Diversity-oriented syntheses: Coupling reactions between electron-deficient olefins and aryl aldehydes via C(sp2)-H functionalization

Article abstract of DOI:10.1021/co500086f

A diversity-oriented syntheses by coupling three electron-deficient olefins (vinyl sulfonamides, methacrylamides, and methyl acrylates, respectively) with aryl aldehydes via C(sp²)-H functionalization were reported. These reactions gave four different skeletal products respectively under environment-friendly and mild conditions. All these reactions are highly regioselective and effective, very suitable for the preparation of synthetic building blocks and compound library, the results will enrich current coupling chemistry of olefins with aldehydes and can be applied to other chemistry areas as well.

Full text of DOI:10.1021/co500086f

Technology Note
pubs.acs.org/acscombsci
Diversity-Oriented Syntheses: Coupling Reactions Between Electron-
Deficient Olefins and Aryl Aldehydes via C(sp2)−H Functionalization
Ben Niu,† Lei Xu,† Ping Xie,§ Min Wang,† Wannian Zhao,† Charles U. Pittman, Jr.,‡ and Aihua Zhou*,†
†Pharmacy School, Jiangsu University, Xuefu Road 301, Zhenjiang, Jiangsu, China, 212013
§Scientific Information Research Institute, Jiangsu University, Xuefu Road 301, Zhenjiang, Jiangsu, China, 212013
‡Department of Chemistry, Mississippi State University, Mississippi State, Mississippi 39762, United States
S
* Supporting Information
ABSTRACT: A diversity-oriented syntheses by coupling
three electron-deficient olefins (vinyl sulfonamides, methacry-
lamides, and methyl acrylates, respectively) with aryl aldehydes
via C(sp2)−H functionalization were reported. These reactions
gave four different skeletal products respectively under
environment-friendly and mild conditions. All these reactions
are highly regioselective and effective, very suitable for the
preparation of synthetic building blocks and compound library,
the results will enrich current coupling chemistry of olefins
with aldehydes and can be applied to other chemistry areas as
well.
KEYWORDS: diversity-oriented synthesis, C(sp2)−H functionalization, environmentally friendly, regioselective, olefin, aldehydes
he oxidative cross coupling of activated aldehyde Csp2−H
functionalization. They generate versatile synthetic substrates
2
Tbonds with another Csp −H bond has attracted a lot of which are very useful for the preparation of natural products
and compound library.2 Normally these reactions are atom-
economic and highly efficient.3 The coupling reaction between
olefins and aldehydes is especially desirable and valuable for
forming carbon−carbon bonds important for constructing
molecular skeletons and synthetic building blocks,4 due to the
ready availability of both reagents, especially aldehydes.
Recently, some progress in this quest has been achieved,
where aldehyde C(O)−H bonds have been activated for
coupling reactions with electron-rich olefins Csp2−H bonds to
afford ketones.5 Despite this initial progresses,6 reactions of
electron-deficient olefins with the aldehyde C(sp2)−H bonds
have great potential for further development of space and
exploration.
recent attention,1 because these reactions involve C(sp2)−H
Table 1. Oxidative Coupling of N,N-Diethyl Vinyl
a
Sulfonamide with Benzaldehyde
catalyst
(mol %)
reaction time
(h)
yield
b
entry
oxidant
solvent
(%)
1
CuBr2 (20)
CuO (20)
CuI (20)
O2
10
10
10
10
10
10
10
10
10
10
10
10
10
2
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
DTBP
TBHP
DTBP
TBHP
70
Reports exist where aldehydes and electron-rich phenyl-
substituted electron-rich olefins were used for oxidative
coupling reactions.7 However, only a couple of reports of
coupling reactions between aldehydes and electron-deficient
olefins were reported.5a,b We have recently communicated an
initial report of cascade cross coupling via C(sp2)−H
functionalization to form carbon−carbon bonds from aldehydes
and electron-deficient methacrylamides.7c We now expand this
chemistry by using another two electron-deficient olefins (vinyl
sulfonamides and methacrylates), and different unexpected
structures of products are obtained in good yields.
3
trace
trace
trace
10
4
CuCl2 (20)
CuCl2 (20)
CuCl2 (20)
CuCl2 (20)
CuCl2 (20)
CuCl2 (10)
CuCl2 (20)
CuCl2 (20)
CuCl2 (20)
DCE
5
dioxane
toluene
CH3CN
DMF
6
7
trace
trace
65
8
9
10
11
12
13
73
70
a
Reaction conditions: benzaldehyde (3.5 equiv), vinyl sulfonamide (1
equiv), aqueous TBHP [tert-butyl hydroperoxide 70 wt % in water (2.5
equiv)], copper catalyst (10 mol %, or 20 mol % of 2a). Isolated yield
is based on reactant 2a, DTBP = di-tert-butyl peroxide.
Received: June 3, 2014
Revised: July 22, 2014
Published: July 25, 2014
b
© 2014 American Chemical Society
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Technology Note
Table 2. Addition of Aromatic Aldehydes to N,N-
Table 3. Oxidative Cross Coupling Cascade Reactions of N-
alkyl-N-phenylmethacrylamide 4a−c with Aryl Aldehydes
a
Disubstituted Vinyl Sulfonamides via C(sp2)−H
a
Functionalization
a
Reaction conditions: benzaldehyde (3.5 equiv), vinyl sulfonamide (1
equiv), aqueous TBHP [tert-butyl hydroperoxide 70 wt % in water (2.5
b
equiv)]. Isolated yield is based on reactant 2.
a
Reaction conditions: aldehyde (3.5 equiv), N-alkyl-N-phenylacryla-
mide (1 equiv), aqueous TBHP (70 wt % in water, 2.5 equiv), copper
catalyst (20 mol % of 4a−c). Isolated yield is based on reactant 4
b
Reaction conditions were screened to search for suitable
oxidative coupling results between the electron-deficient olefins
and aryl aldehydes. Benzaldehyde and N,N-diethyl vinyl
sulfonamide were selected as representative reactants for
screening, and various catalysts, solvents, reaction times (h)
and yields were screened. On the basis of previous research,8
metal catalyst screening focused mainly on copper systems
which had proved to be good for promoting oxidative coupling
of aldehydes with other nucleophiles or aromatic Csp2−H
bonds to form new C−C bonds.9 But some reactions without
metal catalysts were also screened. Example screening results
are presented in Table 1.
Scheme 1. Oxidative Coupling of N,N-
Diethylmethacrylamide 6 with Aryl Aldehydes
Screening reactions between benzaldehyde and N,N-diethyl
vinyl sulfonamide10 (Table 1), demonstrated that excess
benzaldehyde (3.5 equiv) and aqueous TBHP (2.5 equiv,
70% in water as an oxidant) promoted conversion to N,N-
diethyl-3-oxo-phenylpropyl-1-sulfonamide 3a. When CuBr2 or
CuI, (20% mol) were used as catalysts in the absence of solvent
(entries 1, 3), none or only trace amounts of product 3a was
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Technology Note
ones without CuCl2 catalyst, so both reaction conditions were
used respectively for the following coupling reactions.
Scheme 2. Oxidative Cross Coupling of Methyl Methacrylate
with Aryl Aldehydes
Eight couplings with different vinyl sulfonamides were
investigated at the selected conditions. All gave N,N-dialkyl-3-
oxo-3-arylpropyl-1-sulfonamides in good yields (Table 2). The
coupling chemistry between electron-deficient vinyl sulfona-
mides and aldehydes was extended to methacrylamides.
Interestingly, when the vinyl sulfonamides were replaced by
N-alkyl-N-phenylamide groups, the couplings proceeded as
cascade reaction sequences where initial Csp2−H/Csp2−H
coupling was followed by intramolecular cyclization. Instead of
giving linear skeletal products analogous to 3a−h, these cascade
reactions gave ketone oxindole derivatives 5a−i in moderate
yields (Table 3). The electron-withdrawing 2-nitrobenzalde-
hyde was also tried for the reactions with N,N-diethyl vinyl
sulfonamide and N-methyl-N-phenylmethacrylamide as de-
scribed in Tables 2 and 3, respectively, but we found that
both reactions did not proceed well affording low yields of
corresponding products.
When N-alkyl-N-phenylamide group of methacrylamide 4
was replaced by N,N-dialkyl amide group, this coupling reaction
could not undergo cascade cyclizations. Instead, linear coupling
occurred similar to that with the N,N-disubstituted vinyl
sulfonamides. However, the original methacrylamide double
bond was still retained in each of the coupling products when
N,N-dialkylamides were employed (Scheme 1). Here N,N-
dialkyl methacrylamide was used as a representative reactant.
Both p-methylbenzaldehyde and p-methoxybenzaldehyde re-
acted well with N,N-diethyl methacrylamide, respectively, to
give N,N-diethyl-2-methyl-4-oxo-4-arylbut-2-enamides 7a, 7b in
good yields.(Scheme 1)
detected. Surprisingly, using CuO gave about 70% yields of 3a.
Using DCE, dioxane, CH3CN or DMF as solvents (entries 4, 5,
7, 8) with CuCl2 as a catalyst did not afford any 3a or only
produced trace amounts of this product. In toluene (entry 6),
the reaction generated only a 10% yield of 3a. Employing
CuCl2 (10% mol) in the absence of organic solvent (entry 9)
unexpectedly gave 3a in 65% yield after 10 h. Increasing the
amount of CuCl2 to 20% mol without solvent (entry 11)
increased the yield of 3a to 73%. When no catalyst was used,
the reaction still proceeded well. After 18 h, a 70% yield was
observed. On the basis of the screening results, we found the
reactions with CuCl2 as a catalyst were not different from the
Scheme 3. Proposed Reaction Mechanisms for the Couplings of Vinyl Sulfonamides, Methacrylamides, and Methacrylates with
Aryl Aldehydes
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These couplings were further extended to using methyl
methacrylate as the electron-deficient reactant. Methacrylate is
a representative electron-deficient ester, p-methylbenzaldehyde,
p-methoxybenzaldehyde and m-nitrobenzaldehyde were em-
ployed as representative aryl aldehydes to react with methyl
methacrylate (Scheme 2). In the absence of metal catalysts,
these coupling reactions proceeded well to give good yields of
corresponding products 9a−c in aqueous TBHP. These
reaction products differ from the couplings shown in Scheme
1, because they do not retain the electron-deficient double
bond as found in coupling products of 7a−b. Instead, a single
carbon−carbon bond exists at this position, 1H NMR and mass
spectroscopy verified that there is an OH function present in
these products. This was also confirmed by IR analysis, which
showed a strong absorption at 3200−3400 cm−1, indicating the
existence of an OH group at the α-positions of 9a−c ester
functions.
How do these three different but similar electron-deficient
olefin substrates (vinyl sulfonamides, methacrylamides and
methacrylates) generate three different types of products? On
the basis of previous reports and these new results, a reaction
mechanism consistent with the products is proposed in Scheme
3. First TBHP is split by heating to give t-BuO• and HO•
radicals, which can also abstract hydrogen from t-BuOOH to
give t-BuOO• radical. The t-BuO• radical abstracts hydrogen
from the aryl aldehyde to generate the acyl radical. The acyl
radical adds to the β-position of the double bond of vinyl
sufonamides to give radical intermediate 11, which sub-
sequently abstracts a hydrogen atom from t-BuOOH to give
product 3a−h. With methacrylamides, the acyl radical adds to
the electron-deficient olefin to generate intermediate radical 12.
This loses a hydrogen atom at the amide’s β-position to give
N,N-diethyl-2-methyl-4-oxo-4-arylbut-2-enamides 7a/7b.
When R2 is aryl, the intermediate radical 12 attacks the aryl
ring of aniline substrate, followed by the abstraction of aryl
hydrogen by TBHP to give products 5a−i in moderate yields.
The intermediate radical 13 from methyl methacrylate
combines with a t-BuOO• radical from TBHP to give
intermediate 14, which undergo subsequent reduction through
O−O bond cleavage to give the α-hydroxy ester 9a−c in good
yield. The radical 12 could take the same route as radical 13,
dehydration of the analogous α-hydroxy product from 12 under
driving reaction conditions could also provide 7a/b. The reason
why the three intermediate radicals 11, 12, 13 took different
reaction routes may be related to their lifetimes and reactivity.
In summary, a diversity-oriented syntheses by coupling three
electron-deficient olefins (vinyl sulfonamides, methacrylamides
and methyl acrylates, respectively) with aryl aldehydes via
C(sp2)−H functionalization were reported. These three
reactions gave four different skeletal products, all these
reactions are atom-economical, effective and highly selective,
These results have enriched the coupling chemistry of olefins
with aldehydes, providing more green and powerful strategies
for the syntheses of molecular building blocks which can be
used for compound library production and syntheses of
different pharmaceutical molecules in the future.
AUTHOR INFORMATION
Corresponding Author
*E-mail: ahz@ujs.edu.cn.
Notes
■
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This investigation was generously supported by funds provided
by Jiangsu University (item number: 1281290006).
REFERENCES
■
(1) (a) Dwight, T. A.; Rue, N. R.; Charyk, D.; Josselyn, R.; DeBoef,
B. C−C Bond Formation via Double C−H Functionalization: Aerobic
Oxidative Coupling as a Method for Synthesizing Heterocoupled
Biaryls. Org. Lett. 2007, 9, 3137−3139. (b) Potavathri, S.; Dumas, A.
S.; Dwight, T. A.; Naumiec, G. R.; Hammann, J. M.; DeBoef, B.
Oxidant-Controlled Regioselectivity in the Oxidative Arylation of N-
Acetylindoles. Tetrahedron Lett. 2008, 49, 4050−4053. (c) Tang, B.-X.;
Song, R.-J.; Wu, C.-Y.; Liu, Y.; Zhou, M.-B.; Wei, W.-T.; Deng, G.-B.;
Yin, D.-L.; Li, J.-H. Copper-Catalyzed Intramolecular C−H
Oxidation/Acylation of Formyl-N-arylformamides Leading to Indo-
line-2,3-diones. J. Am. Chem. Soc. 2010, 132, 8900−8092. (d) Shi, Z.;
Schroder, N.; Glorius, F. Rhodium(III)-Catalyzed Dehydrogenative
̈
Heck Reaction of Salicylaldehydes. Angew. Chem. 2012, 124, 8216−
8220; Angew. Chem., Int. Ed. 2012, 51, 8092−8096. (e) Jia, C.;
Kitamura, T.; Fujiwara, Y. Catalytic Functionalization of Arenes and
Alkanes via C−H Bond Activation. Acc. Chem. Res. 2001, 34, 633−639.
(f) Allen, S. E.; Walvoord, R. R.; Salinas, R. P.; Kozlowski, M. C.
Aerobic Copper-Catalyzed Organic Reactions. Chem. Rev. 2013, 113,
6234−6458. (g) Li, Z.; Ma, L.; Tang, C.; Xu, J.; Wu, X.; Yao, H.
Palladium(II)-Catalyzed Oxidative Heck Coupling of Thiazole-4-
carboxylates. Tetrahedron Lett. 2011, 52, 5643−5647. (h) Weng, J.;
Yu, Z.; Liu, X.; Zhang, G. Palladium-Catalyzed Direct Oxidative ortho-
Acylation of Anilides with Toluene Derivatives. Tetrahedron lett. 2013,
54, 1205−1207. (i) Potavathri, S.; Kantak, A.; DeBoef, B. Increasing
Synthetic Efficiency via Direct C−H Functionalization: Formal
Synthesis of an Inhibitor of Botulinum Neurotoxin. Chem. Commun.
2011, 47, 4679−4681.
(2) (a) Sahu, N. K.; Balbhadra, S. S.; Choudhary, J.; Kohli, D. V.
Exploring Pharmacological Significance of Chalcone Scaffold: A
Review. Curr. Med. Chem. 2012, 19, 209−225. (b) Tsujimoto, S.;
Iwahama, T.; Sakaguchi, S.; Ishii, Y. The Radical-Chain Addition of
Aldehydes to Alkenes by the Use of N-Hydroxyphthalimide (NHPI)
as a Polarity-Reversal Catalyst. Chem. Commun. 2001, 2352−2353.
(c) Murugan, K.; Srimurugan, S.; Chen, C. A Mild, Catalytic and
Efficient Nazarov Cyclization Mediated by Phosphomolybdic Acid.
Chem. Commun. 2010, 46, 1127−1129.
(3) (a) Wasa, M.; Yu, J.-Q. Synthesis of β-, γ-, and δ-Lactams via
Pd(II)-Catalyzed C−H Activation Reactions. J. Am. Chem. Soc. 2008,
130, 14058−14059. (b) Jia, C.; Kitamura, T.; Fujiwara, Y. Catalytic
Functionalization of Arenes and Alkanes via C−H Bond Activation.
Acc. Chem. Res. 2001, 34, 633−639.
(4) (a) Evano, G.; Blanchard, N.; Toumi, M. Copper-Mediated
Coupling Reactions and Their Applications in Natural Products and
Designed Biomolecules Synthesis. Chem. Rev. 2008, 108, 3054−3131.
(b) Galliford, C. V.; Scheidt, K. A. Pyrrolidinyl-Spirooxindole Natural
Products as Inspirations for the Development of Potential Therapeutic
Agents. Angew. Chem., Int. Ed. 2007, 46, 8748−8758.
(5) (a) Chudasama, V.; Fitzmaurice, R. J.; Caddick, S. Hydro-
acylation of α,β-Unsaturated Esters via Aerobic C−H Activation. Nat.
Chem. 2010, 2, 592−596. (b) Tsujimoto, S.; Sakaguchi, S.; Ishii, Y.
Addition of Aldehydes and Their Equivalents to Electron-Deficient
Alkenes Using N-Hydroxyphthalimide (NHPI) as a Polarity-Reversal
Catalyst. Tetrahedron Lett. 2003, 44, 5601−5604. (c) Liu, W.; Li, Y.;
Liu, K.; Li, Z. Iron-Catalyzed Carbonylation-Peroxidation of Alkenes
with Aldehydes and Hydroperoxides. J. Am. Chem. Soc. 2011, 133,
10756−10759.
ASSOCIATED CONTENT
■
S
* Supporting Information
Experimental details and spectral characterization for all
compounds. This material is available free of charge via the
Internet at http://pubs.acs.org.
457
dx.doi.org/10.1021/co500086f | ACS Comb. Sci. 2014, 16, 454−458

ACS Combinatorial Science
Technology Note
(6) (a) Jun, C.-H.; Lee, H.; Hong, J.-B. Chelation-Assisted
Intermolecular Hydroacylation: Direct Synthesis of Ketone from
Aldehyde and 1-Alkene. J. Org. Chem. 1997, 62, 1200−1201.
(b) Wang, J.; Wang, X.; Ge, Z.; Cheng, T.; Li, R. Highly
Enantioselective Michael Addition of Cyclopentanone with Chalcones
via Novel Di-Iminium Mechanism. Chem. Commun. 2010, 46, 1751−
1753. (c) Zhou, M.-B.; Song, R.-J.; Ouyang, X.-H.; Liu, Y.; Wei, W.-T.;
Deng, G.-B.; Li, J.-H. Metal-Free Oxidative Tandem Coupling of
Activated Alkenes with Carbonyl C(sp2)−H Bonds and Aryl C(sp2)−
H Bonds Using TBHP. Chem. Sci. 2013, 4, 2690−2694. (d) Fitzmaur-
ice, R. J.; Ahem, J. M.; Caddick, S. Synthesis of Unsymmetrical
Ketones via Simple C−H Activation of Aldehydes and Concomitant
Hydroacylation of Vinyl Sulfonates. Org. Biomol. Chem. 2009, 7, 235−
237.
(7) (a) Wang, J.; Liu, C.; Yuan, J.; Lei, A. Copper-Catalyzed
Oxidative Coupling of Alkenes with Aldehydes: Direct Access to α,β-
Unsaturated Ketones. Angew. Chem., Int. Ed. 2013, 52, 2256−2259.
(b) Zhou, M.-B.; Song, R.-J.; O, X.-H.; Li, Y.; Wei, W.-T.; Deng, G.-B.;
Li, J.-H. Metal-Free Oxidative Tandem Coupling of Activated Alkenes
with Carbonyl C(sp2)−H Bonds and Aryl C(sp2)−H Bonds Using
TBHP. Chem. Sci. 2013, 4, 2690−2694. (c) Gong, W.; Xu, L.; Ji, T.;
Xie, P.; Qi, X.; Pittman, C. U.; Zhou, A. Copper-Catalyzed Oxidative
Cascade Coupling of N-Alkyl-N-phenylacrylamides with Aryl
Aldehydes. RSC Adv. 2014, 4, 6854−6857.
(8) (a) Wendlandt, A. E.; Suess, A. M.; Stahl, S. S. Copper-Catalyzed
Aerobic Oxidative C−H Functionalizations: Trends and Mechanistic
Insights. Angew. Chem., Int. Ed. 2011, 50, 11062−11087. (b) Rathke,
M. W.; Lindert, A. Reaction of Ester Enolates with Copper(II) Salts.
Synthesis of Substituted Succinate Esters. J. Am. Chem. Soc. 1971, 93,
4605−4606. (c) Schmittel, M.; Burghhart, D.-C. A. Understanding
Reactivity Patterns of Radical Cations. Angew. Chem. 1997, 109,
2658−2699; Angew. Chem., Int. Ed. 1997, 36, 2550−2589. (d) Meng,
Y.; Guo, L.-N.; Wang, H.; Duan, X.-H. Metal-Free Oxidative
Hydroxyalkylarylation of Activated Alkenes by Direct sp3 C−H
Functionalization of Alcohols. Chem. Commun. 2013, 49, 7540−7542.
(e) Xie, J.; Xu, P.; Li, H.; Xue, Q.; Jin, H.; Cheng, Y.; Zhu, C. A Room
Temperature Decarboxylation/C−H functionalization Cascade by
Visible-Light Photoredox Catalysis. Chem. Commun. 2013, 49,
5672−5674. (f) Li, X.; Xu, X.; Hu, P.; Xiao, X.; Zhou, C. Synthesis
of Sulfonated Oxindoles by Potassium Iodide Catalyzed Arylsulfony-
lation of Activated Alkenes with Sulfonylhydrazides in Water. J. Org.
Chem. 2013, 78, 7343−7348. (g) Egami, H.; Shimizu, R.; Sodeoka, M.
Concise Synthesis of Oxindole Derivatives Bearing a 3-Trifluoroethyl
Group: Copper-Catalyzed Trifluoromethylation of Acryloanilides. J.
Fluorine Chem. 2013, 152, 51−55. (h) Wu, T.; Mu, X.; Li, G.
Palladium-Catalyzed Oxidative Arylalkylation of Activated Alkenes:
Dual C−H Bond Cleavage of an Arene and Acetonitrile. Angew. Chem.,
Int. Ed. 2011, 50, 12578−12581. (i) Wu, T.; Zhang, H.; Liu, G.
Organocatalyzed Arylalkylation of Activated Alkenes via Decarbox-
ylation of PhI(O2CR)2: Efficient Synthesis of Oxindoles. Tetrahedron
2012, 68, 5229−5233.
Aldehydes: A Facile Access to ortho-Acylacetanilides. Org. Lett. 2011,
13, 3258−3261.
(10) (a) Zhou, A.; Rayabarapu, D.; Hanson, P. R. “Click, Click,
Cyclize”: A DOS Approach to Sultams Utilizing Vinyl Sulfonamide
Linchpins. Org. Lett. 2009, 11, 531−534. (b) Zhou, A.; Hanson, P. R.
Synthesis of Sultam Scaffolds via Intramolecular Oxa-Michael and
Diastereoselective Baylis−Hillman Reactions. Org. Lett. 2008, 10,
2951−2954. (c) Ji, T.; Wang, Y.; Wang, M.; Niu, B.; Xie, P.; Pittman,
C. U.; Zhou, A. Parallel Syntheses of Eight-Membered Ring Sultams
via Two Cascade Reactions in Water. ACS Comb. Sci. 2013, 15, 595−
600. (d) Tong, K.; Tu, J.; Qi, X.; Wang, M.; Wang, Y.; Fu, H.; Pittman,
C. U.; Zhou, A. Syntheses of Five- and Seven-Membered Ring Sultam
Derivatives by Michael Addition and Baylis−Hillman Reactions.
Tetrahedron 2013, 69, 2369−2375. (e) Wang, M.; Wang, Y.; Qi, X.;
Xia, G.; Tong, K.; Tu, J.; Pittman, C. U.; Zhou, A. Selective Synthesis
of Seven- and Eight-Membered Ring Sultams via Two Tandem
Reaction Protocols from One Starting Material. Org. Lett. 2012, 14,
3700−3703. (f) Zang, Q.; Javed, S.; Hill, D.; Ullah, F.; Bi, D.;
Porubsky, P.; Neuenswander, B.; Lushington, G. H.; Santini, C.;
Organ, M. G.; Hanson, P. R. Automated Synthesis of a Library of
Triazolated 1,2,5-Thiadiazepane 1,1-Dioxide via a Double aza-Michael
Strategy. ACS Combi. Sci. 2012, 14, 456−459. (g) Faisal, S.; Ullah, F.;
Maity, P. K.; Rolfe, A.; Samarakoon, T.; Porubsky, P.; Neunswander,
B.; Lushington, G.; Basha, F.; Organ, M. G.; Hanson, P. R. Facile
(Triazolyl)methylation of MACOS-Derived Benzofused Sultams
Utilizing ROMP-Derived OTP Reagents. ACS Comb. Sci. 2012, 14,
268−272.
(9) (a) Zhang, C.; Zong, X.; Zhang, L.; Jiao, N. Copper-Catalyzed
Aerobic Oxidative Cross-Dehydrogenative Coupling of Amine and α-
Carbonyl Aldehyde: A Practical and Efficient Approach to α-
Ketoamides with Wide Substrate Scope. Org. Lett. 2012, 14 (13),
3280−3283. (b) Rout, S. K.; Guin, S.; Ghara, K. K.; Banerjee, A.; Patel,
B. K. Copper Catalyzed Oxidative Esterification of Aldehydes with
Alkylbenzenes via Cross Dehydrogenative Coupling. Org. Lett. 2012,
14, 3982−3985. (c) Yoo, W.-J.; Li, C.-J. Highly Stereoselective
Oxidative Esterification of Aldehydes with β-Dicarbonyl Compounds.
J. Org. Chem. 2006, 71, 6266−6268. (d) Jia, X.; Zhang, S.; Wang, W.;
Luo, F.; Cheng, J. Palladium-Catalyzed Acylation of sp2 C−H bond:
Direct Access to Ketones from Aldehydes. Org. Lett. 2009, 11, 3120−
3123. (e) Tang, B.-X.; Song, R.-J.; Wu, C.-Y.; Liu, Y.; Zhou, M.-B.;
Wei, W.-T.; Deng, G.-B.; Yin, D.-L.; Li, J.-H. Copper-Catalyzed
Intramolecular C−H Oxidation/Acylation of Formyl-N-arylforma-
mides Leading to Indoline-2,3-diones. J. Am. Chem. Soc. 2010, 132,
8900−8902. (f) Wu, Y.; Li, B.; Mao, F.; Li, X.; Kwong, F. Y. Palladium-
Catalyzed Oxidative C-H Bond Coupling of Steered Acetanilides and
458
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