Well-Defined β-Diketiminatocobalt(II) Complexes for Alkene Cyclohydroamination of Primary Amines

Article abstract of DOI:10.1021/acscatal.8b00631

A well-defined low-coordinate β-diketiminatocobalt(II) alkyl complex is reported as an active precatalyst for the selective alkene cyclohydroamination of unprotected primary amines under mild conditions (rt-90 °C). The reaction mechanism has been investigated by deuterium-labeling, kinetics, and stoichiometric experiments and in-depth computational DFT studies. On the basis of these studies, we propose a stepwise noninsertive mechanism that features a rate-determining nucleophilic attack of the amido group of a monomeric cobalt(II) amidoalkene-aminoalkene adduct intermediate to the noncoordinated pendant alkene followed by a rapid proton transfer from the coordinated aminoalkene to the cyclized adduct.

Full text of DOI:10.1021/acscatal.8b00631

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Well-Defined #-Diketiminatocobalt(II) Complexes
For Alkene Cyclohydroamination of Primary Amines
Clement Lepori, Pablo Gómez-Orellana, Allissa Ouharzoune, Régis
Guillot, Agusti Lledos, Gregori Ujaque, and Jerome Hannedouche
ACS Catal., Just Accepted Manuscript • DOI: 10.1021/acscatal.8b00631 • Publication Date (Web): 13 Apr 2018
Downloaded from http://pubs.acs.org on April 13, 2018
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ACS Catalysis
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clohydroamination of Primary Amines
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Clément Lepori,† Pablo Gómez-Orellana,‡ Allissa Ouharzoune,† Régis Guillot,† ┴ Agusti Lledós,* ‡
Gregori Ujaque,* ‡ and Jérôme Hannedouche*†┴
†
Institut de Chimie Moléculaire et des Matériaux d’Orsay, UMR 8182, Université Paris-Sud, Rue du doyen Georges Poitou,
Orsay, F-91405, France, ‡ Departament de Química, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Valles,
Catalonia, Spain, ┴ CNRS, Orsay, F-91405, France.
hydroamination, cobalt, primary amines, alkenes, mechanistic studies, DFT calculations.
ABSTRACT:
A
well-defined
low-coordinate
β-
diketiminatocobalt(II) alkyl complex is reported as an active
precatalyst for the selective alkene cyclohydroamination of unpro-
tected primary amines under mild conditions (rt-90 °C). The
reaction mechanism has been investigated by deuterium-labelling,
kinetics and stoichiometric experiments and in-depth computa-
tional DFT studies. On the basis of these studies, we propose a
stepwise non-insertive mechanism that features a rate-determining
nucleophilic attack of the amido group of a monomeric cobalt(II)
amidoalkene-aminoalkene adduct intermediate to the non-
coordinated pendant alkene followed by a rapid proton transfer
from the coordinated aminoalkene to the cyclized adduct.
Scheme 1. (a) Seminal Work on Related Co-catalysed N-H
Addition on Unactivated Alkenes; (b) This Work
Over the years, the catalytic alkene hydroamination − the di-
rect addition of an amine across a carbon-carbon double bond
− has received considerable interest among the scientific commu-
nity as an appealing route to valuable nitrogen-containing com-
Some of us have recently reported that structurally defined β-
diketiminatoiron(II)-alkyl or -amido complexes, such as 1a-Fe
(Scheme 2), have the ability to catalytically promote the highly
selective cyclohydroamination of primary aliphatic alkenylamines
at mild temperatures, as the first example of iron-catalyzed hy-
droamination of such electronically unbiased amines. With our
concern in base metal catalysis, we have explored the reactivity of
analogue complexes derived from cobalt in alkene hydroamina-
tion.
1
pounds from ubiquitous amines and olefins. The general concern
4
a
for sustainable metal catalysis has recently stimulated the explora-
tion of earth-abundant, first-row late transition metals for the
development of eco-compatible hydroamination catalysts with a
1c
wide applicability. Although still in its infancy, this exploration
2
3
4
has already led to outstanding advances with Zn, Cu or Fe
metal relying on either a classical
2
,3a-b,4a-b
or a formal hydroamina-
tion approach such as metal-hydride mediated umpolung electro-
3c,4c
4d
philic amination
or hydrogen atom transfer. However, alt-
hough these reports by formal hydroamination have advanced the
state of the art, they are far from the concept of atom and step
economy of the original hydroamination reaction, and so progress
in the direction of “truly” hydroamination systems from earth
abundant transition metal is still in high demand. In this context,
there is, to our knowledge, no report on the cobalt-catalyzed
hydroamination of unactivated alkenes. Only a single but interest-
ing report by Shigehisa et al. has disclosed a Co-catalyzed intra-
molecular C-N bond formation by a closely related formal hy-
droamidation reaction of protected amines bearing electron-
withdrawing groups (EWG) and requiring a substoichiometric
amount of oxidizing electrophilic fluorine agent and reducing
Scheme 2. Structures of β-diketiminatometal(II) complexes
Firstly, the β-diketiminatocobalt(II) alkyl complex 1a-Co
(Scheme
2)
was
prepared
from
2,4-bis(2,4,6-
trimethylphenylimido)pentane, CoCl and LiCH SiMe by a two-
2
2
3
step metathesis route (via the formation of chloro ate complex
6
S1). Complex 1a-Co was isolated as a dark-brown air-sensitive
crystalline solid that can be stored for weeks at rt without noticea-
ble decomposition. Solid-state analysis of a single crystal reveals
that the four-coordinate cobalt atom adopts a pseudotetrahedral
geometry with a smaller trigonal pyramidal distortion than that
5
silane agent (Scheme 1 (a)). Herein, we report the first example
of cobalt-catalyzed alkene hydroamination of unprotected primary
amines under co-reagent-free conditions using well-defined low-
coordinate β-diketiminatocobalt(II) complexes (Scheme 1 (b)).
6
7,8
found in 1a-Fe (τ = 0.31 vs τ = 0.55) (Figure 1).
Co
Fe
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Table 2. Reaction Scope
Page 2 of 14
a
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6
R1
R1
NH
2
R
R
NH
10 mol % 1a-Co
1
R2
R2
1
toluene, 90 °C
R3
b-m
R3
3b-m
2
Figure 1. ORTEP drawing of 1a-Co (left) and [1b-Co] (right).
2
Thermal ellipsoids are shown at the 30% level. H atoms have
been omitted for clarity.
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Our initial evaluation of the catalytic efficiency of 1a-Co fo-
cused on the reaction of 2a as a benchmark reaction under our
previously optimized conditions for the iron-catalyzed hydroami-
4a
nation. To our surprise, heating 2a in toluene at 90 °C in the
presence of 10 mol % of 1a-Co leads to the formation of 3a, 4a,
5
a and 6a in a 4:9:18:61 ratio respectively after 92% conversion
(Table 1, entry 1). This result is in strong contrast with 1a-Fe
which delivers under identical conditions the hydroamination
a
Reaction conditions: [2] = 0.81 M, 10 mol % 1a-Co, toluene,
product 3a in 80% yield with no trace of olefin isomerization
4a
90 °C, 24 h. RMN yield determined using an internal standard
unless otherwise stated and isolated yield in brackets. Deter-
mined by GC analysis.
product 6a. To our delight, introducing a phenyl ring at the
terminal position of the C=C bond of the substrate prevents the
alkene isomerization to occur.
b
To investigate the reaction mechanism, kinetic analysis of the
cyclohydroamination of 2b was performed by monitoring the
concentration of substrate 2b over the course of the reaction. Plots
of ln[2b] vs time are linear to at least 3 half-lives over a 0.51–1.41
M initial concentration range and are consistent with first-order
kinetics in [2b]. A linear relationship between kobs and [1a-Co]
over a fourfold concentration range ([1a-Co] = 0.041-0.161 M)
indicates a first order dependence in catalyst concentration and
Table 1. Screening of Substrates and Conditions of the
Cyclohydroamination reaction
a
1
R1
R1
R1
R1
R1
R1
R1
R1
R
R
NH
2
NH
N
NH
2
NH
2
1
+
2+
+
2
2
R2
2
R
R
R
R
2
3
4
5
6
entry
substrate
2
3
4
5
(%)
6
(%)
b
b
b
b
b
provides the empirical rate law displayed in eq 1 with k (363 K)=
.6 × 10 M s .
(%)
(%)
(%)
H
-4
-1 -1
6
c
1
8
4
9
18
61
dꢁꢂꢃꢄ
dt
ꢌ
ꢌ
ꢍꢍꢍꢍꢍꢍꢍꢍꢍꢍꢍꢍꢍꢍꢍꢍꢍꢍꢍꢍꢍꢍꢍꢍꢍꢍꢍꢍꢍꢍꢎ1ꢏꢍ
ꢀ
ꢅ ꢆ ꢁꢈꢉ_ꢊꢋꢄ ꢁꢂꢃꢄ
ꢇ
d
2
5
93
72
2
2
0
0
0
0
This second-order rate law may reflect mono-association of
e
the substrate with a monomeric cobalt species during the rate-
limiting step and is consistent with several reported mechanisms
such as a proton-assisted concerted C-N/C-H bond-forming
mechanism
over-limiting aminolysis event. Further measurement of the rate
of cyclization of N-deutero-amine [D ]-2b with 1a-Co gives k
363 K) = 6.8 × 10 M s and leads to no observation of primary
kinetic isotope effect (KIE) (k /k = 0.97 (90 °C)). Eyring analy-
3
25
f
4
[1b-Co]2
[1b-Co]2
[1b-Co]2
8
90
1
1
0
9a-d
9e,4a
or a stepwise insertive mechanism
with a turn-
g
5
56
58
0
44
17
0
0
0
0
g,h
2
D
6
25
-4
-1 -1
(
a
Reaction conditions: [2] = 0.96 M, 10 mol % 1a-Co, toluene,
H
D
b
90 °C, 24 h unless otherwise stated. Determined by GC analysis.
sis for the cyclization of 2b over a 353-383 K temperature range
afford the following activation parameters: ∆H = +15.9 kcal mol
, ∆S = −29.7 cal mol K .
c
d
e
f
≠
-
3
h. [2b] = 0.81 M. [2b] = 0.73 M, rt, 47 h. 5.55 mol % [1b-
g
1
≠
-1 -1
Co] as catalyst. [[1b-Co] ] = 2.6 mM, toluene, 90 °C, 24 h.
2
2
h
With cyclopentylamine (1 equiv per Co).
To gain a better insight into the nature of the cyclization step,
Indeed, the hydroamination of 2b catalyzed by 10 mol % of
we endeavor to isolate the initial catalyst−substrate intermediate
and study its reactivity. The stoichiometric reaction of 1a-Co and
2b at rt leads to the isolation of cobalt amido complex [1b-Co] as
a dark green solid in 89% (Scheme 2). X-ray diffraction analysis
confirms the solid-state structure of [1b-Co] as a centrosymmet-
ric amido-bridged dimer (Figure 1). The stoichiometric reactivity
of isolated [1b-Co] was then tested by heating a toluene slurry of
the dimer for 24 h at 90 °C. GC analysis reveals the formation of
4b in 44% yield as the sole insertion product, concomitantly with
unreacted 2b in 56% yield (Table 1, entry 5). It is worth noting
1
a-Co provides 3b in 93% yield as almost the sole product with-
out any sign of substrate isomerization (Table 1, entry 2). The
reaction can also be run at rt with similar selectivity despite a
lower efficiency (Table 1, entry 3). By this methodology, various
five- and six-membered nitrogen-heterocycles featuring a phenyl
ring attached to the terminal alkene which is either unsubstituted
(3b-d, 3j) or substituted by an halogen atom (3f-h), an alkyl (3e)
or a methoxy (3i) group were isolated in convenient yields from
the corresponding aminoalkenes (Table 2). The exo-cyclization
also occurs efficiently from primary amines bearing a dime-
thylsubstituted allene (2k) or an alkyne (2l-m) functionality.
Nevertheless, up to know, the reaction does not proceed with
aminoalkenes unbiased towards cyclization or having a trisubsti-
2
2
2
that [1b-Co] is also capable of catalytically mediating the hy-
2
droamination of 2b with similar efficiency as its alkyl precursor
(Table 1, entries 4 vs 2) (vide infra for more details on the selec-
tivity change). As C-N bond formation clearly occurs directly
6
tuted olefin.
from [1b-Co] in the absence of additional proton source, this
2
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stoichiometric experiment militates against a proton-assisted
concerted mechanism. The stereochemistry of the cyclization was
the product by a new aminoalkene molecule closes the catalytic
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9
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cycle (Scheme 3). This proposed stepwise non-insertive mecha-
nism is the most favorable one among, inter alia, the insertive
mechanism. All the attempts to find a concerted non-insertive
pathway has conducted to this stepwise mechanism. The absence
of KIEs is explained by the fact that the proton transfer step
1
3
further elucidated by H NMR J , coupling constant measure-
H H
ments of the tosylated products arising from cyclization of N-
deutero-amines [D ]-(E)-3d and [D ]-(Z)-3d. These experiments
2
2
provide exclusively products with deuterium located at the β-
position of the nitrogen atom and with a formal syn-addition of
-1
(TS_IV_A3 at 6.8 kcal mol ) is lower in energy than the cycliza-
6
-1
the N-D bond across the C=C bond.
tion step (TS_III_A3 at 11.2 kcal mol ) (Figures 2 and 3).
The reaction mechanism for 2b was also investigated by
1
0
means of DFT calculations. Among the mechanisms evaluated,
the one with the most feasible Gibbs energy profile is shown in
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Figure 2. The relative stability of doublet and quartet spin states
were systematically evaluated obtaining the later as the most
6
stable one. The mechanism can be divided in two parts, one for
generating the active species, III_A3, and another for the catalytic
cycle itself. The generation of the active species, III_A3 takes
place by a proton transfer from the coordinated reactant to the –
CH SiMe ligand, I_A1 (Figure 2 and Scheme 3). This step pro-
2
3
duces intermediate II_A1, with a Gibbs energy barrier of 29.2
-
1
12
kcal mol , generating an amido group ligand and SiMe . The
4
formed SiMe of II_A1 is then replaced by a second aminoalkene
4
Figure 3. Optimized structures for TS_III_A3 (left) and
TS_IV_A3 (right) (distances in Å).
reactant molecule producing active species III_A3 at −11.4 kcal
-
1
mol . In turn, intermediate II_A1 can also form [1b-Co] that
2
The observation of a syn-addition of N-D bond across the C=C
bond, can be justified by the proposed mechanism if the rotation
around C -C bond (see IV_A3 in Scheme 3) is higher in energy
probably corresponds to the resting state of the catalyst once the
1
3
reactant is consumed (Figure 2 and Scheme 3). Its optimized
structure resembles that of X-ray analysis. This species can cata-
lyze the reaction by forming back the monomeric species (Table
1
2
than the proton transfer. Then, proton transfer would be fast
enough to avoid rotation around C -C bond, producing a formal
1
, entry 4).
1
2
syn-addition of the N-H bond across the C=C bond. The relative
-1
barrier for the proton transfer is 5.6 kcal mol , whereas the rota-
Ar
N
TS_I_A1
9.2
27.1)
NHR1
H
Ar = 2,4,6-(Me)
3
C
6
H
2
-1
R1
tion is estimated to be 14.4 kcal mol , thus explaining the exper-
2
(
Co
NH
2
=
2b
N
Ar
imental observation of a syn-addition. The mechanism is also in
agreement with the experimental observation that the reaction of
[1b-Co]2 in the presence of cyclopentylamine (1 equiv) as an
additional proton source generates 3b (and 4b) (Table 1, entry 6).
2 3
CH SiMe
Ar
N
HN
Co
H
N
Ph
Ar
Ar
R
1
NH
2
N
HN
H
TS_III_A3
Co
NA r R1HN
Ph
SiMe4
Ar
N
11.2
(12.0)
H
R1
proton
transfer
1
NH
NHR
2
NHR1
TS_IV_A3
Co
LCo
LCo
[1b-Co]2
N
Ar
6.8
(7.6)
CH
3
SiMe
3
CH
I_A1
2b
2
SiMe
3
3
CH SiMe
3
II_A1
IV_A3
I_A1
II_A1
Ar
N
0.7
(0.5)
1.2
(1.9)
2b
0.0
0.0)
R1
CH2SiMe3
NH
2
(
2b
SiMe
Co
Ar
HN
Co
NA r R1NH
N
Ar
N
H
2b
Ph
1a-Co
4
2
III_A3
Ar
N
−11.4
(−11.3)
Ar
N
Ar
3b
Co NHR1
NHR1
HN
H
N
N
[1b-Co]
2
Co
Co
Ph VI
Ar
R1
H
2
−17.4
N
Ar
NH
2
N
NHR1
−17.1
(−16.6)
NH
Ph
TS_III_A3
(
−18.7)
Ar
LCo
Figure 2. Calculated Gibbs energy profile (T = 298 K (in brackets
rate-limiting
nucleophilic
amido attack
2b
1
amine
2
NH R
-
1
T = 363K); energies in kcal mol )
exchange
III_A3
The catalytic cycle contains three steps: (i) intramolecular cy-
clization by nucleophilic attack of coordinated amido group to the
non-coordinated alkene, (ii) proton transfer from a second coordi-
nated aminoalkene to the cyclized amino ligand, and (iii) substitu-
tion of the product by a new reactant (Scheme 3). The C-N bond
C
1
HN
H
H
HN
LCo
NH
IV_A3
H
C
2
LCo
Ph
NHR1
Ph
1
2
R
-1
formation step, with a relative barrier of 22.6 kcal mol , corre-
VI
proton transfer
sponds to the rate determining cyclization step, and is in very
≠
-1
TS_IV_A3
good agreement with ꢀG =24.6 kcal mol calculated from exper-
imental activation parameters at T = 298.15 K. The large and
negative activation entropy determined experimentally also agrees
with a step that involves a cyclization process. Intermediate
a
1
NH R = 2b, L represents β-diketiminate ligand.
2
a
-
1
IV_A3, which lies at 1.2 kcal mol , does not have direct interac-
Scheme 3. Proposed Reaction Mechanism
tion between Co and C (distance of 3.649 Å; Scheme 3 and
2
In conclusion, we have established that novel well-defined β-
diketiminatocobalt(II) alkyl complex 1a-Co is an efficient precat-
alyst for the hydroamination of unprotected primary amines teth-
ered to an aryl alkene under mild and co-reagent free conditions.
This is the first example of cobalt-catalyzed alkene hydroamina-
Figure S11). From this intermediate, there is a proton transfer
between the coordinated aminoalkene and the cyclized amino
-
1
ligand, with an energy barrier of 5.6 kcal mol . It generates in-
-
1
termediate VI, with a relative Gibbs energy of −17.1 kcal mol ,
that has the hydroamination product coordinated. Replacement of
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Page 4 of 14
tion reaction of unprotected and electronically unbiased primary
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
amines. DFT studies, supported by stoichiometric reactivity ex-
periments, have shown that the reaction operates through a step-
wise non-insertive mechanism as original alternative to the classi-
cally reported hydroamination mechanisms. This mechanism
entails nucleophilic attack of the amido group of monomeric
cobalt(II) amidoalkene-aminoalkene adduct intermediate to the
non-coordinated pendant alkene as the rate-determining cycliza-
tion step associated subsequently to a rapid proton transfer from
the coordinated substrate to the resulting cyclized adduct. This
proposed mechanism is in agreement with the empirical second-
order rate law, no KIE observation, the syn-addition of N-D bond
across the C=C bond, and the activation parameters determined
experimentally. The outcome of this work will help guide the
rational design of base metal catalysts with improved reactivity
and alternative selectivity patterns. Further studies in this direc-
tion are currently ongoing.
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K.; Ghorai, P. K.; Samuel, P. P.; Schulzke, C.; Mandal, S. K. Phenalenyl-
Based Organozinc Catalysts for Intramolecular Hydroamination Reac-
tions: A Combined Catalytic, Kinetic, and Mechanistic Investigation of
the Catalytic Cycle. Chem. Eur. J. 2012, 18, 10530-10545. (c) Pissarek, J.-
W.; Schlesiger, D.; Roesky, P. W.; Blechert, S. Diethylzinc: A Simple and
Efficient Catalyst for the Swift Hydroamination at Room Temperature.
Adv. Synth. Catal. 2009, 351, 2081-2085.
(3) (a) Blieck, R.; Bahri, J.; Taillefer, M.; Monnier, F. Copper-
Catalyzed Hydroamination of Terminal Allenes. Org. Lett. 2016, 18,
1482-1485. (b) Ohmiya, H.; Moriya, T.; Sawamura, M. Cu(I)-Catalyzed
Intramolecular Hydroamination of Unactivated Alkenes Bearing a Primary
or Secondary Amino Group in Alcoholic Solvents. Org. Lett. 2009, 11,
2145-2147. (c) review on copper hydride-catalyzed formal hydroamina-
tion: Pirnot, M. T.; Wang, Y.-M.; Buchwald, S. L. Copper Hydride Cata-
lyzed Hydroamination of Alkenes and Alkynes. Angew. Chem. Int. Ed.
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(
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Hydroamination of Primary Aliphatic Alkenylamines. Angew. Chem. Int.
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Simple and Efficient Iron-Catalyzed Intramolecular Hydroamination of
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nation of Styrenes. Org. Lett. 2014, 16, 3620-3623. (d) Gui, J.; Pan, C.-
M.; Jin, Y.; Qin, T.; Lo, J. C.; Lee, B. J.; Spergel, S. H.; Mertzman, M. E.;
Pitts, W. J.; La Cruz, T. E.; Schmidt, M. A.; Darvatkar, N.; Natarajan, S.;
Baran, P. S. Organic chemistry. Practical olefin hydroamination with
nitroarenes. Science 2015, 348, 886-891.
ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website.
Experimental procedures, kinetic and isotopic labelling studies,
characterization, computational details and copies of NMR spec-
tra (PDF)
Crystallographical data for complex S1 (CIF)
Crystallographical data for complex 1a-Co (CIF)
(5) Shigehisa, H.; Koseki, N.; Shimizu, N.; Fujisaw, M.; Niitsu, M.;
Hiroya, K. Catalytic Hydroamination of Unactivated Olefins Using a Co
Catalyst for Complex Molecule Synthesis. J. Am. Chem. Soc. 2014, 136,
Crystallographical data for complex [1b-Co] (CIF)
2
1
3534-13537.
6) See Supporting Information for details and/or other explored mech-
anisms and spin states.
AUTHOR INFORMATION
Corresponding Author
(
3
(7) For examples of three-coordinate β-diketiminatocobalt(II) sp -alkyl
complexes: (a) Young, J. F.; Yap, G. P. A.; Theopold, K. H. 2,4-Pentane
N,N′-Bis(2,6-Diisopropylphenyl) ketiminato cobalt (II) (trimethylsi-
lyl)methyl. J. Chem. Crystallogr. 2009, 39, 846-848. (b) Chen, C.; Dugan,
T. R.; Brennessel, W. W.; Weix, D. J.; Holland, P. L. Z-Selective Alkene
Isomerization by High-Spin Cobalt(II) Complexes. J. Am. Chem. Soc.
*jerome.hannedouche@u-psud.fr
*gregori.ujaque@uab.cat
*agusti@klingon.uab.es
ORCID
2
014, 136, 945-955.
8) DFT optimized structure of 1a-Co is very similar to that obtained
Jérôme Hannedouche: 0000-0001-5278-3906
Gregori Ujaque: 0000-0001-5896-9998
Agusti Lledós: 0000-0001-7909-422X
(
by X-ray analysis and assigns a quartet spin state to this compound as
6
noticed by solution magnetic moment measurement.
(9) (a) Manna, K.; Kruse, M. L.; Sadow, A. D. Concerted C–N/C–H
Notes
Bond Formation in Highly Enantioselective Yttrium(III)-Catalyzed Hy-
droamination. ACS Catal., 2011, 1, 1637-1642. (b) Leitch, D. C.; Platel,
R. H.; Schafer, L. L. Mechanistic Elucidation of Intramolecular Aminoal-
kene Hydroamination Catalyzed by a Tethered Bis(ureate) Complex:
Evidence for Proton-Assisted C–N Bond Formation at Zirconium. J. Am.
Chem. Soc. 2011, 133, 15453-15463. (c) Dunne, J. F.; Fulton, D. B.;
Ellern, A.; Sadow, A. D. Concerted C−N and C−H Bond Formation in a
Magnesium-Catalyzed Hydroamination. J. Am. Chem. Soc. 2010, 132,
The authors declare no competing financial interests.
ACKNOWLEDGMENT
Financial supports from MENSR, Univ Paris Sud, CNRS, the
Spanish MINECO: CTQ2017-87889-P, Red ORFEO-CINQA
(CTQ2016-81797-REDC) and FPI grant to P. Gómez-Orellana,
are gratefully acknowledged.
1
7680-17683. (d) Arrowsmith, M.; Crimmin, M. R.; Barrett, A. G. M.;
Hill, M. S.; Kociak-Köhn, G.; Procopiou, P. A. Cation Charge Density
and Precatalyst Selection in Group 2-Catalyzed Aminoalkene Hydroami-
nation. Organometallics 2011, 30, 1493-1506. (e) Tobisch, S. Mechanistic
elucidation of the yttrium(III)-catalysed intramolecular aminoalkene
hydroamination: DFT favours a stepwise σ-insertive mechanism. Dalton
Trans. 2012, 41, 9182-9191.
REFERENCES
(1) (a) Huang, L.; Arndt, M.; Gooßen, K.; Heydt, H.; Gooßen, L. J.
(10) Related DFT analysis of hydroamination reactions: (a) Couce-
Rios, A.; Lledós, A.; Ujaque, G. The Origin of Anti-Markovnikov Regi-
oselectivity in Alkene Hydroamination Reactions Catalyzed by
Late Transition Metal-Catalyzed Hydroamination and Hydroamidation.
Chem. Rev. 2015, 115, 2596-2697. (b) Bernoud, E.; Lepori, C.; Mellah,
M.; Schulz, E.; Hannedouche, J. Recent advances in metal free- and late
transition metal-catalysed hydroamination of unactivated alkenes. Catal.
Sci. Technol. 2015, 5, 2017-2037. (c) Lepori, C.; Hannedouche, J. First-
Row Late Transition Metals for Catalytic (Formal) Hydro-amination of
Unactivated Alkenes. Synthesis 2017, 49, 1158-1167. (d) Hesp K. D.;
Stradiotto, M. Rhodium- and Iridium-Catalyzed Hydroamination of Al-
kenes. ChemCatChem 2010, 2, 1192-1207.
+
[Rh(DPEphos)] .Chem. Eur. J. 2016, 22, 9311-9320. (b) Couce-Rios, A.;
Kovács, G.; Ujaque, G.; Lledós, A. Hydroamination of C–C Multiple
Bonds with Hydrazine Catalyzed by N-Heterocyclic Carbene–Gold(I)
Complexes: Substrate and Ligand Effects. ACS Catal. 2015, 5, 815-829.
(c) Kovács, G.; Lledós, A.; Ujaque, G. Hydroamination of Alkynes with
Ammonia: Unforeseen Role of the Gold(I) Catalyst. Angew. Chem. Int.
Ed. 2011, 50, 11147-11151. (d) Strom, A. E.; Balcells, D.; Hartwig, J. F.
Synthetic and Computational Studies on the Rhodium-Catalyzed Hy-
(2) (a) Chilleck, M. A.; Hartenstein, L.; Braun, T.; Roesky, P. W.;
Braun B. Cationic Zinc Organyls as Precatalysts for Hydroamination
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droamination of Aminoalkenes. ACS Catal. 2016, 6, 5651-5665. (e)
Tobisch, S. CuH-catalysed hydroamination of arylalkynes with hydroxyl-
amine esters – a computational scrutiny of rival mechanistic pathways.
Chem. Sci. 2017, 8, 4410-4423.
(11) Optimization geometries and Gibbs energies are computed in tolu-
ene at M06 level; for Co the SDD pseudopotential along with its associat-
ed basis set, adding f orbitals, and a triple-ς basis set for the rest of atoms
6
was employed.
(
12) Monitoring the reaction of 1a-Co (1 equiv) and 2b (2 equiv) at
1
90°C by H NMR experiments reveals full disappearance of the methyl
signals of CH SiMe fragment of 1a-Co in less than 10 minutes. Addition-
ally, no induction period was noticed under catalytic conditions.
13) This dimer is also generated under stoichiometric reaction condi-
tions.
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