Hydroamination of 2-vinylpyridine, styrene, and isoprene with pyrrolidine catalyzed by alkali and alkaline-earth metal complexes

Article abstract of DOI:10.1007/s11172-016-1673-8

The complexes (dpp-bian)Mg(thf)₃, (dpp-bian)Ca(thf)₄ and (dpp-bian)Mg(pyr)₃ (dpp-bian is the 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene dianion; pyr is the pyrrolidine) catalyze the addition of pyrrolidine to 2-viny

Full text of DOI:10.1007/s11172-016-1673-8

Russian Chemical Bulletin, International Edition, Vol. 65, No.12, pp. 2887—2894, December, 2016
2887
Hydroamination of 2ꢀvinylpyridine, styrene, and isoprene
with pyrrolidine catalyzed by alkali and alkalineꢀearth metal complexes*
A. M. Yakub, M. V. Moskalev, N. L. Bazyakina, A. V. Cherkasov, A. S. Shavyrin, and I. L. Fedushkin
G. A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences,
49 ul. Tropinina, 603137 Nizhny Novgorod, Russian Federation.
Fax: +7 (831) 462 7497. Eꢀmail: igorfed@iomc.ras.ru
The complexes (dppꢀbian)Mg(thf)3, (dppꢀbian)Ca(thf)4 and (dppꢀbian)Mg(pyr)3 (dppꢀbian
is the 1,2ꢀbis[(2,6ꢀdiisopropylphenyl)imino]acenaphthene dianion; pyr is the pyrrolidine) catꢀ
alyze the addition of pyrrolidine to 2ꢀvinylpyridine at room temperature. The compound (dppꢀ
bian)Mg[N(SiMe3)2] containing a dppꢀbian radical anion catalyzes the addition of pyrrolidine
to styrene at 60 °C. The dppꢀbian radical anion lithiumꢀsodium salt [(dppꢀbian)Li{Nꢀ
(SiMe3)2}][Na(C7H8)] is an active catalyst of the addition of pyrrolidine to styrene and isoꢀ
prene at 60 °C. In all the case, the content of the catalyst was from 1 to 2 mol.%. For styrene and
2ꢀvinylpyridine, the reactions proceeded with the formation of antiꢀMarkovnikov addition
product, while 1,4ꢀaddition product was obtained in the case of isoprene.
Key words: alkenes, hydroamination, group 1 and 2 metals.
Intermolecular hydroamination reactions proceed
through the addition of an NH group to multiple C—C
bonds. This approach is attractive from the synthetic point
of view as an "atom economic" method for the synthesis of
organic compounds with N—C bonds. As a rule, alkynes
undergo hydroamination more readily than alkenes. These
reactions are catalyzed by transition metal complexes,1—5
lanthanoid compounds,4,5,6—14 as well as by the main subꢀ
group metal derivatives.14—22 The reaction can give both
Markovnikov and antiꢀMarkovnikov addition products.
There are also known enantioselective versions of these
reactions.5,12,13
metal, while one of the ligand nitrogen atom binds the
proton (Scheme 1).
Scheme 1
Earlier, we have shown that 13 group metal complexes
with functionallyꢀlabile 1,2ꢀbis[(2,6ꢀdiisopropylphenyl)ꢀ
imino]acenaphthene (dppꢀbian) catalyze hydroaminaꢀ
tion23—26 and hydroarylation27 of alkynes and carbodiimꢀ
ides. The catalytic activity of the binuclear compounds
(dppꢀbian)M—M(dppꢀbian) (M = Al, Ga) towards
alkynes can be related to their ability to "coordinate"
alkynes (cycloaddition reactions).28,29 The compounds
(dppꢀbian)M—M(dppꢀbian) (M = Al, Ga) are inert toꢀ
wards alkenes, as well as to amines, and, therefore, do not
catalyze reactions between these substrates. At the same
time, the group 2 metal complexes containing dppꢀbian
react with terminal alkynes30 and anilines.31 For example,
in the reaction of (dppꢀbian)Mg(thf)3 (1) with phenylꢀ
acetylene the dppꢀbian ligand exhibits its functional labilꢀ
ity: the phenylacetylide fragment forms a bond with the
Ar = 2,6ꢀPriC6H3
There is a recent report14—18 on the antiꢀMarkovnikov
intermolecular hydroamination of olefins in the presence
of alkalineꢀearth metal alkyls and amides. To broaden the
scope of catalytic hydroamination of olefins, we tested
some group 1 and 2 metal complexes with the functionalꢀ
lyꢀlabile dppꢀbian ligand as a catalysts of the addition
reactions of pyrrolidine to styrene, 2ꢀvinylpyridine, and
isoprene. We used the complexes (dppꢀbian)Mg(thf)3
(1),32 (dppꢀbian)Ca(thf)4 (2),32 (dppꢀbian)Mg(pyr)3 (3)
containing the dppꢀbian dianion, the complex (dppꢀ
bian)Mg[N(SiMe3)2] (4)33 containing its radical anion,
* Dedicated to Academician of the Russian Academy of Sciences
R. Z. Sagdeev on the occasion of his 75th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2887—2894, December, 2016.
1066ꢀ5285/16/6512ꢀ2887 © 2016 Springer Science+Business Media, Inc.

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Yakub et al.
as well as a mixed lithiumꢀsodium salt [(dppꢀbian)Liꢀ
{N(SiMe3)2}][Na(C7H8)] (5).
N(3)
N(2)
C(2)
Mg
N(5)
C(1)
N(4)
N(1)
Fig. 1. Molecular structure of compound 3. Thermal ellipsoids
are given with 50% probability. Hydrogen atoms are omitted.
Note. Figures 1 and 2 are available in full color on the webꢀpage
of the journal (http://www.link.springer.com).
Ar = 2,6ꢀPriC6H3
The molecular structures of complexes 3 and 5 were
found Xꢀray diffraction analysis and are shown in Figs 1
and 2, respectively.
Compound
M
L
n
3
4
3
1
2
3
Mg
Ca
Mg
thf
thf
pyr
Compound 3 is a monomeric fiveꢀcoordinate magneꢀ
sium complex and its molecular structure is similar to the
structure of complex 1 (see Ref. 32). However, in contrast
to complex 1 the bond distances Mg—N(1) and Mg—N(2)
in 3 are very close (2.045(5) and 2.105(5) Å for 1 and
2.086(2) and 2.090(2) Å for 3) (Table 1). Compound 1 has
three different Mg—O(thf) bond distances (2.070(4),
2.084(4), and 2.224(4) Å). In compound 3, one of three
Mg—N(pyrrolidine) bonds is also elongated as compared
to two others. The shortening of the C(1)—C(2) bond and
the elongation of the C(1)—N(1) and C(2)—N(2) bonds
in compound 3 as compared to neutral ligand dppꢀbian
(both C(1)—N(1) and C(2)—N(2) 1.282(4) Å; C(1)—C(2)
1.534(6) Å)34 confirm the dianionic state of the redoxꢀ
active ligand in complex 3.
In compound 5, the ligand dppꢀbian chelates the liꢀ
thium cation and coordinates by one of the nitrogen
atoms with the sodium cation (Fig. 2). The Li—N(1) and
Li—N(2) bonds slightly differ (1.956(2) and 2.033(2) Å,
respectively, Table 2) and are considerably shorter than
the distances between the Na and N(2) atoms (2.825(2) Å).
Both cations also coordinate the nitrogen atom of the
Results and Discussion
The compounds (dppꢀbian)Mg(thf)3 (1) and (dppꢀ
bian)Ca(thf)4 (2) were obtained by the reduction of
dppꢀbian with an excess of the corresponding alkalineꢀ
earth metal upon reflux in THF32 and isolated from the
resulting solutions as dark red crystals. A pyrrolidine anaꢀ
log of complex 1, namely, the compound (dppꢀbian)ꢀ
Mg(pyr)3 (3), was obtained by the reaction of an excess of
metallic magnesium with dppꢀbian in toluene (110 °C,
60 h) in the presence of 10 molar equivalents of pyrroliꢀ
dine. Compound 3 was isolated as dark red crystals (69%)
from toluene. The threeꢀcoordinate monomeric and conꢀ
taining no coordinated solvent complex (dppꢀbian)ꢀ
Mg[N(SiMe3)2] (4) was obtained by the reaction of MgCl2
with (dppꢀbian)Na and KN(SiMe3)2 in toluene.33 The reꢀ
action between (dppꢀbian)Na and LiN(SiMe3)2 in toluꢀ
ene leads to the formation of complex [(dppꢀbian)ꢀ
Li{N(SiMe3)2}][Na(C7H8)] (5), which was isolated as dark
red crystals (64%) from toluene. The compounds 3 and 5
were characterized by elemental analysis and spectroscopic
methods: NMR (3), IR (3, 5), and ESR spectroscopy (5).
At room temperature in toluene, compound 5 gives a poorꢀ
ly resolved ESR signal (a quintet, g = 2.0031), which inꢀ
dicates the presence of the dppꢀbian radical anion. The
1H NMR spectrum of diamagnetic compound 3 exhibits
an expected set of signals characteristic of the Nꢀligands
present in this molecule (see Experimental section).
Table 1. Selected bond distances in compound 3
Bond
d/Å
Bond
d/Å
Mg—N(1)
Mg—N(2)
Mg—N(3)
Mg—N(4)
2.086(2)
2.090(2)
2.196(2)
2.271(2)
Mg—N(5)
N(1)—C(1)
N(2)—C(2)
C(1)—C(2)
2.221(2)
1.391(2)
1.390(2)
1.391(2)

Reactions catalyzed by group 1 and 2 metals
Russ.Chem.Bull., Int.Ed., Vol. 65, No. 12, December, 2016 2889
teresting specific feature of the structure of compound 5 is
the coordination of toluene with sodium cation. The disꢀ
tances Na—C(toluene) are in the range of 2.848(2)—
3.071(2) Å (Na—toluene(centroid) 2.930(2) Å). The coorꢀ
dination of the neutral toluene molecule by sodium is
effected, apparently, through the interaction of the dipole
πꢀsystem of the ring with the alkali metal cation. Some
examples of such coordination are known.35,36
The catalytic activity of complexes 1—5 was studied in
the hydroamination reactions of styrene, 2ꢀvinylpyridine,
and isoprene with pyrrolidine (Scheme 2, Table 3). The
listed substrates have been chosen for the most correct
comparison of considered reactions relative to the recentꢀ
ly published results.14—18 We found that complexes 1 and
2 do not catalyze the reaction of styrene with pyrrolidine
neither in benzene, nor in the absence of a solvent. Comꢀ
pound 3, which contains a coordinated pyrrolidine, does
not exhibit catalytic activity in the addition reaction of
pyrrolidine to styrene either. However, in the presence of
complexes 1, 2, and 3, pyrrolidine reacts with 2ꢀvinylpyrꢀ
idine. In all the cases (see Table 3), the reactions proceed
at room temperature, giving rise to product 8a in high
yield (see Scheme 2).
N(1)
C(1)
C(2)
Si(2)
Si(1)
Li
N(3)
N(2)
Na
Fig. 2. Molecular structure of compound 5. Thermal ellipsoids
are given with 50% probability. Hydrogen atoms are omitted.
Table 2. Selected bond distances in compound 5
Bond
d/Å
Bond
d/Å
Scheme 2
Li—N(1)
Li—N(2)
N(1)—C(1)
N(2)—C(2)
1.956(2)
2.033(2)
1.320(2)
1.335(2)
C(1)—C(2)
Li—N(3)
Na—N(3)
Na—N(2)
1.444(2)
1.948(2)
2.341(2)
2.825(2)
N(SiMe3)2 group. The Li—N(3) bond (1.948(2) Å) is
noticeably shorter than the Na—N(3) bond (2.341(2) Å).
The bond distances C(1)—C(2), N(1)—C(1), and
N(2)—C(2) in compound 5 have the intermediate values
between those in free dppꢀbian and complex 3. This conꢀ
firms the radical anionic state of the dppꢀbian ligand in
complex 5. Taking into account the metal—nitrogen bond
distance values in compound 5, this complex can be conꢀ
sidered as an ateꢀcomplex [(dppꢀbian)Li{N(SiMe3)2}]–
[Na(C7H8)]+ containing a dppꢀbian radical anion. An inꢀ
X = N (6a, 8a), CH (6b, 8b)
Cat is the catalyst (see Tables 3 and 4).
The reactions with magnesium catalysts 1 and 3 reꢀ
quire longer time than with the calcium analog 2. Howevꢀ
Table 3. Addition of pyrrolidine to 2ꢀvinylpyridine (6a), styrene (6b), and isoprene (7) in the presence of catalysts (Cat)
group 1 and 2 metals
Alkene
Conditions
Catalyst (mol.%)
Product
Yield (%)*
Solvent
T/°C
τ/h
of hydroamination product
of polymer
6a
C6D6
C6D6
C6D6
—
—
—
20
20
20
60
60
60
60
1 (1)
2 (1)
3 (1)
4 (2)
5 (2)
4 (2)
5 (2)
4.10
0.08
4.80
31.0
47.5
20.0
48.0
8a
8a
8a
8b
8b
8c
8c
97
84
98
79
65
10
67
—
14
—
—
—
—
—
6b
7
—
* The yields were calculated from the 1H NMR spectroscopy data, using naphthalene (0.2 equiv.) as an internal standard.

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Yakub et al.
er, the high reactivity of calcium derivative 2 leads to the
formation of polyꢀ2ꢀvinylpyridine as a byꢀproduct. It is
probable that the initial step of the hydroamination proꢀ
cess of 2ꢀvinylpyridine with pyrrolidine in the presence of
complex 1 consists of the addition of the amine with the
formation of the amide derivative B (Scheme 3), which
reacts with the alkene with the formation of the insertion
product C. The latter in the process of sigmaꢀbonds meꢀ
tathesis disintegrates to the starting complex 1 and hyꢀ
droamination product, tertiary amine 8a (see Scheme 3).
In contrast to styrene, 2ꢀvinylpyridine can be bound by
complex 1 via coordination of the 2ꢀvinylpyridine nitroꢀ
gen atom by the magnesium atom. We found that the
coordination of pyrrolidine and 2ꢀvinylpyridine by comꢀ
plex 1 leads to an upfield shift of the signals for the pyrroꢀ
lidine and 2ꢀvinylpyridine protons in the 1H NMR spectra
(free pyrrolidine: δ 2.54 (αꢀCH2) and 1.36 (βꢀCH2); coꢀ
ordinated pyrrolidine: δ 2.47 (αꢀCH2) and 1.20 (βꢀCH2);
free 2ꢀvinylpyridine: δ 6.37 and 5.28 (CH2); coordinated
2ꢀvinylpyridine: δ 5.65 and 5.03 (CH2)). The mechanism
given in Scheme 3 is confirmed by the fact that complex 1
is present in the reaction mixture (1H NMR data) until
a complete conversion of the substrates. At the same time,
the formation of magnesium amide species was confirmed
by 1H NMR spectroscopy, as well as by the Xꢀray diffracꢀ
tion data of the products formed in the reactions of comꢀ
plex 1 with anilines in toluene.31
The process of the addition of pyrrolidine to 2ꢀvinylꢀ
pyridine was monitored by NMR spectroscopy (Fig. 3).
Figure 3, a shows the 1H NMR spectrum recorded immeꢀ
diately after addition of 2ꢀvinylpyridine to a mixture of
pyrrolidine and complex 3 (1 mol.%) in C6D6 before the
substrates began to react. In this spectrum, the signals at
δ 6.25 and 5.26 are attributed to the protons of the CH2
group in 2ꢀvinylpyridine. The signal for the proton
ArCH=CH2 (δ 6.63) overlaps with the signal of one of the
aromatic protons. Three other protons of the aromatic
ring give the signals at δ 8.43, 7.22, and 6.98. The signals
at δ 2.62 and 1.39 correspond to the pyrrolidine αꢀ and
βꢀprotons, the NH group of which gives a broad signal in
the region of δ 1.5—1.0.
1
The H NMR spectrum of the reaction mixture 4.8 h
(20 °C) after mixing the substrates and the catalyst 1 conꢀ
firms the complete conversion of the substrates to the prodꢀ
uct, the protons of the acyclic fragment of which are found
as multiplets in the range of δ 3.0—2.75. Note that the
Scheme 3
i. Insertion. ii. Metathesis of σꢀbond.

Reactions catalyzed by group 1 and 2 metals
Russ.Chem.Bull., Int.Ed., Vol. 65, No. 12, December, 2016 2891
and 2ꢀvinylpyridine (6a) (without solvents) initiated polyꢀ
merization of the latter. It is worth noting that complex 4
acted as a catalyst of polymerization of racꢀlactide with
the ring opening.33 In the presence of 2 mol.% of comꢀ
pound 4 or 5, the less active styrene (6b) undergoes hyꢀ
droamination with pyrrolidine at 60 °C (see Scheme 2 and
Table 3). The efficiency of catalysts 4 and 5 can be comꢀ
pared with the activity of group 2 metal complexes, as well
as with yttrium, ytterbium, and lithium derivatives. The
a
8.5 7.5 6.5 5.5 4.5 3.5 2.5 1.5 0.5
δ
comparison data are given in Table 4.
Most of the catalytic tests (see Table 4) was carried out
at 60 °C in the solventꢀfree version and using 2 mol.% of
the catalyst. Strictly speaking, the complexes listed in
Table 4 are precursors of the catalyticallyꢀactive species:
in all the cases, the formation of metal pyrrolidinates is an
initial step of the catalytic cycle. Thus, the catalytic activꢀ
ity of complexes under consideration is a function of the
ligands (L1—L6) included in their composition. These
compounds can be separated into two groups: (i) metal
amides and (ii) alkylmetals. The analysis of the obtained
results leads to the following conclusions. First, the cataꢀ
lytic activity of the alkalineꢀearth metal complexes inꢀ
creases with the increase in the ionic radius of the metal.
Note that the barium complexes containing an iminoꢀ
anilide ligand possess the highest activity among all the
catalysts of the reactions under consideration known by
the present moment. Second, alkyl derivatives exhibit betꢀ
ter activity as compared to amides. Apparently, this can be
explained by the more rapid formation of pyrrolidinates,
which are the true catalysts. Apart from that, the chelating
ligands included in the composition of the complex also
affect the hydroamination reaction rate. The catalytic acꢀ
tivity of silylamides 4 and 5 is comparable with that of
structurally similar ytterbium amides based on amidinate
and carbazolate ligands. The activities of complex 4 and
complex L6MgCH2Ph,18 which, as far as we know, by
now is the only example of magnesium catalyst of interꢀ
molecular hydroamination, are comparable. Compound 5,
in turn, is only the second example of the alkali metal
complex catalyzing intermolecular hydroamination of
alkenes. Earlier,21 there was a report on the addition of
pyrrolidine to styrene in the presence of 5 mol.% of
LiN(SiMe3)2/TMEDA at 120 °C in C6D6 with the formaꢀ
tion of antiꢀMarkovnikov hydroamination product in 82%
yield within 1.5 h.
b
8.5 7.5 6.5 5.5 4.5 3.5 2.5 1.5 0.5
δ
Fig. 3. 1H NMR spectrum (200 MHz, C6D6, 20 °C) of a mixture
of 2ꢀvinylpyridine—pyrrolidine—complex 3 (1 mol.%) immediꢀ
ately after mixing the reagents (a) and after 4.8 h (b).
addition of pyrrolidine to 2ꢀvinylpyridine in the presence
of catalysts 1, 2, and 3 proceeds as exclusive antiꢀMarkovꢀ
nikov process. By all accounts, the formation of the Marꢀ
kovnikov addition product is not possible because of the
steric factors.
The catalytic activity of complexes 1, 2, and 3 in the
addition reaction of pyrrolidine to 2ꢀvinylpyridine is comꢀ
parable with the activity of complex Rh(cod)2BF4/PPh3 (9)
and alkylyttrium binaphthylamide derivative [{(1ꢀC10H7)ꢀ
(PhCH2)N}2Y(CH2SiMe3)2][Li(thf)4] (10). The use of the
catalytic amounts of complex 9 (2.5 mol.%) gave comꢀ
pound 8a in 21% yield over 20 h at 66 °C.37 The yttrium
complex 10 demonstrated an excellent activity: the transꢀ
formation of the substrates to the antiꢀMarkovnikov hydroꢀ
amination product (98%) in the presence of 1 mol.% of
the catalyst was reached at room temperature just within
5 min.8 In some cases, the hydroamination of 2ꢀvinylpyriꢀ
dine with pyrrolidine was accompanied by the formation
of polyꢀ2ꢀvinylpyridine.8 We also observed partial polyꢀ
merization of 2ꢀvinylpyridine in the presence of calcium
derivative 2, which exhibited the highest activity among
compounds 1, 2, and 3. In its presence, a full conversion
of the substrates was reached within 5 min.
In the last stage of our work, we tested complexes 4 and
5 as the catalysts the addition reaction of pyrrolidine to
isoprene (7) (see Scheme 2). By the present time, it is known
only one nontransition metal compound capable of cataꢀ
lyzing this reaction. Thus, the use of 2 mol.% of barium
complex L1Ba[N(SiMe3)2](thf)217 at 60 °C gives product 8c
(see Table 3) in 99% yield. The silylamide 4 does not
catalyze the addition of pyrrolidine to isoprene, while the
heterometallic complex 5 (2 mol.%) leads to the formation
of the 1,4ꢀaddition product in 67% yield at 60 °C for 48 h.
To study the catalytic activity of metal amides conꢀ
taining dppꢀbian in the hydroamination reactions, we have
chosen the unsolvated monomeric tricoordinated comꢀ
plex (dppꢀbian)Mg[N(SiMe3)2]33 (4) and the complex
[(dppꢀbian)Li{N(SiMe3)2}][Na(C7H8)] (5), which does
not contain donor solvents.
We have shown that the addition of small amounts of
complexes 4 and 5 to an equimolar mixture of pyrrolidine

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Yakub et al.
Table 4. Addition of pyrrolidine to styrene (6b) catalyzed by group 2 metal complexes, as well as by yttrium,
ytterbium, and lithium derivatives
Catalyst [Cat]
[Cat] (mol.%)
Solvent
T/°C
τ/h
Yield (%)
Ref.
Ca[N(SiMe3)2]2(thf)2
Sr[N(SiMe3)2]2(thf)2
{Sr[N(SiMe3)2]2}2
0.2
0.2
5
2(0.2)
2
2
2
10
2
2
2
2
5
—
—
—
—
—
—
—
C7D8
—
—
60
60
60
60
60
60
60
130
60
60
70
70
60
120
2
2
<1
10
65
99(85)
90
85
97
38(49)
85
96
25
17
17
16
17
14
14
14
18
17
17
19
19
18
21
3.5
1(2)
0.5
0.08
0.08
24(48)
31
31
72
72
16
L1Ba[N(SiMe3)2](thf)2
L1Ca[CH(SiMe3)2](thf)
L1Sr[CH(SiMe3)2](thf)2
L1Ba[CH(SiMe3)2](thf)2
[L2Y(CH2SiMe3)2][Li(thf)4]
L3YbN(SiMe3)2(thf)
L4Yb[N(SiMe3)2](thf)
L5Y(CH2SiMe3)(thf)2
[L5Y(CH2SiMe3)2][Li(thf)4]
L6MgCH2Ph
—
—
—
C6D6
100
87
82
LiN(SiMe3)2/TMEDA
5
1.5
Ar = 2,6ꢀPriC6H3, Ar´ = 2,6ꢀButC6H3
In conclusion, we studied two types of complexes conꢀ
taining a functionallyꢀlabile ligand dppꢀbian as the cataꢀ
lysts of the addition reaction of pyrrolidine to styrene.
Magnesium and calcium derivatives of dppꢀbian dianion
(compounds 1, 2, and 3) were the type 1 complexes, magꢀ
nesium and lithium derivatives of dppꢀbian radical anion
(compounds 4 and 5) belong to the type 2. In contrast to
compounds 4 and 5, complexes 1, 2, and 3 do not contain
an amide group, at the metal—nitrogen bond of which the
insertion of an alkene takes place. The obtained results
demonstrate that the type 2 complexes are more active
than the type 1 derivatives in the intermolecular hydroamꢀ
ination reactions. However, the catalytic cycles of these
two types of catalysts should be different. First, for the 1st
type of complexes the active catalytic species can be formed
not through the protonation of the auxiliary ligand (amide
or alkyl groups), but via the addition of an amine,
for example, pyrrolidine, at the M—N(dppꢀbian) bond.
Second, for the 1st type complexes the formation of the
hydroamination product from the catalyst proceeds not
through the protonation of the addition product by an
"external" amine, but via the intramolecular proton transꢀ
fer from [dppꢀbian(H)]– to the carbanion.
Experimental
Compounds 1—5 are sensitive to air oxygen and moisture,
therefore, all the operations including their preparation, as well
as catalytic tests, were carried out in vacuo or under nitrogen of
high purity grade, using glass tubes, Schlenk flasks, and NMR
tube. Diimine dppꢀbian,34 as well as the complexes (dppꢀbian)ꢀ
Mg(thf)3 (1),32 (dppꢀbian)Ca(thf)4 (2),32 and (dppꢀbian)MgNꢀ
(TMS)2 (4)33 were synthesized according to the described proꢀ
cedures.32,33 Toluene (Vekos), THF (DalKhim), and benzeneꢀd6
(Aldrich) were dried over sodium benzoketyl and distilled/conꢀ
densed in vacuo into the reaction tube or NMR tube immediately
before use; CDCl3 (DalKhim) was used without preliminary puꢀ
1
rification. H NMR spectra were recorded on a Bruker DPXꢀ
200 spectrometer, IR spectra were recorded on a FSMꢀ1201

Reactions catalyzed by group 1 and 2 metals
Russ.Chem.Bull., Int.Ed., Vol. 65, No. 12, December, 2016 2893
spectrometer. Pyrrolidine, styrene, and isoprene (all from
Aldrich) were dried with a small amount of sodium metal and
distilled in vacuo immediately before use.
CHMe2, J = 6.7 Hz); 1.25 (d, 12 H, CHMe2, J = 6.7 Hz);
1.18 (s, 12 H, C4H8NH); 1.12—1.04 (br.s, 3 H, C4H8NH).
1,2ꢀBis[(2,6ꢀdiisopropylphenyl)imino]acenaphthenidelithiumꢀ
1,2ꢀBis[(2,6ꢀdiisopropylphenyl)imino]acenaphthenidemagꢀ
nesiumtripyrrolidinate, (dppꢀbian)Mg(pyr)3 (3). Magnesium turnꢀ
ings (2.4 g, 100 mmol) and iodine (0.013 g, 0.05 mmol)) were
placed into a 100ꢀmL tube equipped with a Teflon stopcock.
After evacuation of the tube, THF (30 mL) was added by conꢀ
densation. Then, the reaction mixture was shaken at room temꢀ
perature until it turned colorless. The formed MgI2(THF)n was
decanted from the metal, which was thrice washed with THF
(30 mL), and dried in vacuo. A mixture of dppꢀbian (0.5 g,
1.0 mmol) and pyrrolidine (0.71 g, 10 mmol) in toluene (20 mL)
was added to the activated metal. During reflux, the color of the
reaction mixture changed from orange to dark green. After 60 h
of reflux, the reaction mixture was cooled to room temperature,
decanted from magnesium, concentrated in vacuo (to 10 mL),
and heated to 80 °C for 2 min. A slow cooling of the resulting
solution to room temperature led to the formation of dark red
crystals of compound 3 (0.51 g, 69%). M.p. 165 °C (decomp.).
Found (%): C, 77.74; H, 8.81. C48H67MgN5 (740.40 g mol–1).
Calculated (%): C, 78.08; H, 9.15. IR (Nujol), ν/cm–1: 1670 w,
1650 w, 1579 m, 1458 s, 1375 s, 1361 s, 1325 m, 1253 m, 1203 w,
1173 w, 1156 w, 1142 w, 1104 w, 1060 m, 1040 m, 999 w, 958 w,
919 m, 894 m, 855 w, 833 w, 795 m, 750 m, 725 m, 681 w, 623 m,
601 w, 568 w, 541 w, 535 w, 513 w, 491 w, 463 w, 452 w. 1H NMR
(200 MHz, benzeneꢀd6, 298 K), δ: 7.35—7.12 (m, 8 H, CHarom);
6.97—6.79 (m, 3 H, CHarom); 6.16 (d, 1 H, CHarom, J = 6.2 Hz);
3.96 (m, 4 H, CHMe2); 2.46 (s, 12 H, C4H8NH); 1.36 (d, 12 H,
[bis(trimethyl)silylamide]sodiumtoluene,
[(dppꢀbian)Liꢀ
{N(SiMe3)2}][Na(C7H8)] (5). A mixture of dppꢀbian (0.5 g,
1 mmol) and sodium (0.023 g, 1 mmol) was refluxed in toluene
(30 mL). After 60 h, the metallic sodium was completely disꢀ
solved and the reaction mixture gradually turned dark red. The
compound (Me3Si)2NLi (0.16 g, 1 mmol) was added to the reꢀ
sulting solution and the mixture was stirred at room temperature
for 30 min. Then, the solution was concentrated in vacuo (to
10 mL) and heated to 80 °C for 2 min. After standing of the
concentrated solution at room temperature, compound 5 was
isolated as dark red crystals (0.45 g, 64%). M.p. 355 °C. Found (%):
C, 75.01; H, 8.28. C49H66LiNaN3Si2 (701.18 g mol–1). Calcuꢀ
lated (%): C, 75.92; H, 8.49. IR (Nujol), ν/cm–1: 1648 w, 1621 w,
1588 w, 1518 m, 1410 s, 1350 w, 1314 s, 1250 s, 1179 s, 1103 w,
1076 w, 1036 s, 932 s, 883 m, 831 s, 816 s, 762 s, 756 s, 739 s,
694 w, 663 w, 600 w, 540 w, 468 w.
Catalytic experiments. All the manipulations concerning
preparation of the samples were carried out in a glovebox
(M. Braun) under nitrogen of high purity grade (the content of
water and oxygen less than 0.1 ppm). In a standard catalytic test,
the catalyst was placed into an NMR tube with a screw cap.
Then, pyrrolidine and styrene or isoprene were added. After
this, the NMR tube was shaken several times to dissolve the
components and placed into an oil bath (60 °C). In the experiꢀ
ment with 2ꢀvinylpyridine, the catalyst, pyrrolidine, and C6D6
were first placed into an NMR tube. Then, the tube was shaken
Table 5. Crystallographic data, parameters of Xꢀray diffraction experiments and refinement for
compounds 3 and 5
Parameter
3
5
Molecular formula
Molecular weight
Crystal system
Space group
a/Å
b/Å
c/Å
α/deg
C48H67MgN5
738.37
Monoclinic
P21/n
12.4656(5)
18.0456(9)
19.2502(8)
90
C49H66LiN3NaSi2
783.15
Monoclinic
P21/n
14.9106(10)
13.1347(9)
24.2920(16)
90
β/deg
96.263(4)
90
4304.5(3)
4
1.139
0.080
104.3560(10)
90
4608.9(5)
γ/deg
V/Å3
Z4
dcalc/mg m–3
1.129
0.122
μ/mm–1
F(000)
1608
1692
Crystal size/mm
θꢀScan range/deg
Number of reflections й
collected
0.40×0.10×0.10
3.05—26.00
0.34×0.26×0.17
2.32—26.00
65383
8452 (0.1249)
1.045
44652
9025 (0.0322)
1.037
unique х (Rint
GOOF (F2)
)
R1 (I > 2σ(I))
0.0672
0.0380
wR2 (based on all parameters )
Residual electron density
(max/min)/e•Å–3
0.1245
0.283/–0.280
0.1028
0.381/–0.240

2894
Russ.Chem.Bull., Int.Ed., Vol. 65, No. 12, December, 2016
Yakub et al.
several times to dissolve the catalyst. After the formation of
a homogeneous mixture, 2ꢀvinylpyridine was added to the soluꢀ
tion. The 1H NMR spectra of the products of hydroamination of
2ꢀ[2ꢀ(pyrrolidinꢀ1ꢀyl)ethyl]pyridine (8a),8 1ꢀphenethylpyrroliꢀ
dine (8b),7 and 1ꢀ(3ꢀmethylbutꢀ2ꢀenꢀ1ꢀyl)pyrrolidine (8c)17 corꢀ
responded to the literature data.
16. C. Brinkmann, A. G. M. Barrett, M. S. Hill, P. A. Procoꢀ
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18. X. Zhang, T. J. Emge, K. C. Hultzsch, Angew. Chem., Int.
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Xꢀray diffraction study of compounds 3 and 5. The Xꢀray
diffraction study of compounds 3 and 5 was carried out on an
Agilent Xcalibur E (3) and Bruker D8 Quest (5) diffractometers
(ωꢀscan technique, MoꢀKα radiation, λ = 0.71073 Å, T = 100(2) K).
The crystallographic data and parameters of the Xꢀray diffracꢀ
tion experiments are given in Table 5. The structures were solved
by direct methods and refined by the fullꢀmatrix least squares
method based on F2hkl with anisotropic displacement parameters
for all the nonhydrogen atoms.
19. M. S. Hill, D. J. Liptrot, C. Weetman, Chem. Soc. Rev.,
2016, 45, 972.
20. Y. Sarazin, J.ꢀF. Carpentier, Chem. Rec., 2016, doi:10.1002/
tcr.201600067.
21. P. HorrilloꢀMartínez, K. C. Hultzsch, A. Gil, V. Branꢀ
chadell, Eur. J. Org. Chem., 2007, 3311.
22. M. Beller, C. Breindl, Tetrahedron, 1998, 54, 6359.
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Skatova, A. V. Cherkasov, G. A. Abakumov, Chem. Eur. J.,
2012, 18, 255.
The pyrrolidine hydrogen atoms H(3), H(4), and H(5) in 3
were localized from the difference Fourier maps of electron denꢀ
sity, all other hydrogen atoms were positioned geometrically and
24. I. L. Fedushkin, O. V. Kazarina, A. N. Lukoyanov, A. A.
Skatova, N. L. Bazyakina, A. V. Cherkasov, E. Palamidis,
Organometallics, 2015, 34, 1498.
refined isotropically with fixed thermal parameters U(H)iso
=
= 1.2U(C)eq (U(H)iso = 1.5U(C)eq for the methyl fragments). The
structure refinement and correction for absorption were carried
out using the APEX2,38 SADABS,39 CrysAlis PRO,40 and
SHELX41,42 software. The structures were deposited with the
Cambridge Crystallographic Data Center (CCDC 1492157 (3) and
1492158 (5)) and are available at ccdc.cam.ac.uk/getstructures.
25. O. V. Kazarina, M. V. Moskalev, I. L. Fedushkin, Russ.
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Abakumov, J. Organomet. Chem., 2013, 747, 235.
27. M. V. Moskalev, A. M. Yakub, A. G. Morozov, E. V. Baranov,
O. V. Kazarina, I. L. Fedushkin, Eur. J. Org. Chem., 2015, 5781.
28. I. L. Fedushkin, A. S. Nikipelov, K. A. Lyssenko, J. Am.
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This work was financially supported by the Russian
Science Foundation (Project No. 14ꢀ13ꢀ01063).
29. I. L. Fedushkin, M. V. Moskalev, A. N. Lukoyanov, A. N.
Tishkina, E. V. Baranov, G. A. Abakumov, Chem. Eur. J.,
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Received October 31, 2016