Palladium-catalyzed annulation of diarylamines with olefins through C-H activation: Direct access to N-arylindoles

Article abstract of DOI:10.1002/anie.201406284

A palladium-catalyzed dehydrogenative coupling between diarylamines and olefins has been discovered for the synthesis of substituted indoles. This intermolecular annulation approach incorporates readily available olefins for the first time and obviates the need of any additional directing group. An ortho palladation, olefin coordination, and β-migratory insertion sequence has been proposed for the generation of olefinated intermediate, which is found to produce the expected indole moiety.

Full text of DOI:10.1002/anie.201406284

Angewandte
Chemie
DOI: 10.1002/anie.201406284
Heterocycle Synthesis
Palladium-Catalyzed Annulation of Diarylamines with Olefins through
À
C H Activation: Direct Access to N-Arylindoles**
Upendra Sharma, Rajesh Kancherla, Togati Naveen, Soumitra Agasti, and Debabrata Maiti*
Abstract: A palladium-catalyzed dehydrogenative coupling
between diarylamines and olefins has been discovered for the
synthesis of substituted indoles. This intermolecular annulation
approach incorporates readily available olefins for the first
time and obviates the need of any additional directing group.
An ortho palladation, olefin coordination, and b-migratory
insertion sequence has been proposed for the generation of
Scheme 1. Synthesis of N-arylated indoles involving olefins.
olefinated intermediate, which is found to produce the expected
indole moiety.
À
I
ndole is one of the most ubiquitous heterocycles found in
ortho C H activation, and in a few cases to achieve further
nature. Owing to significant biological activities,[1] indole has
become an important component in many pharmaceutical
agents.[2] Consequently, their preparation has been a major
area of research for well over a hundred years and innumer-
able methods,[3] including Fischer[4] and Buchwald[5] indole
synthesis have been reported. Recently, transition-metal-
catalyzed directing-group-assisted heteroannulation of
amines with carbonyl compounds[6] and alkynes have
emerged for their synthesis.[7]
heteroannulations.[12f] Recently, Patureau and co-workers
À
disclosed the dehydrogenative C N cross-coupling of unpro-
tected secondary anilines through ortho-N-carbazolation
using a ruthenium catalyst.[13]
In continuation of our research to utilize widely available
olefins for the synthesis of valuable products,[14] here we
disclose a palladium-catalyzed method for the synthesis of 2-
substituted N-arylindoles by directly reacting various diaryl-
amines and olefins. Because of the low cost and wide
availability of various olefins, such an approach would allow
straight-forward synthesis of N-arylindoles. The generality of
this strategy is described here by synthesizing an exemplary
set of indole compounds (> 40 examples), most of which
represent new chemical entities.
N-arylindoles are present in many biologically as well as
pharmaceutically important compounds.[8,9] In 2012, the
group of Zheng constructed 1,2-disubstituted indoles from
styryl anilines by using a ruthenium-based photocatalytic
method (Scheme 1).[10] Unfortunately, this intramolecular
reaction does not proceed without an p-alkoxyphenyl amine
moiety.
In this context, we envisaged that a direct intermolecular
oxidative coupling of diaryl amine with abundantly available
olefins (Fujiwara–Moritani reaction)[11] may be utilized for N-
arylindole synthesis. Previously, various nitrogen-containing
substrates including sulfonyl aniline,[12a] carbonyl aniline,[12b,c]
aniline,[12d] and benzyl amine[12e] were successfully applied as
the directing group to enhance the reactivity, selectivity for
Systematic studies revealed that 1,2-disubstituted indole
moieties can be synthesized (89% GC yield; 85% isolated)
from diphenylamine (1 mmol) and styrene (0.25 mmol) by
using Pd(OAc)2 (10 mol%) and 1,10-phenanthroline
(20 mol%), in acetic acid without any additional oxidant.
To explore the substrate scope of this simple system, we
reacted different styrenes with diphenylamine under the
optimized reaction conditions (Table 1). Along with the
expected product, the 1,3-disubstituted indole regioisomer
was also formed. Notably, in most of the cases, the ratio of 1,2-
diarylated and 1,3-diarylated indole is limited to 99:1.[15] In
a few cases, such as for 3a, 3c, 3j, and 3q, and increased
amount of the 1,3-disubstituted indole product was observed.
Styrenes with ortho/meta/para substituents reacted with
diphenylamine to produce the 1,2-diarylated indole in 41-
85% yield (3a–i and 3o–q). Various halides at the ortho/
para position were well tolerated (3d–f and 3o–p). Styrene
with functional groups such as acetoxy, ester, and cyano
reacted successfully (3g–i). Switching to a substituted diaryl-
amine did not affect the outcome of the reaction and the
expected indoles were obtained in preparatively useful yield
(3j–n and 3r). A sterically demanding trisubstituted styrene
succeeded in producing 1,2-diarylated indole compound (3s).
Notably, heterocyclic olefins can also be employed to prepare
N-arylindoles (3u and 3v). Efforts to incorporate ArNHR
[*] Dr. U. Sharma,[+] Dr. R. Kancherla, T. Naveen, S. Agasti,
Prof. D. Maiti
Department of Chemistry, Indian Institute of Technology Bombay
Powai, Mumbai-400 076 (India)
E-mail: dmaiti@chem.iitb.ac.in
[+] Current address: Natural Plant Product Division
CSIR-IHBT, Palampur, H.P., India
[**] This activity is supported by Science and Engineering Research
Board, India (No. SR/S1/IC-24/2011). Financial support received
from DST under Fast Track Scheme (U.S. and R.K.) and CSIR (T.N.
and S.A.) is gratefully acknowledged. D.M. sincerely thanks
reviewers for insightful discussions. Palladium catalysts were
obtained as a gift from Johnson Matthey Chemicals, MIDC Taloja,
India. This activity is supported by BRNS, India.
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.201406284.
Angew. Chem. Int. Ed. 2014, 53, 1 – 6
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1
These are not the final page numbers!

.
Angewandte
Communications
Table 1: Scope with symmetrical diphenylamines and styrenes.[a][18]
Table 2: Scope with respect to unsymmetrical diarylamines.[a]
Amine
Product
[a] Yield is that of the isolated product and the average of two runs. Ratio
of 1,2-diarylated and 1,3-diarylated indole is 99:1.[15] [b] Ratio is 91:9.
[c] Ratio is 3:1. [d] Ratio is 4:1. [e] Ratio is 85:15. brsm=based on
recovered starting material.
(R = Me, Et, iPr, Ts, and Ac) in place of ArNH(Ar’), either
gave low yields of desired the indole products or formed
a mixture of inseparable compounds.
[a] Yield is that of the isolated product and an average of two runs. A/B
ratio was determined by GC-MS analysis of the crude reaction mixture.
[b] Isolated as an inseparable mixture of two products. [c] Isolated yield
of the major isomer.
In the case of unsymmetrical diarylamines, there was
a preference for cyclization of the electron-deficient aromatic
ring with good regioselectivity (Table 2). For example, 4a and
4b preferentially cyclized to form the indole in a 3:1 (74%)
and 6:1 (73%) ratio, respectively. In the case of 4-(phenyl-
amino)benzonitrile (4c), a 47% yield of the isolated major
product (5cA) was obtained through cyclization of the
electron-deficient ring. Following a similar reactivity pattern,
a single regioisomer was observed for 4-morpholino-N-
phenylaniline (4d). When N-phenylpyridin-2-amine (4 f)
was reacted with styrene, cyclization occurred selectively
towards the benzene ring albeit in low yield. Simplicity of the
method was further demonstrated by incorporating an ortho-
chloro-substituted amine (4e) as the coupling partner.
After evaluating the scope with styrene derivatives,
different unactivated olefins were tested under the optimal
reaction conditions (Table 3). Reaction of cis- and trans-b-
methyl styrene (6a and 6b) with diphenylamine provided the
same product (7a; 53 and 23%, respectively). This difference
in the yield may be attributed to the steric hindrance for the
nucleophilic attack of the amine. In the case of simple
terminal olefins for example, 1-octene and 1-decene, the
desired 2-alkylated indole (7eA and 7 fA, respectively) was
obtained as the major product along with the 3-methyl isomer
(7eB and 7 fB). With vinylcyclohexane, 2-cyclohexylindole
7cA was isolated in 56% yield (7cA/7cB, 4:1).
The efficiency of the method was further tested by the
heteroannulation of cyclic olefins with diphenylamine to
synthesize tricyclic indole derivatives, which are present in
many bioactive natural products.[16] These scaffolds were
previously synthesized from heteroannulation of internal
alkynes or dienes through intramolecular approaches.[17]
Under the present reaction conditions both cyclic olefins as
well as cyclic dienes afforded the desired N-phenyl tricyclic
indole compounds (Table 4). In spite of the possibility of
forming regioisomeric mixtures, only one product was gen-
erated exclusively in most of the cases. Regioisomeric 1,5- and
1,3-cyclooctadiene provided the same product 9a as a result
2
www.angewandte.org
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2014, 53, 1 – 6
These are not the final page numbers!

Angewandte
Chemie
Table 3: Scope with terminal/internal olefins.[a]
Table 4: Scope with cyclic olefins (mono and dienes).[a],[18]
Olefin
Product
Olefin
Product
[a] Yield is that of isolated product and an average of two runs. Isolated
compounds were characterized by HRMS, 1D (1H NMR, 13C NMR and
DEPT) and 2D NMR (HSQC, HMBC, COSY and NOESY) spectroscopy
wherever required. [b] Yield of one isolated isomer. The other regioiso-
mer was detected by GC-MS. [c] A/B ratio was determined by GC-MS and
was isolated as an inseparable mixture.
[a] Yield is that of isolated product and an average of two runs. Isolated
compounds were characterized by HRMS, 1D (1H NMR, 13C NMR and
DEPT), and 2D NMR (HSQC, HMBC, COSY and NOESY) spectroscopy
wherever required. [b] Run without Cu(OAc)2. [c] Two isomers obtained
as an inseparable mixture.
of the isomerization of the 1,5-cyclooctadiene under the
reaction conditions. In both these cases the product can be
obtained in crystalline form and was confirmed by single-
crystal X-ray structure.[15] Cycloheptene and cyclooctene had
provided the desired compounds in synthetically useful yield
(9e and 9 f). In the case of bicyclic olefins, for example,
norbornene (8g–8h), the corresponding indoline product was
obtained because of an unfavorable b-hydride elimination.
To understand the reaction mechanism, a number of
competition experiments between electronically different
styrenes and diphenyl amines were carried out. Based on
experimental findings, we realized that electron-rich styrene
as well as electron-rich diphenylamine was cyclized prefer-
entially over the neutral and electron-deficient analogues.[15]
However, the use of unsymmetrical diarylamines caused the
olefin to preferably annulate towards the electron-deficient
aromatic ring (Table 2). It is therefore likely that the electron-
deficient ring favors the initial ortho palladation and the
electron-rich phenyl ring supports the sequential N-pallada-
tion step.
Scheme 2. Deuterium-labelling experiments.
that palladium is trapped in the ortho position by the nitrogen
atom of the diarylamine. This nitrogen-atom-coordinated
palladium center is involved in an irreversible step, which
might be the alkene insertion leading to the intermediate C
À
with a N Pd bond (Scheme 3). Based on these experiments,
ortho palladation of the diarylamine was proposed for the
generation of the intermediate A. Interaction of A with olefin
will lead to the species B. Subsequently b-migratory insertion
will form the intermediate C, which can undergo b-hydride
elimination to provide 2-(N-arylated)stilbene (D). The final
product G can be produced via D and/or an indoline
intermediate F. Separate study on these putative intermedi-
ates (D and F) showed that both of them can be converted
successfully into the final product G (Scheme 4).[15] Further,
in the absence of a stoichiometric oxidant, F was generated
from D under the standard reaction conditions. Therefore, F is
The observed deuteration (Scheme 2) at the ortho/para
positions in the absence of an alkene indicated that reversible,
À
electrophilic C H palladation occurred under the reaction
conditions.[19] However, no para C H olefination of diaryl-
À
amines was observed in presence of olefins, thus indicating
Angew. Chem. Int. Ed. 2014, 53, 1 – 6
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
3
These are not the final page numbers!

.
Angewandte
Communications
[2] a) B. P. Smart, R. C. Oslund, L. A. Walsh, M. H. Gelb, J. Med.
Chem. 2006, 49, 2858 – 2860; b) A. Dandia, R. Singh, S. Khaturia,
C. Merienne, G. Morgant, A. Loupy, Bioorg. Med. Chem. 2006,
14, 2409 – 2417; c) S. Petit, Y. Duroc, V. Larue, C. Giglione, C.
Lꢀon, C. Soulama, A. Denis, F. Dardel, T. Meinnel, I. Artaud,
ChemMedChem 2009, 4, 261 – 275; d) H. Johansson, T. B.
Jorgensen, D. E. Gloriam, H. Brauner-Osborne, D. S. Pedersen,
RSC Adv. 2013, 3, 945 – 960; e) J. Alvarez-Builla, J. J. Vaquero, J.
Barluenga, Modern Heterocyclic Chemistry, Vol. 1, Wiley-VCH,
Weinheim, 2011.
[3] For selected examples of indole synthesis, see: a) R. Mçhlau,
Ber. Dtsch. Chem. Ges. 1881, 14, 171 – 175; b) A. Bischler, Ber.
Dtsch. Chem. Ges. 1892, 25, 2860 – 2879; c) R. C. Larock, E. K.
Yum, J. Am. Chem. Soc. 1991, 113, 6689 – 6690; d) R. C. Larock,
E. K. Yum, M. D. Refvik, J. Org. Chem. 1998, 63, 7652 – 7662;
e) M. Shen, B. E. Leslie, T. G. Driver, Angew. Chem. Int. Ed.
2008, 47, 5056 – 5059; Angew. Chem. 2008, 120, 5134 – 5137; f) K.
Alex, A. Tillack, N. Schwarz, M. Beller, Angew. Chem. Int. Ed.
2008, 47, 2304 – 2307; Angew. Chem. 2008, 120, 2337 – 2340; g) O.
Leogane, H. Lebel, Angew. Chem. Int. Ed. 2008, 47, 350 – 352;
Angew. Chem. 2008, 120, 356 – 358; h) R. Bernini, G. Fabrizi, A.
Sferrazza, S. Cacchi, Angew. Chem. Int. Ed. 2009, 48, 8078 – 8081;
Angew. Chem. 2009, 121, 8222 – 8225; i) Y. Tan, J. F. Hartwig, J.
Am. Chem. Soc. 2010, 132, 3676 – 3677; j) S. Jana, M. D.
Clements, B. K. Sharp, N. Zheng, Org. Lett. 2010, 12, 3736 –
3739; k) Z. Shi, F. Glorius, Angew. Chem. Int. Ed. 2012, 51,
9220 – 9222; Angew. Chem. 2012, 124, 9354 – 9356; l) D. Shan, Y.
Gao, Y. Jia, Angew. Chem. Int. Ed. 2013, 52, 4902 – 4905; Angew.
Chem. 2013, 125, 5002 – 5005.
[4] For selected examples of Fischer indole syntheses, see: a) E.
Fischer, F. Jourdan, Ber. Dtsch. Chem. Ges. 1883, 16, 2241 – 2245;
b) E. Fischer, O. Hess, Ber. Dtsch. Chem. Ges. 1884, 17, 559 – 568;
c) B. Robinson, Chem. Rev. 1963, 63, 373 – 401; d) B. Robinson,
Chem. Rev. 1969, 69, 227 – 250; e) S. Mꢁller, M. J. Webber, B.
List, J. Am. Chem. Soc. 2011, 133, 18534 – 18537; f) S. Gore, S.
Baskaran, B. Konig, Org. Lett. 2012, 14, 4568 – 4571; g) A.
Porcheddu, M. G. Mura, L. De Luca, M. Pizzetti, M. Taddei,
Org. Lett. 2012, 14, 6112 – 6115; h) D. McAusland, S. Seo, D. G.
Pintori, J. Finlayson, M. F. Greaney, Org. Lett. 2011, 13, 3667 –
3669.
[5] For selected examples of Buchwald indole synthesis, see: a) S.
Wagaw, B. H. Yang, S. L. Buchwald, J. Am. Chem. Soc. 1998, 120,
6621 – 6622; b) S. Wagaw, B. H. Yang, S. L. Buchwald, J. Am.
Chem. Soc. 1999, 121, 10251 – 10263; c) J. L. Rutherford, M. P.
Rainka, S. L. Buchwald, J. Am. Chem. Soc. 2002, 124, 15168 –
15169; d) J. Y. Chae, S. L. Buchwald, J. Org. Chem. 2004, 69,
3336 – 3339; e) A. DeAngelis, D.-H. Wang, S. L. Buchwald,
Angew. Chem. Int. Ed. 2013, 52, 3434 – 3437; Angew. Chem. 2013,
125, 3518 – 3521.
[6] Recent examples of indole synthesis through heteroannulation
of amines with carbonyl compounds: a) S. Wꢁrtz, S. Rakshit, J. J.
Neumann, T. Drçge, F. Glorius, Angew. Chem. Int. Ed. 2008, 47,
7230 – 7233; Angew. Chem. 2008, 120, 7340 – 7343; b) J. J.
Neumann, S. Rakshit, T. Drçge, S. Wꢁrtz, F. Glorius, Chem.
Eur. J. 2011, 17, 7298 – 7303; c) Y. Wei, I. Deb, N. Yoshikai, J.
Am. Chem. Soc. 2012, 134, 9098 – 9101.
Scheme 3. Plausible mechanism.
Scheme 4. Mechanistic study in support of formation of G.
an intermediate between D and G. The palladium(0) formed
can be reoxidized to palladium(II) by oxygen (air) possibly
via a peroxopalladium(II) complex.[20]
An alternative mechanism (Wacker-type) involving acti-
vation of the alkene by palladium(II), nucleophilic attack of
À
the amine followed by intramolecular C H activation to
produce F can also be proposed (Scheme 3).[15] Detailed
studies are planned to gain further insights into the plausible
mechanisms.
In summary, a versatile catalytic method for the synthesis
of substituted indoles through palladium-catalyzed intermo-
lecular annulation has been disclosed. Widely available
olefins and diarylamines are used as coupling partners.
Different styrenes with diphenylamine result in 1,2- (major)
and 1,3- (minor) diarylated indoles with a ratio of 99:1 in most
of the cases. With unsymmetrical diarylamines, cyclization is
preferred for the electron-deficient aromatic ring. Cyclic
aliphatic olefins, including dienes, afford tricyclic indole
compounds. Detailed studies for further understanding of
the mechanism and the regioselective synthesis of 3-substi-
tuted indoles are currently underway in our laboratory.
Received: June 16, 2014
Revised: August 1, 2014
Published online: && &&, &&&&
[7] For selected recent examples of indole synthesis using alkynes,
see: a) D. Zhao, Z. Shi, F. Glorius, Angew. Chem. Int. Ed. 2013,
52, 12426 – 12429; Angew. Chem. 2013, 125, 12652 – 12656; b) L.
Ackermann, A. V. Lygin, Org. Lett. 2012, 14, 764 – 767; c) Z. Shi,
C. Zhang, S. Li, D. Pan, S. Ding, Y. Cui, N. Jiao, Angew. Chem.
Int. Ed. 2009, 48, 4572 – 4576; Angew. Chem. 2009, 121, 4642 –
4646; d) D. R. Stuart, P. Alsabeh, M. Kuhn, K. Fagnou, J. Am.
Chem. Soc. 2010, 132, 18326 – 18339; e) C. Wang, H. Sun, Y.
Fang, Y. Huang, Angew. Chem. Int. Ed. 2013, 52, 5795 – 5798;
Angew. Chem. 2013, 125, 5907 – 5910; f) D. R. Stuart, M.
À
Keywords: C H activation · cyclization · indoles · palladium ·
reaction mechanisms
.
[1] a) A. J. Kochanowska-Karamyan, M. T. Hamann, Chem. Rev.
2010, 110, 4489 – 4497; b) L. D. Quin, J. A. Tyrell, Fundamentals
of Heterocyclic Chemistry: Importance in Nature and in the
Synthesis of Pharmaceuticals, Wiley, Hoboken, NJ, 2007.
4
www.angewandte.org
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2014, 53, 1 – 6
These are not the final page numbers!

Angewandte
Chemie
Bertrand-Laperle, K. M. N. Burgess, K. Fagnou, J. Am. Chem.
Soc. 2008, 130, 16474 – 16475.
[13] M.-L. Louillat, A. Biafora, F. Legros, F. W. Patureau, Angew.
Chem. Int. Ed. 2014, 53, 3505 – 3509; Angew. Chem. 2014, 126,
3573 – 3577.
[8] For use of N-arylindoles as biologically important scaffolds, see:
a) K. Andersen, T. Liljefors, J. Hyttel, J. Perregaard, J. Med.
Chem. 1996, 39, 3723 – 3738; b) E. Von Angerer, J. Strohmeier, J.
Med. Chem. 1987, 30, 131 – 136; c) E. J. Glamkowski, J. M.
Fortunato, T. C. Spaulding, J. C. Wilker, D. B. Ellis, J. Med.
Chem. 1985, 28, 66 – 73; d) P. C. Unangst, M. E. Carethers, K.
Webster, G. M. Janik, L. J. Robichaud, J. Med. Chem. 1984, 27,
1629 – 1633; e) J. Perregaard, J. Arnt, K. P. Boegesoe, J. Hyttel,
C. Sanchez, J. Med. Chem. 1992, 35, 1092 – 1101.
[9] For selected examples of N-arylindole synthesis, see: a) J.
Barluenga, A. Jimenez-Aquino, F. Aznar, C. Valdes, J. Am.
Chem. Soc. 2009, 131, 4031 – 4041; b) J. Barluenga, A. Jimꢀnez-
Aquino, C. Valdꢀs, F. Aznar, Angew. Chem. Int. Ed. 2007, 46,
1529 – 1532; Angew. Chem. 2007, 119, 1551 – 1554; c) J. Bar-
luenga, A. Jimꢀnez-Aquino, F. Aznar, C. Valdꢀs, Chem. Eur. J.
2010, 16, 11707 – 11711; d) N. Ototake, Y. Morimoto, A.
Mokuya, H. Fukaya, Y. Shida, O. Kitagawa, Chem. Eur. J.
2010, 16, 6752 – 6755; e) A. Bunescu, C. Piemontesi, Q. Wang, J.
Zhu, Chem. Commun. 2013, 49, 10284 – 10286; f) L. Ackermann,
S. Barfusser, H. K. Potukuchi, Adv. Synth. Catal. 2009, 351,
1064 – 1072; g) J. C. Antilla, A. Klapars, S. L. Buchwald, J. Am.
Chem. Soc. 2002, 124, 11684 – 11688; h) A. Klapars, J. C. Antilla,
X. H. Huang, S. L. Buchwald, J. Am. Chem. Soc. 2001, 123,
7727 – 7729.
[14] a) S. Maity, S. Manna, S. Rana, T. Naveen, A. Mallick, D. Maiti,
J. Am. Chem. Soc. 2013, 135, 3355 – 3358; b) A. Deb, S. Manna,
A. Modak, T. Patra, S. Maity, D. Maiti, Angew. Chem. Int. Ed.
2013, 52, 9747 – 9750; Angew. Chem. 2013, 125, 9929 – 9932; c) U.
Sharma, T. Naveen, A. Maji, S. Manna, D. Maiti, Angew. Chem.
Int. Ed. 2013, 52, 12669 – 12673; Angew. Chem. 2013, 125, 12901 –
12905; d) T. Naveen, S. Maity, U. Sharma, D. Maiti, J. Org.
Chem. 2013, 78, 5949 – 5954; e) S. Rana, S. Bag, T. Patra, D.
Maiti, Adv. Synth. Catal. 2014, 356, 2453 – 2458; f) S. Maity, N.
Togati, U. Sharma, D. Maiti, Org. Lett. 2013, 15, 3384 – 3387.
[15] See the Supporting Information for a detailed description.
[16] a) A. Shafiee, A. Ahond, A. M. Bui, Y. Langlois, C. Riche, P.
Potier, Tetrahedron Lett. 1976, 17, 921 – 924; b) M. Andriantsi-
ferana, R. Besselievre, C. Riche, H.-P. Husson, Tetrahedron Lett.
1977, 18, 2587 – 2590; c) A. R. Carroll, E. Hyde, J. Smith, R. J.
Quinn, G. Guymer, P. I. Forster, J. Org. Chem. 2005, 70, 1096 –
1099; d) M. Amat, N. Llor, B. Checa, E. Molins, J. Bosch, J. Org.
Chem. 2010, 75, 178 – 189.
[17] D. Shu, W. Song, X. Li, W. Tang, Angew. Chem. Int. Ed. 2013, 52,
3237 – 3240; Angew. Chem. 2013, 125, 3319 – 3322.
[18] CCDC 1001842 (3i), 1001844 (3j), 1001841 (9a), and 1001843
(9 f) contain the supplementary crystallographic data for this
paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.
uk/data_request/cif.
[10] S. Maity, N. Zheng, Angew. Chem. Int. Ed. 2012, 51, 9562 – 9566;
Angew. Chem. 2012, 124, 9700 – 9704.
[11] For selected examples on the Fujiwara–Moritani reaction, see:
a) S. Moritani, Y. Fujiwara, Tetrahedron Lett. 1967, 8, 1119 –
1122; b) Y. Fujiwara, I. Moritani, M. Matsuda, S. Teranishi,
Tetrahedron Lett. 1968, 9, 3863 – 3865; c) Y. Fujiwara, I. Mor-
itani, S. Danno, R. Asano, S. Teranishi, J. Am. Chem. Soc. 1969,
91, 7166 – 7169; d) Y. Fujiwara, I. Moritani, M. Matsuda, S.
Teranishi, Tetrahedron Lett. 1968, 9, 633 – 636; e) L. Zhou, W.
Lu, Chem. Eur. J. 2014, 20, 634 – 642.
[12] a) M. Miura, T. Tsuda, T. Satoh, S. Pivsa-Art, M. Nomura, J. Org.
Chem. 1998, 63, 5211 – 5215; b) T. Nishikata, B. H. Lipshutz,
Org. Lett. 2010, 12, 1972 – 1975; c) J.-R. Wang, C.-T. Yang, L. Liu,
Q.-X. Guo, Tetrahedron Lett. 2007, 48, 5449 – 5453; d) C. S. Yi,
S. Y. Yun, Org. Lett. 2005, 7, 2181 – 2183; e) G. Cai, Y. Fu, Y. Li,
X. Wan, Z. Shi, J. Am. Chem. Soc. 2007, 129, 7666 – 7673; f) H.
Zhang, E. M. Ferreira, B. M. Stoltz, Angew. Chem. Int. Ed. 2004,
43, 6144 – 6148; Angew. Chem. 2004, 116, 6270 – 6274.
[19] a) E. M. Simmons, J. F. Hartwig, Angew. Chem. Int. Ed. 2012, 51,
3066 – 3072; Angew. Chem. 2012, 124, 3120 – 3126; b) M. Gꢂmez-
Gallego, M. A. Sierra, Chem. Rev. 2011, 111, 4857 – 4963;
c) K. B. Wiberg, Chem. Rev. 1955, 55, 713 – 743; d) J. J. Gajewski,
N. D. Conrad, J. Am. Chem. Soc. 1979, 101, 6693 – 6704; e) F. H.
Westheimer, Chem. Rev. 1961, 61, 265 – 273.
[20] For the oxidation of Pd0 to PdII by O2, see: a) D. Wang, Y. Izawa,
S. S. Stahl, J. Am. Chem. Soc. 2014, 136, 9914 – 9917; b) M. M.
Konnick, N. Decharin, B. V. Popp, S. S. Stahl, Chem. Sci. 2011, 2,
326 – 330; c) Y. Izawa, D. Pun, S. S. Stahl, Science 2011, 333, 209 –
213; d) A. N. Campbell, P. B. White, I. A. Guzei, S. S. Stahl, J.
Am. Chem. Soc. 2010, 132, 15116 – 15119; e) B. V. Popp, S. S.
Stahl, Chem. Eur. J. 2009, 15, 2915 – 2933; f) S. S. Stahl, J. L.
Thorman, R. C. Nelson, M. A. Kozee, J. Am. Chem. Soc. 2001,
123, 7188 – 7189.
Angew. Chem. Int. Ed. 2014, 53, 1 – 6
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
5
These are not the final page numbers!

.
Angewandte
Communications
Communications
Heterocycle Synthesis
U. Sharma, R. Kancherla, T. Naveen,
S. Agasti, D. Maiti*
&&&& — &&&&
Palladium-Catalyzed Annulation of
À
Diarylamines with Olefins through C H
Activation: Direct Access to N-
Arylindoles
No group help needed: A palladium-
catalyzed dehydrogenative coupling
between diarylamines and olefins has
been discovered for the synthesis of
substituted indoles. This intermolecular
annulation approach incorporates readily
available olefins and obviates the need of
any additional directing group. An ortho
palladation, olefin coordination, and b-
migratory insertion sequence has been
proposed for the generation of an olefi-
nated intermediate.
6
www.angewandte.org
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2014, 53, 1 – 6
These are not the final page numbers!