Iron-catalyzed esterification of allylic sp3 C–H bonds with carboxylic acids: Facile access to allylic esters

Article abstract of DOI:10.1016/j.tetlet.2017.05.039

The first general and efficient iron-catalyzed esterification of allylic sp³ C–H bonds with carboxylic acids using ionic iron(III) complexes (1–4) as a catalyst and DTBP (DTBP?=?di-tert-butyl peroxide) as an oxidant is achieved. A variety of allylic esters were synthesized in good to excellent yields using the ionic iron(III) complex 2 as a catalyst in a 5?mol% loading. This reaction is characterized by its high efficiency, broad substrate scope with excellent steric hindrance tolerance and good functional group compatibility.

Full text of DOI:10.1016/j.tetlet.2017.05.039

Accepted Manuscript
Iron-catalyzed esterification of allylic sp3 C−H bonds with carboxylic acids:
facile access to allylic esters
Bing Lu, Fan Zhu, Dan Wang, Hongmei Sun, Qi Shen
PII:
S0040-4039(17)30624-X
DOI:
http://dx.doi.org/10.1016/j.tetlet.2017.05.039
TETL 48932
Reference:
Tetrahedron Letters
To appear in:
Received Date:
Revised Date:
Accepted Date:
10 April 2017
10 May 2017
12 May 2017
Please cite this article as: Lu, B., Zhu, F., Wang, D., Sun, H., Shen, Q., Iron-catalyzed esterification of allylic sp3 C
−H bonds with carboxylic acids: facile access to allylic esters, Tetrahedron Letters (2017), doi: http://dx.doi.org/
10.1016/j.tetlet.2017.05.039
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Tetrahedron Letters
journal homepage: www.els evier.com
Iron-catalyzed esterification of allylic sp3 C−H bonds with carboxylic acids: facile
access to allylic esters
Bing Lu, Fan Zhu, Dan Wang, Hongmei Sun*, Qi Shen
The Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chenistry, Chemical Engineering and Materials Science, Soochow University, Suzhou
215123, China
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
The first general and efficient iron-catalyzed esterification of allylic sp3 C–H bonds with
carboxylic acids using ionic iron(III) complexes (1−4) as a catalyst and DTBP (DTBP = di-tert-
butyl peroxide) as an oxidant is achieved. A variety of allylic esters were synthesized in good to
excellent yields using the ionic iron(III) complex 2 as a catalyst in a 5 mol% loading. This
reaction is characterized by its high efficiency, broad substrate scope with excellent steric
hindrance tolerance and good functional group compatibility.
Available online
Keywords:
2017 Elsevier Ltd. All rights reserved.
Iron(III) complex
Imidazolinium salt
Oxidative cross-coupling
C−H bond functionalization
Allylic ester
Introduction
cant progress. However, iron-catalyzed functionalization of
allylic sp3 C–H bonds is still highly desired but challenging,
Allylic esters are of growing interest in organic synthesis, as
they are important structural units in bioactive and medical
molecules1 as well as fine chemicals.2 They have been
traditionally synthesized by the reaction of acids or their
derivatives (acyl chlorides and anhydrides) with the
corresponding allylic alcohols.3 However, the limited substrate
scope and harsh reaction conditions restrict their applications.
During the past decade, the direct functionalization of sp3 C–H
bonds through oxidative cross-coupling has emerged as one of
the most important strategies for the development of new
synthetic methodologies in organic synthesis from green and
sustainable points of view.4 For example, oxidative esterification
of allylic sp3 C–H bonds has shown remarkable potential as an
alternative to traditional protocols for the synthesis of allylic
esters. In this context, several types of transition metals-based
catalytic systems, including palladium,5 copper,6 and copper–
aluminum mixed oxide,7 have been developed for the
esterification of allylic sp3 C–H bonds. Also, a metal-free
esterification of allylic sp3 C–H bonds with carboxylic acids
using Bu4NI as a catalyst has been developed.8 Nevertheless,
there remains ample opportunity for improving such
transformation into a routine tool for synthesis of allylic ester in
the laboratory and on an industrial scale.
possibly owing to the difficulty of selective functionalization of
allylic sp3 C–H bond without an active group (i.e., a heteroatom
and/or an aromatic ring).4f In 2010, the Jiao group reported the
first example of an FeCl2-catalyzed cyanation of allylic sp3 C–H
bonds via the oxidative cross-coupling of allylarenes with
Me3SiN3 using DDQ (DDQ = 2,3-dichloro-5,6-dicyano-1,4-
benzoquinone) as an oxidant.13 Later, the White group described
the first example of intramolecular amination of allylic sp3 C–H
bonds to sulfamide using [FePc]Cl (Pc = phthalocyaninato) as a
catalyst.14 However, in terms of iron-catalyzed esterification of
3
−H bonds
allylic sp C
to the synthesis of allylic esters, only the
Pan group mentioned one example of the esterification of
cyclohexene with thiophene-2-carboxylic acid in a 45% yield
catalyzed by Fe(acac)3 at a 20 mol% loading.11e Therefore, the
development of a general methodology for iron-catalyzed
oxidative esterification of allylic sp3 C–H bonds to the synthesis
of allylic esters is highly desired.
We recently reported the synthesis of a series of ionic iron(III)
complexes containing an imidazolinium cation (Scheme 1) and
their catalytic potential in the esterification of benzylic sp3 C–H
bonds with carboxylic acids using di-tert-butyl peroxide (DTBP)
as an oxidant.15h Herein, we continue our studies15 by developing
the synthetic route of such kind of ionic iron(III) complexes and
their application in the esterification of allylic sp3 C–H bonds
with carboxylic acids.
Over the past decade, significant efforts have been devoted to
the development of iron-catalyzed functionalization sp3 C–H
9
bonds
because iron is inexpensive, nontoxic, and
environmentally benign.10 In this context, a large number of
studies focused on the transformation of sp3 C–H bonds adjacent
to a heteroatom11 or benzylic sp3 C–H bonds12 have made signifi-
∗ Corresponding author. Tel.: +86-512-65880330
e-mail: sunhm@suda.edu.cn

2
Tetrahedron
Scheme 1 Ionic iron(III) complexes containing an
imidazolinium cation
Results and discussion
In our previous work, complexes 2–4 were synthesized via the
reaction
dihydrocarbylimidazolinium
of
FeBr3
with
the
corresponding
The
1,3-
present
bromide.15h
investigation reveals that these iron(III) bromides could be
directly synthesized using 1,3-dihydrocarbylimidazolinium
chlorides as starting materials. As shown in Scheme 2, the
Fig. 1 Molecular structure of complex 3 with thermal ellipsoids at
the 30% probability level. Hydrogens are omitted for clarity.
Selected bond lengths (Å) and angles (o): Fe(1)–Br(1) 2.324(12),
Fe(1)–Br(2) 2.337(12), Fe(1)–Br(3) 2.327(12), Fe(1)–Br(4)
2.341(12); Br(1)–Fe(1)–Br(2) 108.78(5), Br(1)–Fe(1)–Br(3)
110.86(5), Br(1)–Fe(1)–Br(4) 108.97(5), Br(2)–Fe(1)–Br(3)
109.56(5), Br(2)–Fe(1)–Br(4) 108.44(5), Br(3)–Fe(1)–Br(4)
110.18(5).
reaction
of
FeBr3
with
1
equiv.
of
1,3-
dihydrocarbylimidazolinium chloride in the presence of NaBr
afforded the desired iron(III) bromides 2–4 as air-stable brown-
red crystals in yields ranging from 87% to 90%, which are very
similar to the data reported previously.15h This protocol avoids
the
employment
of
the
corresponding
1,3-
dihydrocarbylimidazolinium bromides, which were generally
synthesized from more expensive alkyl bromides or more
corrosive hydrobromide as compared with their chloride
derivatives.16
Scheme 2 Synthesis of ionic iron(III) complexes 2–4.
Complexes 2−4 were characterized by elemental analysis,
Raman spectroscopy and electrospray ionization mass
spectroscopy. The characterization results agreed well with those
reported previously.15h
Fig. 2 Molecular structure of complex 4 with thermal ellipsoids at
the 30% probability level. Hydrogens and solvent are omitted for
clarity. Selected bond lengths (Å) and angles (o): Fe(1)–Br(1)
2.301(11), Fe(1)–Br(2) 2.311(13), Fe(1)–Br(3) 2.319(13), Fe(1)–
Br(4) 2.301(14); Br(1)–Fe(1)–Br(2) 108.47(5), Br(1)–Fe(1)–Br(3)
109.02(5), Br(1)–Fe(1)–Br(4) 108.33(5), Br(2)–Fe(1)–Br(3)
109.09(6), Br(2)–Fe(1)–Br(4) 110.74(6), Br(3)–Fe(1)–Br(4)
111.14(5).
The solid-state structures of complexes 3 and 4 were further
confirmed by X-ray crystallography. Single crystals suitable for
X-ray diffraction studies were grown from cold THF/hexane. The
crystallographic data are listed in Table S1 (see the ESI†). Their
molecular structures are depicted in Figs. 1–2, with selected bond
lengths and angles given in the captions. It is worth noting that
the molecular structures of this type of ionic iron(III) complexes
have been seldom reported, even if the application of
imidazolinium salts as ligands in iron-based catalytic systems has
received increasing attention during the past decade.17 To date,
only two scientific articles have described structural data for
imidazolinium cation-containing ionic iron(III) complexes.15h,18
We began our investigation with the oxidative cross-coupling
reaction of 4-methoxybenzoic acid (5a) and cyclohexene (6a)
with catalysts 1−4 and related iron(III) salts. The results are
summarized in Table 1. Under the optimized conditions, there
were obviously different catalytic activities for these iron(III)-
based catalysts. For example, complex 2 exhibited the highest
activity and gave the desired product 7a in 95% yield at a 5
mol% loading (entry 2). The desired product 7a was still
obtained in high yield of 81% even when the loading of 2 was
reduced to 3 mol%. In comparison, complexes 3 and 4 showed a
relatively lower activity, affording the desired product in yields
of 73% (entry 6) and 84% (entry 7), respectively. The chloride
analogue (1) showed very poor activity, giving 7a in 32% yield
(entry 1). Notably, an iron(III) complex of [Me4N][FeBr4], which
containing a tetramethylammonium cation, also exhibited very
poor activity (entry 8). As expected, FeBr3 alone gave 7a in
merely 16% yield (entry 9). A mixture of FeBr3 and 1,3-di-tert-
butylimidazolinium bromide ([HSItBu]Br) in a 1:1 molar ratio
gave the desired product 7a in 88% yield (entry 10), and no 7a
was detected when [HSItBu]Br was employed alone (entry 11).
Oxidant screening disclosed that TBHP and DDQ showed no
activity (entries 4 and 5).
As seen in Figs. 1 and 2, each of the two solid-state structures
contained one 1,3-dihydrocarbylimidazolinium cation and one
[FeBr4]−
anion.
The
structure
of
the
1,3-
dihydrocarbylimidazolinium cation presented either in 3 or 4
changed little after the reaction of the corresponding 1,3-
dihydrocarbylimidazolinium salt with FeBr3.19 In both [FeBr4]−
anions, each iron atom is coordinated by four bromine atoms in a
slightly distorted tetrahedral geometry with a mean Br–Fe–Br
angle of 109.5 ° for both of 3 and 4, which is close to the ideal
tetrahedral angle of −50 °.20 The Fe–Br bond lengths were found
to lie in the ranges of 2.301(11)–2.341(12) Å, wherein the mean
Fe–Br bond length was 2.333 Å in 3 and 2.308 Å in 4. These
values were in the expected range as found for other
imidazolinium cation-containing ionic iron(III) complexes
reported previously.15h, 18
To date, 10 mol% or higher loadings of other transition metal-
based catalysts5-7 or metal-free catalyst8 are usually required to
achieve satisfactory yields for such kind of transformation. The
present results indicates that complex 2 might be among the most

efficient catalyst for the oxidative esterification of allylic sp3 C–H
bonds to the synthesis of allylic esters, and the presence of a
sterically bulky imidazolinlium cation with electron-donating N-
substitutents is of benefit to its high catalytic activity. 22
cyclooctene gave the desired product in a lower yield under the
same reaction conditions (8b). Notably, 2,3-dimethylbut-2-ene
exhibited very high selectivity, affording merely the mono-
esterification product 8c in a yield of 90%. Interestingly, a very
high regioselectivity is also observed in our protocol when
allylbenzene and allylnaphthalene were employed, wherein linear
allylic ester was isolated in yields of 86% (8d) and 82% (8e),
respectively. This phenomenon is quite different from that
observed with palladium-based catalysts, wherein π−allyl-Pd(II)
intermediates could lead to a L/B (L = linear product, B =
Table 1 Screening of optimal conditionsa
branched product) regioselectivity. To date,
regioselectivity to the linear isomer is still highly desired in the
a
control
Entry
Catalyst
Oxidant
Yield (%)
−H
field of palladium-catalyzed esterification of allylic sp3 C
1
2
DTBP
DTBP
DTBP
TBHPd
DDQe
DTBP
DTBP
DTBP
DTBP
DTBP
DTBP
32
95(88b)
81c
0
1
bond.5. Somewhat to our surprise, methylenecylcohexene failed
to participate in this esterification reaction (8f). Finally, a simple
conjugated diene was tested under optimized conditions,
however, the reaction was too complicated and no obvious
amount of desired product 8g could be detected, similar to that
reported previously.13
2
3
2
4
2
5
0
2
Table 2 Esterification of various carboxylic acids with cyclohexenea
6
73
3
7
84
4
8
[Me4N][FeBr4]f
FeBr3
[HSItBu]Brg+FeBr3
28
9
16
O
O
O
10
88
O
O
O
11
[HSItBu]Br
0
a
Conditions: 4-methoxybenzoic acid (0.5 mmol), cyclohexene (7.5
mmol), catalyst (5 mol%), oxidant (1.0 mol), EtOAc (0.5 mL), 110 oC,
24 h, GC yield using n-hexadecane as internal standard, an average of
7c, 99%
7d, 94%
7b, 99%
O
O
O
O
b
c
d
two runs.
hydroperoxide.
isolated yield.
2
(3 mol%),
TBHP = tert-butyl
O
O
e
DDQ
=
2,3-dicyano-5,6-dichlorobenzoquinone.
Ph
f[Me4N] = tetramethylammonium cation (ref 21). g[HSItBu]Br = 1,3-di-
tert-butylimidazolinium bromide.
tBu
O
7f, 80%
7e, 91%
7g, 95%
Encouraged by the above results, we explored the substrate
scope of this iron-catalyzed esterification of allylic C–H bonds
with carboxylic acids to obtain allylic esters. Firstly, a series of
carboxylic acids were investigated, as shown in Table 2. Both
electron-donating and electron-withdrawing aryl carboxylic acids
were successfully coupled with cyclohexene to form
corresponding allylic esters in moderate to excellent yields (7b–
7n). Interestingly, steric hindrance was well tolerated in this
reaction, as the highly hindered 2,4,6-triiso-propylbenzoic acid
was converted to corresponding ester in a 91% yield without
enhanced reaction conditions (7i). To date, such highly hindered
carboxylic acids have rarely been explored as substrates in other
sp3 C–H bond esterification reported previously.23 Another
notable merit of this protocol is that a series of functional groups
can been tolerated in our oxidative conditions, including cyano
(7m), nitro (7n), hydroxyl (7o), and ester (7p). Additionally,
biphenyl 4-carboxylic acid (7p), biphenyl 2-carboxylic acid (7r),
1-naphthoic acid (7s) and 2-naphthoic acid (7t) gave the desired
products in 95%-98% yields. Notably, furan-2-carboxylic acid
(7u) and thiophene-2-carboxylic acid (7v) were also excellent
coupling partners under the optimized conditions. Such kind of
heteroaromatic carboxylates have been widely used in organic
synthesis,24 however, they were usually less employed as
substrates or showed low activities in previously reported
studies.8 Several kinds of aliphatic carboxylic acids were also
found to be compatible with this esterification protocol,
furnishing the corresponding ester products (7w–7y) in 67%–
76% yields.
O
O
O
O
O
O
F
7h, 95%
7i, 91%
7j, 91%
O
O
O
O
O
O
Br
NC
Cl
7k, 81%
7m, 47%
7l, 81%
O
OH
O
O
O
O
O
O2N
H3CO2C
7o, 87%
7n, 51%
7p, 57%
O
O
Ph
O
O
O
O
Ph
7r, 95%
7q, 97%
7s, 98%
O
O
O
O
O
O
O
S
7u, 95%
7v, 94%
7t, 98%
O
O
O
O
3
O
O
We also investigated the substrate scope of various alkenes to
further explore the potential of the present protocol. As shown in
Table 3, cyclopentene reacted well with benzoic acid (8a), while
7y, 70%
7w, 67%
7x, 76%
a Conditions: carboxylic acids (0.5 mmol), cyclohexene (7.5 mmol), 2 (5 mol%),
EtOAc (0.5 mL), DTBP (1.0 mmol), 110 oC, 24 h, isolated yield.

4
Tetrahedron
Table 3 Esterification of benzoic acid with various alkenesa
oxidant. The present reaction is suitable for a wide range of
carboxylic acids and derivatives of cyclohexene with outstanding
tolerance to sterically hindered substrates and good compatibility
to various functional groups. As these ionic iron(III) complexes
containing an 1,3-dihydrocarbylimidazolinium cation are easily
prepared as well as stable in air, this work provides a new and
general synthetic tool for the synthesis of allylic esters with easy-
to-hand or on large scale. Further studies on the detailed reaction
mechanism and other direct functionalization of sp3 C−H bonds
are currently underway in our laboratory.
O
O
O
O
O
O
8c, 90%
8a, 74%
8b, 36%
O
O
Acknowledgements
O
O
This project was supported by the National Natural Science
Foundation of China (Grant No. 21172164 and 21472134), the
Key Laboratory of Organic Chemistry of Jiangsu Province, and
the Priority Academic Program Development of Jiangsu Higher
Education Institutions (PAPD).
8d, 86%b
8e, 82%b
O
O
O
O
References and Notes
8g, tracec
8f, trace
a
1
(a) Quang, D. N.; Hashimoto, T.; Stadler, M.; Asakawa, Y. J. Nat.
Prod. 2004; 67: 1152; (b) Ankisetty, S.; ElSohly, H. N.; Li, X.-C.;
Khan, S. I.; Tekwani, B. L.; Smillie T.; Walker, L. J. Nat. Prod. 2006;
69: 692; (c) Covell, D. J.; Vermeulen, N. A.; Labenz, N. A.; White,
M. C. Angew. Chem. Int. Ed. 2006; 45: 8217; (d) Saito, T.; Fuwa H.;
Sasaki, M.; Org. Lett. 2009; 11: 5274; (e) Jogalekar, A. S.; Kriel, F.
H.; Shi, Q.; Cornett, B.; Cicero, D.; Snyder, J. P. J. Med. Chem. 2010;
53: 155; (f) Chang, C.-L.; Zhang, L.-J.; Chen, R. Y.; Kuo, L.-M. Y.;
Huang, J.-P.; Huang, H.-C.; Lee, K.-H.; Wu, Y.-C.; Kuo, Y.-H.; J.
Nat. Prod. 2010; 73: 1482.
Conditions: benzoic acid (0.5 mmol), alkene (7.5 mmol ), 2 (5 mol%), EtOAc
(0.5 mL), DTBP (1.0 mmol), 110 oC, 24 h, isolated yield. 2 (10 mol%),
allylarenes (1.5 mL), no solvent, 16 h. c The reaction was too complicated and no
obvious amount of the desired product was obtained.
b
2
3
(a) Nicolaou, K. C.; Winssinger, N.; Hughes, R.; Smethurst C.; Cho,
S. Y. Angew. Chem. Int. Ed. 2000; 39: 1084; (b) Stanley, L. M.; Bai,
C.; Ueda M.; Hartwig, J. F.; J. Am. Chem. Soc. 2010; 132: 8918.
(a) Xiang, J.; Orita, A.; Otera, J.; Angew. Chem. Int. Ed. 2002; 41:
4117; (b) Mohan, K. V. V. K.; Narender, N.; Kulkarni, S. J.; Green
Chem. 2006; 8: 368; (c) Meyer, M. E.; Ferreira E. M.; Stoltz, B. M.
Chem. Commun. 2006; 1316; (d) Zhang, L.; Luo, Y.; Fan R.; Wu, J.
Green Chem. 2007; 9: 1022; (e) Otera, J. Esterification: methods,
reactions, and applications; Wiley-VCH: Weinheim, 2010.
4
(a) Giri, R.; Shi, B.-F.; Engle, K. M.; Maugel N.; Yu, J.-Q.; Chem.
Soc. Rev. 2009; 38: 3242; (b) Li, H.; Li B.-J.; Shi, Z.-J. Catal. Sci.
Technol. 2011; 1: 191; (c) Baudoin, O.; Chem. Soc. Rev. 2011; 40:
4902; (d) Girard, S. A.; Knauber, T.; Li; C.-J.; Angew. Chem. Int. Ed
.
2014; 53: 74; (e) Noisier A. F. M.; Brimbl, M. A.; Chem. Rev. 2014;
114: 8775; (f) Li, C.-J. From C-H to C-C bonds: cross-
Scheme 3 Investigation of reaction mechanism
Although an exact mechanism of the present reaction requires
further investigation, our current experimental studies suggest
that this transformation may involve radical species because the
reaction was completely stopped by the addition of TEMPO as a
radical inhibitor (Scheme 3, eqn. 1). Cyclohex-2-enol was not
detected during the reaction (Scheme 3, eqn. 2), which suggests
that the present esterification reaction possibly occurred without
an alcohol intermediate. When tert-butyl perester was used as a
reactant, the allylic ester 7b was obtained only in 31% yield
(Scheme 3, eqn. 3), indicating that this reaction may not proceed
through a tert-butyl perester intermediate. Recently, Pan11e group
proposed that a µ-oxo, µ-carboxylate diiron(III) intermediate
might be formed in iron-catalyzed esterification of sp3 C–H
bonds adjacent an oxygen atom. We suggest that the present
esterification reaction possibly also proceeded via a µ-oxo, µ-
carboxylate diiron(III) intermediate (see supplementary material
S5). The role of an imidazolinium cation should be of benefit to
form the diiron(III) intermediate.25
dehydrogenative-coupling
;
The Royal Society of Chemistry,
Cambridge, 2014; (g) Liu, C.; Liu, D.; Lei, A.; Acc. Chem. Res. 2014;
47: 3459.
5
(a) Chen, M. S.; White, M. C.; J. Am. Chem. Soc. 2004; 126: 1346; (b)
Chen, M. S.; Prabagaran, N.; Labenz, N. A.; White, M. C. J. Am.
Chem. Soc. 2005; 127: 6970; (c) Mitsudome, T.; Umetani, T.; Nosaka,
N.; Mori, K.; Mizugaki, T.; Ebitani K.; Kaneda, K.; Angew. Chem. Int.
Ed. 2006; 45: 481; (d) Covell, D. J.; White, M. C.; Angew. Chem. Int.
Ed. 2008; 47: 6448; (e) Campbell, A. N.; White, P. B.; Guzei, I. A.; S.
S. Stahl, J. Am. Chem. Soc. 2010; 132: 15116; (f) Vermeulen, N. A.
Delcamp, J. H.; White, M. C.; J. Am. Chem. Soc. 2010; 132: 11323;
(g) Thiery, E. Aouf, C.; Belloy, J.; Harakat, D.; Bras J. L.; Muzart, J.;
J. Org. Chem. 2010; 75: 1771; (h) Henderson, W. H.; Check, C. T.;
Proust N.; Stambuli, J. P. Org. Lett. 2010; 12: 824; (i) Gormisky, P.
E.; White, M. C.; J. Am. Chem. Soc. 2011; 133: 12584; (j) Stang E.
M.; White, M. C. Angew. Chem. Int. Ed. 2011; 50: 2094; (k)
Takenaka, K.; Akita, M.; Tanigaki, Y.; Takizawa S.; Sasai, H.; Org.
Lett. 201; 13: 3506; (l) Kondo, H.; Yu, F.; Yamaguchi, J.; Liu, G.;
Itami, K.; Org. Lett. 2014; 16: 4212.
6
7
(a) Kharasch, M. S.; Sosnovsky G.; Yang, N. C.; J. Am. Chem. Soc
1959; 81: 5819; (b) Eames J.; Watkinson, M.; Angew. Chem. Int. Ed
.
.
2001; 40: 3567; (c) Andrus M. B.; Lashley. J. C.; Tetrahedron, 2002;
58: 845; (d) Marín-Barrios, R.; Guerra, F. M.; García-Cabeza, A. L.;
Moreno-Dorado, F. J.; Massanet, G. M.; Tetrahedron 2012; 68: 1105.
García-Cabeza, A. L.; Marín-Barrios, R.; Moreno-Dorado, F. J.;
Ortega, M. J.; Massanet, G. M.; Guerra, F. M.; Org. Lett. 2014; 16:
1598.
Conclusions
An efficient iron-catalyzed oxidative esterification of allylic
sp3 C–H bonds with carboxylic acids is realized using well-
defined ionic iron(III) complex as a catalyst and DTBP as an

8
9
Shi, E.; Shao, Y.; Chen, S.; Hu, H.; Liu, Z.; Zhang, J.; Wan, X.; Org.
Lett. 2012; 14: 3384.
(a) Sun, C.-L.; Li, B.-J.; Shi, Z.-J.; Chem Rev. 2011; 111: 1293; (b)
Jia F.; Li, Z.; Org. Chem. Front. 2014; 1: 194.
24 (a) Waetzig, S. R.; Tunge, J. A.; J. Am. Chem. Soc. 2007; 129: 4138;
(b) Chen, L.; Bruneau, C.; Dixneuf, P. H.; Doucet, H. Green Chem
.
2012; 14: 1111.
25 (a) Neuse E. W.; Meirim, M. G.; Transition Met. Chem. 1984; 9: 205;
(b) Marlin, D. S.; Olmstead M. M.; Mascharak, P. K.; Inorg. Chem.
2003, 42, 1681.
10 (a) Bolm, C.; Legros, J.; Paih J. L.; Zani, L.; Chem. Rev. 2004; 104:
6217; (b) Sherry, B. D.; Fürstner, A.; Acc. Chem. Res. 2008; 41:
1500; (c) Czaplik, W. M.; Mayer, M.; Cvengroš, J.; A. J. V.;
Wangelin, ChemSusChem 2009; 2: 396; (d) Bauer, I.; Knölker, H. -J.;
Chem. Rev. 2015; 115: 3170.
11 For selected examples of iron-catalyzed direct functionalization of sp3
C-H bonds adjacent to an oxygen atom: (a) Li, Z.; Yu R.; Li, H.;
Angew. Chem. Int. Ed. 2008; 47: 7497; (b) Guo, X.; Pan, S.; Liu, J.;
Li, Z. J. Org. Chem. 2009; 74: 8848; (c) Pan, S.; Liu, J.; Li, H.; Wang,
Z.; Guo X.; Li, Z. Org. Lett. 2010; 12: 1932; (d) Wei, W.-T.; Zhou,
M.-B.; Fan, J.-H.; Liu, W.; Song, R.-J.; Liu, Y.; Hu, M.; Xie, P.; Li,
J.-H.; Angew. Chem. Int. Ed. 2013; 52: 3638; (e) Zhao, J.; Fang, H.;
Zhou, W.; Han J.; Pan, Y.; J. Org. Chem. 2014; 79: 3847; For
selected examples of iron-catalyzed direct functionalization of sp3 C-
H bonds adjacent to a nitrogen atom: (f) Volla C. M. R.; Vogel, P.;
Org. Lett. 2009, 11, 1701; (g) Han W.; Ofial, A. R.; Chem. Commun
.
2009; 6023; (h) Liu, P.; Zhou, C.-Y.; Xiang S.; Che, C.-M.; Chem.
Commun. 2010; 46: 2739 (i) Ratnikov, M. O.; Xu X.; Doyle, M. P. J.
Am. Chem. Soc. 2013; 135: 9475.
12 (a) Li, Z.; Cao L.; Li, C.-J. Angew. Chem. Int. Ed. 2007; 46: 6505; (b)
Wang, Z.; Zhang, Y.; Fu, H.; Jiang Y.; Zhao, Y.; Org. Lett. 2008; 10:
1863; (c) Li, Y.-Z.; Li, B.-J.; Lu, X.-Y.; Lin S.; Shi, Z.-J. Angew.
Chem., Int. Ed. 2009; 48: 3817; (d) Song, C.-X.; Cai, G.-X.; Farrell,
T. R.; Jiang, Z.-P.; Li, H.; Gan, L.-B.; Shi, Z.-J.; Chem. Commun.
2009; 6002; (e) Xia, Q.; Chen W.; Qiu, H.; J. Org. Chem. 2011; 76:
7577; (f) Pan, S.; Liu, J.; Li Y.; Li, Z.; Chin. Sci. Bull. 2012; 57: 2382;
(g) Liu, X.; Chen, Y.; Li, K.; Wang, D.; Chen, B.; Chin. J. Chem
.
2012, 30, 2285; (h) Cheng, Y.; Dong, W.; Wang, L.; Parthasarathy K.;
Bolm, C.; Org. Lett. 2014; 16: 2000; (i) He, Y.; Mao, J.; Rong, G.;
Yan, H.; Zhang, G. Adv. Synth. Catal. 2015: 357; 2125; (j) Guo, S.;
Li, Y.; Wang, Y.; Guo, X.; Meng X.; Chen, B.; Adv. Synth. Catal
2015; 357: 950; (k) Guo, L.-N.; Wang, S.; Duan X.-H.; Zhou, S.-L.;
Chem. Commun. 2015; 51: 4803; (l) Yang, K.; Song, Q.; Org. Lett
.
.
2015; 17: 548; (m) Shi, J.-L.; Zhang, J.-C.; Wang, B.-Q.; Hu, P.;
Zhao, K.-Q.; Shi, Z.-J.; Org. Lett. 2016; 18: 1238.
13 Qin C.; Jiao, N.; J. Am. Chem. Soc. 2010; 132: 15893.
14 Paradine, S. M.; White, M. C.; J. Am. Chem. Soc. 2012; 134: 2036.
15 (a) Yan, C. H.; Wang, L. L.; Gao, H. H.; Sun, H. M.; Shen, Q. Chin.
Sci. Bull. 2012; 57: 1953; (b) Deng, H.-N.; Xing, Y.-L.; Xia, C.-L.;
Sun, H.-M.; Shen, Q.; Zhang, Y. Dalton Trans. 2012; 41: 11597;(c)
Xia, Y.; Yan, C. H.; Li, Z.; Gao, H. H.; Sun, H. M.; Shen, Q.; Zhang,
Y. Chin. Sci. Bull. 2013; 58: 493; (d) Wang, L. L.; Lu, B.; Zhu, A. D.;
Sun, H. M.; Shen, Q. Chin. Sci. Bull. 2013; 58: 3624; (e) Xia, C.-L.;
Xie, C.-F.; Wu, Y.-F.; Sun, H.-M.; Shen, Q.; Zhang, Y. Org. Biomol.
Chem. 2013; 11: 8135; (f) Zhang, Q.; Li, Z.; Sun, H.; Shen, Q. Chin.
Sci. Bull. 2014; 59: 4728; (g) Zhu, F.; Lu, B.; Sun, H.; Shen Q.
Tetrahedron Lett. 2016; 57: 4152; (h) Lu, B.; Zhu, F.; Sun H.-M.;
Shen, Q.; Org. Lett. 2017; 19: 1132.
16 (a) Naumann, S.; Schmidt, F. G.; Schowner, R.; Frey, W.;
Buchmeiser, M. R.; Polym. Chem. 2013; 4: 2731; (b) Iglesias, M.;
Beetstra, D. J.; Knight, J. C.; Ooi, L.-L.; Stasch, A.; Coles, S.; Male,
L.; Hursthouse, M. B.; Cavell, K. J.; Dervisi, A.; Fallis, I. A.;
Organometallics 2008; 27: 3279.
17 (a) Hatakeyama, T.; Hashimoto, S.; Ishizuka K.; Nakamura, M.; J.
Am. Chem. Soc 2009; 131: 11949; (b) Rosa, J. N.; Reddy, R. S.;
Candeias, N. R.; Cal, P. M. S. D.; Gois, P. M. P. Org. Lett. 2010; 12:
2686; (c) Reddy, R. S.; Rosa, J. N.; Veiros, L. F.; Caddick S.; Gois, P.
M. P. Org. Biomol. Chem. 2011; 9: 3126; (d) Chua, Y.-Y.; Duong, H.
A.; Chem. Commun. 2014; 50: 8424; (e) Chua Y.-Y.; Duong, H. A.;
Chem. Commun. 2016; 52: 1466.
18 Demir, S.; Gköçe, Y.; Roisnel, T.; Sortais, J.-B.; Darcel, C.; Özdemir,
İ.; C. R. Chimie. 2014; 17: 541.
19 Arduengo III, A. J.; Goerlich, J. R.; Marshall. W. J.; J. Am. Chem.
Soc. 1995; 117: 11027.
20 Bäcker, T.; Breunig, O.; Valldor, M.; Merz, K.; Vasylyeva V.;
Mudring, A.-V.; Cryst. Growth Des. 2011; 11: 2564.
21 Wyrzykowski, D.; Kruszyński, R.; Kłak, J.; Mroziński, J.; Warnke, Z.
Inorganica Chimica Acta 2008; 361: 262.
22 Ye, S.; Yang, W.; Coon, T.; Fanning, D.; Neubert, T.; Stamos D.; Yu,
J.-Q. Chem. Eur. J. 2016; 22: 4748.
23 Majji, G.; Rout, S. K.; Rajamanickam, S.; Guin S.; Patel, B. K. Org.
Biomol. Chem. 2016; 14: 8178.

6
Tetrahedron
Highlights:
ꢀ
A novel method for the synthesis of ionic
iron(III) complexes
ꢀ
ꢀ
First general and efficient iron-catalyzed
esterification of allylic sp3 C–H bonds
A new method for synthesis of allylic esters

Graphical abstract: