Aminoquinoline-directed, cobalt-catalyzed carbonylation of sulfonamide sp2 C-H bonds

Article abstract of DOI:10.1039/c7cc02062g

We report a method for cobalt-catalyzed, aminoquinoline-directed sp² C-H bond carbonylation of sulfonamides. The reactions proceed in a dichloroethane solvent, and employ diisopropyl azodicarboxylate as a carbon monoxide source, Mn(OAc)₂

Full text of DOI:10.1039/c7cc02062g

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Aminoquinoline-directed, cobalt-catalyzed
carbonylation of sulfonamide sp2 C–H bonds†
Cite this:DOI: 10.1039/c7cc02062g
Tung Thanh Nguyen, Liene Grigorjeva and Olafs Daugulis
*
Received 17th March 2017,
Accepted 18th April 2017
DOI: 10.1039/c7cc02062g
rsc.li/chemcomm
We report a method for cobalt-catalyzed, aminoquinoline-directed amides possessing an appropriate directing group, preferably
sp2 C–H bond carbonylation of sulfonamides. The reactions using a first-row transition metal catalyst.2 While the second-
proceed in a dichloroethane solvent, and employ diisopropyl azodi- row transition metal-catalyzed carbonylation of C–H bonds has
carboxylate as a carbon monoxide source, Mn(OAc)2 as a cooxidant emerged as an efficient synthetic methodology,3 the use of first-
and potassium pivalate as a base. Halogen, ester, and amide func- row metals in these reactions is rare.4 The cobalt-catalyzed
tionalities are compatible with the reaction conditions. This method carbonylation of azobenzene and Schiff bases disclosed by
allows for a short and efficient synthesis of saccharin derivatives.
Murahashi is perhaps the earliest example of directed C–H
bond functionalization.4a Previously, we have shown that
2-Sulfobenzoic acid imide functionality is important in pharma- aminoquinoline benzamide carbonylation can be effected at
ceutical and food chemistry (Fig. 1).1 For example, Repinotan 1 room temperature under 1 atm of CO by employing oxygen
acts as a highly selective 5-HT1A receptor agonist and is effective from air as the terminal oxidant.4b Following this report,
in counteracting the respiratory depression produced by several groups have used aminoquinoline to direct cobalt- or
morphine.1a Ipsapirone 2 has been investigated for generalized nickel-catalyzed sp2 and sp3 C–H bond carbonylation.4c–e All
anxiety disorder treatment.1b Another imide of sulfobenzoic of these reports describe aminoquinoline amide C–H bond
acid, supidimide 3, has been used as a non-teratogenic analogue functionalization that results in the synthesis of substituted
of thalidomide.1c Saccharin 4 is an artificial sweetener,1d while phthalic acids. Sulfonamide C–H bond carbonylation under
6-nitrosaccharin 5 is its bitter derivative that activates G protein- first-row transition metal catalysis has not been reported
coupled receptors hT2R44 and hT2R61, which are thought to yet.5a–c A single paper by the group of Yu describes two
mediate a bitter taste response in humans.1d,e
examples of palladium-catalyzed C–H carbonylation.5d We
The most direct synthesis of 2-sulfobenzoic acid imides report here a method for cobalt-catalyzed, aminoquinoline-
would involve the direct carbonylation of arylsulfonic acid directed sp2 C–H bond carbonylation of sulfonamides. The
cleavage of the directing group affords saccharin derivatives.
Based on cobalt-catalyzed, aminoquinoline-directed C–H
functionalization reactions developed previously by our group,4b,6
simple cobalt salts were used as catalysts and manganese(II)
acetate was chosen as a co-oxidant. Reaction optimization is
illustrated in Table 1. The use of carbon monoxide gas gives low
conversion to 7 (entry 1). Previously, we have shown that amino-
quinoline benzamide carboxylation proceeds efficiently with
carbon monoxide at room temperature.4b At higher tempera-
tures, required for the corresponding sulfonamide carbonyla-
tion, the use of gaseous carbon monoxide is technically
challenging. A less volatile source of CO is needed for an
Fig. 1 2-Sulfobenzoic acid imides.
efficient reaction. It is known that azodicarboxylate esters
Department of Chemistry, University of Houston, Houston, TX 77204-5003, USA.
decompose at elevated temperatures releasing carbon monoxide,7a
E-mail: olafs@uh.edu
and dialkyl azodicarboxylates have been used in directed alkoxy-
† Electronic supplementary information (ESI) available: Detailed experimental
carbonylation and carbonylation of sp2 C–H bonds.7b,c When
procedures and characterization data for new compounds. See DOI: 10.1039/
c7cc02062g
diisopropyl azodicarboxylate (DIAD) was used as a CO source,
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Table 1 Optimization of reaction conditionsa
Table 2 Carbonylation of aminoquinoline sulfonamidesa
Entry
Catalyst
Cooxidant
Yield of 7, %
Yield,
%
Entry Ar
Product
1b
Co(OAc)2
Co(OAc)2
Co(OAc)2
Co(acac)2
Co(acac)3
Co(OAc)2
None
Co(OAc)2
Co(OAc)2
Co(OAc)2
Mn(OAc)2
Mn(OAc)2
Mn(OAc)2
Mn(OAc)2
Mn(OAc)2
Mn(OAc)3Á2H2O
Mn(OAc)2
None
o5
38
71
31
25
18
0
o5
62
0
2c,d
3d
4d
71
1
2
3
4
5
6
7
4-MeC6H4
68b
5d
6d
7d
8
9d,e
10d, f
Mn(OAc)2
Mn(OAc)2
4-MeOC6H4
4-tBuC6H4
4-PhC6H4
4-IC6H4
59
72
57
73
61
63
a
Sulfonamide 6 (0.5 mmol), DIAD (2.5 mmol, added 4 times, 0.625 mmol
per time), catalyst (0.15 mmol), cooxidant (1 mmol), KOPiv (1 mmol),
DCE (10 mL), 100 1C, 24 h. Yields are isolated yields. Please see the ESI
for details. Abbreviations: DIAD = diisopropyl azodicarboxylate, OPiv =
pivalate, DCE = 1,2-dichloroethane, acac = acetylacetonate, and Q = 8-
b
c
quinolinyl. Carbon monoxide was used instead of DIAD. DIAD
(2.5 mmol) was added at once at the beginning of the reaction. Reac-
tion vessel periodically opened to air. tert-Butyl azodicarboxylate used
instead of DIAD. Molybdenum hexacarbonyl used instead of DIAD.
d
e
f
38% yield of 7 was obtained (entry 2). The batchwise addition of
DIAD increases the yield to 71% (entry 3). Cobalt(II) and (III)
acetylacetonate catalysts afford lower yields compared with those
of cobalt(II) acetate (entries 4 and 5). When manganese(III)
acetate was used as a cooxidant, the yield decreased to 18%
(entry 6). The presence of cobalt is necessary (entry 7), while the
reaction under air without any cooxidant gave less than 5% of 7
(entry 8). The reaction under nitrogen gave a substantially
lowered product yield. The use of trifluoroethanol as a solvent,
which was used for previous cobalt-catalyzed reactions, gave no
product. The use of tert-butyl azodicarboxylate instead of DIAD
gave the product in lower yield (entry 9), while Mo(CO)6 was
inefficient as a carbon monoxide source (entry 10).
4-BrC6H4
4-CF3OC6H4
8
2-MeC6H4
55
The reaction scope with respect to substitution in sulfonamides
is shown in Table 2. Both electron-rich (entries 1–3, 8 and 12) and
electron-poor (entries 5–7 and 9–11) substrates afford products in
moderate to good yields. Scaling up of the reaction is feasible
without the loss of yields (entry 1). Substitution at the ortho-
position is tolerated, as sterically hindered 2-methylbenzene-
sulfonamide gives the product in 55% yield (entry 8). Similar to
cobalt-catalyzed aminoquinoline carboxamide carbonylation,4b
meta-substituted substrates react selectively at the less hindered
C–H bond (entries 9–14) due to preferential metalation at the less
sterically hindered position. The reaction is functional group
tolerant, with alkoxy (entry 2), iodo (entry 5), bromo (entry 6),
trifluoromethoxy (entry 7), trifluoromethyl (entry 9), chloro
(entry 10), fluoro (entry 11), naphthyl (entry 12), unsaturated
ester (entry 13), and amide (entry 14) substituents compatible
with the reaction conditions. The trifluoroacetylated 1,2,3,4-
tetrahydroisoquinoline derivative is carbonylated in 50% yield
(entry 14), showing the relevance of the methodology in drug-
like molecule derivatization.8 Nitro-substituted sulfonamides
9
3-CF3C6H4
3-ClC6H4
47
48
69
51
10
11
12c
3,4-F2C6H3
2-Naphthyl
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and amides are compatible with the reaction conditions. The
removal of the directing group affords saccharin derivatives.
We thank the Welch Foundation (Chair E-0044) and NIGMS
(Grant No. R01GM077635) for supporting this research.
Table 2 (continued)
Notes and references
Yield,
%
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Entry Ar
Product
13
2-Oxo-2H-1-benzo-pyranyl
65
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2-CF3CO-tetra-
hydroisoquinolinyl
14
50d
a
Sulfonamide (0.5 mmol), DIAD (2.5 mmol, added 4 times, 0.625 mmol
per time), Co(OAc)2 (0.15 mmol), Mn(OAc)2 (1 mmol), KOPiv (1 mmol),
DCE (10 mL), 100 1C, 24 h. Yields are isolated yields. Reaction vessel
b
periodically opened to air. Please see the ESI for details. Scale:
c
2.5 mmol, 30 h. Cobalt(II) chloride (20 mol%) catalyst, DIAD (1.5 mmol),
d
24 h at 120 1C. Temperature: 85 1C, 30 h.
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did not give any carbonylation product. The reaction mechanism
likely includes aminoquinoline-directed cobaltation, carbon
monoxide coordination, and migratory insertion followed by
reductive elimination from acylcobalt(III) species. Reoxidation
to cobalt(III) would complete the catalytic cycle. The reaction
mechanism is under investigation and will be published as a
full paper.
Chen introduced an 8-amino-5-methoxyquinoline auxiliary
that can be oxidatively cleaved.9 The carbonylation of sulfonamide
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5-methoxyaminoquinoline auxiliary under the original conditions
employing ceric ammonium nitrate was unsuccessful. However,
the removal of the methyl group with BBr3 followed by oxidation
with an iodine(III) reagent afforded methylsaccharin 10 in 63%
yield.10
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In conclusion, we have developed a method for cobalt-
catalyzed, aminoquinoline-directed carbonylation of aryl sulfo-
namides. The reactions proceed in the presence of DIAD as a
carbon monoxide source, Mn(OAc)2 as a cooxidant, and employ
KOPiv as a base. Functional groups such as halogens, esters,
10 A. Nakazaki, A. Mori, S. Kobayashi and T. Nishikawa, Tetrahedron
Lett., 2012, 53, 7131.
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