2,6-Bis(amido)benzoic Acid with Internal Hydrogen Bond as Br?nsted Acid Catalyst for Friedel-Crafts Reaction of Indoles

Article abstract of DOI:10.1002/adsc.201401189

Benzoic acid catalysts bearing two amide groups that increase the Br?nsted acidity of the carboxylic acid moiety by internal hydrogen-bonding interactions were designed as a novel class of carboxylic acid catalysts for the Friedel-Crafts reaction of indol

Full text of DOI:10.1002/adsc.201401189

UPDATES
DOI: 10.1002/adsc.201401189
2,6-Bis(amido)benzoic Acid with Internal Hydrogen Bond as
Brønsted Acid Catalyst for Friedel–Crafts Reaction of Indoles
Katsuhiko Moriyama,a,* Toru Sugiue,a Yuki Saito,a Shoichi Katsuta,a
and Hideo Togoa,*
a
Department of Chemistry, Graduate School of Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522,
Japan
Fax: (+81)-42-290-3693; e-mail: moriyama@faculty.chiba-u.jp or togo@faculty.chiba-u.jp
Received: December 26, 2014; Revised: March 26, 2015; Published online: June 10, 2015
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201401189.
Abstract: Benzoic acid catalysts bearing two amide
groups that increase the Brønsted acidity of the car-
boxylic acid moiety by internal hydrogen-bonding
interactions were designed as a novel class of car-
boxylic acid catalysts for the Friedel–Crafts reaction
of indoles with b-nitrostyrenes and 3,3-disubstituted
3H-indoles to obtain the corresponding Friedel–
Crafts adducts in high yields. The internal hydro-
gen-bonding benzoic acid catalysts have a relatively
high Brønsted acidity compared with benzoic acid
based on the pKa measurements in DMSO by UV
spectrophotometric titration.
Keywords: Brønsted acids; carboxylic acids; Frie-
del–Crafts reaction; hydrogen bonds; indoles
Figure 1. Designed organocatalysts with internal interactions
of functional groups.
Brønsted acids are widely utilized as an organocata- bis(triflyl)methyl-2’-hydroxy-1,1’-binaphthyl catalyst
lyst for the advanced and practical transformation of reported by Ishihara and Yamamoto et al.,[5] the
organic molecules.[1] Following the development of chiral binaphthyl bis-phosphoric acid catalyst de-
chiral binaphthyl phosphoric acids by Akiyama scribed by Terada et al.,[6] and the chiral binaphthyl
et al.[2] and Terada et al.[3] for the enantioselective bis-carboxylic acid catalyst developed by Maruoka
Mannich reaction, various chiral Brønsted acid cata- et al.[7] Furthermore, organocatalysts activated by
lysts have been contrived for the corresponding enan- a Lewis acid have been developed, examples of which
tioselective reactions.[1,4] Strong acids, such as phos- are the chiral boronate carboxylic acid catalyst that is
phoric acid, sulfonic acid, and their derivatives, are es- composed of an achiral borono-carboxylic acid and
sential to promote the acid-catalyzed transformations. a chiral diol reported by Maruoka et al.,[8] as well as
However, carboxylic acid has a lower Brønsted acidity a boronate urea catalyst[9] and an achiral boronate
than these strong acids. Accordingly, improving the carboxylic acid catalyst[10] published by Mattson et al.
acidity of a carboxylic acid by non-covalent interac- However, the activation of carboxylic acids by the in-
tions is a very attractive topic. On the other hand, ternal hydrogen-bonding interaction with a neutral
Brønsted acid catalysts characterized by internal in- hydrogen of an amide has not been established so far.
teractions of the functional groups have gathered at- The hydrogen bond formed between the hydrogen of
tention because the internal interactions enhance the the amide and the oxygen of the carbonyl group is es-
Brønsted acidity of the catalyst (Figure 1). Indeed, sential for the highly ordered architecture of peptides,
Brønsted acid catalysts activated by another Brønsted and this construction opens the door to new possibili-
acid group have now emerged, including the chiral 2-
Adv. Synth. Catal. 2015, 357, 2143 – 2149
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2143

UPDATES
Katsuhiko Moriyama et al.
atoms were reported by Crane et al.[13] However, they
have never been utilized as a Brønsted acid catalyst
for organic reactions.
We report herein the preparation of 2,6-bis(amido)-
benzoic acid as the design of a powerful carboxylic
acid catalyst and the designed benzoic acid-catalyzed
Friedel–Crafts reaction of indoles with b-nitrostyrenes
and 3,3-disubstituted 3H-indoles.
First, we screened for benzoic acid derivatives as
Brønsted acid catalysts and solvents for the Friedel–
Crafts reaction of indole (1a) with b-nitrostyrene (2a)
(Table 1).[14] When 1a (1.5 equiv.) was treated with 2a
using bis(pivalamido)benzoic acid (A) as the designed
benzoic acid catalyst in CHCl3 at room temperature,
Friedel–Crafts adduct (3aa) was obtained in 88%
yield (entry 1). Whereas the reactions in CH2Cl2 and
toluene showed similar reactivity to that in CHCl3
(entries 2 and 3), the reactions in THF, EtOAc, and
MeCN gave rise to decreases in the yield of 3aa (en-
tries 4–6).
Figure 2. Design of benzoic acid with internal hydrogen
bonding as organocatalyst.
Table 1. Screening of benzoic acid and solvent for Friedel–
Crafts reactions of indole (1a) with b-nitrostyrene (2a).
ties in the catalytic transformations of organic mole-
cules.[11]
Regarding the relationship between the internal hy-
drogen-bonding interaction and the Brønsted acidity
of organic molecules, salicylic acid bearing a hydroxy
group at the ortho position of the aromatic ring has
higher acidity (pKa =16.7, in MeCN) than benzoic
acid (pKa =21.5, in MeCN) due to the formation of
an internal hydrogen bond, and the acidity of 2,6-di-
hydroxybenzoic acid having two hydroxy groups at
the ortho positions of benzoic acid is drastically in-
creased by the two internal hydrogen bonds (pKa =
12.6, in MeCN) (Figure 2, upper part).[12] Therefore,
the internal hydrogen bond formed by the carbonyl
group of benzoic acid and the neighboring hydrogen
bond donors can create a new scaffold on the benzoic
acid unit and at the same time increase the acidity of
the Brønsted acid group. However, hydroxybenzoic
acid derivatives may be inappropriate for the design
of organocatalysts because they cannot form bonds
with various functional groups while retaining the in-
Entry
Cat.
Solvent
Yield [%]
1
2
3
4
5
6
7
8
A
A
A
A
A
A
CHCl3
CH2Cl2
toluene
THF
EtOAc
MeCN
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
88
70
80
30
35
43
62
78
56
14
63
5
À
ternal hydrogen bond, i.e., O H, and are poorly solu-
ble in organic solvents. The introduction of amide
groups at the ortho positions of the benzoic acid unit,
in contrast, would allow attachment of various func-
tional groups and at the same time retain the internal
hydrogen bonds (Figure 2, lower part). The C2-sym-
metrical bis(amido)benzoic acid and its calcium(II)
complex with the internal hydrogen bonds between
benzoic acid
salicylic acid
2,6-dihydroxybenzoic acid
o-phthalic acid
thiourea catalyst
–
A
9
10
11
12
13[a]
92
[a]
À
the two amide N H groups and carboxylate oxygen
The reaction was carried out at 408C.
2144
asc.wiley-vch.de
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2015, 357, 2143 – 2149

UPDATES
2,6-Bis(amido)benzoic Acid with Internal Hydrogen Bond as Brønsted Acid Catalyst
Table 2. The effect of the functional group on the benzoic
acid catalyst.
Table 3. Friedel–Crafts reactions of indoles and pyrroles (1)
with b-nitrostyrenes (2) using the designed benzoic acid cat-
alyst.
In a control experiment of benzoic acid catalysts,
the use of benzoic acid and salicylic acid was much
less effective than that of A for the Friedel–Crafts re-
action (entries 7 and 8). It is noteworthy that use of
the highly acidic 2,6-dihydroxybenzoic acid and o-
phthalic acid led to a drastic decrease in the yield of
3aa because these acids have low solubility in CHCl3
(entries 9 and 10). When bis[3,5-bis(trifluoromethyl)
phenyl]thiourea, a previously used catalyst for the
Friedel–Crafts reaction,[13a] was used to compare its
catalytic activity with that of 2,6-bis(amido)benzoic
acid, the product was obtained in 63% yield
(entry 11). Whereas the absence of catalyst A the
Friedel–Crafts reaction gave a trace of product, eleva-
tion of the reaction temperature afforded a similar
yield to that obtained at room temperature (entries 12
and 13). Furthermore, we investigated the effect of
the functional groups on the aromatic ring or the
amide groups on the benzoic acid catalysts for this re-
action (Table 2). The use of 4-bromo-2,6-bis(pivaloy-
lamido)benzoic acid (B), 2,6-bis(acetamido)benzoic
acid (C), 2,6-bis(benzamido)benzoic acid (D), 2,6-
bis(benzensulfonamido)benzoic acid (E), and N-piva-
loyl-anthranilic acid (F) gave the Friedel–Crafts
adduct (3aa) in 83%, 40%, 78%, 75%, and 91%
yields, respectively. The significant decrease in the
yield of 3aa with catalysts C–E is attributable to their
low solubilities in CHCl3 for the present reaction.
To explore the scope of the benzoic acid-catalyzed
Friedel–Crafts reaction, various indoles (1) and b-ni-
trostyrenes (2) were examined under the optimum
conditions (Table 3). The reaction of indole 1a with b-
nitrostyrenes bearing 4-Me (2b), 3-Me (2c), 2-Me
(2d), 4-Br (2e), 4-Cl (2f), 4-CF3 (2g), 4-MeO (2h),
[a]
The reaction was carried out for 48 h.
Adv. Synth. Catal. 2015, 357, 2143 – 2149
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
2145

UPDATES
Katsuhiko Moriyama et al.
and 3-NO2 (2i) gave the corresponding products (3ab– tion with catalyst A proceeded more rapidly than that
3ai) in high yields (75–99%), respectively. When 1a with benzoic acid.
was treated with aliphatic nitropentene (2j), the de-
To elucidate the high Brønsted acidity of the inter-
sired adduct (3aj) was obtained in 78% yield. The nal hydrogen-bonding activated catalyst compared
Friedel–Crafts reaction of indoles with b,b-disubstitut- with that of the simple carboxylic acid, we measured
ed nitroalkenes, which produces synthetically useful the pKa values of benzoic acid and catalysts (A and
indole derivatives bearing a quaternary carbon center, C–F) in DMSO by UV/Vis spectrophotometry follow-
is extremely difficult because the intrinsic steric hin- ing Berkessel and OꢁDonoghueꢁs method,[16] and the
drance at the b-carbon of nitrostyrene decreases the final pKa values are summarized in Table 4.
reactivity.[14] The reaction of a-methoxycarbonyl-b-
The pKa value of benzoic acid against 4-nitrophenol
styrene (2k) with indole (1a) was also effective to (NP) as indicator was 10.6 in DMSO. Predictably, the
give the desired product (3ak) in 75% yield. pKa values of 2,6-bis(amido)benzoic acids A and C–D
The designed benzoic acid A-catalyzed transforma- were decreased to 4.28–5.17 against 4-chloro-2,6-dini-
tion was applied to the reaction of various indoles trophenol (CDNP), and that of catalyst F was 7.56
and pyrrole (1) with b-nitrostyrene 2a. Reactions of against 9-cyanofluorene (CN-FH) in DMSO. In par-
indoles bearing 5-MeO (1b), 5-Br (1c), 6-Cl (1d), 7- ticular, the acidity of 2,6-bis(benzensulfonyl)benzoic
Me (1e), and 2-Me (1f) with 2a gave the correspond- acid (E) is higher than that of 2,6-bis(amido)benzoic
ing products (3ba–3fa) in high yields (74–99%), re- acid (pKa =2.72). It is interesting to note that the
spectively. N-Methyl-protected indole (1e) was also acidities of 2,6-bis(amido)benzoic acids A, D, and E
converted into Friedel–Crafts adduct (3ga) in 98% are similar to those of the phosphoric acid catalysts
yield. Treatment of 2-methylpyrrole (1h) with 2a gave (pKa =2.42–4.22) in DMSO (see ref.[16]).
the 5-position adduct (3ha) in 85% yield.
The results suggest that the two amide groups at
The time course of the Friedel–Crafts reaction of the 2,6-positions of benzoic acid increase the Brønst-
indole (1a) with b-nitrostyrene (2a) using catalyst A ed acidity of the carboxylic acid group on an identical
or benzoic acid was monitored, and the efficiencies of molecule by the internal hydrogen bond (Table 4 and
the two catalysts were compared (Figure 3). The reac- Figure 4a), especially, the pivaloyl group has high sol-
ubility in organic solvents due to its hydrophobic
property (Figure 4b).
Next, we investigated the Friedel–Crafts reaction of
indoles with 3,3-disubstituted 3H-indoles using the de-
signed internal hydrogen-bonding benzoic acid cata-
lyst. Marchelli et al. reported this reaction under
acidic conditions, that is, in acetic acid solution.[19]
However, the catalytic reaction was never achieved.
Interestingly, treatment of indole (1a) with spiro[cy-
clohexane-1,3-[3H]indole] (4a) using catalyst A in
CH2Cl2 at 08C provided the desired 2-(3-indolyl)-spi-
ro[cyclohexane-1,3-[3H]indole] (5aa) in 92% yield,
whereas use of benzoic acid and catalyst F as Brønst-
ed acid catalysts, aswell as the thiourea catalyst drasti-
Table 4. The pKa values of benzoic acid and catalysts (A and
C-F) in DMSO solution at 208C based on Berkessel and
OꢁDonoghueꢁs method.
HA
Indicator[a]
pKa [HIn][b]
pKa [HA]
benzoic acid
NP
10.8
3.56
3.56
3.56
3.56
8.3
10.6 [11.0][c]
4.60
5.17
4.28
2.72
A
C
D
E
F
CDNP
CDNP
CDNP
CDNP
CN-FH
7.56
[a]
NP=4-nitrophenol, CDNP=4-chloro-2,6-dinitrophenol,
CN-FH=9-cyanofluorene.
Figure 3. Plot of percentage conversion for the Friedel–
Crafts reaction of indole (1a) with b-nitrostyrene (2a) using
[b]
[c]
Numbers were taken from ref.[17]
~
*
a catalytic amount of A ( ) or benzoic acid ( ) versus time
Number in brackets indicates pKa value based on Bord-
(min).
wellꢁs method taken from ref.[18]
2146
asc.wiley-vch.de
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2015, 357, 2143 – 2149

UPDATES
2,6-Bis(amido)benzoic Acid with Internal Hydrogen Bond as Brønsted Acid Catalyst
Table 5. Friedel–Crafts reactions of indoles (1) with 3,3-di-
substituted 3H-indoles (4) using the designed benzoic acid
catalyst A.
Figure 4. Effect of functional groups on the increase of
Brønsted acidity of the catalyst.
[a]
The reaction was carried out in CH2Cl2 (1.0M).
The reaction was carried out for 48 h.
[b]
Scheme 1. Friedel–Crafts reaction of indole (1a) with 3,3-
disubstituted 3H-indole (4a).
cally decreased the yield of 5aa (6%, 33%, and 14%, and 2-Me (1f) with 4a also occurred to provide the
respectively) for the present reaction (Scheme 1). As desired products (1ba–1fa) in high yields (90–94%),
a result, this reaction depends dramatically on the respectively. Moreover, 2-methylpyrrole (1h) reacted
Brønsted acidity of the catalyst to activate 3,3-disub- with 4a at the 5-position selectively to give product
stituted 3H-indole (4). Moreover, the substrate scope (5ha) in 88% yield.
of the internal hydrogen-bonding Brønsted acid-cata-
In conclusion, we have developed 2,6-bis(amido)-
lyzed Friedel–Crafts reaction was investigated with benzoic acid as a powerful carboxylic acid catalyst
various indoles and pyrroles (1), and 3,3-disubstituted that activates the Brønsted acidity of the carboxylic
3H-indoles (4) (Table 5). Reacting 3,3-disubstituted acid by internal hydrogen-bonding interactions. The
3H-indoles bearing 5-Br-3,3-cyclohexyl (4b) and 3,3- designed catalyst was more active than benzoic acid
dimethyl (4c) groups with indole (1a) provided the for the Friedel–Crafts reaction of indoles (1) with b-
corresponding products (5ab and 5ac) in quantitative nitrostyrenes (2) and 3,3-disubstituted 3H-indoles (4),
yields. The diastereomeric reaction of 3-Ph-3-Me-3H- and showed a relatively high Brønsted acidity as com-
indole (4d) with 1a furnished Friedel–Crafts adduct pared with benzoic acid based on pKa measurements
(5ad) in quantitative yield with a moderate diastereo- in DMSO by UV spectrophotometric titration.
selectivity (dr=77:23). The reaction of various indoles
bearing 5-MeO (1b), 5-Br (1c), 6-Cl (1d), 7-Me (1e),
Adv. Synth. Catal. 2015, 357, 2143 – 2149
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
2147

UPDATES
Katsuhiko Moriyama et al.
[5] A. Hasegawa, Y. Naganawa, M. Fushimi, K. Ishihara,
H. Yamamoto, Org. Lett. 2006, 8, 3175–3178.
Experimental Section
[6] N. Momiyama, T. Konno, Y. Furiya, T. Iwamoto, M.
Terada, J. Am. Chem. Soc. 2011, 133, 19294–19297.
[7] a) T. Hashimoto, K. Maruoka, J. Am. Chem. Soc. 2007,
129, 10054–10055; b) T. Hashimoto, K. Maruoka, Syn-
thesis 2008, 3703–3706; c) T. Hashimoto, N. Uchiyama,
K. Maruoka, J. Am. Chem. Soc. 2008, 130, 14380–
14381; d) T. Hashimoto, M. Hirose, K. Maruoka, J. Am.
Chem. Soc. 2008, 130, 7556–7557; e) T. Hashimoto, H.
Kimura, K. Maruoka, Tetrahedron: Asymmetry 2010,
21, 1187–1188; f) T. Hashimoto, H. Kimura, K. Maruo-
ka, Angew. Chem. 2010, 122, 6996–6999; Angew. Chem.
Int. Ed. 2010, 49, 6844–6847; g) T. Hashimoto, M.
Omote, K. Maruoka, Angew. Chem. 2011, 123, 3551–
3554; Angew. Chem. Int. Ed. 2011, 50, 3489–3492; h) T.
Hashimoto, H. Kimura, Y. Kawamata, K. Maruoka,
Nat. Chem. 2011, 3, 642–646; i) T. Hashimoto, H.
Kimura, Y. Kawamata, K. Maruoka, Angew. Chem.
2012, 124, 7391–7393; Angew. Chem. Int. Ed. 2012, 51,
7279–7281; j) T. Hashimoto, S. Isobe, C. K. A. Callens,
K. Maruoka, Tetrahedron 2012, 68, 7630–7635; k) T.
Hashimoto, H. Nakatsu, Y. Takiguchi, K. Maruoka, J.
Am. Chem. Soc. 2013, 135, 16010–16013.
Friedel–Crafts Reaction of Indoles (1) with b-Nitro-
styrenes (2) using 2,6-Bis(amido)benzoic Acid
Catalyst
To a solution of 2a (37.3 mg, 0.25 mmol) and A (16.0 mg,
0.050 mmol) in CHCl3 (125 mL) was added 1a (43.9 mg,
0.375 mmol) at room temperature, and the reaction mixture
was stirred at 408C for 24 h. Saturated aqueous NaHCO3 so-
lution (5 mL) was added to the reaction mixture, and the
product was extracted with AcOEt (10 mL”3). The com-
bined extracts were washed with brine (10 mL) and dried
over Na2SO4. The organic phase was concentrated under re-
duced pressure and the crude product was purified by silica
gel column chromatography (eluent: hexane/AcOEt=4/1)
to give desired product 3aa; yield: 57.2 mg (86%).
Friedel–Crafts Reactions of Indoles (1) with 3,3-
Disubstituted 3H-Indoles (4) using 2,6-Bis(amido)-
benzoic Acid Catalyst
To a solution of 4a (69.5 mg, 0.375 mmol) and A (8.0 mg,
0.025 mmol) in CH2Cl2 (750 mL) was added 1a (29.3 mg,
0.25 mmol) at 08C, and the reaction mixture was stirred for
24 h. Saturated aqueous NaHCO3 solution (5 mL) was
added to the reaction mixture, and the product was extract-
ed with AcOEt (10 mL”3). The combined extracts were
washed with brine (10 mL) and dried over Na2SO4. The or-
ganic phase was concentrated under reduced pressure and
the crude product was purified by silica gel column chroma-
tography (eluent: hexane/AcOEt=9/2) to give desired prod-
uct 5aa; yield: 69.6 mg (92%).
[8] T. Hashimoto, A. O. Gµlvez, K. Maruoka, J. Am.
Chem. Soc. 2013, 135, 17667–17670.
[9] a) S. S. So, J. A. Burkett, A. E. Mattson, Org. Lett.
2011, 13, 716–719; b) S. S. So, T. J. Auvil, V. J. Garza,
A. E. Mattson, Org. Lett. 2012, 14, 444–447; c) S. S. So,
A. E. Mattson, J. Am. Chem. Soc. 2012, 134, 8798–
8801; d) D. M. Nickerson, V. V. Angeles, T. J. Auvil,
S. S. So, A. E. Mattson, Chem. Commun. 2013, 49,
4289–4291; e) A. M. Hardman, S. S. So, A. E. Mattson,
Org. Biomol. Chem. 2013, 11, 5793–5797; f) T. J. Auvil,
S. S. So, A. E. Mattson, Angew. Chem. Int. Ed. 2013,
52, 11317–11320; g) S. S. So, S. Oottikkal, J. D. Badjic,
C. M. Hadad, A. E. Mattson, J. Org. Chem. 2014, 79,
4832–4842; h) E. D. Couch, T. J. Auvil, A. E. Mattson,
Chem. Eur. J. 2014, 20, 8283–8287.
Acknowledgements
Financial support in the form of a Grant-in-Aid for Scientific
Research (No. 20550033) from the Ministry of Education,
Culuture, Sports, Science and Technology in Japan and the
Iodine Research Project in Chiba University is gratefully ac-
knowledged.
[10] T. J. Auvil, A. E. Mattson, Synthesis 2012, 44, 2173–
2180.
[11] For reviews on peptide catalysts, see: a) E. R. Jarvo,
S. J. Miller, Tetrahedron 2002, 58, 2481–2495; b) S. J.
Miller, Acc. Chem. Res. 2004, 37, 601–610; c) E. A. Col-
by Davie, S. M. Mennen, Y. Xu, S. J. Miller, Chem. Rev.
2007, 107, 5759–5812; d) H. Wennemers, Chem.
Commun. 2011, 47, 12036–12401.
[12] F. Eckert, I. Leito, I. Kaljurand, A. Kütt, A. Klamt, M.
Diedenhofen, J. Comput. Chem. 2009, 30, 799–810.
[13] J. D. Crane, D. J. Moreton, E. Rogerson, Eur. J. Inorg.
Chem. 2004, 4237–4241.
References
[1] For a review on Brønsted acid catalysts, see: a) T.
Akiyama, Chem. Rev. 2007, 107, 5744–5758.
[2] T. Akiyama, J. Itoh, K. Yokota, K. Fuchibe, Angew.
Chem. 2004, 116, 1592–1594; Angew. Chem. Int. Ed.
2004, 43, 1566–1568.
[14] a) G. Dessole, R. P. Herrera, A. Ricci, Synlett 2004,
2374–2378; b) R. P. Herrera, V. Sgarzani, L. Bernardi,
A. Ricci, Angew. Chem. 2005, 117, 6734–6737; Angew.
Chem. Int. Ed. 2005, 44, 6576–6579; c) E. M. Fleming,
T. McCabe, S. J. Connon, Tetrahedron Lett. 2006, 47,
7037–7042; d) J. Itoh, K. Fuchibe, T. Akiyama, Angew.
Chem. 2008, 120, 4080–4082; Angew. Chem. Int. Ed.
2008, 47, 4016–4018; e) M. Ganesh, D. Seidel, J. Am.
Chem. Soc. 2008, 130, 16464–16465; f) A. G. Scafer,
J. M. Wieting, A. E. Mattson, Org. Lett. 2011, 13, 5228–
[3] D. Uraguchi, M. Terada, J. Am. Chem. Soc. 2004, 126,
5356–5357.
[4] For reviews on chiral Brønsted acid catalysts, see:
a) M. Terada, Synthesis 2010, 1929–1982; b) J. Yu, F.
Shi, L.-Z. Gong, Acc. Chem. Res. 2011, 44, 1156–1171;
c) M. Rueping, B. J. Nachtsheim, W. Ieawsuwan, I. Ato-
diresei, Angew. Chem. 2011, 123, 6838–6853; Angew.
Chem. Int. Ed. 2011, 50, 6706–6720; d) D. Parmar, E.
Sugiono, S. Raja, M. Rueping, Chem. Rev. 2014, 114,
9047–9153.
2148
asc.wiley-vch.de
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2015, 357, 2143 – 2149

UPDATES
2,6-Bis(amido)benzoic Acid with Internal Hydrogen Bond as Brønsted Acid Catalyst
5231; g) E. MarquØs-López, A. Alcaine, T. Tejero, R. P.
[17] a) F. G. Bordwell, J. C. Branca, D. L. Hughes, W. N.
Olmstead, J. Org. Chem. 1980, 45, 3305–3313; b) F. G.
Bordwell, Acc. Chem. Res. 1988, 21, 456–463.
[18] a) W. S. Matthews, J. E. Bares, J. E. Bartmess, F. G.
Bordwell, F. J. Cornforth, G. E. Drucker, Z. Margolin,
R. J. McCallum, G. J. McCollum, N. R. Vanier, J. Am.
Chem. Soc. 1975, 97, 7006–7014; b) G. Jakab, C.
Tancon, Z. Zhang, K. M. Lippert, P. R. Schreiner, Org
Lett. 2012, 14, 1724–1727.
Herrera, Eur. J. Org. Chem. 2011, 3700–3705.
[15] a) J.-R. Gao, H. Wu, B. Xiang, W.-B. Yu, L. Han, Y.-X.
Jia, J. Am. Chem. Soc. 2013, 135, 2983–2986; b) K.
Mori, M. Wakazawa, T. Akiyama, Chem. Sci. 2014, 5,
1799–1803.
[16] P. Christ, A. G. Lindsay, S. S. Vormittag, J.-M. Neudçrfl,
A. Berkessel, A. M. C. OꢁDonoghue, Chem. Eur. J.
2011, 17, 8524–8528.
[19] V. Bocchi, R. Marchelli, V. Zanni, Synthesis 1977, 343–
345.
Adv. Synth. Catal. 2015, 357, 2143 – 2149
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
2149