Palladium-Catalyzed Synthesis of Indoles and Isoquinolines with in Situ Generated Phosphinimine

Article abstract of DOI:10.1021/acs.joc.6b01864

A palladium-catalyzed synthesis of polysubstituted indoles and isoquinolines through the coupling of aryl bromides with 2-alkynyl arylazides or 2-alkynyl benzylazides has been developed. This method provides straightforward access to indoles and isoquinolines with high efficiency and excellent functional group compatibility. In this transformation, the iminophosphorane in situ generated from azides is served as the nucleophile that attacks the alkyne moiety in the cyclization process.

Full text of DOI:10.1021/acs.joc.6b01864

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Article
Palladium-Catalyzed Synthesis of Indoles and
Isoquinolines with in-situ Generated Phosphinimine
Qi Zhou, Zhikun Zhang, Yujing Zhou, Shichao Li, Yan Zhang, and Jianbo Wang
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.6b01864 • Publication Date (Web): 06 Dec 2016
Downloaded from http://pubs.acs.org on December 7, 2016
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The Journal of Organic Chemistry
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Palladium-Catalyzed Synthesis of Indoles and Isoquinolines with in
situ Generated Phosphinimine
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Qi Zhou,† Zhikun Zhang,† Yujing Zhou,† Shichao Li,† Yan Zhang† and Jianbo Wang*,†,‡
†Beijing National Laboratory of Molecular Sciences (BNLMS), Key Laboratory of Bioorganic
Chemistry and Molecular Engineering of Ministry of Education, College of Chemistry, Peking
University, Beijing 100871, China; ‡The State Key Laboratory of Organometallic Chemistry, Chinese
Academy of Sciences, Shanghai 200032, China
RECEIVED DATE (to be automatically inserted after your manuscript is accepted if required
according to the journal that you are submitting your paper to)
ABSTRACT. A palladium-catalyzed synthesis of poly-substituted indoles and isoquinolines through the
coupling of arylbromides with 2-alkynyl arylazides or 2-alkynyl benzylazides has been developed. This
method provides straightforward access to indoles and isoquinolines with high efficiency and excellent
functional group compatibility. In this transformation, the iminophosphorane in situ generated from
azides is served as the nucleophile that attacks the alkyne moiety in the cyclization process.
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INTRODUCTION
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Transition-metal-catalyzed carbene transfer reactions constitute one of the major domains of modern
synthetic organic chemistry.1 While diazo compounds are generally recognized as the most common
precusors for the generation of metal carbene species, other metal carbene precusors, such as alkynes,
cyclopropenes and enynones have also attracted significant attentions in recent years.2 In particular,
alkynes are known to serve as carbene precursors by reacting with nucleophiles bearing a leaving group
under Au- or Pt-catalyzed conditions (Scheme 1a).3 Alkynes also serve as precursors for generating α-
oxo and α-imino gold carbenes, which undergo typical carbene transformations, such as X-H bond
insertion, 1,2-migration, cyclopropanation, ylide reaction and others.4 The azido moiety has been known
as a useful nucleophile bearing an excellent leaving group (N2). Consequently, the generation of metal
carbene intermediate from azide and alkyne moiety has been recently established for the synthesis of
nitrogen-containing heterocycles.5
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Scheme 1. Alkynes as Metal Carbene Precursors
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On the other hand, diazo compounds have been extensively explored as palladium carbene
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precursors for cross-coupling reactions.6,7 Recently, we have also demonstrated the use of ene-yne-
ketones and allenyl ketones as the palladium carbene precursors in cross-coupling reactions.8 As a
continuation of our interest in carbene-based coupling reactions, we have conceived that azido moiety
may serve as nucleophiles for generating palladium carbenes from alkynes, similar to the coressponding
Au- and Pt-catalyzed reactions (Scheme 1b).3 With 2-alkynyl arylazides as the substrates, the palladium
carbene generated may be involved in cross-coupling reactions for the synthesis of poly-substituted
indole,9 as proposed in Scheme 1c. Although generating palladium carbene from alkynes has been
reported,10 the combination of such type of transformation with cross-coupling is not known in the
literature. Similar strategy should also be applied to the synthesis of isoquinolines by employing 2-
alkynyl benzylazides as the substrates instead of 2-alkynyl arylazides.11
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RESULTS AND DISCUSSIONS
To achive the proposed transformation, we have initially investigated the cross-coupling reaction by
using alkynyl-substituted azides 1a and aryl bromide 2a as the substrates, and Et3B was used as the
reductant (Table 1, entry 1). The expected indole product 3a could be isolated in 22% yield with 5 mol%
Pd2dba3 and 20 mol% dpppe [1,5-bis(diphenylphosphino)pentane]. We suspected that the low yield
might be attributed to the deactivation of the palladium catalyst. Indeed the reaction could be improved
by increasing the loading of Pd2dba3 and dpppe (Table 1, entry 2). However, when the loading of dpppe
was reduced, a sharp decrease of the yield was observed (Table 1, entry 3). On the contrast, only lowing
the loading of Pd2dba3 does not lead to the reduction of the yield (Table 1, entries 4 and 5). It was thus
speculated that dpppe not only acted as the ligand but also played other vital role in this transformation.
Since dpppe may play the role as a reductant in the reaction, the reaction was then carried out with 50
mol% dpppe but in the absence of Et3B. Indeed the reaction went smoothly to afford the indole 3a in an
improved yield (Table 1, entry 6). When the concentration of the substrates was increased, the yield
could be slightly improved with 1.5 equiv of base (Table 1, entry 7). The yield was diminished slightly
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when 1 equiv of water was added (Table 1, entry 8). Notably, dpppe could be replaced by PPh3, but
affording the product with slightly diminished yield (Table 1, entry 9). Moreover, base was found
necessary for the reaction (Table 1, entry 10). In additon to LiOtBu, other types of bases could also make
the reaction work smoothly (Table 1, entries 11-16).
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Table 1. Optimization of the Palladium-Catalyzed Synthesis of Indolea
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additive
Pd2dba3
entry
base (equiv)
[P] (mol%)d
yield(%)b
(mol%)
5
(equiv)
1
LiOtBu (2)
LiOtBu (2)
LiOtBu (2)
LiOtBu (2)
LiOtBu (2)
LiOtBu (2)
LiOtBu (1.5)
LiOtBu (1.5)
LiOtBu (1.5)
Et3B (1.5)
dpppe (20)
dpppe (40)
dpppe (20)
dpppe (40)
dpppe (40)
dpppe (50)
dpppe (50)
dpppe (50)
PPh3 (100)
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10
Et3B (1.5)
Et3B (1.5)
Et3B (1.5)
Et3B (1.5)
none
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5
2.5
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2.5
2.5
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none
H2O (1)
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2.5
2.5
2.5
2.5
2.5
2.5
2.5
none
none
none
none
none
none
none
none
PPh3 (100)
PPh3 (100)
PPh3 (100)
PPh3 (100)
PPh3 (100)
PPh3 (100)
PPh3 (100)
trace
33e
67e
53e
23e
29e
69e
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NaOtBu (1.5)
NaOMe (1.5)
KOMe (1.5)
LiOMe (1.5)
K2CO3 (1.5)
Cs2CO3 (1.5)
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aIf not otherwise noted, the reaction was performed with 1a (0.1 mmol), 2a (0.15 mmol) in toluene (2
mL) at 100 oC. bYields of isolated product are given. cThe reaction was carried out with 1a (0.2 mmol),
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2a (0.3 mmol) in toluene (2 mL) at 100 C. dpppe = 1,5-bis(diphenylphosphino)pentane. NMR yields
of the products are given.
With the optimized reaction conditions in hand, we then proceeded to study the substrate scope
of the reaction with a series of 2-alkynyl arylazides and aryl bromides (Scheme 2). The substrates with
para-substituted aryl bromides all afforded the corresponding products in the good yields (Scheme 2,
3a-j), except the p-CO2Me substituted bromide 2g. With meta-substituted bromides, the reaction also
went smoothly to give the corresponding products in good yields (Scheme 2, 3k-n). The low yield in
the case of 2p may be attributed to steric effect of the ortho-substitution (Scheme 2, 3p). In addition,
The reaction with 4-bromo-1, 1’-biphenyl and 2-bromonaphthalene could deliever the corresponding
indole products in the good yields (Scheme 2, 3q, r). Notably, the reaction with the azide substrate
bearing aryl substituent also afforded the corresponding products in moderate to good yields (Scheme 2,
3t-w). The structure of indole product 3t was further confirmed by X-ray crystallography.13
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Scheme 2. Reaction Scope of the Aryl Bromidesa
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aIf not otherwise noted, the reaction conditions are as following: 2-alkynyl arylazides 1a-f (0.2 mmol),
ary bromides 2a-r (0.3 mmol), Pd2dba3 (2.5 mol%), dpppe (50 mol%), LiOtBu (1.5 equiv), toluene (2
mL), 100 oC, 24 h. bAll the yields refer to the isolated indole products.
For the reaction mechanism, it was initially considered that the azide moiety of the substrate attack
the arylpalladium(II)-activated triple bond to afford the cyclized intermediate. However, because the
arylazide moiety can easily react with phosphine to generate phosphinimine under the current reaction
conditions (Staudinger reaction),14,15 it was thus speculated that the phosphinimine might be first formed
and then the nucleophilic nitrogen of the phosphinimine attacked the arylpalladium(II)-activated triple
bond. To substantiate such speculation, mechanistic experiments were carried out. The arylazide 1a was
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first subjected to the reaction with triphenylphosphine in dichloromethane. After stirring at room
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temperature for 6 h, the arylazide 1a was completely disappeared. The solvent was removed and the
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formation of phosphinimine 4 was confirmed by H and 13C NMR spectra. The crude phosphinimine
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was then submitted to the Pd-catalyzed coupling reaction with arylbromide. The expected indole product
3a was obtained in 56% yield. Similar experiment with dpppe afforded the indole product 3a in 72%
yield (Scheme 3a).
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Scheme 3. Control Experiments
In another control experiment, 2-alkynyl azidobenzene 1a was replaced with 2-(hex-1-yn-1-
yl)aniline 1a' under the standard conditions. The formation of 3a was not observed, as shown in Scheme
3b. The experiment rules out the mechanism in which the azide is first converted to the amine in situ
and then the cyclization occurs. Notably, in Cacchi’s aminopalladation/reductive elimination domino
reaction for the construction of indole rings, a trifluoroacetyl substituent on the nitrogen is required.9d,e
The proposed reaction mechanism is shown in Scheme 4. There are two possible pathways. In path a,
arylpalladium(II) species B is first formed through oxidative addition of aryl bromide 2 to Pd(0) catalyst,
while iminophosphorane C is formed in situ from 2-alkynyl arylazide by Staudinger reaction. Then, the
5-endo-dig cyclized intermediate D is generated through nucleophilic attack of the arylpalladium(II)-
activated triple bond by the nitrogen of the phosphinimine moiety. Reductive elimination of
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intermediate D leads to the intermediate J, which is further converted to the product by hydrolysis. The
alternative mechanism involving the carbene process is shown in path b. From intermediate D,
palladium(II) carbene species F is formed through back electron donating from palladium. Subsequent
migratory insertion gives intermediate G, which is isomerized to intermediate H. Protonation of the
intermediate H affords product 3 and Pd(II) species, which is reduced to Pd(0) catalyst by E.
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Scheme 4. Proposed Reaction Mechanism
Encourged by the above results, we further conceived to extend the reaction to the synthesis of
poly-substituted isoquinolines with 2-alkynyl benzylazide 5a (Table 2). However, when the reaction was
performed under the standard conditions for indole synthesis as described above, the desired product 6a
was only obtained in 29% yield (Table 2, entry 1). We then optimized the reaction conditions
byscreening different bases, however, with K2CO3 and KOMe as the bases, only trace amount of the
products were detected (Table 2, entries 2, 3). To our delight, when dpppe was replaced by PPh3, the
yield could be improved to 39% (Table 2, entry 4). The reaction with other solvents, such as dioxane,
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MeCN and DCE, did not show improved results (Table 2, entries 5-7). Finally, it was observed that the
yield of 6a could be significantly improved by increasing the loading of arylbromide 2a (Table 2, entries
8-11).
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Table 2. Reaction Condition Optimization for Isoquinoline Synthesisa
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entry
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2a (equiv)
1.5
base (equiv)
LiOtBu (1.5)
K2CO3 (1.5)
KOMe (1.5)
LiOtBu (3.0)
LiOtBu (2.0)
LiOtBu (2.0)
LiOtBu (2.0)
LiOtBu (2.8)
LiOtBu (2.8)
LiOtBu (2.8)
LiOtBu (2.8)
solvent
toluene
toluene
toluene
toluene
dioxane
MeCN
DCE
[P] (mol%)
dpppe (50)
dpppe (50)
dpppe (50)
PPh3 (100)
PPh3 (100)
PPh3 (100)
PPh3 (100)
PPh3 (150)
PPh3 (150)
PPh3 (150)
PPh3 (150)
yield (%)b
29
2c
3c
4c
5c
6c
7c
8
1.0
trace
trace
39
1.0
1.0
1.0
22
1.0
trace
trace
45
1.0
1.5
toluene
toluene
toluene
toluene
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2.0
58
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2.5
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3.0
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o
aIf not otherwise noted, the reaction was performed with 5a (0.2 mmol), in toluene (1 mL) at 100 C.
bYields refer to the isolated product. cThe reaction was carried out with 5a (0.1 mmol) in toluene (1 mL)
at 100 oC.
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With the optimized reaction conditions (with 3 equivalents of arylbromide) (Table 2, entry 11), we
proceeded to investigate the scope of the reaction (Scheme 5). Moderate to good yields could be
obtained with a series of arylbromides (Scheme 5, 6a-i). Besides, the reaction also worked well with 2-
alkynyl benzylazides bearing various substituents (Scheme 5, 6j-l).
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Scheme 5. The Scope for the Synthesis of Isoquinolinea
aIf not otherwise noted, the reaction conditions are as following: 2-alkynyl benzylazides 5a-e (0.2 mmol),
ary bromides (0.6 mmol), Pd2dba3 (2.5 mol%), PPh3 (1.5 equiv), LiOtBu (2.8 equiv), toluene (1 mL),
100 oC，24 h. bAll the yields refer to the isolated products.
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For the synthesis of isoquinolines, same control experiments as above-mentioned were carried
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out and similar results were obtained as shown in Scheme 6. Therefore, the mechanism for isoquinoline
formation should be similar as that shown in Scheme 4.12
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Scheme 6. Control Experiments for the Reaction of Isoquinolines Synthesis.
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CONCLUSION
In conclusion, we have developed an efficient method for the synthesis of poly-substituted indoles and
isoquinolines via the iminophosphorane intermediates generated in situ through Staudinger reaction. The
iminophosphoranes are versatile synthetic intermediates which have found many applications in organic
chemistry. The reaction of iminophosphorane with palladium-activated alkyne described herein opens
up new possibilities for the application of iminophosphorane in developing new reactions.
EXPERIMENTAL SECTION
General Methods. All the reactions of palladium-catalyzed synthesis of poly-substituted indoles and
isoquinolines were performed under nitrogen atmosphere in a flame-dried reaction tube. All the solvents
were distilled under nitrogen atmosphere prior to use. Toluene was dried over Na with benzophenone-
ketyl intermediate as indicator. For chromatography, 200-300 mesh silica gel was employed. Chemical
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shifts for H NMR (400 MHz) and 13C NMR (100 MHz) were reported relative to those of
tetramethylsilane (TMS): chemical shifts (δ) were reported in ppm, and coupling constants (J) are in
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Hertz (Hz). IR spectra were performed neat on an FT-IR spectrophotometer and reported in wave
numbers, cm−1. For HRMS measurements, the mass analyzer is FT-ICR. 2-Alkynyl azidobenzenes and
2-alkynyl benzylazides were prepared according to the literature procedures.16-18 Other starting materials
were obtained from commercial suppliers and were used without further purification. PE: petroleum
ether; EA: ethyl acetate.
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General procedure for the synthesis of poly-substituted indoles. Under N2 atmosphere, Pd2dba3
(4.6 mg, 0.005 mmol, 2.5 mmol%), dpppe (44 mg, 0.1 mmol, 50 mmol%), LiOtBu (24 mg, 0.3 mmol)
were successively added to a flame-dried 10 mL Schlenk tube. The reaction tube was degassed three
times with N2 and dry toluene (2 mL) was added by syringe. Then, the 2-alkynyl azidobenzene (0.2
mmol) and the arylbromides (0.3 mmol) were added with syringe, respectively (Note: 2-alkynyl
azidobenzenes or the arylbromides in solid form were added to the reaction tube prior to LiOtBu). The
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reaction was heated at 100 C with stirring for 24 h. Then the reaction mixture was cooled to room
temperature and then it was filtered through a short plug of silica gel with ethyl acetate as eluents. The
solvent was removed in vacuo to leave a crude mixture, which was purified by column chromatography
on silica gel with petroleum ether/ethyl acetate (10:1) to afford the pure indole product 3a-w.
2-Butyl-3-(4-methoxyphenyl)-1H-indole (3a).5b Yield: 42 mg (75%), pale yellow liquid, Rf = 0.4 (PE :
EA = 10 : 1); 1H NMR (400 MHz, CDCl3) δ 7.90 (s, 1H), 7.59 (d, J = 7.7 Hz, 1H), 7.41-7.38 (m, 2H),
7.28 (d, J = 7.9 Hz, 1H), 7.16-7.07 (m, 2H), 7.02-6.99 (m, 2H), 3.85 (s, 3H), 2.79 (t, J = 7.8 Hz, 2H),
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1.67-1.59 (m, 2H), 1.39-1.30 (m, 2H), 0.87 (t, J = 7.3 Hz, 3H); C NMR (100 MHz, CDCl3) δ 157.9,
135.7, 135.1, 130.6, 128.1, 127.8, 121.4, 119.7, 118.8, 113.9, 110.3, 55.3, 32.0, 26.0, 22.5, 13.8; IR
(film): 1330, 1459, 1487, 1557, 1613, 2931, 2957, 3408 cm-1.
2-Butyl-3-(p-tolyl)-1H-indole (3b). Yield: 42 mg (79%), pale yellow liquid, Rf = 0.5 (PE : EA = 10 : 1);
1H NMR (400 MHz, CDCl3) δ 7.86 (s, 1H), 7.62 (d, J = 7.8 Hz, 1H), 7.37 (d, J = 8.0, 2H), 7.29-7.25 (m,
3H), 7.17-7.07 (m, 2H), 2.81 (t, J = 7.8 Hz, 2H), 2.40 (s, 3H), 1.68-1.60 (m, 2H), 1.40-1.30 (m, 2H),
0.88 (t, J = 7.3 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 135.8, 135.4, 135.2, 132.4, 129.5, 129.2, 128.0,
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121.4, 119.7, 118.9, 114.2, 110.3, 32.0, 26.1, 22.5, 21.2, 13.8; HRMS (ESI, m/z): calcd for C19H22N
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[M+H]+ 264.1747, found 264.1750; IR (film): 1017, 1257, 1330, 1458, 1510, 1558, 2957, 3406 cm-1.
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2-Butyl-3-(4-(tert-butyl)phenyl)-1H-indole (3c). Yield:
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48 mg (79%), pale yellow liquid, Rf = 0.5 (PE : EA = 10 : 1); 1H NMR (400 MHz, CDCl3) δ 7.91 (s,
1H), 7.66 (d, J = 7.8 Hz, 1H), 7.48-7.41 (m, 4H), 7.30 (d, J = 7.9 Hz, 1H), 7.17-7.13 (m, 1H), 7.11-7.07
(m, 1H), 2.84 (t, J = 7.9 Hz, 2H), 1.71-1.63 (m, 2H), 1.43-1.33 (m, 11H), 0.90 (t, 7.3 Hz, 3H); 13C NMR
(100 MHz, CDCl3) δ 148.5, 135.9, 135.2, 132.4, 129.1, 128.0, 125.3, 121.4, 119.7, 119.1, 114.2, 110.3,
34.5, 32.1, 31.4, 26.1, 22.6, 13.9; HRMS (ESI, m/z): calcd for C22H28N [M+H]+ 306.2216, found
306.2219; IR (film): 1268, 1330, 1363, 1459, 1509, 1563, 2960, 3408 cm-1.
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2-Butyl-3-(4-(trimethylsilyl)phenyl)-1H-indole (3d). Yield: 52 mg (81%), pale yellow liquid, Rf = 0.5
(PE : EA = 10 : 1); 1H NMR (400 MHz, CDCl3) δ 7.89 (s, 1H), 7.66 (d, J = 7.8 Hz, 1H), 7.61 (d, J = 8.0
Hz, 2H), 7.48 (d, J = 8.0 Hz, 2H), 7.28 (d, J = 7.9 Hz, 1H), 7.18-7.07 (m, 2H), 2.83 (t, J = 7.9 Hz, 2H),
1.69-1.61 (m, 2H), 1.41-1.32 (m, 2H), 0.89 (t, J = 7.4 Hz, 3H), 0.32 (s, 9H); 13C NMR (100 MHz,
CDCl3) δ 137.3, 136.2, 135.9, 135.2, 133.5, 128.9, 127.8, 121.5, 119.8, 119.0, 114.3, 110.4, 32.1, 26.2,
22.6, 13.9, -1.0; HRMS (ESI, m/z): calcd for C21H28NSi [M+H]+ 322.1986, found 322.1988; IR (film):
839, 1108, 1248, 1329, 1459, 1600, 2956, 3409 cm-1.
2-Butyl-3-(4-(trifluoromethyl)phenyl)-1H-indole (3e). Yield: 56 mg (88%), pale yellow liquid, Rf =
0.4 (PE : EA = 10 : 1); 1H NMR (400 MHz, CDCl3) δ 8.05 (s, 1H), 7.70 (d, J = 8.2 Hz, 2H), 7.60 (t, J =
7.6 Hz, 3H), 7.35 (d, J = 8.0 Hz, 1H), 7.21-7.17 (m, 1H), 7.15-7.11 (m, 1H), 2.85 (t, J = 7.8 Hz, 2H),
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1.72-1.64 (m, 2H), 1.42-1.33 (m, 2H), 0.90 (t, J = 7.3Hz, 3H); C NMR (100 MHz, CDCl3) δ 139.4,
136.8, 135.2, 129.6, 127.8 (q, J2 = 32.3 Hz), 127.5, 125.4 (q, J3 = 3.7 Hz), 124.5 (q, J1 = 271.7 Hz),
121.9, 120.5, 120.3, 118.6, 113.2, 110.5, 31.9, 26.1, 22.5, 13.8; HRMS (ESI, m/z): calcd for C19H19F3N
[M+H]+ 318.1464, found 318.1467; IR (film): 1321, 1407, 1440, 1459, 1560, 1615, 2958, 3400 cm-1.
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o
4-(2-Butyl-1H-indol-3-yl)benzonitrile (3f). Yield: 47 mg (86%), yellow solid, mp: 120-121 C; Rf =
0.2 (PE : EA = 10 : 1); 1H NMR (400 MHz, CDCl3) δ 8.22 (s, 1H), 7.62 (d, J = 8.3 Hz, 2H), 7.50 (t, J =
8.7 Hz, 3H), 7.28 (d, J = 7.9 Hz, 1H), 7.14-7.09 (m, 1H), 7.07-7.03 (m, 1H), 2.76 (t, J = 7.8 Hz, 2H),
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137.3, 135.2, 132.3, 129.7, 127.0, 122.0, 120.4, 119.4, 118.3, 112.7, 110.7, 108.7, 31.8, 26.1, 22.4, 13.7;
HRMS (ESI, m/z): calcd for C19H19N2 [M+H]+ 275.1543, found 275.1545; IR (film): 1174, 1262, 1460,
1504, 1605, 2231, 2959, 3336 cm-1.
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Methyl 4-(2-butyl-1H-indol-3-yl)benzoate (3g).19 Yield: 24 mg (40%), pale yellow solid, mp: 121-122
oC; Rf = 0.2 (PE : EA = 10 : 1); 1H NMR (400 MHz, CDCl3) δ 8.18 (s, 1H), 8.14-8.12 (m, 2H), 7.64 (d,
J = 7.8 Hz, 1H), 7.57 (d, J = 8.4 Hz, 2H), 7.35 (d, J = 7.9 Hz, 1H), 7.21-7.11 (m, 2H), 3.95 (s, 3H), 2.86
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(t, J = 7.8, 2H), 1.72-1.64 (m, 2H), 1.41-1.31 (m, 2H), 0.89 (t, J = 7.3 Hz, 3H); C NMR (100 MHz,
CDCl3) δ 167.3, 140.7, 136.9, 135.2, 129.8, 129.2, 127.4, 127.2, 121.8, 120.2, 118.7, 113.5, 110.5, 52.0,
31.9, 26.2, 22.5, 13.8; IR (film): 1287, 1309, 1437, 1459, 1606, 1700, 2955, 3372 cm-1.
2-Butyl-3-(4-fluorophenyl)-1H-indole (3h). Yield: 41 mg (77%), pale yellow solid, mp: 49-50 oC; Rf =
0.4 (PE : EA = 10 : 1); 1H NMR (400 MHz, CDCl3) δ 7.91 (s, 1H), 7.55 (d, J = 7.8 Hz, 1H), 7.44-7.39
(m, 2H), 7.30 (d, J = 8.0 Hz, 1H), 7.18-7.08 (m, 4H), 2.79 (t, J = 7.8 Hz, 2H), 1.67-1.60 (m, 2H), 1.39-
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1.30 (m, 2H), 0.88 (t, J = 7.3 Hz, 3H); C NMR (100 MHz, CDCl3) δ 161.4 (d, J = 244.4 Hz), 136.0,
135.1, 131.3 (d, J = 3.3 Hz), 131.0 (d, 7.6 Hz), 127.9, 121.6, 119.9, 118.6, 115.3 (d, J = 21,2 Hz), 113.4,
110.4, 31.9, 26.0, 22.4, 13.8; HRMS (ESI, m/z): calcd for C18H19FN [M+H]+ 268.1496, found 268.1497;
IR (film): 1330, 1459, 1506, 1560, 2861, 2929, 2957, 3401 cm-1.
2-Butyl-3-(4-chlorophenyl)-1H-indole (3i).19 Yield: 48 mg (85%), pale yellow solid, mp: 41-43 oC; Rf
= 0.4 (PE : EA = 10 : 1); 1H NMR (400 MHz, CDCl3) δ 7.94 (s, 1H), 7.57 (d, J = 7.8 Hz, 1H), 7.42-7.38
(m, 4H), 7.31 (d, J = 7.9 Hz, 1H), 7.21-7.08 (m, 2H), 2.79 (t, J = 7.8 Hz, 2H), 1.67-1.60 (m, 2H), 1.39-
1.30 (m, 2H), 0.88 (t, J = 7.3 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 136.2, 135.1, 134.0, 131.6, 130.8,
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128.6, 127.7, 121.7, 120.04, 118.6, 113.2, 110.4, 31.9, 26.0, 22.5, 13.8; IR (film): 1186, 1258, 1329,
1458, 1491, 1555, 2957, 3404 cm-1.
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3-(4-Bromophenyl)-2-butyl-1H-indole (3j). Yield: 48 mg (73%), pale yellow liquid, Rf = 0.4 (PE : EA
= 10 : 1); 1H NMR (400 MHz, CDCl3) δ 7.97 (s, 1H), 7.58-7.55 (m, 3H), 7.35-7.31 (m, 3H), 7.17 (t, J =
7.5 Hz, 1H), 7.10 (t, J = 7.4 Hz, 1H), 2.80 (t, J = 7.8 Hz, 2H), 1.68-1.61 (m, 2H), 1.40-1.30 (m, 2H),
0.89 (t, J = 7.3 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 136.2, 135.1, 134.4, 131.6, 131.2, 127.6, 121.7,
120.1, 119.7, 118.6, 113.3, 110.4, 31.9, 26.0, 22.5, 13.8; HRMS (ESI, m/z): calcd for C18H19BrN
[M+H]+ 328.0695, found 328.0697; IR (film): 1186, 1257, 1329, 1458, 1488, 1552, 2958, 3406 cm-1.
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2-Butyl-3-(3-methoxyphenyl)-1H-indole (3k). Yield: 44 mg (78%), pale yellow liquid, Rf = 0.4 (PE :
EA = 10 : 1); 1H NMR (400 MHz, CDCl3) δ 7.98 (s, 1H), 7.65 (d, J = 7.8 Hz, 1H), 7.38-7.31 (m, 2H),
7.18-7.14 (m, 1H), 7.12-7.05 (m, 3H), 6.88-6.85 (m, 1H), 3.85 (s, 3H), 2.86(t, J = 7.8 Hz, 2H), 1.71-
1.63 (m, 2H), 1.42-1.33 (m, 2H), 0.89 (t, J = 7.3 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 159.7, 136.9,
136.1, 135.1, 129.4, 127.8, 122.1, 121.5, 119.9, 118.9, 115.1, 114.3, 111.5, 110.3, 55.2, 32.0, 26.1, 22.5,
13.8; HRMS (ESI, m/z): calcd for C19H22NO [M+H]+ 280.1696, found 280.1696; IR (film): 1262, 1329,
1419, 1490, 1571, 1603, 2956, 3406 cm-1.
3-(3-(1,3-Dioxolan-2-yl)phenyl)-2-butyl-1H-indole (3l). Yield: 35 mg (55%), pale yellow liquid, Rf =
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0.2 (PE : EA = 10 : 1); H NMR (400 MHz, CDCl3) δ 8.02 (s, 1H), 7.62-7.60 (m, 2H), 7.49-7.46 (m,
2H), 7.44-7.41 (m, 1H), 7.31 (d, J = 7.9 Hz, 1H), 7.17-7.13 (m, 1H), 7.11-7.07 (m, 1H), 5.89 (s, 1H),
4.16-4.13 (m, 2H), 4.06-4.03 (m, 2H), 2.82 (t, J = 7.8 Hz, 2H), 1.70-1.62 (m, 2H), 1.40-1.31 (m, 2H),
0.88 (t, J = 7.3 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 138.1, 136.2, 135.6, 135.2, 130.4, 128.5, 127.9,
127.7, 123.9, 121.5, 119.9, 118.8, 114.1, 110.3, 103.9, 65.3, 32.0, 26.0, 22.5, 13.8; HRMS (ESI, m/z):
calcd for C21H24NO2 [M+H]+ 322.1802, found 322.1801; IR (film): 1327, 1378, 1459, 1491, 1601, 1668,
2956, 3396 cm-1.
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2-Butyl-3-(3-(trifluoromethyl)phenyl)-1H-indole (3m).20 Yield: 50 mg (78%), pale yellow liquid, Rf =
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7.60-7.54 (m, 3H), 7.33 (d, J = 7.9 Hz, 1H), 7.21-7.11 (m, 2H), 2.82 (t, J = 7.8 Hz, 2H), 1.70-1.63 (m,
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2H), 1.41-1.32 (m, 2H), 0.89 (t, J = 7.3 Hz, 3H); C NMR (100 MHz, CDCl3) δ 136.6, 136.3, 135.2,
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132.7, 130.8 (q, J = 31.9 Hz), 128.9, 127.5, 126.1 (q, J = 3.8 Hz), 124.3 (q, J = 272.4 Hz), 122.5 (q, J =
3.8 Hz), 121.9, 120.3, 118.4, 113.1, 110.5, 31.9, 26.0, 22.4, 13.7; IR (film): 1322, 1460, 1492, 1558,
1612, 2931, 2958, 3396 cm-1.
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2-Butyl-3-(3-chlorophenyl)-1H-indole (3n). Yield: 48 mg (84%), pale yellow liquid, Rf = 0.4 (PE : EA
= 10 : 1); 1H NMR (400 MHz, CDCl3) δ 7.95 (s, 1H), 7.60 (d, J = 7.8 Hz, 1H), 7.47-7.46 (m, 1H), 7.36-
7.35 (m, 2H), 7.31 (d, J = 7.9 Hz, 1H), 7.28-7.25 (m, 1H), 7.21-7.15 (m, 1H), 7.13-7.09 (m, 1H), 2.81 (t,
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J = 7.8 Hz, 2H), 1.68-1.61 (m, 2H), 1.40-1.31 (m, 2H), 0.89 (t, J = 7.3 Hz, 3H); C NMR (100 MHz,
CDCl3) δ 137.4, 136.4, 135.1, 134.2, 129.7, 129.4, 127.7, 127.6, 125.9, 121.7, 120.1, 118.6, 113.1,
110.4, 31.9, 26.0, 22.4, 13.8; HRMS (ESI, m/z): calcd for C18H19ClN [M+H]+ 284.1201, found 284.1204;
IR (film): 1253, 1327, 1404, 1458, 1561, 1596, 2957, 3402 cm-1.
2-(2-Butyl-1H-indol-3-yl)benzonitrile (3o). Yield: 41 mg (75%), pale yellow liquid, Rf = 0.2 (PE : EA
= 10 : 1); 1H NMR (400 MHz, CDCl3) δ 8.30 (s, 1H), 7.79-7.77 (m, 1H), 7.66-7.61 (m, 1H), 7.56-7.54
(m, 1H), 7.42-7.38 (m, 2H), 7.31 (d, J = 7.9 Hz, 1H), 7.18-7.08 (m, 2H), 2.83-2.67 (m, 2H), 1.69-1.48
(m, 2H), 1.30-1.19 (m, 2H), 0.79 (t, J = 7.4 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 139.7, 137.8, 135.2,
133.3, 132.5, 131.9, 127.8, 126.7, 121.8, 120.1, 119.0, 118.3, 113.5, 111.0, 110.6, 31.2, 26.4, 22.2, 13.6;
HRMS (ESI, m/z): calcd for C19H19N2 [M+H]+ 275.1543, found 275.1545; IR (film): 1017, 1327, 1459,
1491, 1597, 2226, 2957, 3390 cm-1.
3-(2-Bromophenyl)-2-butyl-1H-indole (3p). Yield: 27 mg (42%), pale yellow liquid, Rf = 0.5 (PE : EA
= 10 : 1); 1H NMR (400 MHz, CDCl3) δ 7.99 (s, 1H), 7.71 (d, J = 7.9Hz, 1H), 7.36-7.33 (m, 3H), 7.28
(d, J = 7.8 Hz, 1H), 7.24-7.19 (m, 1H), 7.18-7.14 (m, 1H), 7.07 (t, J = 7.5 Hz, 1H), 2.76-2.60 (m, 2H),
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1.66-1.53 (m, 2H), 1.34-1.26 (m, 2H), 0.84 (t, J = 7.3 Hz, 3H); C NMR (100 MHz, CDCl3) δ 136.7,
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136.3, 134.8, 133.1, 132.8, 128.4, 128.2, 127.0, 125.7, 121.4, 119.7, 119.2, 114.1, 110.3, 31.4, 26.4,
22.3, 13.7; HRMS (ESI, m/z): calcd for C18H19BrN [M+H]+ 328.0695, found 328.0697; IR (film): 1025,
1056, 1256, 1330, 1458, 1474, 2955, 3407 cm-1.
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3-([1,1'-Biphenyl]-4-yl)-2-butyl-1H-indole (3q). Yield: 54 mg (82%), pale yellow liquid, Rf = 0.4 (PE :
EA = 10 : 1); 1H NMR (400 MHz, CDCl3) δ 7.93 (s, 1H), 7.70-7.66 (m, 5H), 7.57-7.55 (m, 2H), 7.45 (t,
J = 7.6 Hz, 2H), 7.35-7.30 (m, 2H), 7.19-7.10 (m, 2H), 2.86 (t, J = 7.8 Hz, 2H), 1.71-1.63 (m, 2H), 1.42-
1.33 (m, 2H), 0.90 (t, J = 7.3 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 141.0, 138.5, 136.2, 135.2, 134.6,
129.9, 128.8, 127.9, 127.1, 127.0, 127.0, 121.5, 119.9, 118.9, 113.9, 110.4, 32.0, 26.2, 22.5, 13.8;
HRMS (ESI, m/z): calcd for C24H24N [M+H]+ 326.1903, found 326.1903; IR (film): 1331, 1458, 1488,
1561, 1610, 2927, 2956, 3414 cm-1.
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2-Butyl-3-(naphthalen-2-yl)-1H-indole (3r).5b Yield: 45 mg (75%), pale yellow liquid, Rf = 0.4 (PE :
EA = 10 : 1); 1H NMR (400 MHz, CDCl3) δ 7.94-7.84 (m, 5H), 7.70-7.64 (m, 2H), 7.50-7.43 (m, 2H),
7.32 (t, J = 7.9 Hz, 1H), 7.20-7.10 (m, 2H), 2.87 (t, J = 7.8 Hz, 2H), 1.70-1.62 (m, 2H), 1.39-1.30 (m,
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2H), 0.87 (t, J = 7.4 Hz, 3H); C NMR (100 MHz, CDCl3) δ 136.4, 135.2, 133.8, 133.1, 131.9, 128.4,
128.1, 127.9, 127.8, 127.7, 125.9, 125.3, 121.6, 120.0, 118.9, 114.3, 110.4, 32.0, 26.1, 22.5, 13.8; IR
(film): 1324, 1458, 1503, 1601, 1629, 2928, 2956, 3415 cm-1.
2-Cyclopropyl-3-(4-methoxyphenyl)-1H-indole (3s).5b Yield: 33 mg (62%), pale yellow liquid, Rf =
0.3 (PE : EA = 10 : 1); 1H NMR (400 MHz, CDCl3) δ 7.72 (s, 1H), 7.63 (d, J = 7.8 Hz, 1H), 7.56-7.53
(m, 2H), 7.27 (d, J = 7.7 Hz, 1H), 7.16-7.07 (m, 2H), 7.03-7.00 (m, 2H), 3.86 (s, 3H), 2.22-2.15 (m, 1H),
0.98-0.93 (m, 2H), 0.73-0.69 (m, 2H); 13C NMR (100 MHz, CDCl3) δ 157.7, 135.8, 134.7, 130.6, 128.2,
127.7, 121.5, 119.9, 118.6, 114.7, 113.8, 110.4, 55.3, 8.1, 7.5; IR (film): 1241, 1333, 1461, 1512, 1558,
1612, 1655, 3403 cm-1.
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3-(4-Methoxyphenyl)-2-phenyl-1H-indole (3t).21 Yield: 43 mg ( 72%), yellow solid, mp: 179-181 C;
Rf = 0.3 (PE : EA = 10 : 1); 1H NMR (400 MHz, CDCl3) δ 8.19 (s, 1H), 7.64 (d, J = 7.9Hz, 1H), 7.43-
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7.40 (m, 3H), 7.37-7.36 (m, 1H), 7.35-7.32 (m, 2H), 7.30-7.28 (m, 1H), 7.25-7.21 (m, 2H), 7.16-7.12 (m,
1H), 6.95-6.91 (m, 2H), 3.84 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 158.1, 135.8, 133.7, 132.8, 131.2,
129.0, 128.6, 128.0, 127.5, 127.3, 122.6, 120.3, 119.7, 114.7, 114.0, 110.8, 55.2; IR (film): 746, 1036,
1177, 1245, 1284, 1456, 1513, 2969 cm-1.
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3-(4-Methoxyphenyl)-2-(p-tolyl)-1H-indole (3u).22 Yield: 48 mg (77 %), yellow solid, mp: 109-110 oC;
Rf = 0.3 (PE : EA = 10 : 1); 1H NMR (400 MHz, CDCl3) δ 8.16 (s, 1H), 7.63 (d, J = 7.9Hz, 1H), 7.40-
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7.30 (m, 5H), 7.21-7.19 (m, 1H), 7.15-7.11 (m, 3H), 6.95-6.91 (m, 2H), 3.84 (s, 3H), 2.34 (s, 3H); C
NMR (100 MHz, CDCl3) δ 158.1, 137.4, 135.7, 133.8, 131.1, 129.9, 129.4, 129.0, 127.9, 127.5, 122.4,
120.2, 119.5, 114.2, 114.0, 110.7, 55.2, 21.2; IR (film): 1175, 1244, 1285, 1329, 1455, 1520, 2959, 3408
cm-1.
3-(4-Methoxyphenyl)-2-(4-(trifluoromethyl)phenyl)-1H-indole (3v). Yield: 61 mg (83 %), pale yellow
liquid, Rf = 0.3 (PE : EA = 10 : 1); 1H NMR (400 MHz, CDCl3) δ 8.23 (s, 1H), 7.63 (d, J = 8.0 Hz, 1H),
7.52 (q, J = 8.4 Hz, 4H), 7.41 (d, J = 8.1 Hz, 1H), 7.34-7.30 (m, 2H), 7.26-7.23 (m, 1H), 7.17-7.13 (m,
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1H), 6.97-6.93 (m, 2H), 3.85 (s, 3H); C NMR (100 MHz, CDCl3) δ158.5, 136.3, 136.1, 131.9, 131.2,
129.1 (q, J = 32.5 Hz), 128.9, 128.0, 126.7, 125.6 (q, J = 3.7 Hz), 124.1 (q, J = 272.0 Hz), 123.3, 120.6,
120.0, 116.3, 114.3, 111.0, 55.23; HRMS (ESI, m/z): calcd for C22H17F3NO [M+H]+ 368.1257, found
368.1258; IR (film): 734, 843, 1064, 1125, 1244, 1323, 1523, 1616 cm-1.
2-(4-Fluorophenyl)-3-(4-methoxyphenyl)-1H-indole (3w).22 Yield: 54 mg (84 %), pale yellow liquid,
Rf = 0.2 (PE : EA = 10 : 1); 1H NMR (400 MHz, CDCl3) δ 8.14 (s, 1H), 7.63 (d, J = 7.9 Hz, 1H), 7.37-
7.30 (m, 5H), 7.21-7.19 (m, 1H), 7.15-7.11 (m, 1H), 7.01-6.95 (m, 2H), 6.94-6.91 (m, 2H), 3.82 (s, 3H);
13C NMR (100 MHz, CDCl3) δ 162.2 (d, J = 247.9 Hz), 158.1, 135.8, 132.8, 131.1, 129.8 (d, J = 8.0
Hz), 128.9 (d, J = 3.4 Hz), 128.8, 127.1, 122.7, 120.4, 119.6, 115.7 (d, J = 21.7 Hz), 114.6, 114.1, 110.8,
55.2; IR (film): 1035, 1159, 1244, 1454, 1496, 1519, 1598, 2971 cm-1.
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Experiments for mechanistic investigations (eq 1). To a solution of PPh3 (52.4 mg, 0.2 mmol) in
dried dichloromethane (1 mL) was added the 2-alkynyl azidobenzene 1a (40 mg, 0.2 mmol) at room
temperature and the mixture was stirred for 6 h. 2-Alkynyl azidobenzene was completely disappeared as
judged by TLC (thin-layer chromatography). The solvent was then removed under vacuum to afford
phosphinimine 4 as the crude product. The structure of phosphinimine 4 was confirmed by comparing
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the H and C NMR spectra with standard spectra.24 Then Pd2dba3 (4.6 mg, 0.005 mmol, 2.5 mol%),
LiOtBu (24 mg, 0.3 mmol), dry toluene (2 mL), arylbromide 2a (56 mg, 0.3 mmol) and the
phosphinimine 4 were added to reaction tube under N2 gas and the solution was stirred at 100 oC for 24
h. The product 3a could be isolated in 56% yield. Similar reaction with dpppe afforded 3a in 72% yield.
General procedure for the synthesis of poly-substituted isoquinolines. Under N2 gas, Pd2dba3 (4.6
mg, 0.005 mmol, 2.5 mol%), PPh3 (78.6 mg, 0.3 mmol), LiOtBu (44.8 mg, 0.56 mmol) are successively
added to a flame-dried 10 mL Schlenk tube. The reaction tube was degassed three times with N2 and dry
toluene (1 mL) was added by syringe. Then, 2-alkynyl benzylazide (0.2 mmol) and arylbromide (0.6
mmol) were added by syringe, respectively. Note that arylbromide in solid form was added to the
reaction tube prior to LiOtBu. The reaction is heated at 100 oC with stirring for 24 h, then it was cooled
to room temperature and filtered through a short plug of silica gel with ethyl acetate as eluents. The
solvent was removed in vacuo to leave a crude mixture, which was purified to afford the pure product
6a-l.
3-Butyl-4-(4-methoxyphenyl)isoquinoline (6a). Yield: 45 mg (76%), pale yellow liquid, Rf = 0.3 (PE :
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EA = 5 : 1); H NMR (400 MHz, CDCl3) δ 9.24 (s, 1H), 7.96-7.94 (m, 1H), 7.55-7.48 (m, 2H), 7.41-
7.39 (m, 1H), 7.21 (d, J = 8.6 Hz, 2H), 7.04 (d, J = 8.6 Hz, 2H), 3.90 (s, 3H), 2.74 (t, J = 7.9 Hz, 2H),
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1.71-1.63 (m, 2H), 1.32-1.22 (m, 2H), 0.82 (t, J = 7.3 Hz, 3H); C NMR (100 MHz, CDCl3) δ 158. 9,
153.4, 151.3, 136.3, 131.2, 130.1, 130.0, 129.5, 127.3, 126.7, 125.9, 125.2, 113.8, 55.2, 35.3, 32.5, 22.7,
13.9; HRMS (ESI, m/z): calcd for C20H22NO [M+H]+ 292.1696, found 292.1689; IR (film): 1235, 1286,
1377, 1463, 1514, 1573, 1610, 2929, 2957 cm-1.
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3-Butyl-4-phenylisoquinoline (6b). Yield: 36 mg (70%), pale yellow liquid, Rf = 0.5 (PE : EA = 5 : 1);
1H NMR (400 MHz, CDCl3) δ 9.25 (s, 1H), 7.97-7.95 (m, 1H), 7.54-7.43 (m, 5H), 7.37-7.34 (m, 1H),
7.30-7.28 (m, 2H), 2.72 (t, J = 7.9 Hz, 2H), 1.71-1.63 (m, 2H), 1.30-1.21 (m, 2H), 0.81 (t, J = 7.3 Hz,
3H); 13C NMR (100 MHz, CDCl3) δ 153.0, 151.5, 137.5, 135.9, 130.4, 130.2, 130.1, 128.4, 127.4, 127.3,
126.6, 126.0, 125.2, 35.3, 32.5, 22.7, 13.9; HRMS (ESI, m/z): calcd for C19H20N [M+H]+ 262.1590,
found 262.1585; IR (film): 1249, 1376, 1443, 1500, 1573, 1619, 2928, 2957 cm-1.
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3-Butyl-4-(4-(trimethylsilyl)phenyl)isoquinoline (6c). Yield: 39 mg (59%), pale yellow liquid, Rf = 0.4
(PE : EA = 5 : 1); 1H NMR (400 MHz, CDCl3) δ 9.25 (s, 1H), 7.96-7.94 (m, 1H), 7.65 (d, J = 8.0 Hz,
2H), 7.53-7.48 (m, 2H), 7.39-7.36 (m, 1H), 7.27 (d, J = 8.0 Hz, 2H), 2.72 (t, J = 7.9 Hz, 2H), 1.72-1.64
(m, 2H), 1.31-1.22 (m, 2H), 0.81 (t, J = 7.3Hz, 3H), 0.36 (s, 9H); 13C NMR (100 MHz, CDCl3) δ 153.0,
151.5, 139.5, 137.8, 135.9, 133.3, 130.5, 130.0, 129.5, 127.3, 126.6, 126.0, 125.3, 35.3, 32.5, 22.6,
13.9, -1.0; HRMS (ESI, m/z): calcd for C22H28NSi [M+H]+ 334.1986, found 334.1988; IR (film): 818,
857, 967, 1105, 1249, 1377, 1572, 2955 cm-1.
3-Butyl-4-(4-fluorophenyl)isoquinoline (6d). Yield: 36 mg (65%), pale yellow liquid, Rf = 0.4 (PE :
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EA = 5 : 1); H NMR (400 MHz, CDCl3) δ 9.25 (s, 1H), 7.98-7.96 (m, 1H), 7.57-7.50 (m, 2H), 7.34-
7.32 (m, 1H), 7.28-7.19 (m, 4H), 2.70 (t, J = 7.9 Hz, 2H), 1.70-1.62 (m, 2H), 1.31-1.22 (m, 2H), 0.82 (t,
J = 7.3 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 162.2 (d, J = 246.5 Hz), 153.2, 151.7, 136.0, 133.3 (d, J
= 3.6 Hz), 131.8 (d, J = 8.0 Hz), 130.3, 129.4, 127.4, 126.6, 126.1, 124.9, 115.5 (d, J = 21.3 Hz), 35.3,
32.4, 22.7, 13.8; HRMS (ESI, m/z): calcd for C19H19FN [M+H]+ 280.1496, found 280.1493; IR (film):
1222, 1378, 1507, 1573, 1604, 1619, 2929, 2958 cm-1.
3-Butyl-4-(4-chlorophenyl)isoquinoline (6e). Yield: 38 mg (65%), pale yellow liquid, Rf = 0.4 (PE :
EA = 5 : 1); 1H NMR (400 MHz, CDCl3) δ 9.25 (s, 1H), 7.98-7.96 (m, 1H), 7.57-7.52 (m, 2H), 7.49 (d,
J = 8.3 Hz, 2H), 7.34-7.31 (m, 1H), 7.25-7.23 (m, 2H), 2.70 (t, J = 7.9 Hz, 2H), 1.70-1.62 (m, 2H), 1.31-
1.22 (m, 2H), 0.82 (t, J = 7.4 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 153.0, 151.9, 135.9, 135.7, 133.6,
131.6, 130.3, 129.2, 128.7, 127.5, 126.6, 126.2, 124.8, 35.3, 32.4, 22.7, 13.9; HRMS (ESI, m/z): calcd
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for C19H19ClN [M+H]+ 296.1201, found 296.1193; IR (film): 1376, 1455, 1487, 1498, 1572, 1619, 2926,
2956 cm-1.
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4-(4-bromophenyl)-3-butylisoquinoline (6f). Yield: 40 mg (59%), pale yellow liquid, Rf = 0.4 (PE :
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EA = 5 : 1); H NMR (400 MHz, CDCl3) δ 9.27 (s, 1H), 7.99-7.96 (m, 1H), 7.65 (d, J = 8.3 Hz, 2H),
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7.57-7.51 (m, 2H), 7.34-7.31 (m, 1H), 7.18 (d, J = 8.3 Hz, 2H), 2.70 (t, J = 7.9 Hz, 2H), 1.70-1.62 (m,
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2H), 1.31-1.22 (m, 2H), 0.83 (t, J = 7.3 Hz, 3H); C NMR (100 MHz, CDCl3) δ 152.9, 151.8, 136.4,
135.7, 131.9, 131.7, 130.4, 129.2, 127.5, 126.6, 126.2, 124.8, 121.7, 35.3, 32.5, 22.7, 13.9; HRMS (ESI,
m/z): calcd for C19H19BrN [M+H]+ 340.0695, found 340.0689; IR (film): 1377, 1455, 1486, 1497, 1572,
1619, 2927, 2955 cm-1.
3-Butyl-4-(3-chlorophenyl)isoquinoline (6g). Yield: 36 mg (61%), pale yellow liquid, Rf = 0.4 (PE :
1
EA = 5 : 1); H NMR (400 MHz, CDCl3) δ 9.26 (s, 1H), 7.98-7.96 (m, 1H), 7.58-7.51 (m, 2H), 7.46-
7.45 (m, 2H), 7.34-7.31 (m, 2H), 7.21-7.18 (m, 1H), 2.71 (t, J = 7.9 Hz, 2H), 1.71-1.64 (m, 2H), 1.32-
1.23 (m, 2H), 0.83 (t, J = 7.4 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 153.0, 152.0, 139.4, 135.6, 134.4,
130.4, 130.2, 129.7, 129.0, 128.5, 127.8, 127.5, 126.6, 126.12, 124.8, 35.3, 32.4, 22.6, 13.8; HRMS
(ESI, m/z): calcd for C19H19ClN [M+H]+ 296.1201, found 296.1194; IR (film): 1078, 1374, 1496, 1571,
1594, 1619, 2927, 2957 cm-1.
4-([1,1'-Biphenyl]-4-yl)-3-butylisoquinoline (6h). Yield: 40 mg (59%), pale yellow liquid, Rf = 0.3
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(PE : EA = 5 : 1); H NMR (400 MHz, CDCl3) δ 9.27 (s, 1H), 7.99-7.96 (m, 1H), 7.76-7.71 (m, 4H),
7.55-7.44 (m, 5H), 7.41-7.36 (m, 3H), 2.77 (t, J = 7.9 Hz, 2H), 1.74-1.67 (m, 2H), 1.33-1.24 (m, 2H),
0.83 (t, J = 7.3 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 153.1, 151.6, 140.6, 140.2, 136.5, 135.9, 130.7,
130.1, 128.8, 127.4, 127.4, 127.1, 126.7, 126.0, 125.2, 35.4, 32.5, 22.7, 13.9; HRMS (ESI, m/z): calcd
for C25H24N [M+H]+ 338.1903, found 338.1897; IR (film): 733, 765, 1377, 1485, 1573, 1619, 2927,
2956 cm-1.
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3-Butyl-4-(naphthalen-2-yl)isoquinoline (6i). Yield: 29 mg (47%), pale yellow liquid, Rf = 0.4 (PE :
EA = 5 : 1); 1H NMR (400 MHz, CDCl3) δ 9.30 (s, 1H), 7.99-7.95 (m, 3H), 7.89-7.86 (m, 1H), 7.78 (s,
1H), 7.58-7.53 (m, 2H), 7.52-7.47 (m, 2H), 7.43-7.40 (m, 1H), 7.37-7.35 (m, 1H), 2.78-2.73 (m, 2H),
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151.7, 136.0, 135.0, 133.3, 132.6, 130.3, 130.1, 129.1, 128.4, 128.1, 128.0, 127.8, 127.4, 126.7, 126.4,
126.2, 126.0, 125.2, 35.4, 32.5, 22.6, 13.9; HRMS (ESI, m/z): calcd for C23H22N [M+H]+ 312.1747,
found 312.1749; IR (film): 1242, 1377, 1465, 1494, 1572, 1618, 2927, 2957 cm-1.
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4-(4-methoxyphenyl)-3-pentylisoquinoline (6j). Yield: 46 mg (76%), pale yellow liquid, Rf = 0.4 (PE :
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EA = 5 : 1); H NMR (400 MHz, CDCl3) δ 9.24 (s, 1H), 7.96-7.94 (m, 1H), 7.54-7.47 (m, 2H), 7.41-
7.39 (m, 1H), 7.22-7.19 (m, 2H), 7.06-7.03 (m, 2H), 3.90 (s, 3H), 2.75-2.71 (m, 2H), 1.72-1.65 (m, 2H),
1.24-1.21 (m, 4H), 0.84-0.80 (m, 3H); 13C NMR (100 MHz, CDCl3) δ 158.9, 153.4, 151.4, 136.3, 131.2,
130.1, 130.0, 129.6, 127.3, 126.7, 125.9, 125.2, 113.8, 55.2, 35.6, 31.8, 30.0, 22.4, 13.9; HRMS (ESI,
m/z): calcd for C21H24NO [M+H]+ 306.1852, found 306.1849; IR (film): 1228, 1286, 1377, 1514, 1573,
1610, 2928, 2956 cm-1.
3-Cyclopropyl-4-(4-methoxyphenyl)isoquinoline (6k). Yield: 47 mg (85%), yellow solid, mp: 135-136
oC; Rf = 0.5 (PE : EA = 5 : 1); 1H NMR (400 MHz, CDCl3) δ 9.12 (s, 1H), 7.91-7.88 (m, 1H), 7.52-7.48
(m, 1H), 7.46-7.42 (m, 2H), 7.33-7.30 (m, 2H), 7.08-7.04 (m, 2H), 3.89 (s, 3H), 1.99-1.92 (m, 1H),
1.18-1.15 (m, 2H), 0.86-0.82 (m, 2H); 13C NMR (100 MHz, CDCl3) δ 158.9, 152.9, 151.4, 135.8, 131.7,
130.0, 129.4, 129.4, 127.3, 126.4, 125.4, 124.7, 113.9, 55.2, 14.4, 9.7; HRMS (ESI, m/z): calcd for
C19H18NO [M+H]+ 276.1383, found 276.1382; IR (film): 1033, 1176, 1228, 1287, 1453, 1513, 1573,
1610 cm-1.
3, 4-Bis(4-methoxyphenyl)isoquinoline (6l).23 Yield: 42 mg (62%), pale yellow solid, mp: 157-159 oC;
Rf = 0.2 (PE : EA = 5 : 1); 1H NMR (400 MHz, CDCl3) δ 9.33 (s, 1H), 8.03-8.01 (m, 1H), 7.70-7.68 (m,
1H), 7.62-7.55 (m, 2H), 7.35-7.32 (m, 2H), 7.18-7.15 (m, 2H), 6.95-6.91 (m, 2H), 6.78-6.75 (m, 2H),
3.86 (s, 3H), 3.78 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 158.7, 158.6, 151.5, 150.4, 136.3, 133.4,
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132.3, 131.5, 130.3, 129.7, 129.6, 127.5, 127.2, 126.5, 125.5, 113.9, 113.1, 55.2, 55.1; IR (film): 829,
1033, 1176, 1244, 1513, 1608, 2834, 2930 cm-1.
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ASSOCIATED CONTENT
Supporting Information
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Copies of 1H and 13C spectra for all products and X-ray crystallographic data (CIF) for product 3t. This
material is available free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*Email: wangjb@pku.edu.cn.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
The project is supported by National Basic Research Program of China (973 Program, No.
2015CB856600) and NSFC (Grant 21472004 and 21332002). We thank Prof. Zhenhua Zhang (China
Agricultural University) for providing azide reagents (supported by the National Key Technologies
R&D Program of China, 2015BAK45B01, CAU).
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2861-2903. (d) Zhang, Z.; Wang, J. Tetrahedron 2008, 64, 6577-6605. (e) Davies, H. M. L.; Denton,
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(4) Zhang, L. Acc. Chem. Res. 2014, 47, 877-888.
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Luo, Y.; Liu, L.; Ye, L.; Wang, Y.; Zhang, L. Angew. Chem. Int. Ed. 2011, 50, 8358-8362. (c) Yan,
Z.-Y.; Xiao, Y.; Zhang, L. Angew. Chem. Int. Ed. 2012, 51, 8624-8627. (d) Wetzel, A.; Gagosz, F.
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