07 (d, J ¼ 28.9, PBPh2); 18.04 (dd, J ¼ 11.1, 29.7,
PCy). Anal. calc. for C54H55Fe2P3 (908.64): C 71.38, H 6.10, P 10.23; found: C 71.42, H 6.30, P 10.26.
General Procedure for Pigiphos-Catalyzed Hydroamination in THF. In a Teflon-valve flask (Young),
Ni(ClO4)2 · 6 H2O (0.02 – 0.1 mmol; 5 mol-%), Pigiphos (0.02 – 0.1 mmol; 5 mol-%), and the chosen salt
were dissolved in THF (3 ml). The resulting red-purple soln. was stirred at r.t. for 20 – 30 min. Then, the
olefin (0.4 – 2.0 mmol) was added, and the soln. was stirred for an additional 10 – 30 min. Finally, the
amine (0.2 – 1.0 mmol) was added, and the mixture was stirred overnight at r.t. After 24 h, hexane was
added to precipitate the catalyst, and the product was purified by FC.
General Procedure for Pigiphos-Catalyzed Hydroamination in Ionic Liquids. In a Schlenk flask,
Ni(ClO4)2 · 6 H2O (0.02 – 0.1 mmol; 5 mol-%) and Pigiphos (0.02 – 0.1 mmol; 5 mol-%) were suspended
in ionic liquid (2 ml), and some THFor acetone (2 – 4 ml) was added to completely dissolve the materials.
The mixture was stirred at r.t. for 15 min, and the org. solvent was removed under reduced pressure. To
the resulting red-purple soln., the olefin (0.4 – 2.0 mmol) was added, and the mixture was stirred for an
additional 10 – 30 min. Then, the amine (0.2 – 1.0 mmol) was added, and the soln. was stirred overnight at
r.t. After 24 h, the org. substrates were extracted with hexane/Et2O 5 :1 (5 – 10ꢀ), and the products were
purified by FC.
General Procedure for Hydroamination Catalysis in a Parallel Synthesizer. In a Schlenk flask,
Ni(ClO4)2 · 6 H2O (0.1 – 0.5 mmol; 5 mol-%) and either Pigiphos or the corresponding isolated complex
[Ni(PPP)(THF)](ClO4)2) (0.1 – 0.5 mmol; 5 mol-%) were dissolved in ionic liquid (20 ml) and THF
(5 ml). The soln. was stirred at r.t. for 15 min, and the org. solvent was removed under reduced pressure.
Then, an aliquot (2 ml) of this standard soln. was added via syringe to each of the ten vials of a Quest-210
manual synthesizer. To the resulting red-purple soln., the olefin (0.2 – 1.0 mmol) was added, and the
mixture was stirred for an additional 10 – 30 min. Finally, the amine (0.1 – 0.5 mmol) was added, and the
soln. was stirred overnight at r.t. After 24 h, the mixture was poured into a vial, hexane was added, and
the products were purified by FC.
2-Methyl-3-(morpholin-4-yl)propanenitrile. Purified by FC (hexane/AcOEt/Et3N 47.5 :47.5 :5.0).
GC (b-dex; 908, isothermal): tR 168.5 (R), 174.3 (S). 1H-NMR (250 MHz, CDCl3): 1.31 (d, J ¼ 7.0,
MeCH); 2.38 (dd, J ¼ 12.5, 12.5, 1 H of CH2); 2.48 (dd, J ¼ 4.75, (CH2)2N); 2.6 (dd, J ¼ 12.5, 12.5, 1 H of
CH2); 2.62 – 2.95 (m, MeCH); 3.67 (t, J ¼ 4.75, (CH2)2O). 13C{DEPT}-NMR (62.9 MHz, CDCl3): 15.74
(Me); 23.98 (CHCN); 53.68 ((CH2)2N); 61.41 (CH2CH); 66.73 ((CH2)2O). GC/MS (1208, isothermal; tR
6.15): 154.1 (0.5, Mþ), 100.0 (100, [M À MeCHCN]þ). Anal. calc. for C8H14N2O (154.21): C 62.31, H 9.15,
N 18.17; found: C 62.49, H 9.15, N 18.36.
3-(Morpholin-4-yl)butanenitrile. Purified by FC (hexane/AcOEt/Et3N 47.5 :47.5 :5.0). GC (b-dex;
1008, isothermal): tR 95.9, 97.1. 1H-NMR (250 MHz, CDCl3): 1.15 (d, J ¼ 6.5, MeCH); 2.38 (dd, J ¼ 7, 13,
1 H of CH2); 2.47 (t, J ¼ 4, (CH2)2N); 2.48 (dd, J ¼ 6, 13, 1 H of CH2); 2.68 – 2.92 (m, MeCH); 3.65 (t, J ¼
5, (CH2)2O). 13C{1H}-NMR (50 MHz, CDCl3): 15.23 (Me); 21.29 (CH2CN); 48.83 ((CH2)2N); 56.31
(CHN); 67.05 ((CH2)2O); 118.58 (CN). GC/MS (1208, isothermal; tR 8.14): 154.1 (1, Mþ), 139.0 (5, [M À
Me]þ), 114 (100, [M À CH2CN]þ). Anal. calc. for C8H14N2O (154.1): C 62.31, H 9.15; found: C 62.42, H
9.27.
2-Methyl-3-(thiomorpholin-4-yl)propanenitrile. Purified by FC (hexane/AcOEt/Et3N 47.5 :47.5 :5.0).
HPLC (OJ; hexane/i-PrOH 95 :5, 0.5 ml/min, 258, detection at 230 nm): tR 26.0, 28.4. 1H-NMR
(250 MHz, CDCl3): 0.79 (d, J ¼ 7.0, MeCH); 1.78 (dd, J ¼ 8.0, 10, 1 H of CH2); 2.06 (dd, J ¼ 8.0, 11, 1 H of
CH2); 2.33 (t, J ¼ 5.0, (CH2)2N); 2.38 (t, J ¼ 5.0, (CH2)2S); 2.70 – 2.95 (m, MeCH). 13C{DEPT}-NMR
(75 MHz, CDCl3): 15.95 (Me); 24.51 (CHCN); 27.96 ((CH2)2N); 55.26 ((CH2)2S); 61.73 (CH2CH). GC/
MS (1208, isothermal; tR 13.21): 170.0 (0.5, Mþ), 116.0 (100, [M À MeCHCN]þ). Anal. calc. for C8H14N2O
(170.28): C 56.43, H 8.29; found: C 56.78, H 8.14.
3-(Thiomorpholin-4-yl)butanenitrile. Purified by FC (hexane/AcOEt/Et3N 47.5 :47.5 :5.0). HPLC
1
(OJ; hexane/i-PrOH 95 :5, 0.5 ml/min, 258, detection at 210 nm): tR 35.45, 38.46. H-NMR (300 MHz,
CD2Cl2): 1.16 (d, J ¼ 7.0, MeCH); 2.35 (dd, J ¼ 7, 12, 1 H of CH2); 2.52 (dd, J ¼ 7, 16, 1 H of CH2); 2.61 –
2.72 (m, (CH2)2N)); 2.75 – 2.90 (m, (CH2)2S); 2.95 – 3.10 (m, CHCH2). 13C{DEPT}-NMR (62.9 MHz,
CDCl3): 15.07 (Me); 21.09 (CH2CN); 28.32 ((CH2)2N); 50.79 ((CH2)2S); 57.75 (CHN). GC/MS (1208,
isothermal; tR 8.14): 154.1 (1, Mþ), 139.0 (5, [M À Me]þ), 114 (100, [M À CH2CN]þ). Anal. calc. for
C8H14N2S (170.28): C 56.43, H 8.29, N 16.45; found: C 56.61, H 8.35, N 16.60.

Helvetica Chimica Acta – Vol. 90 (2007)
423
2-Methyl-3-(piperidin-1-yl)propanenitrile. Purified by FC (hexane/AcOEt/Et3N 47.5 :47.5 :5.0). GC
(a-dex; 528, isothermal): tR 447.9, 453.2. 1H-NMR (250 MHz, CDCl3): 1.29 (d, J ¼ 8.0, MeCH); 1.30 – 1.50
(m, CH2); 1.55 – 1.65 (m, 2 CH2); 2.33 (dd, J ¼ 7.0, 1 H of CH2); 2.43 (q, J ¼ 7.0, (CH2)2N); 2.57 (dd, J ¼
8.0, 1 H of CH2); 2.70 – 2.92 (m, MeCH). 13C{DEPT}-NMR (62.9 MHz, CDCl3): 13.33 (CH2), 19.41
(Me); 29.70 (CHCN); 36.42 ((CH2)2); 69.95 ((CH2)2N); 70.22 (CH2CH). GC/MS (1208, isothermal; tR
5.32): 152 (0.5, Mþ), 98.0 (100, [M À MeCHCN]þ).
2-Methyl-3-(4-methylpiperazin-1-yl)propanenitrile. Purified by FC (hexane/AcOEt/Et3N
1
47.5 :47.5 :5.0). GC (a-dex; 808, isothermal): tR 230.8, 234.9. H-NMR (250 MHz, CDCl3): 1.30 (d, J ¼
7.0, MeCH); 2.28 (s, MeN); 2.41 (dd, J ¼ 6.2, 12.5, CH2); 2.47 (br. s, (CH2)2N); 2.55 (br. s, (CH2)2NMe);
2.62 (dd, J ¼ 8.0, 12.5, 1 H of CH2); 2.65 – 2.75 (m, MeCH). 13C{DEPT}-NMR (75 MHz, CDCl3): 16.02
(Me); 24.45 (CHCN); 45.60 (MeN); 52.71 ((CH2)2N); 54.78 ((CH2)2N); 60.80 (CH2CH). GC/MS (1208,
isothermal; tR 11.37): 167.1 (16, Mþ), 113.1 (67.2, [M À MeCHCN]þ), 70.0 (100, [M À
CH2CH(Me)CN]þ). Anal. calc. for C8H14N2O (167.25): C 64.63, H 10.24; found: C 64.01; H 9.24.
2-Methyl-3-(phenylamino)propanenitrile. Purified by FC (hexane/AcOEt/Et3N 47.5 :47.5 :5.0).
1
HPLC (OD-H; hexane/i-PrOH 98 :2, 1.0 ml/min, 258, detection at 254 nm): tR 38.09, 39.53. H-NMR
(300 MHz, CD2Cl2): 1.37 (d, J ¼ 8.0, MeCH); 2.90 – 3.05 (m, MeCH); 3.39 (dd, J ¼ 6.0, 8.0, 2 CH2); 4.11
(br. s, NH); 6.65 (d, J ¼ 9, 2 o-H of Ph); 6.75 (dd, J ¼ 8, 9, 1 m-H of Ph); 7.20 (dd, J ¼ 8, 9, 2 p- H of Ph).
13C{DEPT}-NMR (75.47 MHz, CDCl3): 15.42 (Me); 25.99 (CHCN); 46.99 (CH2NH); 113.04 (CH of Ph);
118.45 (CH of Ph), 129.53 (CH of Ph). GC/MS (1208, isothermal; tR 18.95): 160.0 (12.5, Mþ), 106.0 (100,
[M À MeCHCN]þ). Anal. calc. for C10H12N2 (160.22): C 74.97, H 7.55, N 17.48; found: C 75.19; H 7.50; N
17.31.
3-[(2,3-Dimethylphenyl)amino]-2-methylpropanenitrile. Purified by FC (hexane/AcOEt/Et3N
47.5 :47.5 :5.0). HPLC (OD-H; hexane/i-PrOH 98 :2, 1.0 ml/min, 258, detection at 254 nm): tR 50.64,
54.35. 1H-NMR (300 MHz, CD2Cl2): 1.37 (d, J ¼ 7.0, MeCH); 2.09 (d, J ¼ 6.0, Me); 2.28 (d, J ¼ 7.0, Me);
2.95 – 3.07 (m, MeCH); 3.36 – 3.48 (m, CH2NH); 3.95 (br. s, NH); 6.40 – 6.70 (m, 2 arom. H); 6.89 (dd,
J ¼ 4, 7, 1 arom. H). 13C{DEPT}-NMR (75 MHz, CDCl3): 12.50 (Me); 15.45 (Me); 20.74 (Me); 25.88
(CHCN); 42.25 (CH2NH); 107.87 (arom. CH); 120.41 (arom. CH); 126.23 (arom. CH). GC/MS (1208,
isothermal; tR 39.38): 188.1 (14.4, Mþ), 134.0 (100, [M À MeCHCN]þ). Anal. calc. for C12H16N2 (188.27):
C 76.56, H 8.57, N 14.88; found: C 76.71, H 8.53, N 14.76. HPLC (OD-H; hexane/i-PrOH 98 :2, 1.0 ml/
min, 258, detection at 254 nm): tR 50.64, 54.35.
3-[(3,5-Dimethylphenyl)amino]-2-methylpropanenitrile. Purified by FC (hexane/AcOEt/Et3N
47.5 :47.5 :5.0). HPLC (OD-H; hexane/i-PrOH 98 :2, 1.0 ml/min, 258, detection at 254 nm): tR 20.79,
1
23.71. H-NMR (300 MHz, CD2Cl2): 1.35 (d, J ¼ 8.0, MeCH); 2.24 (s, 2 Me); 2.90 – 3.02 (m, MeCH);
3.21 – 3.44 (m, CH2NH); 4.0 (br. s, NH); 6.28 (s, 2 arom. H); 6.43 (s, 1 arom. H). 13C{DEPT}-NMR
(62.90 MHz, CDCl3): 15.18 (Me); 21.1 (2 Me); 25.9 (CHCN); 46.9 (CH2NH); 110.8 (arom. CH); 120.1
(arom. CH). GC/MS (1208, isothermal; tR 47.56): 188.1 (13.8, Mþ), 134.0 (100, [M À MeCHCN]þ). Anal.
calc. for C12H16N2 (188.27): C 76.56, H 8.57, N 14.88; found: C 76.74, H 8.69, N 14.76.
3-(Phenylamino)butanenitrile. Purified by FC (hexane/AcOEt/Et3N 47.5 :47.5 :5.0). GC (a-dex;
1208, isothermal): tR 116.2 (S), 118.5 (R). HPLC (OD-H; hexane/i-PrOH 98 :2, 1.0 ml/min, 258, detection
at 254 nm): tR 49.8 (S), 52.6 (R). 1H-NMR (250 MHz, C6D6): 0.91 (d, J ¼ 6.0, MeCH); 1.77 (ddd, J ¼ 5.0,
13.0, 30, CH2); 3.19 (br. s, NH); 3.23 (br. s, MeCH); 6.31 (d, J ¼ 8, 2 arom. H); 6.79 (dd, J ¼ 7, 8, 1 arom.
H); 7.20 (dd, J ¼ 8, 2 arom. H). 13C{DEPT}-NMR (75 MHz, CDCl3): 20.42 (Me); 24.35 (CH2CN); 45.43
(CHNH); 113.56 (arom. CH); 118.57 (arom. CH); 129.60 (arom. CH). GC/MS (1208, isothermal; tR
17.24): 160.0 (15, Mþ), 120.0 (100, [M À CH2CN]þ). Anal. calc. for C10H12N2 (160.22): C 74.97, H 7.55, N
17.48; found: C 75.22, H 7.68, N 17.21.
3-[(2,3-Dimethylphenyl)amino]butanenitrile. Purified by FC (hexane/t-BuOMe/Et3N
47.5 :47.5 :5.0). GC (a-dex; 1208, isothermal): tR 206.7, 207.1. 1H-NMR (300 MHz, CD2Cl2): 0.98 (d,
J ¼ 6.0, MeCH); 1.66 (dd, J ¼ 3.0, 16.0, 1 H of CH2); 1.82 (s, Me); 1.94 (dd, J ¼ 6.0, 17.0, 1 H of CH2); 2.18
(s, Me); 3.24 (br. s, NH); 3.14 – 3.36 (m, MeCH); 6.43 (d, J ¼ 9.0, 1 arom. H); 6.75 (dd, J ¼ 8, 1 arom. H);
7.01 – 7.16 (m, 1 arom. H). 13C{DEPT}-NMR (62.9 MHz, CDCl3): 12.59 (Me); 20.65, 20.85 (2 Me); 24.38
(CH2CN); 45.44 (CHNH); 108.81 (arom. CH); 120.43 (arom. CH); 126.34 (arom. CH). GC/MS (1208,
isothermal; tR 44.23): 188.1 (19.9, Mþ), 148.0 (100, [M À CH2CN]þ). Anal. calc. for C12H16N2 (188.27): C
76.56; H 8.57; N 14.88; found: C 76.81; H 8.33, N 14.63.

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Helvetica Chimica Acta – Vol. 90 (2007)
3-[(3,5-Dimethylphenyl)amino]butanenitrile. Purified by FC (hexane/t-BuOMe/Et3N
47.5 :47.5 :5.0). HPLC (OD-H; hexane/i-PrOH 98 :2, 1.0 ml/min, 258, detection at 254 nm): tR 18.9,
22.5. 1H-NMR (250 MHz, C6D6): 0.94 (d, J ¼ 7.0, MeCH); 1.68 (dd, J ¼ 4.0, 15.0, 1 H of CH2); 1.89 (dd,
J ¼ 5.0, 14.0, 1 H of CH2); 2.25 (s, 2 Me); 3.09 (br. s, NH); 3.11 – 3.31 (m, MeCH); 6.02 (s, 2 arom. H); 6.50
(s, arom. H). 13C{DEPT}-NMR (62.9 MHz, CDCl3): 20.45 (Me); 21.55 (2 Me); 24.38 (CH2CN); 45.44
(CHN); 111.57 (arom. CH); 120.53 (arom. CH). GC/MS (1208, isothermal; tR 42.26): 188.1 (17.8, Mþ),
148.1 (100, [M À CH2CN]þ). Anal. calc. for C12H16N2 (188.27): C 76.56, H 8.57, N 14.88; found: C 76.63, H
8.41, N 14.69.
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Received September 19, 2006