Cobalt-Catalyzed Esterification of Amides

Article abstract of DOI:10.1002/chem.201702608

The first cobalt-catalyzed amide activation of N-Boc-amides, and their conversion into esters, is reported here. This new methodology presents a very practical process that does not require an inert atmosphere, uses an inexpensive cobalt catalyst, and proceeds under mild reaction conditions. This catalytic system has a broad substrate scope and has been shown to be highly efficient, with catalyst loadings as low as 1 mol %.

Full text of DOI:10.1002/chem.201702608

A Journal of
Accepted Article
Title: Cobalt-Catalyzed Esterification of Amides
Authors: Yann Bourne-Branchu, Corinne Gosmini, and Grégory
Danoun
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Cobalt-Catalyzed Esterification of Amides
Yann Bourne-Branchu, Corinne Gosmini* and Grégory Danoun*
Abstract: The first cobalt-catalyzed amide activation of N-Boc-
amides, and their conversion into esters, is reported herein. This
new methodology presents a very practical process, that does not
require an inert atmosphere, uses an inexpensive cobalt catalyst,
and proceeds under mild reaction conditions. This catalytic system
has a broad substrate scope and has been shown to be highly
efficient, with catalyst loadings as low as 1 mol%.
(typically 10-15 mol%) and the use of unstable (i.e. not easy-to-
handle) catalytic systems.[14]
Amides are versatile building blocks commonly found in natural
organic molecules. They exhibit high stability and good
coordination to metals due to the delocalization of the nitrogen
lone pair into orbitals on the carbonyl moiety.[1] As such, this
functional group has recently been used as metal-coordinating
directing group to activate ortho C–H bonds.[2] The development
of a palette of ortho-metalation reactions has shown the amide
functional group to be one of the most powerful and versatile
directing groups employed in C–H bond activation reactions.[3]
Several transformations using amides as O- or N-chelating
monodentate or bidentate directing groups have been developed
and have shown high efficiency in C(sp2)–H or C(sp3)–H bond
activation reactions with different metal catalysts. In comparison
with its important utility in organometallic coordination chemistry,
the metal-catalyzed activation of amides has not been
extensively studied.[4]
Scheme 1: Previous metal-catalyzed coupling reaction of amides.
Among the several metals that are active enough to insert
into these unreactive bonds,[15] cobalt seems promising to avoid
these drawbacks. Indeed, mixing a simple, cheap and easy-to-
handle cobalt precursor in combination with the appropriate
reductant form in-situ low-valent cobalt species. The latter has
already demonstrated high activity in catalytic processes and
possessed a remarkable robustness regarding oxygen or water
contamination of the reaction media.[16] Moreover, to the best of
our knowledge, no cobalt catalytic system has been previously
reported in the activation of benzamides.
Based on Garg’s mechanism, we envisaged the oxidative
addition of a low-valent cobalt complex into the C–N bond. Then,
an exchange of the N-Boc amine moiety for an alkoxide at the
acyl-cobalt intermediate would occur, followed by reductive
elimination (Figure 1).
Since the seminal reports by Hanessian and Charette of
the transformation of amides into esters or nitriles using unstable
and potent electrophiles such as trialkyloxonium or triflic
anhydride,[5] the pursuit of developing new methodologies for the
activation of amides has been dormant.[6] In 2015, Garg and co-
workers described an elegant nickel(0)-catalyzed conversion of
benzamides into esters using a Ni(0)/NHC catalyst system that
involves the first direct oxidative addition into the amidic C–N
bond.[7] Independently, Szostak and co-workers developed a
sterically and electronically twisted amide derived from
glutarimide which disfavored the delocalization of the nitrogen
lone-pair. This particular configuration of the amide allowed
oxidative addition of palladium catalytic system into the amidic
C–N bond.[8] This peculiar strategy to twist amides notably via
the introduction of a Boc or a Tosyl group proved to be highly
efficient in various coupling reactions.[9] In particular, oxidative
addition of palladium,[10] nickel[11] or rhodium[12] was greatly
eased using these twisted amides that allowed the development
of new methodologies to form C–X (X= O, N, B) or C–C
bonds.[13]
Figure 1. Possible mechanism of the cobalt-catalyzed esterification.
To probe our hypothesis, we began our study with N-Boc-
benzanilide (1) as a test substrate and ethanol as coupling
partner. The use of classical reaction conditions developed in
our group – CoBr2 as precursor, bipyridine as ligand, TMSCl
However, these two esterification methodologies[7,11a]
suffer from drawbacks such as significant catalyst loadings
activated manganese as reductant and
a
mixture of
[*]
Y. Bourne-Branchu, Dr. C. Gosmini, Dr. G. Danoun
LCM, CNRS, Ecole Polytechnique, Université Paris-Saclay
91128 Palaiseau Cedex (France)
E-mail: gregory.danoun@polytechnique.edu
corinne.gosmini@polytechnique.edu
DMF/pyridine as the solvent – allowed the formation of a
substantial amount of ethyl benzoate (2) in only 3 h with no
precautions to exclude oxygen and water from the reaction
mixture (Table 1, entry 1). Encouraged by this preliminary result,
we decided to further optimize these reaction conditions.
Supporting information for this article is given via a link at the end of
the document.((Please delete this text if not appropriate))
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Table 1. Optimization of the coupling reaction between N-Boc-benzanilide and
ethanol.[a] Bipy = 2,2’-bipyridine. TMSCl = trimethylsilylchloride. Py = pyridine.
Boc = tert-butylcarbamate. Phen= 1,10-phenantroline.
Among all the solvents tested, polar and aprotic solvents such
as DMF and NMP, gave the best yields (see supporting
information). Decreasing the catalytic loading from 20 mol% to 5
mol% slightly enhanced the reaction yield (Table 1, entry 1 vs
entry 13). In order to reduce waste, the amount of manganese
was reduced to one equivalent which allowed to obtain 2 in 84%
yield. Of note, a further decrease in the amount of reductant to a
catalytic amount dramatically affected the yield which dropped to
2% (Table1, entries 14 and 15).
Entry
Deviation from standard conditions
Yield %[b]
With these optimal reaction conditions in hand, we then
explored the scope of N,N-disubstituted benzamides (Figure 2).
Different benzanilides protected by methyl carbamate (3) or a p-
toluenesulfonyl (4) groups were tested but only low to moderate
yields were observed, even after 20 h. The lack of reactivity of
amide 3 may arise from the scission of the methyl carbamate
group that led to a deactivated benzanilide. No scission of the
tosyl group was observed for amide 4 and only the starting
material remained as observed by GC after 20 h. Interestingly,
N-methylbenzanilide (5) used by Garg was completely
unreactive under our reaction conditions. This result highlights
the complementarity of those metal-catalyzed esterification
methods. Some other N-Boc-benzamides bearing benzyl (6) or
methyl (7) groups were also reacted and converted successfully
into the corresponding ester with excellent yields. Two amides
that are commonly used as C–H bond activation directing
groups, N-methoxy- and N-quinolin-8-yl amides, were first
activated by Boc protection (8 and 9) and transformed efficiently
into ethyl benzoate 2.[18] Of note, only the unprotected
benzamide was observed by GC as side product when using
Boc-protected benzamides substrates in reaction.
1
2
3
4
None
67
No CoBr2 / No Bipy / No Mn / No TMSCl
n.d.
n.d.
n.d.
No Mn
No CoBr2
5
6
No TMSCl
CoCl2 instead of CoBr2
Co(OAc)2 instead of CoBr2
Phen instead of bipy
No bipy
24, 65[c]
52
7
63
8
65
9
15
10
11
12
13[d]
14[d]
15[d]
No Py
11
Zn instead of Mn
In instead of Mn
none
51
7
80
1 equiv. Mn
84
20 mol% Mn
2
[a] reaction conditions: N-Boc-benzanilide (0.5 mmol), CoBr2 (20 mol%), bipy
(40 mol%), Mn (3 equiv.), EtOH (2 equiv.) in DMF (2.3 mL) and pyridine (0.2
mL) was activated by TMSCl (traces) and stirred at 60 °C during 3 h. [b] GC
yield using dodecane as internal standard. [c] during 20 h. [d] 5 mol% CoBr2
10 mol% bipy.
/
First, a series of control experiments was examined. The
blank reaction without any metal did not yield any ester (Table 1,
entry 2). In order to identify any Lewis-acid assisted reactivity of
the cobalt or manganese, reactions in the presence of only
CoBr2 and bipyridine without any reductant (Table 1, entry 3),
and in the presence of only activated reductant (Mn(II) or Mn(III))
(Table 1, entry 4) were performed and none of the desired ester
was detected. Only starting material was observed in all control
experiments, consistent with the oxidative addition of a low-
valent cobalt complex which is in turn consistent with the
observation of traces of benzophenone and biphenyl in initial
reactions. Finally, removal of TMSCl from the reaction mixture
dramatically slowed down the catalysis process which only
attained 24% conversion after 3h – albeit the reaction could be
pushed to 65% yield after 20 h (Table 1, entry 5 vs entry1). This
important difference in rate points out the specific role of TMSCl
as a manganese activating agent.[17]
Figure 2. Scope of N,N-bis-substituted benzamide. GC yield using dodecane
as internal standard are given. Reaction conditions: benzamide (0.5 mmol),
CoBr2 (5 mol%), bipy (10 mol%), Mn (1 equiv.), EtOH (2 equiv.) in DMF (2.3
mL) and pyridine (0.2 mL) was activated by TMSCl (traces) and stirred at
60 °C. [a] reaction was heated at 80 °C. Ts = p-toluenesulfonyl.
The catalytic system was next examined and different
Co(II) sources were tested. Changing cobalt bromide for the
chloride or acetate precursor had no influence on the process
(Table 1, entries 6 and 7). The use of a ligand, and in particular
N-heteroaromatics, was detrimental for the reaction to proceed
(Table 1, entry 1 and 8 vs entry 9). Similarly, the use of pyridine
as co-solvent greatly enhanced the reactivity (Table 1, entry 10).
Replacing the manganese reductant with either zinc or indium
led to a decrease of reactivity (Table 1, entries 11 and 12).
We then subjected N-methyl-N-Boc-benzamides to our
methodology (Figure 3). Gratifyingly, the reaction tolerates a
wide variety of functionalities, such as methyl (10 to 12),
methoxy (13), dimethylamino (14), cyano (15), ester (16) and
even aldehyde (17). In the case of the benzamide bearing
methyl ester group (16), transesterification of the latter was also
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observed. Iodo-, bromo- and even chlorobenzamides (18) were
completely converted, with concomitant protodehalogenation,
into ethyl benzoates (2) .The process could even be extended to
the cinnamyl amide (19), as well as heteroaromatic compounds
(20 to 22) and gave the desired esters in high yields. We were
pleased to see that our methodology could also successfully be
applied to aliphatic amides. In our reaction conditions, primary
(23), neopentylic (24) and secondary (25 and 26) aliphatic
amides were smoothly converted into esters. Gratifyingly, no
epimerization of the chiral α-stereocenter of aminoacid 26
occurred during the process.[19]
Finally, we examined the reactivity of a variety of alcohol
coupling partners which were used in only a slight excess (1.2
equiv.) (Figure 4). Numerous primary alcohols bearing various
functional groups were reacted. Different chain lengths (27 to
29) as well as functional groups such as aryl (30), methoxy (31)
and even dimethylamino (32) groups were smoothly activated.
Interestingly, the presence of a secondary amino group (33) on
the alcohol chain completely inhibited the catalysis. Nonetheless,
we were delighted to observe the full conversion of the
chlorinated alcohol into its corresponding ester (34) though the
protodehalogenated side product was also observed (83:17 ratio
of chlorinated to dechlorinated products). Surprisingly, while
allylic alcohol (35) was completely unreactive, homoallylic
alcohol (36) was successfully converted and the corresponding
ester was isolated in good yield. Noteworthy, a small amount of
Z to E isomerization of ca. 10% was observed for the latter.
Benzylic (37 and 38) or heterobenzylic (39) alcohols also proved
to be efficient coupling partners in the reaction. In contrast with
previously used halogenated aryl partners (38 vs 18),
chlorinated benzylic
alcohol
did not
undergo
any
protodehalogenation side reactions yielding the corresponding
ester 38 in 80% yield. Poor nucleophiles such as phenol (40 and
41) were converted into esters in moderate yields along with a
substantial amount of unprotected benzamide. This
methodology was next applied to various secondary alcohols.
Interestingly, the reaction was significantly influenced by their
steric hindrance. Indeed less sterically hindered secondary
alcohols such as cyclobutanol (43) were esterified very
efficiently while isopropanol (42), cyclopentanol (44) and
cyclohexanol (45) led to around 65% yields of the corresponding
esters. Hexafluoroisopropanol could also be used as a partner
despite its poor nucleophilicity and the corresponding ester 46
was isolated in 26% yield.
Figure 3. Scope of N-methyl-N-Boc-amides. Isolated yields are given.
Reaction conditions: amide (0.5 mmol), CoBr2 (5 mol%), bipy (10 mol%), Mn
(1 equiv.), EtOH (2 equiv.) in DMF (2.3 mL) and pyridine (0.2 mL) was
activated by TMSCl (traces) and stirred at 60 °C during 20 h. [a] reaction was
heated at 80 °C. [b] 1-butanol instead of ethanol. Ad = adamantyl
Figure 4. Scope of the alcohol coupling partner. Isolated yields are given. Reaction conditions: benzamide (1 mmol), CoBr2 (5 mol%), bipy (10 mol%), Mn (1
equiv.), alcohol (1.2 equiv.) in DMF (4.6 mL) and pyridine (0.4 mL) was activated by TMSCl (traces) and stirred at 60 °C during 20 h. Ar = p-anisol [a] reaction was
heated at 80 °C. [b] 2 equiv. of alcohol was used.
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Tertiary alcohols such as 1-adamantanol (47) were completely
inert under these reaction conditions and only the starting
material was recovered.
CNRS and the Ecole Polytechnique. We acknowledge Sophie
Bourcier for HRMS analysis, the members of Laboratoire de
Synthèse Organique for donating chemicals and Stéphanie
Dupuy for manuscript corrections.
As a proof of concept of our methodology for late-stage
functionalization, we tackled the coupling of N-Boc-
methoxybenzamide with structurally complex alcohols such as
natural products or fragrances which would give access to
advanced compounds. Under our reaction conditions, L-
citronellol (48), (+)-p-Menth-1-en-9-ol (49), (+)-menthol (50) and
(-)-myrtenol (51) were successfully acylated and gave access to
the ester derivatives in moderate to excellent isolated yields.
The scalability of this cobalt-catalyzed esterification of amides
was evaluated. Thus, with a reduced catalyst loading of 1 mol%,
we were pleased to isolate 76% yield of ester 48 on a 10 mmol
scale. This result demonstrates the high activity of the cobalt
catalytic system for the conversion of benzamide derivatives into
esters.
Moreover this methodology can be directly carried out in a
one-pot sequence starting from N-methylbenzamide. First, the
latter is converted into N-Boc-benzamide and is subsequently
reacted in the cobalt catalysis without any intermediary workup.
Importantly, both the t-butanol, generated in the Boc introduction
step, as well as the DMAP catalyst used, did not interfere at all
with the catalytic process and the corresponding ester was
obtained in 84% yield.
To conclude, we have developed a new cobalt-catalyzed
esterification of N-Boc-benzamides allowing a straightforward
route to access esters. The particular advantages of this newly
discovered methodology include the use of an inexpensive,
simple and low loading catalyst system, the direct and practical
process which requires neither distilled solvents nor inert
atmosphere, as well as mild reaction conditions. A broad scope
of variously functionalized alcohols and amides were compatible
with this methodology. Moreover, a one-pot process enables the
direct synthesis of these esters from benzamides. Deeper
mechanistic investigations are currently on-going as well as
developing a second generation catalytic system that would be
even more active.
Keywords: Cobalt • Amides • Esterification • Cross-coupling •
Homogeneous catalysis
[1]
[2]
For reviews in C–N bond activation see: a) K. Ouyang, W. Hao, W.-X.
Zhang, Z. Xi, Chem. Rev. 2015, 115, 12045-12090; b) Q. Wang, Y. Su,
L. Li, H. Huang, Chem. Soc. Rev. 2016, 45, 1257-1272.
For reviews on amides directed ortho-metallation see: a) M. C. Whisler,
S. MacNeil, V. Snieckus, P. Beak, Angew. Chem. Int. Ed. 2004, 43,
2206-2225; Angew. Chem. 2004, 116, 2256-2276; b) V. Snieckus,
Chem. Rev. 1990, 90, 879-933.
[3]
For some recent reviews on C–H activation see: a) M. Pichette-
Drapeau, L. J. Gooßen, Chem. Eur. J. 2016, 22, 18654-18677; b) J. R.
Hummel, J. A. Boerth, J. A. Ellman, Chem. Rev. 2016, DOI:
10.1021/acs.chemrev.6b00661; c) T. Gensch, M. N. Hopkinson, F.
Glorius, J. Wencel-Delord, Chem. Soc. Rev. 2016, 45, 2900-2936; d)
M.-L. Louillat, F. W. Patureau, Chem. Soc. Rev. 2014, 43, 901-910; e)
C. S. Yeung, V. M. Dong, Chem. Rev. 2011, 111, 1215-1292; f) J.
Wencel-Delord, T. Droge, F. Liu, F. Glorius, Chem. Soc. Rev. 2011, 40,
4740-4761; g) L. Ackermann, Chem. Rev. 2011, 111, 1315-1345; for
review in C–H activation using rhodium catalyst see: h) D. A. Colby, A.
S. Tsai, R. G. Bergman, J. A. Ellman, Acc. Chem. Res. 2012, 45, 814-
825; using palladium catalyst see: i) T. W. Lyons, M. S. Sanford, Chem.
Rev. 2010, 110, 1147-1169; j) X. Chen, K. M. Engle, D.-H. Wang, J.-Q.
Yu, Angew. Chem. Int. Ed. 2009, 48, 5094-5115; Angew. Chem. 2009,
121, 5196-5217; using ruthenium catalyst see: k) P. B. Arockiam, C.
Bruneau, P. H. Dixneuf, Chem. Rev. 2012, 112, 5879-5918; using
cobalt catalyst see: l) D. Wei, X. Zhu, J.-L. Niu, M.-P. Song,
ChemCatChem 2016, 8, 1242-1263; m) M. Moselage, J. Li, L.
Ackermann, ACS Catal. 2016, 6, 498-525; n) K. Gao, N. Yoshikai, Acc.
Chem. Res. 2014, 47, 1208-1219; using first-row metals catalyst see:
o) W.-H. Rao, B.-F. Shi, Org. Chem. Front. 2016, 3, 1028-1047; p) J.
Miao, H. Ge, Eur. J. Org. Chem. 2015, 7859-7868; q) A. A. Kulkarni, O.
Daugulis, Synthesis 2009, 4087-4109; for review in C(sp3)–H activation
see: r) R. Jazzar, J. Hitce, A. Renaudat, J. Sofack-Kreutzer, O. Baudoin,
Chem. Eur. J. 2010, 16, 2654-2672.
[4]
[5]
For reviews in others electrophile carbonyl compounds such as acyl
chlorides see: a) J. Yang, M. Deng, T. Yu, Chin. J. Org. Chem. 2013,
33, 693-703; anhydrides see: b) W. I. Dzik, P. P. Lange, L. J. Gooßen,
Chem. Sci. 2012, 3, 2671-2678; thioesters see: c) H. Prokopcová, C. O.
Kappe, Angew. Chem. Int. Ed. 2009, 48, 2276-2286; Angew. Chem.
2009, 121, 2312-2322; or their use in reductive cross coupling see: d) T.
Moragas, A. Correa, R. Martin, Chem. Eur. J. 2014, 20, 8242-8258.
a) S. Hanessian, Tetrahedron Lett. 1967, 8, 1549-1552; b) A. Charette,
P. Chua, Synlett 1998, 163-165; for others examples see: c) T. A.
Dineen, M. A. Zajac, A. G. Myers, J. Am. Chem. Soc. 2006, 128,
16406-16409; d) D. A. Evans, P. H. Carter, C. J. Dinsmore, J. C.
Barrow, J. L. Katz, D. W. Kung, Tetrahedron Lett. 1997, 38, 4535-4538;
e) E. H. White, S. Paik, Tetrahedron Lett. 1994, 35, 7731-7734; f) E. H.
White, J. Am. Chem. Soc. 1955, 77, 6011-6014; g) M. Hutchby, C. E.
Houlden, M. F. Haddow, S. N. G. Tyler, G. C. Lloyd-Jones, K. I.
Booker-Milburn, Angew. Chem. Int. Ed. 2012, 51, 548-551; Angew.
Chem. 2012, 124, 563-566; h) M. C. Bröhmer, S. Mundinger, S. Bäse,
W. Bannwarth, Angew. Chem. Int. Ed. 2011, 50, 6175-6177; Angew.
Chem. 2011, 123, 6299 -6301.
Experimental Section
Typical procedure for amide conversion into ester: a 20 mL reaction tube was
charged with N-Boc-amide (1.0 mmol), bipyridine (0.10 mmol, 15.6 mg),
manganese powder (1.0 mmol, 54.9 mg), CoBr2 (0.050 mmol, 10.9 mg), alcohol
(1.2 mmol), DMF (4.6 mL) and pyridine (0.4 mL). Then, TMSCl (0.32 mmol,
40 µL) was added to the reaction medium and the tube was sealed and placed
into heated aluminium block. The tube was stirred at the indicated temperature
for 20 h. After cooling to room temperature, the reaction medium was diluted
with Et2O and filtered through a pad of silica gel. The resulting organic layer
was washed with HCl (1N) and LiCl aqueous solution (5%) three times, and
dried over MgSO4, filtered and evaporated. The crude product was purified by
flash chromatography and characterized by NMR spectroscopy (1H, 13C).
Acknowledgements ((optional))
[6]
Review about amides reactivity towards organometallics reagents see:
V. Pace, W. Holzer, B. Olofsson, Adv. Synth. Catal. 2014, 356, 3697-
3736.
We thank the Ministère de l’Enseignement Supérieur et de la
Recherche (PhD grant to Y.B.). This work was supported by
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10.1002/chem.201702608
Chemistry - A European Journal
COMMUNICATION
[7]
a) L. Hie, N. F. Fine Nathel, T. K. Shah, E. L. Baker, X. Hong, Y.-F.
Yang, P. Liu, K. N. Houk, N. K. Garg, Nature 2015, 524, 79-83; for
highlight see: b) S. A. Ruider, N. Maulide, Angew. Chem. Int. Ed. 2015,
54, 13856-13858; Angew. Chem. 2015, 127, 14062-14064.
[13] For reviews see: a) C. Liu, M. Szostak, Chem. Eur. J. 2016,
DOI:.10.1002/chem.201605012; b) G. Meng, S. Shi, M. Szostak,
Synlett 2016, 27, 2530-2540; c) J. E. Dander, N. K. Garg, ACS Catal.
2017, 1413-1423; for the use of twisted amide in Friedel-Crafts reaction
see: d) Y. Liu, G. Meng, R. Liu, M. Szostak, Chem. Commun. 2016, 52,
6841-6844.
[8]
[9]
a) G. Meng, M. Szostak, Angew. Chem. Int. Ed. 2015, 54, 14518-
14522; Angew. Chem. 2015, 127, 14726-14730; b) G. Meng, M.
Szostak, Org. Lett. 2015, 17, 4364-4367.
[14] For the use of Ni(cod)2 paraffin capsules see: J. E. Dander, N. A.
Weires, N. K. Garg, Org. Lett. 2016, 18, 3934-3936.
a) V. Pace, W. Holzer, G. Meng, S. Shi, R. Lalancette, R. Szostak, M.
Szostak, Chem. Eur. J. 2016, 22, 14494-14498; b) C. Liu, M.
Achtenhagen, M. Szostak, Org. Lett. 2016, 18, 2375-2378; c) R.
Szostak, S. Shi, G. Meng, R. Lalancette, M. Szostak, J. Org. Chem.
2016, 81, 8091-8094; for preliminary result see: d) J. Symersky, P.
Malon, L. Grehn, U. Ragnarsson, Acta Cryst 1990, C46, 683-686.
[15] For review in earth-abundant metals to activate unreactive bonds see :
B. Su, Z.-C. Cao, Z.-J. Shi, Acc. Chem. Res. 2015, 48, 886-896.
[16] a) Y. Cai, A. D. Benischke, P. Knochel, C. Gosmini, Chem. Eur. J. 2017,
23, 250-253; b) S. Pal, S. Chowdhury, E. Rozwadowski, A. Auffrant, C.
Gosmini, Adv. Synth. Catal. 2016, 358, 2431-2435; c) X. Qian, A.
Auffrant, A. Felouat, C. Gosmini, Angew. Chem. Int. Ed. 2011, 50,
10402-10405; Angew. Chem. 2011, 123, 10586-10589; d) M. Amatore,
C. Gosmini, Angew. Chem. Int. Ed. 2008, 47, 2089-2092; Angew.
Chem. 2008, 120, 2119-2122; for reviews on reductive cross-coupling
see: e) D. J. Weix, Acc. Chem. Res. 2015, 48, 1767-1775; f) C. E. I.
Knappke, S. Grupe, D. Gärtner, M. Corpet, C. Gosmini, A. Jacobi-von-
Wangelin, Chem. Eur. J. 2014, 20, 6828-6842; for reviews on cobalt
catalyzed cross coupling see: g) C. Gosmini, A. Moncomble, Isr. J.
Chem. 2010, 50, 568-576; h) G. Cahiez, A. Moyeux, Chem. Rev. 2010,
110, 1435-1462.
[10] For C–C bond formation see: a) X. Li, G. Zou, Chem. Commun. 2015,
51, 5089-5092; b) G. Meng, M. Szostak, Org. Biomol. Chem. 2016, 14,
5690-5707; c) C. Liu, G. Meng, Y. Liu, R. Liu, R. Lalancette, R. Szostak,
M. Szostak, Org. Lett. 2016, 18, 4194-4197; d) G. Meng, S. Shi, M.
Szostak, ACS Catal. 2016, 6, 7335-7339; e) S. Shi, M. Szostak, Org.
Lett. 2016, 18, 5872-5875; f) P. Lei, G. Meng, M. Szostak, ACS Catal.
2017, 1960-1965; for C–N bond formation see: g) G. Meng, P. Lei, M.
Szostak, Org. Lett. 2017, DOI:.10.1021/acs.orglett.7b00796.
[11] For C–O bond formation see: a) L. Hie, E. L. Baker, S. M. Anthony, J.-N.
Desrosiers, C. Senanayake, N. K. Garg, Angew. Chem. Int. Ed. 2016,
55, 15129-15132; Angew. Chem. 2016, 128, 15353-15356; for C–N
bond formation see: b) E. L. Baker, M. M. Yamano, Y. Zhou, S. M.
Anthony, N. K. Garg, Nat. Commun. 2016, 7, 11554; for other
transamidation process see: c) N. A. Stephenson, J. Zhu, S. H.
Gellman, S. S. Stahl, J. Am. Chem. Soc. 2009, 131, 10003-10008; for a
nickel-catalyzed amidation of ester see: d) L. Hie, N. F. Fine Nathel, X.
Hong, Y.-F. Yang, K. N. Houk, N. K. Garg, Angew. Chem. Int. Ed. 2016,
55, 2810-2814; Angew. Chem. 2016, 128, 2860-2864; for C–C bond
formation see: e) S. Shi, M. Szostak, Chem. Eur. J. 2016, 22, 10420-
10424; f) S. Shi, G. Meng, M. Szostak, Angew. Chem. Int. Ed. 2016, 55,
6959-6963; Angew. Chem. 2016, 128, 7073-7077; g) B. J. Simmons, N.
A. Weires, J. E. Dander, N. K. Garg, ACS Catal. 2016, 6, 3176-3179; h)
N. A. Weires, E. L. Baker, N. K. Garg, Nat. Chem. 2016, 8, 75-79; for
C–B bond formation see: i) J. Hu, Y. Zhao, J. Liu, Y. Zhang, Z. Shi,
Angew. Chem. Int. Ed. 2016, 55, 8718-8722; Angew. Chem. 2016, 128,
8860-8864.
[17] For example of TMSCl used as activating agent see: a) G. Picotin, P.
Miginiac, J. Org. Chem. 1987, 52, 4796-4798; b) b) A. Fürstner, N. Shi,
J. Am. Chem. Soc. 1996, 118, 12349-12357.
[18] For review of N-methoxy-amide as directing group see: a) R.-Y. Zhu, M.
E. Farmer, Y.-Q. Chen, J.-Q. Yu, Angew. Chem. Int. Ed. 2016, 55,
10578-10599; Angew. Chem. 2016, 128, 10734–10756; for review of
bidentate directing group see: b) X. Yang, G. Shan, L. Wang, Y. Rao,
Tetrahedron Lett. 2016, 57, 819-836; c) O. Daugulis, J. Roane, L. D.
Tran, Acc. Chem. Res. 2015, 48, 1053-1064; d) G. Rouquet, N. Chatani,
Angew. Chem. Int. Ed. 2013, 52, 11726-11743; Angew. Chem. 2013,
125, 11942-11959.
[19] The enantiomeric excess was assessed by determining the
diastereoselectivty in 1H NMR of the crude reaction using (S)-1-
phenylethanol as coupling partner.
[12] G. Meng, M. Szostak, Org. Lett. 2016, 18, 796-799.
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10.1002/chem.201702608
Chemistry - A European Journal
COMMUNICATION
COMMUNICATION
Yann Bourne-Branchu, Corinne
Gosmini,* Grégory Danoun*
Page No. – Page No.
Cobalt-Catalyzed Esterification of
Amides
A practical mild and efficient cobalt-catalytic system is described that converts
amides into esters. This methodology is complementary to previous nickel-
catalyzed systems, affording new selectivity and a more diverse range of amide
substrates, including common C–H bond activation directing groups. This new
reaction requires neither inert atmosphere nor distilled solvents and even proceeds
at low catalyst loading such as 1 mol% catalyst.
This article is protected by copyright. All rights reserved.