FeCl3·6H2O and TfOH as catalysts for allylic amination reaction: A comparative study

Article abstract of DOI:10.1002/ejoc.201101844

The use of FeCl₃·6H₂O and TfOH as readily available and easy-to-handle catalysts for the direct allylic amination reaction using a wide variety of nitrogenated nucleophiles onto different free allylic alcohols is described. Comparative studies between these catalysts, as representative Lewis and Bronsted acids are conducted, concluding that both are suitable catalysts for this transformation. The reactions are performed in a flask open to air and using technical grade 1,4-dioxane. In light of the results obtained from this study it can be asserted that TfOH turned out to be slightly superior than the Fe^III salt since similar or better yields are obtained in most of the cases using lower catalyst loadings and milder reaction conditions. A similar trend is observed when carbonucleophiles were employed in the allylic substitution reaction. Studies for the elucidation of the reaction mechanism are in agreement with a carbocationic intermediate, being the regioselectivity governed by the stability of the final product. Copyright

Full text of DOI:10.1002/ejoc.201101844

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FULL PAPER
DOI: 10.1002/ejoc.201101844
FeCl3·6H2O and TfOH as Catalysts for Allylic Amination Reaction:
A Comparative Study
Paz Trillo,[a] Alejandro Baeza,[a] and Carmen Nájera*[a]
Dedicated to the memory of Professor Balbino Mancheño
Keywords: Homogeneous catalysis / Iron / Amination / Allylic compounds / Nucleophilic substitution
The use of FeCl3·6H2O and TfOH as readily available and
easy-to-handle catalysts for the direct allylic amination reac-
tion using a wide variety of nitrogenated nucleophiles onto
different free allylic alcohols is described. Comparative stud-
ies between these catalysts, as representative Lewis and
Brønsted acids are conducted, concluding that both are suit-
able catalysts for this transformation. The reactions are per-
formed in a flask open to air and using technical grade 1,4-
dioxane. In light of the results obtained from this study it can
be asserted that TfOH turned out to be slightly superior than
the FeIII salt since similar or better yields are obtained in most
of the cases using lower catalyst loadings and milder reaction
conditions. A similar trend is observed when carbonucleo-
philes were employed in the allylic substitution reaction.
Studies for the elucidation of the reaction mechanism are in
agreement with a carbocationic intermediate, being the re-
gioselectivity governed by the stability of the final product.
sition metal complexes or salts have been described to ef-
ficiently accomplish this purpose.[1b] Thus, from the first
group, it is worth to mention the employment of sulfonic
acids[3] and iodine[4] as allylic amination reaction catalysts.
Notably more extended is the use metal complexes and salts
Introduction
The intermolecular allylic amination is one of the most
straightforward methods to get access to different allylic
amines. However, it has been considered as low atom-econ-
omy process due to the use of allylic alcohols derivatives.
In this sense, free allylic alcohols are becoming common
substrates in these allylic amination reactions because they
are readily available and do not require a previous manipu-
lation, which implies the formation of a stoichiometric
amount of salt waste, in order to activate the hydroxy func-
tionality. In addition, the global process can be considered
as environmental friendly, sustainable and with a perfect
atom economy, generating water as the only by-product.[1]
However, the use of free allylic alcohols has two main
problems: the poor ability of the hydroxy function as leav-
ing group and the formation a stoichiometric amount of
water which requires the use of a water tolerant catalyst.
Those are the reasons why it was not until 2002 when the
group of Ozawa reported a breakthrough in this field by
using a cationic PdII complex for the intermolecular amin-
ation of free allylic alcohols with anilines as nitrogenated
nucleophiles.[2] Since then, not only palladium catalysts[1a]
but also others based on Brønsted or Lewis acids and tran-
based on PtII,[5] MoVI,[6] BiIII [7] InIII [8] FeIII [9] AgI,[10]
, ,
,
AuI[10,11] and AuIII[11] to carry out this transformation,
working under different types of mechanism. Thus, the for-
mation of a π-allyl intermediate is assumed when metal
salts or complexes derived PdII[1a] or PtII[5] are employed,
whereas the use of gold and silver salts seems to imply a
hydroamination type reaction through a double bond acti-
vation.[10,11a] Finally, when typical Lewis or Brønsted acids
act as catalysts of such transformation, carbocationic inter-
mediates are normally postulated.[1b]
Among all the above mentioned salts and complexes, the
use of inexpensive and accessible catalysts, such as iron(III)
salts, are highly desirable. In this sense, the group of Jana
has recently described the use of anhydrous FeCl3 acting
as catalyst of different allylic substitution reactions using
activated free allylic alcohols as substrates under anhydrous
conditions.[9] In addition, the use of a Brønsted acid as cata-
lyst for this transformation have been scarcely reported.[3]
Therefore, the scope of the direct allylic amination of free
allylic alcohols using TfOH as representative catalyst would
be of interest.
[a] Departamento de Química Orgánica, Facultad de Ciencias, and
Instituto de Síntesis Orgánica (ISO), Universidad de Alicante,
Apdo. 99, 03080 Alicante, Spain
Here, we present a comprehensive comparative study be-
tween the intermolecular reaction of free allylic alcohols
with different nitrogen- and carbo-nucleophiles catalyzed
by inexpensive FeCl3·6H2O and TfOH as two readily avail-
Fax: +34-96-5903549
E-mail: cnajera@ua.es
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201101844.
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FULL PAPER
able and easy-to-handle representative examples of Lewis tries 1 and 2). When the more basic sulfonamide 2b was
and Brønsted acids-based catalysts using technical grade employed, high yields were obtained with FeCl3·6H2O
solvents reaction flasks open to air.
(Table 2, Entry 3). However, the TfOH catalyzed reaction
gave rise to the amination product 3ab in modest yields
(Table 2, Entry 4). Similar behavior was observed when the
4-substituted arylsulfonamides 2c and 2d were used as
nitrogenated nucleophiles regardless the electronic proper-
ties of the para-substituent. In both cases, excellent results
were achieved when the reaction was conducted at 50 °C
using iron(III) chloride and TfOH as catalysts (Table 2, En-
tries 5–8). High yields were also obtained with methanesul-
fonamide (2e) (Table 2, Entries 9 and 10). Finally, the fluo-
rescent sulfonamide dansylamide (2f) was tested, giving rise
to the corresponding amination product 3af in modest
yields at the best, even when more forcing conditions or
higher catalysts loading were employed (Table 2, Entries 11
and 12). Next, benzyl carbamate (2g) was examined as nu-
cleophile achieving excellent yields in both cases (Table 2,
Entries 13 and 14). A similar result was obtained when tert-
butyl carbamate (2h) was employed in the case of the
iron(III) salt. Surprisingly, high yields were also obtained
under Brønsted acid catalysis (Table 2, Entries 15 and 16).
The use of benzamide (2i) led to the formation of the prod-
uct 3ai in high yields (Table 2, Entries 17 and 18) although
when FeCl3·6H2O was used as catalyst, heating at 50 °C
was necessary to get comparable results to those obtained
with TfOH.
Results and Discussion
Firstly, the search for the optimal reaction conditions
was tackled. In this context, the reaction between (E)-1,3-
diphenylprop-2-en-1-ol (1a) and p-toluenesulfonamide (2a)
in 1,4-dioxane was chosen as a model reaction (Scheme 1)
conducting a parallel study with different iron sources and
TfOH (Table 1). Two different iron oxides, magnetite
among them, were tested but did not produce any result
(Table 1, Entries 1 and 2) even when more forcing condi-
tions (90 °C) and higher catalyst loadings (10 mol-%) were
employed. Anhydrous iron(III) chloride was then examined,
leading to the corresponding amination product 3aa in high
yields when 5 mol-% of catalyst loading was used at room
temperature (Table 1, Entry 3). Exactly the same results
were obtained when the reaction was conducted with the
more easy-to-handle FeCl3·6H2O under the same reaction
conditions (Table 1, Entry 4). The reaction ran also to com-
pletion even when 2.5 mol-% of FeCl3·6H2O was used as
catalyst loading, but heating at 80 °C was necessary
(Table 1, Entry 5). Finally TfOH was also screened as cata-
lyst for the direct allylic amination of alcohol 1a with sulf-
onamide 2a. In this case only 1 mol-% was enough to pro-
mote the reaction in excellent yields (Table 1, Entry 6). In
all the cases the reactions were performed in flasks open to
air using technical grade 1,4-dioxane.
Scheme 2. Direct allylic amination reaction onto alcohol 1a.
Allylic alcohol 1a was also submitted to the direct amin-
ation reaction using anilines bearing an electron-with-
drawing group at the 4-position, 2j and 2k, at room tem-
perature affording products 3aj and 3ak in excellent yields,
respectively (Table 2, Entries 19–22). On the contrary, the
more basic N-methylaniline (2l) gave rise, to the corre-
sponding allylaniline 3al in slightly lower yields, and more-
over heating at 50 °C was necessary in order to reach good
results (Table 2, Entries 23 and 24). Finally, benzotriazole
2m was evaluated as nucleophile, obtaining excellent results
with the iron(III) catalyst (Table 2, Entry 25). Surprisingly,
TfOH only produced the corresponding product 3am in
63% yield in spite of using 50 °C as reaction temperature
(Table 2, Entry 26). More basic aliphatic amines such as
BnNH2 and BuNH2, as well as phthalimide and aqueous
Scheme 1. Reaction conditions optimization.
Table 1. Optimization of the reaction conditions.[a]
Entry
Catalyst [mol-%]
T [°C]
Yield [%][b]
1
2
3
4
5
6
Fe2O3 (5)
Fe3O4 (5)
FeCl3 (5)
FeCl3·6H2O (5)
FeCl3·6H2O (2.5)
TfOH (1)
25
25
25
25
80
25
–
–
95 (92)
95 (93)
95 (92)
95 (92)
[a] Reaction conditions: allylic alcohol 1a (1 mmol), TsNH2 2a
(2 equiv.), 1,4-dioxane (2 mL). [b] Calculated from 1H NMR, in
brackets isolated yields after flash chromatography.
In light of the results obtained from the optimization of ammonia failed completely under several reaction condi-
reaction parameters, we decided to further explore the reac- tions evaluated.
tivity of allylic alcohol 1a using different nitrogenated nu-
Once the applicability of this methodology for the direct
cleophiles (Scheme 2). For this purpose FeCl3·6H2O and allylic amination of alcohol 1a with different nitrogenated
TfOH were the catalysts of choice to carry out a compara- nucleophiles has been demonstrated, the scope of the reac-
tive study (Table 2) under the optimized conditions men- tion using different allylic alcohols 1b–1i reacting with p-
tioned above (Table 1, Entries 4 and 6). Firstly, different toluenesulfonamide 2a was taken into account (Table 3).
sulfonamides were tested.[12] Excellent results were obtained Firstly, regioisomeric alcohols 1b and 1c were submitted to
with p-toluenesulfonamide (2a) as nucleophile (Table 2, En- the allylic amination, leading to the formation of the same
2
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Fe Catalyst for Allylic Amination
Table 2. Direct allylic amination of alcohol 1a catalyzed either by FeCl3·6H2O or TfOH.[a]
[a] Reaction conditions: allylic alcohol 1a (1 mmol), R1R2NH 2a–2m (2 equiv.), 1,4-dioxane (2 mL). [b] Isolated yields after flash
chromatography. [c] In brackets isolated yields for the reaction performed at 50 °C.
product 3ba in high yields when FeCl3·6H2O and TfOH in irradiation with FeCl3·6H2O as catalyst (Table 3, Entry 13).
dioxane were used as catalysts, being necessary 50 °C in the Other different substrates such as allyl alcohol, diols [i.e.
former case (Table 3, Entries 1–4). The allylic alcohols 1d but-3-ene-1,2-diol or (Z)-but-2-ene-1,4-diol], diallylic
and 1e proved to be even less reactive, being necessary the alcohols [i.e. (E)-1-phenylpenta-1,4-dien-3-ol or hexa-1,5-
use of higher catalyst loadings and temperatures (Table 3, diene-3,4-diol] and terpene derived allylic alcohols (geraniol
Entries 5–8), giving rise, in both cases, to the same linear and linalool) turned out to be unreactive even when more
allylic sulfonamide 3da in low yields when FeCl3·6H2O was forcing conditions were applied.
used (Table 3, Entries 5 and 7). In contrast, the reaction
Afterwards, we decided to expand the comparative study
performed with 1 mol-% of TfOH at 50 °C afforded the between these two catalysts towards other nucleophiles than
same amination products in better yields (Table 3, Entries nitrogenated. Thus, carbonucleophiles were taken into ac-
6 and 8). Next, cyclic alcohol 1f was examined, obtaining count and were allowed to react with standard allylic
good results in both cases (Table 3, Entries 9 and 10). When alcohol 1a at 50 °C, in 1,4-dioxane for 1 day (Scheme 3).
crotyl alcohol 1g was submitted to the allylic amination re- When allyltrimethylsilane 2n was employed as nucleophile,
action, a mixture of linear and branched regioisomers in very good results were obtained in all the cases (Table 4,
approximately 2:1 ratio was obtained either using Entry 1 and 2). Next, p-anisole 2o and indole 2p were also
FeCl3·6H2O or TfOH as catalysts. Nevertheless, 90 °C and evaluated, obtaining high yields for the Friedel–Crafts alk-
higher catalyst loadings, in the case of the iron(III) salt, ylation products 3ao and 3ap, respectively (Table 4, Entries
were necessary to achieve good results (Table 3, Entries 11 3–6). Finally, high yields were also achieved with
and 12). The diallylic alcohol 1h turned out to be unreactive FeCl3·6H2O as catalyst when diethyl malonate 2q was tested
with the catalysts tested under several conditions (Table 3, as carbonucleophile (Table 4, Entry 7). Surprisingly, the use
Entries 13 and 14) and only a 36% isolated yield was ob- of TfOH did not produce any result despite several reaction
tained when the reaction was performed under microwave conditions evaluated (Table 4, Entry 8). It is important to
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P. Trillo, A. Baeza, C. Nájera
Table 3. Direct allylic amination of alcohols 1b–1h with TsNH2 catalyzed either by FeCl3·6H2O or TfOH.[a]
FULL PAPER
[a] Reaction conditions: allylic alcohol 1b–1i (1 mmol), TsNH2 2a (2 equiv.), 1,4-dioxane (2 mL), 24 h. [b] Isolated yields after flash
chromatography. [c] In brackets, isolated yields when the reaction was carried out under MW irradiation (40 W, 36 psi, T = 90 °C). [d]
Reaction time: 60 min. [e] Reaction time: 30 min. [f] Regiosiomer ratio: 3ga/3gaЈ.
mention that 50 °C were necessary in all the cases using
both catalysts, FeCl3·6H2O and TfOH, in order to achieve
high yields.
Scheme 4. Direct allylic amination using enantioenriched alcohol
1i.
Scheme 3. Allylic substitution reaction using carbonucleophiles.
Although FeCl3·6H2O seems to clearly play a role as ascribed as result of an equilibrium between the formation
Lewis acid activating the hydroxy functionality due to its of the most stable olefin and/or carbocation. The former
oxophilicity and hence, generating carbocationic species, we might be generated prior to the amination reaction through
decided to corroborate this point by submitting the enantio- an isomerisation of the allylic alcohol catalyzed by Lewis
enriched alcohol (S)-1j (65% ee) to the direct allylic amin- or Brønsted acids.[13] In order to confirm this point allylic
ation with TsNH2 2a in 1,4-dioxane under the same condi- alcohol 1c was allowed to react under identical reaction
tions applied to allylic alcohol 1b (Scheme 4). Thus, as ex- conditions described above (Table 3, Entries 3 and 4) in the
pected, the allylic amination product 3ia was obtained in presence of both catalysts, FeCl3·6H2O and TfOH, and
high yield but as racemic mixture, confirming the presence with the absence of any nucleophile. Isomeric alcohol 1b
of a carbocationic intermediate. This reaction mechanism was obtained after 24 h as main product,[14] which explains
was unambiguously assumed when Brønsted acid, TfOH, the same regioselectivity obtained with both substrates.
was the catalyst employed.
Finally and with the aim of gaining more knowledge
Since the hydroamination of the double bond or an all- about the regiochemical course of this transformation, all-
ylic amination through a π-allyl-metal complex was com- ylic alcohol (Z)-4-phenylbut-3-en-2-ol (1bЈ) was submitted
pletely discarded according to the above mentioned experi- to direct allylic amination reaction using TsNH2 (2a) as nu-
ment (Scheme 4), the regioselectivity of the process can be cleophile under the optimized reaction conditions (Table 3,
4
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Fe Catalyst for Allylic Amination
Table 4. Allylic substitution of 1a with carbonucleophiles catalyzed either by FeCl3·6H2O or TfOH.[a]
[a] Reaction conditions: allylic alcohol 1a (1 mmol), 2n–2q (2 equiv.), 1,4-dioxane (2 mL). [b] Isolated yields after flash chromatography.
Entries 1 and 2). After the reaction time, (E)-3ba was ob- mechanism, it can be deduced that both catalysts gave rise
tained as sole isomer (Scheme 5).[15] This evidence, together to a similar cationic intermediates, and the regioselectivity
with the fact that the (E)-isomer of alcohol 1b was obtained of the process can be explained by the stability of the
after 24 h when (Z)-1bЈ was submitted to an identical isom- alcohol intermediacy which is formed as result of an isom-
erization test to that above mentioned for alcohol 1c,[15] erization of the double bond prior the direct nucleophilic
confirmed that the isomerization of the double bond attack occurs or by the stability of the final product.
towards the most energetically favorable isomer, catalyzed
by FeCl3·6H2O and TfOH, takes place before the allylic
amination reaction.
Experimental Section
Typical Procedure for Direct Allylic Amination: To a round-bot-
tomed flask open to air containing the allylic alcohol (1 mmol), the
correspondig nucleophile (2 mmol) and FeCl3·6H2O (see Tables),
1,4-dioxane (2 mL) was added. The reaction mixture was then
stirred for 24 h at the above indicated temperature. TfOH was
added after the solvent when it was used as catalyst. When the
reaction was carried out under MW irradiation the same general
procedure was followed but under the conditions indicated inTable
Table 3 (footnote [c]). After the reaction time H2O (5 mL) and
brine (1 mL) were added and the mixture was extracted with ethyl
acetate (3ϫ 10 mL). The combined organic phases were dried with
MgSO4, and the solvents evaporated under vacuum. The pure com-
Scheme 5. Direct allylic amination using allylic alcohol (Z)-1aЈ.
pounds were obtained after flash chromatography. Physical and
spectroscopic data for new compounds are given below.
(E)-5-(Dimethylamino)-N-(1,3-diphenylallyl)-1-naphthalenesulfon-
amide (3af): Yellow sticky oil; Rf = 0.34 (hexane/ethyl acetate, 4:2).
Conclusions
1
IR (ATR): ν = 3284, 1734, 1574, 1453, 1320, 1142, 1044 cm–1. H
˜
NMR (300 MHz, CDCl3): δ = 2.78 (s, 6 H), 5.07 (t, J = 7.5 Hz, 1
H), 5.34 (d, J = 7.5 Hz, 1 H), 5.89 (dd, J = 15.9, 6.6 Hz, 1 H), 6.14
(d, J = 15.9 Hz, 1 H), 6.93 (d, J = 7.4 Hz, 2 H), 7.05–7.15 (m, 9
H), 7.32 (t, J = 7.9 Hz, 1 H), 7.51 (t, J = 8.2 Hz, 1 H), 8.16 (d, J
= 7.3 Hz, 1 H), 8.28 (d, J = 8.6 Hz, 1 H), 8.35 (d, J = 8.5 Hz, 1 H)
ppm. 13C NMR (75 MHz, CDCl3): δ = 45.2, 59.7, 114.9, 118.6,
122.9, 126.2, 126.8, 127.6, 127.7, 128.2, 129.5, 129.6, 129.8, 130.2,
131.8, 132.0, 132.4, 135.2, 135.8, 136.4, 139.2, 151.8 ppm. MS (EI):
m/z (%) = 251 (15) [M – 192]+, 250 (100), 207 (19), 171 (23), 170
(15), 169 (19), 168 (58), 154 (26), 127 (24), 126 (11), 115 (21).
From this study it can be concluded that both,
FeCl3·6H2O and TfOH, can act as excellent, easy-to-handle
catalysts for the allylic amination reaction using a wide vari-
ety of nitrogenated nucleophiles onto different free allylic
alcohols. The results exposed point out that the Brønsted
acid turned out to be slightly superior since, with some ex-
ceptions, better or comparable results are obtained with
only 1 mol-% of catalyst loading and milder reaction condi-
tions. The same trend was observed for allylic substitution
reactions with carbonucleophiles. Concerning the reaction HRMS calcd. for C27H26N2O2S: 442.1715, found 442.1712.
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P. Trillo, A. Baeza, C. Nájera
FULL PAPER
[3] a) R. Sanz, A. Martínez, D. Miguel, J. M. Álvarez-Gutierrez,
F. Rodriguez, Adv. Synth. Catal. 2006, 348, 1841; b) S. Shirak-
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[4] W. Wu, W. Rao, Y. Q. Er, J. K. Loh, C. Y. Poh, P. W. H. Chan,
Tetrahedron Lett. 2008, 49, 2620.
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Mashima, Org. Lett. 2007, 9, 3371; b) G. Mora, O. Piechaczyk,
R. Houdard, N. Mezailles, X. f. Le Goff, P. Le Floch, Chem.
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shi, M. Utsunomiya, J. Am. Chem. Soc. 2009, 131, 14317.
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666.
[7] H. Qin, N. Yamagiwa, S. Matsunaga, M. Shibasaki, Angew.
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[8] Y. L. Liu, L. Liu, D. Wang, Y.-J. Chen, Tetrahedron 2009, 65,
3473.
[9] a) U. Jana, S. Biswas, S. Maiti, Tetrahedron Lett. 2007, 48,
4065; b) U. Jana, S. Maiti, S. Biswas, Tetrahedron Lett. 2007,
48, 7160; c) U. Jana, S. Maiti, S. Biswas, Tetrahedron Lett. 2008,
49, 858.
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696, 357; b) M. Rueping, C. Vila, U. Uria, Org. Lett. 2012, 14,
768.
(E)-N-(1,3-Diphenylallyl)-N-methylaniline (3al): Yellow oil; Rf
=
0.36 (hexane/ethyl acetate, 4:1). IR (ATR): ν = 3416, 3022, 1613,
˜
1518, 1491, 1317, 1265, 1185, 1153 cm–1. 1H NMR (300 MHz,
CDCl3): δ = 2.81 (s, 3 H), 4.79 (d, J = 7.5 Hz, 1 H), 6.32 (d, J =
15.9 Hz, 1 H), 6.56–6.69 (m, 3 H), 7.05 (d, J = 8.7 Hz, 2 H), 7.24–
32 (m, 11 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 30.9, 53.3,
112.5, 126.1, 126.2, 127.1, 128.3, 128.4, 128.6, 129.4, 130.7, 132.2,
133.3, 137.4, 144.1, 147.1 ppm. MS (EI): m/z (%) = 299 (100)
[M]+, 298 (54), 222 (19), 192 (22), 191 (26), 165 (21), 120 (26), 115
(16), 91 (13). HRMS calcd. for C22H21N: 299.1674, found
299.1700.
(E)-1-(1,3-Diphenylallyl)-1H-benzotriazole (3am): White solid; m.p.
129 °C; R = 0.34 (hexane/ethyl acetate, 4:1). IR (ATR): ν = 3064,
˜
f
2923, 1598, 1562, 1494, 1455, 1380, 1313, 1261, 1185 cm–1. 1H
NMR (400 MHz, CDCl3): δ = 6.60 (d, J = 16 Hz, 1 H), 6.77 (d, J
= 7.2 Hz, 1 H), 6.98 (dd, J = 15.6, 7.2 Hz, 1 H), 7.26–7.37 (m, 13
H, ArH), 8.10 (d, J = 8.8 Hz, 1 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 65.4, 110.2, 120.0, 123.8, 125.4, 126.7, 127.1, 128.3,
128.4, 128.5, 128.9, 129.3, 132.2, 134.4, 135.6, 137.7, 146.3 ppm.
MS (EI): m/z (%) = 311 (2) [M]+, 193 (26), 192 (100), 191 (60),
189 (26), 165 (18), 115 (15), 91 (10). HRMS calcd. for C21H17N3:
311.1422, found 311.1425.
[11] For recent examples of AuI-catalyzed allylic amination, see: a)
P. Murkherjee, R. A. Widenhoefer, Org. Lett. 2010, 12, 1184.
For recent examples of AuIII allylic amination reaction, see: b)
S. Guo, F. Song, Y. Liu, Synlett 2007, 964; c) M. Georgy, V.
Boucard, O. Debleds, C. Dal Zotto, J.-M. Campagne, Tetrahe-
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Y. Miyamoto, K. Mashima, Chem. Commun. 2011, 47, 8322.
[12] When sulfonamides were employed as nitrogenated nucleo-
philes in the FeCl3·6H2O catalyzed reaction, small amounts
(Ͻ 5% of each) of chalcone and 1,3-diphenylpropene were ob-
served as by-products as result of the known disproportiona-
tion of 1a catalyzed by this metal species: W. Jialiang, H. Wen,
Z. Zhengxing, X. Xu, L. Ruiting, Z. Xigeng, J. Org. Chem.
2009, 74, 3299.
Supporting Information (see footnote on the first page of this arti-
1
cle): H and 13C NMR data for known compounds.
Acknowledgments
Spanish Ministerio de Ciencia e Innovación (MICINN) (projects
CTQ 2007-62771/BQU, CTQ2010-20387 and Consolider Ingenio
2010, CSD2007-00006; Juan de la Cierva contract to A. B., JCI-
2009-03710), Fondos Europeos para el Desarrollo Regional
(FEDER), the Generalitat Valenciana (PROMETEO 2009/039)
and the Universisty of Alicante are gratefully acknowledged for
financial support.
[13] During the preparation of this manuscript an isomerisation of
allylic alcohols mediated by salicylic acid was reported: J. A.
McCubbin, S. Voth, O. V. Krokhin, J. Org. Chem. 2011, 76,
8537.
[14] Determined by 1H NMR spectroscopy. In both cases any trace
of alcohol 1c was detected in the crude mixture, being alcohol
1b the main product (Ͼ 85%), together with some unidentified
products, which were more abundant in the case of the reaction
carried out with TfOH.
[1] For recent reviews about the use of free allylic alcohols in all-
ylic substitution reactions, see: a) J. Muzart, Eur. J. Org. Chem.
2007, 3077; b) E. Emer, R. Sinisi, M. Guiteras-Capdevila, D.
Petruzzielo, F. De Vicentiis, P. G. Cozzi, Eur. J. Org. Chem.
2011, 647; c) M. Bandini, Angew. Chem. Int. Ed. 2011, 50, 994;
d) B. Biannic, A. Aponick, Eur. J. Org. Chem. 2011, 6605.
[2] F. Ozawa, H. Okamoto, S. Kawagishi, S. Yamamoto, T. Min-
ami, M. Yoshifuji, J. Am. Chem. Soc. 2002, 124, 10968.
[15] Determined by 1H NMR spectroscopy. In both cases any trace
of alcohol (Z)-1bЈ or (Z)-1baЈ product were detected in the
crude mixture. In the case of TfOH small amounts of unidenti-
fied products were also observed in both experiments.
Received: December 22, 2011
Published Online: ᭿
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© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 0000, 0–0

Job/Unit: B11844
/KAP1
Date: 10-04-12 15:04:41
Pages: 7
Fe Catalyst for Allylic Amination
Allylic Amination
A comparative study for the direct allylic
amination employing FeCl3·6H2O and
TfOH as efficient and readily available
catalysts is described. From the results of
this study it can be concluded that, with
some exceptions, TfOH performed better
with lower catalyst loading and milder re-
action conditions. The stereochemical co-
urse of the reaction is also discussed con-
cluding that depends on the stability of the
final product.
P. Trillo, A. Baeza, C. Nájera* ......... 1–7
FeCl3·6H2O and TfOH as Catalysts for Al-
lylic Amination Reaction: A Comparative
Study
Keywords: Homogeneous catalysis / Iron /
Amination / Allylic compounds / Nucleo-
philic substitution
Eur. J. Org. Chem. 0000, 0–0
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