Hydrogen-Bond-Promoted Metal-Free Hydroamination of Alkynes

Article abstract of DOI:10.1055/s-0039-1690988

An original metal-free regio- A nd stereoselective intermolecular hydroamination of alkynes is described. Various (E)-enamines were obtained from arylacetylenes and aliphatic secondary amines in the presence of ethylene glycol as a solvent. The latter is

Full text of DOI:10.1055/s-0039-1690988

SYNLETT
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© Georg Thieme Verlag Stuttgart · New York
2019, 30, A–E
letter
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J. Bahri et al.
Letter
Synlett
Hydrogen-Bond-Promoted Metal-Free Hydroamination of
Alkynes
Janet Bahria
0
0
0
0-0
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0
2-8
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3
9-9
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Alk1
Alk1
Alk2
Nour Tanbouzab
Thierry Ollevier*b
Marc Taillefer*a
0
0
0
0-0
0
0
2-9
7
2
9-
0
9
1
8
N
ethylene glycol
150 °C, 8 h
+
HN
Alk2
0
0
0
0-0
0
0
2-6
0
8
4-
7
9
5
4
R
R
0
0
0
0-0
0
0
3-
2
9
9
1-5
4
1
8
No metal catalyst
Florian Monnier*a,c
0
0
0
0-0
0
0
2-9
9
2
4-
2
0
1
2
Stereo- and regioselective
30 examples
a École Nationale Supérieure de Chimie de Montpellier, Institut
Charles Gerhardt, CNRS UMR 5253, AM2N, 8 rue de l’école
normale, 34296 Montpellier Cedex 05, France
marc.taillefer@enscm.fr
b Département de Chimie, 1045 avenue de la Médecine, Université
Laval, Québec, QC, G1V 0A6, Canada
Yields of up to 96%
thierry.ollevier@chm.ulaval.ca
c IUF Institut Universitaire de France, 1 rue Descartes, 75231 Paris,
France
florian.monnier@enscm.fr
Received: 07.08.2019
Accepted after revision: 09.09.2019
Published online: 07.10.2019
1,4-disubstituted (1E,3E)-1,4-dienes regioselectively15 and
by CuCN to produce anti-Markovnikov (E)-enamines.16 The
use of hydroxylamines and hydrazines to perform metal-
free hydroamination of alkynes has also been reported.17,18
Inspired by these results, we investigated the possibility of
conducting a catalyst-free hydroamination of alkynes to
form enamines from arylacetylenes and secondary aliphat-
ic amines. Here, we report the first example of a metal- and
additive-free hydroamination of alkynes with secondary
amines. This metal-free and atom-economic reaction uses
the green solvent ethylene glycol (EG), which is presumed
to be involved in driving the reaction forward. EG is recog-
nized as green because it can be produced sustainably from
biomass and is also a byproduct of the petrochemical indus-
try.19 Therefore, this is an appealing and original method for
the stereoselective (only the (E)-enamine is obtained),
efficient, and environmentally friendly synthesis of anti-
Markovnikov enamines.
Our initial experiments were performed by using ethyn-
ylbenzene (1a) and dibutylamine (2a; 3 equiv) as model
substrates in various solvents at 135 °C. No reactivity was
detected in MeCN or THF, but traces of the anti-Mar-
kovnikov enamine 3a were obtained in N-methylpyrrolidi-
none (NMP) (Table 1, entries 1–3). Slightly better yields
were obtained by using hexan-1-ol as an alcoholic medium
(entry 4). An encouraging yield of 50% of 3a, albeit with in-
complete conversion, was obtained by using EG as solvent
(entry 5). Lower yields were obtained in diethylene glycol,
triethylene glycol, or pinacol (entries 6–8). Therefore, we
continued our studies by using ethylene glycol and raising
the temperature from 135 °C to 150 °C. Doing so afforded
an excellent 98% yield of the anti-Markovnikov enamine
(E)-3a (entry 9). We found that when three equivalents of
ethylene glycol were used in the reaction of ethynylben-
zene (1a) with dibutylamine (2a) at 150 °C for eight hours,
only a 76% yield of the corresponding enamine was ob-
DOI: 10.1055/s-0039-1690988; Art ID: st-2019-d0415-l
Abstract An original metal-free regio- and stereoselective intermolecular
hydroamination of alkynes is described. Various (E)-enamines were ob-
tained from arylacetylenes and aliphatic secondary amines in the pres-
ence of ethylene glycol as a solvent. The latter is assumed to play a ma-
jor role in the mechanism through hydrogen bonding and proton
exchange.
Key words hydroamination, alkynes, amines, metal-free, enamines,
green chemistry
Developing and streamlining the construction of C–N
bonds constitutes an important goal in organic synthesis.
Nitrogen-containing molecules are often used as synthetic
intermediates,1 and they are present in a plethora of natural
substances.2 Among these, enamines are interesting build-
ing blocks because of their versatile reactivity toward al-
kylation, cycloaddition, and a range of related bond-
forming reactions for heterocycle synthesis.3 Hydroamina-
tion of alkynes is an atom-efficient process that affords
enamines through Markovnikov or anti-Markovnikov direct
addition of an amine onto an unsaturated C≡C bond.4 This
transformation is often catalyzed by systems involving lan-
thanides,5 alkaline earth metals,6 acids,7 bases,8 or transi-
tion metals.4e,9 Catalytic systems based on Pd,10 Rh,11 and
Au12 have been successfully used, but they exhibit limita-
tions that include the cost and toxicity of reagents, narrow
reaction scope, and poor functional-group compatibility.
Copper also shows an interesting catalytic activity for this
transformation.13,14 The ability of copper systems to cata-
lyze the intramolecular hydroamination of alkynes has
been known for decades13 but there are few intermolecular
examples of this reaction.14 Recently, our group showed
that this transformation can be catalyzed by CuCl to afford
© 2019. Thieme. All rights reserved. Synlett 2019, 30, A–E
Georg Thieme Verlag KG, Rüdigerstraße 14, 70469 Stuttgart, Germany

B
J. Bahri et al.
Letter
Synlett
tained (entry 10). Decreasing the amount of the amine from
three to two equivalents lowered the yield to 70% (entry
11), whereas the use of only one equivalent of the amine
led to a 40% yield of 3a (entry 12). Microwave irradiation
did not reduce the reaction time for this transformation, as
only 15% of the expected product was obtained after 15
minutes at 150 °C (entry 13). Other solvents were tried, but
led to poor conversions (see the Supporting Information).
Consequently, further screening was conducted with two
equivalents of the amine in EG at 150 °C for eight hours.
and thiomorpholine (2i) afforded the desired anti-Mar-
kovnikov compounds 3f, 3g, and 3i in good to excellent iso-
lated yields (80–98%). With piperidine (2e) or N-methylpip-
erazine (2h), a 70% yield of the corresponding anti-
Markovnikov products 3e and 3h were obtained but when
five equivalents of the amines were used, the yields in-
creased to 90 and 91%, respectively. It should be noted that
no reactivity was observed with aliphatic or internal
alkynes, nor with primary or aromatic amines. The differ-
ence in the reactivity of the amines appears to correlate
with their acidity/basicity and nucleophilicity; however,
these differences cannot be rationalized at this stage.
Table 1 Hydroamination of Ethynylbenzene with Dibutylamine in Vari-
ous Solventsa,b
Alk1
n-Bu
Alk1
N
n-Bu
ethylene glycol
solvent
N
+
Ph
HN
Ph
Alk2
HN
Ph
+
150 °C, 8 h
Alk2
T °C, 8 h
Ph
n-Bu
n-Bu
1a
2a–i
3a–i
(E)-3a
1a
2a
n-Bu
n-Bu
n-Pent
N
n-Pr
n-Pr
Entry
Solvent
2a (equiv)
Temp (°C)
Yield (%)
N
N
Ph
Ph
n-Pent
Ph
1
2
MeCN
THF
3
3
3
3
3
3
3
3
3
3
2
1
3
135
135
135
135
135
135
135
135
150
150
150
150
MWd
NR
NR
9
3a (98%)
3b (60%), (75%)a
3c (96%),a (95%)b
3
NMP
n-Bu
N
N
N
4
hexan-1-ol
EG
17
50
34
28
26
98
76
70
40
15
Ph
Ph
Ph
Ph
Et
5
3d (80%)
3e (70%), (90%)a
3f (95%)
6
diethylene glycol
N
S
7
triethylene glycol
N
N
N
O
Ph
Ph
8
pinacol
EG
3h (70%), (91%)a
9
3g (98%)
3i (80%)
10
11
12
13
EGc
EG
Scheme 1 Hydroamination of phenylacetylene with various aliphatic
secondary amines. Reagents and conditions: 1a (0.5 mmol), amine (1.5
mmol), 150 °C, 8 h, ethylene glycol (250 L). a General conditions, but
with 2.5 mmol of amine.b Performed on a gram scale.
EG
EG
a Reaction conditions: 1a (0.5 mmol), 2a (1.5 mmol), solvent (250 L),
Next, we studied the influence of aromatic substituents
on the terminal aromatic alkynes (Scheme 2). Reactions of
derivatives of arylacetylenes bearing electron-donating
groups such as methyl or ethyl in the para-position were
tolerant toward both cyclic and acyclic secondary amines,
the corresponding enamines 3j–o being obtained in good
yields (70–88%). Electron-withdrawing groups, such as halo
substituents, in the meta- or para-positions showed better
reactivity with various secondary cyclic or acyclic amines,
and afforded the anti-Markovnikov (E)-enamines 3p–t in
excellent yields (81–98%). 1-Ethynyl-4-nitrobenzene and 1-
ethynyl-3,5-bis(trifluoromethyl)benzene were also con-
verted into the corresponding enamines 3u, 3v, and 3w in
excellent yields. We then proceeded to examine the reac-
tions of heterocyclic acetylenes, and we found that 3-ethyn-
ylpyridine reacted with both cyclic and acyclic secondary
amines to give the corresponding hydroamination products
3x–z in excellent yields (95–96%). Products 3aa–ad were
obtained in yields ranging from 90 to 98% by the reaction of
2-ethynylpyridine with butyl(ethyl)amine, dipropylamine,
135 °C, 8 h, sealed vessel.
b NMR yield determined by using 1,3,5-trimethoxybenzene as internal stan-
dard.
c Reaction performed in the presence of three equivalents of ethylene gly-
col.
d Reaction performed under microwave irradiation at 150 °C and 200 °C for
15 min.
We then explored the substrate scope and functional-
group tolerance of the reaction under the optimized condi-
tions (Table 1, entry 9). Symmetrical and unsymmetrical
secondary aliphatic amines, such as dipentylamine (2b),
dipropylamine (2c), or butyl(ethyl)amine (2d), readily re-
acted with ethynylbenzene (1a) to give the anti-Mar-
kovnikov enamines 3b–d in good to excellent isolated yields
(60–96%) (Scheme 1). In the case of 3b, the use of five
equivalents of the corresponding amine improved the yield
from 60 to 75%. The reaction of ethynylbenzene with amine
2c proceeded on a gram scale with an unchanged yield. In
the cases of cyclic secondary amines, those bearing differ-
ent heteroatoms, such as azepane (2f), morpholine (2g),
© 2019. Thieme. All rights reserved. Synlett 2019, 30, A–E

C
J. Bahri et al.
Letter
Synlett
Alk1
Alk2
Alk1
Alk2
ethylene glycol
150 °C, 8 h
N
+
(Het)Ar
HN
(Het)Ar
3j–ad
Et
Et
N
n-Pr
N
N
N
N
N
N
n-Bu
Et
n-Bu Et
n-Pr Et
3j (83%)
3k (81%)
3l (85%)
3q (90%)
3m (75%)
3r (81%)
3n (88%)
3s (91%)
n-Pr
n-Pr
n-Pr
n-Pr
N
N
N
N
N
N
Et
Br
Br
Br
F
3o (70%)
3p (95%)
F3C
Et
i-Pr
i-Pr
N
N
N
O
N
O
N
N
N
O2N
n-Bu
O2N
N
F
F3C
3t (90%)
3u (93%), neat
3v (91%), neat
3w (95%), neat
3x (96%)
Et
n-Pr
N
N
N
O
N
N
O
N
N
n-Bu
n-Pr
N
N
N
N
N
N
3y (95%)
3z (95%)
3aa (98%)
3ab (90%)
3ac (97%)
3ad (98%)
Scheme 2 Hydroamination-substituted (het)arylacetylenes with aliphatic secondary amines. Reagents and conditions: arylacetylene (0.5 mmol), amine
(2.5 mmol), 150 °C, 8 h, ethylene glycol (250 L).
N-methylpiperazine, and morpholine. This protocol exhib-
its excellent regio- and stereoselectivity, is experimentally
simple to carry out, and does not require the presence of
any catalyst or additive. At the end of the reaction, a simple
extraction to remove the ethylene glycol suffices, while the ex-
cess amine was removed under vacuum to furnish the pure
product.20
A radical mechanism was ruled out, as the addition of
trapping agents such as galvinoxyl, TEMPO, or 2,6-di-tert-
butylphenol did not inhibit the hydroamination reaction of
ethynylbenzene (1a) with dipropylamine (2c); no products
derived from a radical species were detected under these
conditions. We then examined the possible involvement of
hydrogen bonds between the amine and ethylene glycol as
a driving force for this reaction by conducting the model re-
action in 2-methoxyethanol and in 1,2-dimethoxyethane
under the standard conditions (150 °C, 8 h; Scheme 3).21
The provision of one hydrogen bond from 2-methoxyetha-
nol halved the yield of the enamine (50%). When both hy-
drogen-bonding sites were eliminated by using 1,2-dime-
thoxyethane, the reaction did not proceed at all. Therefore,
the presence of the two hydroxy groups of ethylene glycol ap-
pears to be crucial to approach a quantitative conversion (98%).
The hydroamination of ethynylbenzene (1a) with dipro-
pylamine (2c) was then carried out under standard condi-
tions (150 °C, 8 h) in ethylene glycol-d2 to test for scram-
bling (Scheme 4). This experiment led to the formation of a
mixture of four compounds 3c, 3c′, 3c′′, and 3c′′′ in a
57:14:15:14 ratio. The detection of 3c as the major product
might correspond to the addition of the nitrogen atom to
the less-hindered carbon atom, followed by the reduction of
the triple bonds by abstraction of hydrogen from the amine
(Scheme 4, path A). The formation of 3c′, albeit in a lower
yield, might result from the abstraction of deuterium from
ethylene glycol-d2 (Scheme 4, path B). Products 3c′′ and 3c′′′
are formed by a similar type of mechanism (routes A′ and
B′, respectively) from the deuterated ethynylbenzene 1a′
formed in situ. We indeed observed in blank experiments
performed under the standard conditions that a significant
amount (35%) of 1a′ was formed as a result of exchange be-
tween the acetylenic proton of ethynylbenzene and eth-
ylene glycol-d2 is formed (Scheme 4).
A preliminary exchange between the deuterated eth-
ylene glycol and the N–H proton of the dipropylamine
might also explain the formation of 3c′ and 3c′′′ from 1a
and 1a′, respectively. These results support the conclusion
that ethylene glycol facilitates proton transfer between the
amine and alkyne reactants.
n-Pr
n-Pr
solvent
N
HN
Ph
+
Ph
H
n-Pr
150 °C, 8 h
n-Pr
1a
2c
(E)-3c
Me
O
O Me
solvent
Me
O
O
H
O
H
O
In summary, we have reported an unprecedented meth-
od for the regio- and stereoselective hydroamination of
range of aromatic terminal acetylenes with aliphatic sec-
ondary amines under metal-free conditions.22 The ethylene
yield of 3c
0%
50%
98%
Scheme 3 Impact of the number of hydroxy groups of the solvent on
the yield of enamine 3c
© 2019. Thieme. All rights reserved. Synlett 2019, 30, A–E

D
J. Bahri et al.
Letter
Synlett
1994, 523. (c) Kobayashi, S.; Ishitani, H. Chem. Rev. 1999, 99,
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n-Pr
n-Pr
1a
Ph
H
+
HN
2c
150 °C, 8 h
(4) For reviews on hydroamination, see: (a) Müller, T. E.; Beller, M.
Chem. Rev. 1998, 98, 675. (b) Alonso, F.; Beletskaya, I. P.; Yus, M.
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Wiley-VCH: Weinheim, 2014, Chap. 15, 1135.
DO
OD
H
n-Pr
D
n-Pr
H
n-Pr
D
n-Pr
n-Pr
N
N
N
N
Ph
n-Pr
Ph
n-Pr
Ph
n-Pr
Ph
H
H
D
D
3c (57%)
3c" (15%)
3c' (14%)
3c''' (14%)
D
O
O
D
D
O
O
D
n-Pr
n-Pr
H
N
H
N
A'
B'
n-Pr
n-Pr
A
B
(5) (a) Hong, S.; Marks, T. J. Acc. Chem. Res. 2004, 37, 673.
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rahedron Lett. 2014, 55, 1310. (f) Patel, M.; Saunthwal, R. K.;
Verma, A. K. Acc. Chem. Res. 2017, 50, 240.
Ph
D
Ph
H
1a'
1a
DO
OD
Ph
D
1a' (35%)
Ph
H
150 °C, 3 h
1a
Scheme 4 Control experiments involving deuterated species
glycol solvent appears to promote this reaction through a
mechanism that might involve hydrogen bonding and pro-
ton exchange. Work is now in progress to extend the appli-
cation of this protocol and to understand the mechanism of
this system in more detail.
Funding Information
Financial support from ANR CD2I (Agence Nationale de la Recherche),
IUF, and CNRS is acknowledged. The authors thank the FRQNT Centre
in Green Chemistry and Catalysis (CGCC) Strategic Cluster FRQNT-
2020-RS4-265155-CCVC.
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Acknowledgment
(9) (a) Doucet, H.; Bruneau, C.; Dixneuf, P. H. Synlett 1997, 807.
(b) Leitch, D. C.; Payne, P. R.; Dunbar, C. R.; Schafer, L. L. J. Am.
Chem. Soc. 2009, 131, 18246. (c) Kocięcka, P.; Czcluśniak, I.;
Szymańska-Buzar, T. Adv. Synth. Catal. 2014, 356, 3319.
(d) Slagbrand, T.; Vockov, A.; Trillo, P.; Tinnis, F.; Adolfsson, H.
ACS Catal. 2017, 7, 1771.
(10) For Pd-catalyzed hydroamination, see: (a) Shimada, T.;
Yamamoto, Y. J. Am. Chem. Soc. 2002, 124, 12670. (b) Salman, G.
A.; Hussain, M.; Iaroshenko, V.; Villinger, A.; Langer, P. Adv.
Synth. Catal. 2011, 353, 331. (c) Bernhammer, J. C.; Chong, N. X.;
Jothibasu, R.; Zhou, B.; Huynh, H. V. Organometallics 2014, 33,
3607. (d) Banerjee, D.; Junge, K.; Beller, M. Angew. Chem. Int. Ed.
2014, 53, 1630; Corrigendum: Angew. Chem. Int. Ed. 2017, 56,
16436. (e) Lhristodoulou, M. S.; Giofrè, S.; Broggini, G.; Mazza,
A.; Sala, R.; Beccalli, E. M. Eur. J. Org. Chem. 2018, 6176. (f) Park,
S.; Malcolmson, S. J. ACS Catal. 2018, 8, 8468.
J.B. thanks FRQNT for an International Training Scholarship. N.T.
thanks the Francis & Geneviève Melançon Foundation for a Graduate
Scholarship. F.M. acknowledges support from IUF.
Supporting Information
Supporting information for this article is available online at
https://doi.org/10.1055/s-0039-1690988.
S
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p
p
orit
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© 2019. Thieme. All rights reserved. Synlett 2019, 30, A–E

E
J. Bahri et al.
Letter
Synlett
Kakiuchi, F. Org. Lett. 2011, 13, 3928. (e) Takano, S.; Kochi, T.;
Kakiuchi, F. Organometallics 2016, 35, 4112. (f) Yang, X.-H.; Lu,
A.; Dong, V. M. J. Am. Chem. Soc. 2017, 139, 14049. (g) Athira, C.;
Changotra, A.; Sunoj, R. B. J. Org. Chem. 2018, 83, 2627. (h) Yang,
S.; Li, Q.; Xu, C.; Xu, Q.; Shi, M. Chem. Sci. 2018, 9, 5074.
Chem. Commun. 2011, 47, 562. (f) Bourgeois, J.; Dion, I.;
Cebrowski, P. H.; Loiseau, F.; Bédard, A.-C.; Beauchemin, A. M.
J. Am. Chem. Soc. 2009, 131, 874. (g) Zhao, S.-B.; Bilodeau, E.;
Lemieux, V.; Beauchemin, A. M. Org. Lett. 2012, 14, 5082.
(h) Beauchemin, A. M. Org. Biomol. Chem. 2013, 11, 7039.
(18) For a metal-free intermolecular hydroamidation of ynamides
with N-sulfonamides, see: Peng, Z.; Zhang, Z.; Tu, Y.; Zeng, X.;
Zhao, J. Org. Lett. 2018, 20, 5688.
(19) Clarke, C. J.; Tu, W.-C.; Levers, O.; Bröhl, A.; Hallett, J. P. Chem.
Rev. 2018, 118, 747.
(20) It is also possible to recover the unused amine in a cold trap and
then totally recycle it.
(12) For Au-catalyzed hydroamination, see: (a) Kang, J.-E.; Kim, H.-
B.; Lee, J.-W.; Shin, S. Org. Lett. 2006, 8, 3537. (b) Lavallo, V.;
Frey, G. D.; Donnadieu, B.; Soleilhavoup, M.; Bertrand, G. Angew.
Chem. Int. Ed. 2008, 47, 5224. (c) Zeng, X.; Frey, G. D.; Kinjo, R.;
Donnadieu, B.; Bertrand, G. J. Am. Chem. Soc. 2009, 131, 8690.
(d) Couce-Rios, A.; Kovács, G.; Ujaque, G.; Lledós, A. ACS Catal.
2015, 5, 815. (e) Timmerman, J. C.; Robertson, B. D.;
Widenhoefer, R. A. Angew. Chem. Int. Ed. 2015, 54, 2251.
(f) Wang, Y.; Ling, B.; Li, P.; Bi, S. Organometallics 2018, 37, 3035.
(g) Liu, D.; Nie, Q.; Zhang, R.; Cai, M. Adv. Synth. Catal. 2018, 360,
3940. (h) Baron, M.; Battistel, E.; Tubaro, C.; Biffis, A.; Armelao,
L.; Ramcan, M.; Graiff, C. Organometallics 2018, 37, 4213.
(13) (a) Stephens, R. D.; Castro, C. E. J. Org. Chem. 1963, 28, 2163.
(b) Stephens, R. D.; Castro, C. E. J. Org. Chem. 1963, 28, 3313.
(c) Kimura, M.; Kure, S.; Yoshida, Z.; Tanaka, S.; Fugami, K.;
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(21) Propargyl alcohol and oct-1-yne have also been tested; how-
ever, no product was obtained. This probably demonstrates that
the solvent is the sole source of hydrogen bonding.
(22) Hydroamination of Alkynes with Amines; General Procedure
Under an atmosphere of argon, a screw-cap vial was charged
with ethylene glycol (250 L, 8.9 equiv) and the appropriate
alkyne (0.5 mmol, 1 equiv) and amine (2.5 mmol) at r.t. The
tube was sealed under a positive pressure of argon and the
mixture was stirred and heated to 150 °C for 8 h. The mixture
was cooled to r.t., diluted with EtOAc (5 mL), and washed with
H2O (3 × 2 mL) and brine (1 × 2 mL). The organic phase was
dried (MgSO4), filtered, and concentrated under reduced pres-
sure (rotary evaporator). Excess amine was then removed from
the residue under high vacuum to give the desired enamine
without any need for further purification. In the case of amines
with high boiling points, such as dibutylamine or dipentyl-
amine, the residues were dried by heating to 50 °C under high
vacuum.
(14) (a) Zhou, L.; Bohle, D. S.; Jiang, H.-F.; Li, C.-J. Synlett 2009, 937.
(b) Robbins, D. W.; Hartwig, J. F. Science 2011, 333, 1423. (c) Shi,
S.-L.; Buchwald, S. L. Nat. Chem. 2015, 7, 38.
(15) Bahri, J.; Jamoussi, B.; Lee, A. V. D.; Taillefer, M.; Monnier, F. Org.
Lett. 2015, 17, 1224.
(16) Bahri, J.; Blieck, R.; Jamoussi, B.; Taillefer, M.; Monnier, M. Chem.
Commun. 2015, 51, 11210.
(17) Beauchemin’s group has recently developed a series of Cope-
type hydroaminations of alkenes and alkynes; see:
(a) Beauchemin, A. M.; Moran, J.; Lebrun, M.-E.; Séguin, C.;
Dimitrijevic, E.; Zhang, L.; Gorelsky, S. I. Angew. Chem. Int. Ed.
2008, 47, 1410. (b) Cebrowski, P. H.; Roveda, J. G.; Moran, J.;
Gorelsky, S. I.; Beauchemin, A. M. Chem. Commun. 2008, 492.
(c) Moran, J.; Gorelsky, S. I.; Dimitrijevic, E.; Lebrun, M. E.;
Bédard, A.-C.; Séguin, C.; Beauchemin, A. M. J. Am. Chem. Soc.
2008, 130, 17893. (d) Moran, J.; Pfeiffer, J. Y.; Gorelsky, S. I.;
Beauchemin, A. M. Org. Lett. 2009, 11, 1895. (e) Loiseau, F.;
Clavette, C.; Raymond, M.; Roveda, J. G.; Beauchemin, A. M.
(E)-N,N-Dipentyl-2-phenylethylenamine (3b)
1
Solid; yield: 97 mg (75%). H NMR (400 MHz, CDCl3):  = 7.20–
7.14 (m, 4 H), 6.95–6.92 (m, 1 H), 6.76 (d, J = 14 Hz, 1 H), 5.07 (d,
J = 14 Hz, 1 H), 3.07 (t, J = 7.1 Hz, 4 H), 1.60–1.54 (m, 4 H), 1.39–
1.33 (m, 4 H), 1.33–1.28 (m, 4 H), 0.92 (t, J = 7.2 Hz, 6 H). 13C
NMR (100 MHz, CDCl3):  = 140.4, 138.5, 128.5, 123, 122.5, 96.3,
51.7, 29.2, 27.6, 22.5, 14.1. HRMS (ESI-TOF): m/z [M + H]+ Calcd
for C18H30N: 260.2300; found: 260.2301.
© 2019. Thieme. All rights reserved. Synlett 2019, 30, A–E