Photoinduced [3+2] Annulation of Alkene with o-Iodoanilines: An Expedient Approach to Indolines

Article abstract of DOI:10.1055/s-0040-1705963

A highly regioselective [3+2] cyclization of alkenes with 2-iodoanilines under the irradiation of UV light is described. This general, metal-free strategy facilitates the direct preparation of 2-mono-/disubstituted indolines as well as spiroindolines through alkene carboamination in one step. Mechanistic studies suggested that the photochemical protocol proceeded via a radical pathway.

Full text of DOI:10.1055/s-0040-1705963

SYNTHESIS
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Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart
2020, 52, A–H
paper
A
en
X. Zhao et al.
Paper
Synthesis
Photoinduced [3+2] Annulation of Alkene with o-Iodoanilines:
An Expedient Approach to Indolines
Xinxin Zhao
R1
N
I
R2
Lin Guo
K2HPO4, hv
Ar
R2
32 examples
up to 74% yield
+
NH
R1
DMSO, N2, r.t.
Ar
Chao Yang
Wujiong Xia*
0
0
0
0
-
0
0
0
1
-9
3
9
6
-
9
5
2
0
metal-free
mild conditions
high regioselectivity
general access to mono-/disubstituted indolines and spiroindolines
State Key Lab of Urban Water Resource and Environment, &
School of Science, Harbin Institute of Technology (Shenzhen),
Shenzhen 518005, P. R. of China
xiawj@hit.edu.cn
WSeMtautajeiColKoxnerigaryewXLsiajpa@bohnoidfti.UendrgbuAa.cnuntWhoarter Resource and Environment, & School of Science, Harbin Institute of Technology (Shenzhen), Shenzhen 518005, P. R. of China
Received: 26.08.2020
Accepted after revision: 29.09.2020
Published online: 04.11.2020
and powerful alternative to the classical synthetic meth-
ods.25 As far as we know, existing intermolecular synthetic
strategies is comparatively rare.
DOI: 10.1055/s-0040-1705963; Art ID: ss-2020-g0453-op
Abstract A highly regioselective [3+2] cyclization of alkenes with 2-
iodoanilines under the irradiation of UV light is described. This general,
metal-free strategy facilitates the direct preparation of 2-mono-/disub-
stituted indolines as well as spiroindolines through alkene carboamina-
tion in one step. Mechanistic studies suggested that the photochemical
protocol proceeded via a radical pathway.
O
O
N
N
HN
N
N
H
O
N
O
H
O
N
O
OH
O
H
O
O
O
O
vindoline
H
tabersonine
6-methoxyspirotryprostatin B
Key words [3+2] cyclization, alkene carboamination, indolines,
spiroindolines, radical pathway
N
H
F
F
O
H
H
N
O
F
H
N
O
HN
As an important class of nitrogen-containing heterocy-
clic compounds, indolines are widespread in many natural-
ly occurring alkaloids, and their framework constitutes the
core of many biologically and pharmaceutically active mol-
ecules (representative examples are listed in Figure 1).1,2
The inherently unique properties of such structural motifs
have stimulated substantial efforts in developing strategies
for their elaboration.3,4 Among them the dearomatization of
indoles represents one of the most straightforward meth-
ods to assemble indolines,5 including hydrogenation,6–9
cycloaddition,10–12 and transition-metal-mediated Heck
arylation or alkylation.13–15 In the past decades, numerous
research efforts have been devoted to building the pyrroli-
dine unit on benzene ring for indoline synthesis through in-
tramolecular C–N or C–C bond formation, thus boosting a
variety of annulation strategies (e.g., the transition-metal-
or organocatalyst-mediated C–H amination16–23 or C–H ary-
lation24). However, in these methods, tedious procedures
were normally required to access the starting precursors,
leading to a reduction on the overall synthetic effectiveness.
As a consequence, the synthesis of such valuable indoline
derivatives through an intermolecular cyclization approach
by using readily available feedstocks becomes an appealing
N
O
O
N
O
O
O
O
strychnine
funapide
phenserine
Figure 1 Selected examples of bioactive indoline derivatives
In this context, intermolecular [3+2] cyclization of ani-
lines with inexpensive alkenes provides an attractive route
for indoline synthesis. For example, the directing group-
assisted, transition-metal-catalyzed C–H activation/alkene
annulation to functionalized indolines have been well
demonstrated by previous studies of Glorious,26 Jana,27,28
Booker-Milburm,29 and others30 (Scheme 1a). Moreover,
similar synthetic pattern have been adopted by Larock,31
Catellani,32 Taylor,33 and Radhakrishnan,34,35 which, respec-
tively, documented the Pd(OAc)2-catalyzed cyclization of
alkenes with o-haloanilines to assemble indolines. Particu-
larly in 2015, Tasker et al. described a highly regioselective
synthesis of 3-substituted indolines from iodoacetanilides
and alkenes by Nickel/photoredox dual catalysis (Scheme
1b).36 Despite significant progresses, in general, those
methods relied on the use of noble transition metal
catalysts under harsh conditions. Moreover, the undesired
© 2020. Thieme. All rights reserved. Synthesis 2020, 52, A–H
Georg Thieme Verlag KG, Rüdigerstraße 14, 70469 Stuttgart, Germany

B
X. Zhao et al.
Paper
Synthesis
-hydride elimination was always unavoidable, and there-
fore they failed to prepare 2,2-disubstituted indolines by
these strategies,37 which greatly limited their application.
Therefore developing a green and mild strategy to address
the aforementioned disadvantages is highly desirable.
(entries 9–14). The result of entry 15 implied the container
material was an important parameter to the reaction. Fur-
thermore, we noticed a sharp decrease on yield when the
photoreaction was performed under air atmosphere (entry
16). Moreover, there is no product observed in the absence
of light, which convincingly confirmed the photoinduced
nature of this protocol (entry 17).
a) C–H activation for indoline synthesis from aniline and alkenes
H
transition metal
(Rh, Pd, Ru)
R
+
Table 1 Selected Optimization of Reaction Conditionsa
R
NH
DG
N
DG
I
additive, hv
Ph
b) Indoline synthesis from o-haloanilines and alkenes
+
Ph
solvent, N2, r.t.
N
N
R
H
I
transition metal
1
(Pd, Ni)
R
or
+
R
N
NH
FG
N
FG
Entry
Additive
Solvent
Yield (%)b
FG
c) This work: photoinduced synthesis of alkenes with o-haloanilines
1
2
none
1,2-DCE
MeCN
DMF
38 (55)
0
I
R1
N
none
R2
K2HPO4, hv
Ar
R2
+
3
none
0
NH
R1
DMSO, N2, r.t.
Ar
4
none
THF
0
Scheme 1 Intermolecular [3+2] strategies for indoline synthesis
5
none
1,4-dioxane
0
6
none
DCM
27 (67)
30 (50)
50 (65)
63
Nowadays, the emergency of photochemistry offered as
a potential solution to activate organohalides as relevant re-
search revealed the fact that haloarenes could be photode-
graded by breaking the Caryl–X bonds.38 Such photochemical
behavior provided an appealing way to access aryl radicals.
Encouraged by this concept in mind and to continue our on-
going interests in developing photoinduced approaches to
heterocycles39–41 we herein report our discovery of a novel,
metal-free strategy to indolines by the cyclization of
alkenes with o-iodoanilines under the irradiation of UV
light at ambient temperature. This complementary inter-
molecular protocol provides a direct and general opportu-
nity to types of 2-substituted indolines, including 2-mono-
/disubstituted indolines as well as valuable spiroindolines,
through highly regioselective alkene carboamination
(Scheme 1c). To the best of knowledge, such a photosyn-
thetic method has never been reported before.
Our initial attempt was commenced to explore the opti-
mal conditions of the photoinduced annulation reaction us-
ing 2-iodo-N-methylaniline and styrene as model sub-
strates (Table 1). After 8 hours of light irradiation (mercury
lamp,  = 300 nm) in 1,2-dichloroethane (1,2-DCE) under N2
atmosphere, the targeted cyclization product 1 was ob-
tained in a 38% isolated yield (55% brsm). Replacing 1,2-DCE
with other solvents such as MeCN, acetone, DMF, THF, and
1,4-dioxane resulted in no product formation (Table 1, en-
tries 2–5). Similar or inferior performance was observed
when DCM or n-hexane was used as solvent (entries 6, 7).
To our delight, the yield of 1 was greatly improved to 50%
when performed in DMSO (65% brsm) (entry 8). Subse-
quent investigation on a wealth of base additives disclosed
K2HPO4 was beneficial for the reaction and delivered 1 in
63% yield, along with the starting styrene fully consumed
7
none
n-hexane
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
8
none
9
K2HPO4
K2CO3
Na2CO3
Cs2CO3
LiOH
10
11
12
13
14
15c
16d
17e
46
36 (58)
0
32 (61)
31 (47)
40 (52)
<5 (39)
0
NaOH
K2HPO4
K2HPO4
K2HPO4
a Reactions conducted with styrene (0.5 mmol), 2-iodo-N-methylaniline
(0.2 mmol), solvent (2.0 mL) in a 10 mL glass tube, N2 atmosphere, irradiat-
ed by 300 nm mercury lamp source.
b Isolated yields are based on 2-iodo-N-methylaniline, yields in parentheses
are based on recovered starting material (brsm).
c Reaction carried out in a 10 mL quartz tube.
d Reactions performed under air atmosphere.
e Reaction performed without light.
With the optimized conditions in hand, the scope of the
robust photoreaction was then investigated. As listed in
Scheme 2, the reactivity of different styrene derivatives was
first evaluated with 2-iodo-N-methylaniline as partner. We
noticed that the corresponding reactions proceeded suc-
cessfully with high regioselectivity, providing a broad range
of 2-phenyl-substituted indolines 2–10 in yields ranging
from 48–74%. Generally speaking, both electron-rich and
electron-poor functional groups on the aromatic ring of
styrene were compatible with the established conditions
regardless of the substituted position. Notably, the synthet-
ically important but sensitive amino and ester groups were
as well competent functional groups, affording products 8
© 2020. Thieme. All rights reserved. Synthesis 2020, 52, A–H

C
X. Zhao et al.
Paper
Synthesis
and 10 in 71% and 59% yield, respectively. In addition, when
replacing styrene with heteroaryl alkenes, the photoin-
duced reaction was also amenable to give 11–13 in accept-
able yields.
17 in 37–73% yields through this photosynthetic method.
Notably, substrate containing two identical alkene moieties
could be selectively reacted in one position. Following a
similar reaction pattern, -cyclopropyl and -cyclohexyl
styrenes were readily incorporated into the indoline prod-
ucts 18 and 19 under the UV irradiation. Besides, replacing
the -methyl with noncyclic alkyl or phenyl group also
proved viable (20, 21). Furthermore, substitution at the ni-
trogen atom of 2-iodoanilines was then probed. An array of
cyclic and noncyclic alkyl groups were evaluated as ade-
quate protecting groups to deliver the corresponding cy-
clization adducts 22–26 in good to moderate yields.
R2
R1
I
Ar
R2
N
K2HPO4, hv
R1
+
Ar
N
H
DMSO, N2, r.t.
N
N
N
N
N
R
11, 51%
12, 53%
R = H, 1, 63%
Subsequently, the alkene scope was extended to alkenes
with a cycloalkane fused-benzene scaffold. Gladly, their
cross-coupling with 2-iodo-N-methylaniline constitutes an
expedient access to spiroindolines, the structure of which is
frequently occurring in pharmaceuticals and natural prod-
ucts,42 whereas relevant preparation methods for this inter-
esting motif are extremely rare. Given this, several types of
structurally diverse spiroindolines were prepared via this
protocol. As exemplified by 27 and 28, the photochemical
transformations proceeded pretty successfully with benzo-
cyclic alkenes. To our delight, incorporating O atom and NH
into the alkyl ring had no detrimental effect on the reaction
outcome, affording 29 and 30 in 56% and 69% yield, respec-
tively. Besides, spiroindolines 31 and 32 were prepared in
moderate yields via this protocol. However, by using 2-
iodo-N,4-dimethylaniline as radical source, the reaction of
styrene delivered only trace of 33 (detected by GC-MS).
Before proposing the mechanism, we carried out a radi-
cal quenching experiment to gain more insight into this
photochemical protocol. In the presence of 1.5 equivalents
of TEMPO, the reaction of styrene and 2-iodo-N-methylani-
line was completely suppressed, convincingly indicating a
radical pathway was involved in the reaction process
(Scheme 3, radical quenching experiment).
R = o-Me, 2, 64%
R = m-Me, 3, 58%
R = p-Me, 4, 69%
R = p-t-Bu, 5, 67%
R = p-OMe, 6, 74%
R = p-Ph, 7, 48%
R = p-NH2, 8, 71%
R = p-NMe2, 9, 66%
N
N
S
R
R = H, 14, 73%
R = Me, 15, 54%
R = F, 16, 37%
13, 35%
N
N
Ph
R = p-OCOMe, 10, 59%
17, 56%
18, 32%
N
N
N
Ph
Ph Ph
20, 61%
Ph
Ph
21, 43%
19, 51%
Ph
Et
R
Et
Ph
N
N
N
N
Ph
Ph
Ph
R = H, 24, 62%
R = Me, 25, 65%
22, 57%
23, 64%
26, 71%
Synthesis of spiroindolines
N
N
N
O
N
NH
27, 72%
28, 71%
29, 56%
30, 69%
Radical quenching experiment
N
N
N
I
TEMPO (1.5 equiv)
K2HPO4, hv
Ph
Ph
+
33, trace
detected by GC-MS
N
N
DMSO, N2, r.t.
31, 58%
32, 55%
H
1, 0%
Scheme 2 Photoinduced preparation of carbazole derivatives. Reac-
tions performed on 0.2 mmol scale with alkenes (0.5 mmol), 2-iodo-
anilines (0.2 mmol), K2HPO4 (0.4 mmol) in DMSO (1.0 mL) in a 10 mL
glass tube, N2 atmosphere, irradiated by 300 nm mercury lamp source.
Isolated yields are based on 2-iodoanilines.
Proposed mechanism
I
R
R
hv
N
N
H
N
H
H
A
B
(1/2) I2
I
I
To further demonstrate the versatility of this annulation
strategy, different gem-disubstituted alkenes were next
subjected to the standard conditions. Gratifyingly, their car-
BH
R
+
R
boamination with 2-iodo-N-methylaniline provided
a
R
N
N +
H
NH
straightforward approach to a variety of 2,2-disubstituted
indolines in a moderate manner. As seen in Scheme 2, sty-
renes with a methyl at the -position of C=C bond were
identified as suitable candidates, furnishing the desired 14–
B
D
C
Scheme 3 Mechanistic studies
© 2020. Thieme. All rights reserved. Synthesis 2020, 52, A–H

D
X. Zhao et al.
Paper
Synthesis
According to the mechanistic studies and previous rele-
vant literature,41 a plausible speculation was proposed for
the photoinduced transformations (Scheme 3, proposed
mechanism). Upon the irradiation of UV light, 2-iodo-N-
methylaniline first underwent a deiodination step to pro-
duce a radical intermediate A and an iodine radical by ho-
molytic cleavage of the Caryl–I bond. Subsequent capture of
A by alkenes afforded another radical species B, which was
then oxidized by the formed iodine radical to generate the
cationic intermediate C. An intramolecular annulation of C
afforded D, which was then transformed to the final indo-
lines by the removal of proton with the assist of base addi-
tive.
In conclusion, we have demonstrated a photoinduced,
metal-free, [3+2] annulation strategy to indolines by using
available alkenes as starting materials with o-haloanilines.
This developed green protocol is well-tolerant with a wide
range of functional groups and provided a general approach
to various 2-mono-/disubstituted indolines as well as valu-
able spiroindolines through highly regioselective alkene
carboamination. Mechanistic studies indicated that a radi-
cal pathway was involved in these photochemical transfor-
mations.
13C NMR (151 MHz, CDCl3):  = 153.29, 142.43, 128.55, 128.54,
127.64, 127.54, 127.31, 123.95, 118.06, 107.13, 72.16, 39.48, 34.23.
HRMS (ESI): m/z calcd for C15H16N [M + H]+: 210.1277; found:
210.1277.
1-Methyl-2-(o-tolyl)indoline (2)
Yield: 28.6 mg (64%); colorless oil.
1H NMR (600 MHz, CDCl3):  = 7.58 (d, J = 7.5 Hz, 1 H), 7.24–7.21 (m, 1
H), 7.20–7.16 (m, 2 H), 7.14 (t, J = 7.7 Hz, 1 H), 7.06 (d, J = 7.2 Hz, 1 H),
6.71 (t, J = 7.3 Hz, 1 H), 6.55 (d, J = 7.8 Hz, 1 H), 4.61 (dd, J = 11.1, 9.0
Hz, 1 H), 3.39 (dd, J = 15.5, 8.9 Hz, 1 H), 2.77 (dd, J = 15.1, 11.6 Hz, 1 H),
2.64 (s, 3 H), 2.36 (s, 3 H).
13C NMR (151 MHz, CDCl3):  = 153.40, 140.41, 135.74, 130.43,
128.20, 127.61, 126.90, 126.36, 124.06, 118.00, 107.19, 37.62, 34.56,
19.13.
HRMS (ESI): m/z calcd for C16H18N [M + H]+: 224.1434; found:
224.1431.
1-Methyl-2-(m-tolyl)indoline (3)
Yield: 25.9 mg (58%); colorless oil.
1H NMR (600 MHz, CDCl3):  = 7.32–7.27 (m, 3 H), 7.17 (dd, J = 15.6,
7.5 Hz, 2 H), 7.10 (d, J = 7.1 Hz, 1 H), 6.75 (t, J = 7.3 Hz, 1 H), 6.56 (d, J =
7.8 Hz, 1 H), 4.34 (dd, J = 11.2, 8.8 Hz, 1 H), 3.33 (dd, J = 15.6, 8.8 Hz, 1
H), 2.95 (dd, J = 15.5, 11.4 Hz, 1 H), 2.64 (s, 3 H), 2.40 (s, 3 H).
13C NMR (151 MHz, CDCl3):  = 153.31, 142.39, 138.19, 128.62,
128.42, 128.30, 127.98, 127.63, 124.43, 123.95, 118.05, 107.14, 72.17,
39.47, 34.30, 21.45.
HRMS (ESI): m/z calcd for C16H17NNa [M + Na]+: 246.1253; found:
246.1259.
All the starting materials were purchased from Aldrich, Energy Chem-
ical Chemicals, and Aladdin, and were used as received. All the rele-
vant solvents were purified according to the procedure from Purifica-
tion of Laboratory Chemicals book. 1H NMR (400 MHz or 600 MHz)
and 13C NMR (151 MHz) spectra were recorded on Bruker AV-400 in-
strument in CDCl3 with TMS as internal standard. Chemical shift in
parts per million relative to the chemical shift of CDCl3 at 7.26 ppm
integration, multiplicities (standard abbreviations) and for 13C NMR
spectra were relative to the center line signal of the CDCl3 triplet at
77.0 ppm. HRMS (ESI) spectra were recorded on a Bruker Esquire LC
mass spectrometer using electrospray ionization. Flash column chro-
matography was performed using 200–300 mesh silica gel and eluted
with PE/EtOAc.
1-Methyl-2-(p-tolyl)indoline (4)
Yield: 30.8 mg (69%); colorless oil.
1H NMR (600 MHz, CDCl3):  = 7.35 (d, J = 7.9 Hz, 2 H), 7.20 (d, J = 7.8
Hz, 2 H), 7.15 (t, J = 7.7 Hz, 1 H), 7.08 (d, J = 7.1 Hz, 1 H), 6.73 (t, J = 7.3
Hz, 1 H), 6.53 (d, J = 7.8 Hz, 1 H), 4.33 (dd, J = 11.1, 8.8 Hz, 1 H), 3.31
(dd, J = 15.6, 8.7 Hz, 1 H), 2.92 (dd, J = 15.5, 11.3 Hz, 1 H), 2.62 (d, J =
7.9 Hz, 3 H), 2.38 (s, 3 H).
13C NMR (151 MHz, CDCl3):  = 153.31, 139.36, 137.21, 129.22,
128.64, 127.61, 127.26, 123.93, 117.99, 107.09, 71.94, 39.49, 34.15,
21.13.
Indolines; General Procedure
HRMS (ESI): m/z calcd for C16H18N [M + H]+: 224.1434; found:
224.1437.
To a 10 mL dry glass tube was added the respective 2-iodoaniline (0.2
mmol), the appropriate alkene (0.5 mmol), K2HPO4 (70 mg, 0.4
mmol), and DMSO (1.0 mL). Then N2 was bubbled through the solu-
tion for 10 min. The reaction system was irradiated under the 300 nm
UV light until completion of the reaction, then diluted with H2O (5
mL), and extracted with EtOAc (3 × 5 mL). The combined organic lay-
ers were dried (Na2SO4) and concentrated under reduced pressure af-
ter filtration. The resulting residue was purified by silica gel column
chromatograph to afford the corresponding indoline product.
2-[4-(tert-Butyl)phenyl]-1-methylindoline (5)
Yield: 35.5 mg (67%); colorless oil.
1H NMR (600 MHz, CDCl3):  = 7.46–7.31 (m, 4 H), 7.15 (t, J = 7.6 Hz, 1
H), 7.07 (d, J = 7.1 Hz, 1 H), 6.72 (t, J = 7.3 Hz, 1 H), 6.53 (d, J = 7.8 Hz, 1
H), 4.33 (dd, J = 11.2, 8.7 Hz, 1 H), 3.30 (dd, J = 15.6, 8.7 Hz, 1 H), 2.94
(dd, J = 15.5, 11.3 Hz, 1 H), 2.62 (d, J = 4.1 Hz, 3 H), 1.35 (s, 9 H).
13C NMR (151 MHz, CDCl3):  = 153.35, 150.43, 139.21, 128.72,
127.60, 127.01, 125.39, 123.94, 117.98, 107.10, 71.88, 39.37, 34.52,
34.24, 31.39.
HRMS (ESI): m/z calcd for C19H24N [M + H]+: 266.1903; found:
266.1900.
1-Methyl-2-phenylindoline (1)
Yield: 26.4 mg (63%); colorless oil.
1H NMR (600 MHz, CDCl3):  = 7.46 (dd, J = 8.0, 0.9 Hz, 2 H), 7.39 (t, J =
7.5 Hz, 2 H), 7.35–7.30 (m, 1 H), 7.16 (t, J = 7.7 Hz, 1 H), 7.09 (d, J = 7.1
Hz, 1 H), 6.74 (t, J = 7.4 Hz, 1 H), 6.55 (d, J = 7.8 Hz, 1 H), 4.37 (dd, J =
11.2, 8.8 Hz, 1 H), 3.34 (dd, J = 15.6, 8.8 Hz, 1 H), 2.94 (dd, J = 15.6, 11.2
Hz, 1 H), 2.63 (s, 3 H).
2-(4-Methoxyphenyl)-1-methylindoline (6)
Yield: 35.4 mg (74%); colorless oil.
© 2020. Thieme. All rights reserved. Synthesis 2020, 52, A–H

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X. Zhao et al.
Paper
Synthesis
1H NMR (400 MHz, CDCl3):  = 7.37 (d, J = 8.6 Hz, 2 H), 7.14 (t, J = 7.6
Hz, 1 H), 7.07 (d, J = 7.2 Hz, 1 H), 6.91 (d, J = 8.6 Hz, 2 H), 6.71 (t, J = 7.3
Hz, 1 H), 6.51 (d, J = 7.8 Hz, 1 H), 4.30 (dd, J = 11.1, 8.7 Hz, 1 H), 3.83 (s,
3 H), 3.29 (dd, J = 15.6, 8.7 Hz, 1 H), 2.91 (dd, J = 15.6, 11.3 Hz, 1 H),
2.59 (s, 3 H).
13C NMR (151 MHz, CDCl3):  = 159.07, 153.25, 134.32, 128.65,
128.46, 127.61, 123.93, 118.01, 113.87, 107.09, 71.66, 55.28, 39.45,
34.06.
HRMS (ESI): m/z calcd for C17H17NO2Na [M + Na]+: 290.1151; found:
290.1158.
1-Methyl-2-(pyridin-4-yl)indoline (11)
Yield: 21.4 mg (51%); colorless oil.
1H NMR (400 MHz, CDCl3):  = 8.61 (d, J = 4.4 Hz, 2 H), 7.37 (d, J = 5.2
Hz, 2 H), 7.16 (t, J = 7.6 Hz, 1 H), 7.07 (d, J = 7.1 Hz, 1 H), 6.75 (t, J = 7.4
Hz, 1 H), 6.56 (d, J = 7.8 Hz, 1 H), 4.41–4.29 (m, 1 H), 3.38 (dd, J = 15.6,
9.0 Hz, 1 H), 2.86 (dd, J = 15.4, 11.1 Hz, 1 H), 2.64 (s, 3 H).
HRMS (ESI): m/z calcd for C16H18NO [M + H]+: 240.1383; found:
240.1380.
13C NMR (151 MHz, CDCl3):  = 152.97, 151.68, 150.14, 127.86,
124.05, 122.26, 118.57, 107.49, 70.95, 39.08, 34.61.
HRMS (ESI): m/z calcd for C14H15N2 [M + H]+: 211.1230; found:
211.1231.
2-([1,1′-Biphenyl]-4-yl)-1-methylindoline (7)
Yield: 27.4 mg (48%); colorless oil.
1H NMR (600 MHz, CDCl3):  = 7.62 (t, J = 7.8 Hz, 4 H), 7.53 (d, J = 8.0
Hz, 2 H), 7.46 (t, J = 7.6 Hz, 2 H), 7.36 (t, J = 7.1 Hz, 1 H), 7.17 (t, J = 7.7
Hz, 1 H), 7.10 (d, J = 7.1 Hz, 1 H), 6.74 (t, J = 7.4 Hz, 1 H), 6.56 (d, J = 7.8
Hz, 1 H), 4.41 (dd, J = 10.9, 9.0 Hz, 1 H), 3.36 (dd, J = 15.6, 8.8 Hz, 1 H),
2.98 (dd, J = 15.5, 11.3 Hz, 1 H), 2.66 (s, 3 H).
13C NMR (151 MHz, CDCl3):  = 153.29, 141.51, 140.85, 140.51,
128.75, 128.55, 127.76, 127.68, 127.29, 127.24, 127.06, 123.99,
118.12, 107.18, 71.88, 39.49, 34.32.
1-Methyl-2-(pyridin-2-yl)indoline (12)
Yield: 22.3 mg (53%); colorless oil.
1H NMR (400 MHz, CDCl3):  = 8.60 (d, J = 4.7 Hz, 1 H), 7.71 (t, J = 7.6
Hz, 1 H), 7.54 (d, J = 7.8 Hz, 1 H), 7.25–7.20 (m, 1 H), 7.15 (t, J = 7.6 Hz,
1 H), 7.08 (d, J = 7.2 Hz, 1 H), 6.73 (t, J = 7.3 Hz, 1 H), 6.56 (d, J = 7.8 Hz,
1 H), 4.63–4.51 (m, 1 H), 3.47 (dd, J = 15.7, 9.2 Hz, 1 H), 2.98 (dd, J =
15.6, 11.0 Hz, 1 H), 2.69 (s, 3 H).
13C NMR (151 MHz, CDCl3):  = 162.40, 153.13, 149.31, 136.91,
128.33, 127.66, 124.09, 122.45, 121.02, 118.31, 107.40, 73.32, 37.95,
34.80.
HRMS (ESI): m/z calcd for C21H20N [M + H]+: 286.1590; found:
286.1592
4-(1-Methylindolin-2-yl)aniline (8)
HRMS (ESI): m/z calcd for C14H15N2 [M + H]+: 211.1230; found:
211.1233.
Yield: 31.8 mg (71%); colorless oil.
1H NMR (600 MHz, CDCl3):  = 7.24 (d, J = 7.9 Hz, 2 H), 7.14 (t, J = 7.6
Hz, 1 H), 7.07 (d, J = 7.1 Hz, 1 H), 6.71 (dd, J = 11.2, 7.7 Hz, 3 H), 6.51 (d,
J = 7.8 Hz, 1 H), 4.24 (dd, J = 10.8, 9.1 Hz, 1 H), 3.67 (s, 2 H), 3.26 (dd,
J = 15.6, 8.6 Hz, 1 H), 2.91 (dd, J = 15.4, 11.4 Hz, 1 H), 2.59 (s, 3 H).
13C NMR (151 MHz, CDCl3):  = 153.29, 145.82, 132.08, 128.80,
128.43, 127.54, 123.89, 117.87, 115.10, 107.02, 71.80, 39.33, 33.96.
1-Methyl-2-(thiophen-2-yl)indoline (13)
Yield: 15.1 mg (35%); colorless oil.
1H NMR (600 MHz, CDCl3):  = 7.27 (d, J = 5.1 Hz, 1 H), 7.16 (t, J = 7.7
Hz, 1 H), 7.10 (d, J = 7.2 Hz, 1 H), 7.07 (d, J = 3.3 Hz, 1 H), 6.99 (dd, J =
5.0, 3.5 Hz, 1 H), 6.75 (t, J = 7.4 Hz, 1 H), 6.54 (d, J = 7.8 Hz, 1 H), 4.61
(dd, J = 10.7, 8.7 Hz, 1 H), 3.37 (dd, J = 15.5, 8.5 Hz, 1 H), 3.06 (dd, J =
15.5, 10.9 Hz, 1 H), 2.68 (s, 3 H).
HRMS (ESI): m/z calcd for C15H17N2 [M + H]+: 225.1386; found:
225.1390.
13C NMR (151 MHz, CDCl3):  = 152.54, 146.60, 128.29, 127.71,
126.48, 125.48, 124.78, 123.92, 118.52, 107.54, 67.43, 40.06, 34.32.
N,N-Dimethyl-4-(1-methylindolin-2-yl)aniline (9)
Yield: 33.3 mg (66%); colorless oil.
HRMS (ESI): m/z calcd for C13H14NS [M + H]+: 216.0841; found:
1H NMR (600 MHz, CDCl3):  = 7.35 (d, J = 8.7 Hz, 2 H), 7.16 (t, J = 7.6
Hz, 1 H), 7.10 (d, J = 7.1 Hz, 1 H), 6.78 (d, J = 8.6 Hz, 2 H), 6.74 (t, J = 7.3
Hz, 1 H), 6.53 (d, J = 7.8 Hz, 1 H), 4.28 (dd, J = 11.3, 8.6 Hz, 1 H), 3.28
(dd, J = 15.6, 8.6 Hz, 1 H), 3.00 (s, 6 H), 2.96 (dd, J = 15.5, 11.4 Hz, 1 H),
2.62 (s, 3 H).
13C NMR (151 MHz, CDCl3):  = 153.34, 150.15, 129.76, 128.89,
128.22, 127.51, 123.88, 117.81, 112.51, 106.99, 71.79, 40.65, 39.29,
33.95.
216.0840.
1,2-Dimethyl-2-phenylindoline (14)
Yield: 32.6 mg (73%); colorless oil.
1H NMR (400 MHz, CDCl3):  = 7.49 (d, J = 7.5 Hz, 2 H), 7.34 (t, J = 7.6
Hz, 2 H), 7.29–7.21 (m, 1 H), 7.12 (t, J = 7.6 Hz, 1 H), 7.01 (d, J = 7.1 Hz,
1 H), 6.64 (t, J = 7.3 Hz, 1 H), 6.39 (d, J = 7.8 Hz, 1 H), 3.15 (d, J = 15.7
Hz, 1 H), 3.03 (d, J = 15.7 Hz, 1 H), 2.58 (s, 3 H), 1.56 (s, 3 H).
13C NMR (151 MHz, CDCl3):  = 151.75, 146.44, 128.29, 127.65,
127.31, 126.74, 126.12, 124.06, 116.80, 105.66, 70.21, 47.29, 29.25,
20.73.
HRMS (ESI): m/z calcd for C17H21N2 [M + H]+: 253.1699; found:
253.1697.
4-(1-Methylindolin-2-yl)phenyl Acetate (10)
HRMS (ESI): m/z calcd for C16H18N [M + H]+: 224.1434; found:
224.1437.
Yield: 31.5 mg (59%); colorless oil.
1H NMR (600 MHz, CDCl3):  = 7.46 (d, J = 8.4 Hz, 2 H), 7.15 (t, J = 7.7
Hz, 1 H), 7.08 (dd, J = 12.1, 7.9 Hz, 3 H), 6.73 (t, J = 7.3 Hz, 1 H), 6.53 (d,
J = 7.8 Hz, 1 H), 4.35 (dd, J = 11.1, 8.9 Hz, 1 H), 3.31 (dd, J = 15.6, 8.8 Hz,
1 H), 2.91 (dd, J = 15.5, 11.2 Hz, 1 H), 2.61 (s, 3 H), 2.32 (s, 3 H).
13C NMR (151 MHz, CDCl3):  = 169.57, 153.18, 149.96, 139.99,
128.40, 128.30, 127.67, 123.97, 121.60, 118.19, 107.19, 71.60, 39.51,
34.29, 21.15.
1,2-Dimethyl-2-(p-tolyl)indoline (15)
Yield: 25.6 mg (54%); colorless oil.
1H NMR (400 MHz, CDCl3):  = 7.42 (d, J = 8.0 Hz, 2 H), 7.17 (dd, J =
16.7, 7.9 Hz, 3 H), 7.04 (d, J = 7.1 Hz, 1 H), 6.67 (t, J = 7.3 Hz, 1 H), 6.42
(d, J = 7.8 Hz, 1 H), 3.17 (d, J = 15.7 Hz, 1 H), 3.06 (d, J = 15.7 Hz, 1 H),
2.61 (s, 3 H), 2.38 (s, 3 H), 1.58 (s, 3 H).
© 2020. Thieme. All rights reserved. Synthesis 2020, 52, A–H

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13C NMR (151 MHz, CDCl3):  = 151.75, 143.43, 136.31, 128.97,
127.61, 127.39, 126.07, 124.04, 116.71, 105.60, 70.02, 47.29, 29.18,
20.95, 20.72.
HRMS (ESI): m/z calcd for C17H20N [M + H]+: 238.1590; found:
238.1590.
1-Methyl-2-(2-methyl-2-phenylpropyl)-2-phenylindoline (20)
Yield: 41.6 mg (61%); colorless oil.
1H NMR (600 MHz, CDCl3):  = 7.34–7.20 (m, 8 H), 7.19–7.12 (m, 2 H),
7.04 (t, J = 7.6 Hz, 1 H), 6.76 (d, J = 7.0 Hz, 1 H), 6.51 (t, J = 7.3 Hz, 1 H),
6.09 (d, J = 7.7 Hz, 1 H), 3.03 (d, J = 16.8 Hz, 1 H), 2.83 (d, J = 16.8 Hz, 1
H), 2.73 (d, J = 14.9 Hz, 1 H), 2.54 (d, J = 14.9 Hz, 1 H), 2.19 (s, 3 H),
1.35 (d, J = 28.6 Hz, 6 H).
2-(4-Fluorophenyl)-1,2-dimethylindoline (16)
13C NMR (151 MHz, CDCl3):  = 151.60, 149.96, 147.39, 128.20,
127.94, 127.45, 127.32, 126.51, 126.02, 125.34, 125.25, 123.60,
115.74, 103.87, 71.03, 48.96, 42.65, 37.83, 31.41, 30.03, 29.42.
Yield: 17.8 mg (37%); colorless oil.
1H NMR (400 MHz, CDCl3):  = 7.48 (dd, J = 8.6, 5.5 Hz, 2 H), 7.15 (t, J =
7.6 Hz, 1 H), 7.09–6.98 (m, 3 H), 6.67 (t, J = 7.3 Hz, 1 H), 6.42 (d, J = 7.8
Hz, 1 H), 3.09 (dd, J = 36.4, 15.7 Hz, 2 H), 2.58 (s, 3 H), 1.57 (s, 3 H).
HRMS (ESI): m/z calcd for C25H28N [M + H]+: 342.2216; found:
13C NMR (151 MHz, CDCl3):  = 161.70 (d, J = 245.2 Hz), 151.57,
142.16 (d, J = 3.0 Hz), 127.82, 127.77, 127.71, 127.14, 124.09, 117.00,
115.04, 114.90, 105.80, 69.82, 47.31, 29.14, 20.78.
342.2214.
1-Methyl-2,2-diphenylindoline (21)
HRMS (ESI): m/z calcd for C16H17FN [M + H]+: 242.1340; found:
Yield: 24.5 mg (43%); colorless oil.
1H NMR (400 MHz, CDCl3):  = 7.31–7.25 (m, 10 H), 7.09 (dd, J = 15.4,
7.5 Hz, 2 H), 6.67 (t, J = 7.1 Hz, 1 H), 6.35 (d, J = 7.8 Hz, 1 H), 3.68 (s, 2
H), 2.49 (s, 3 H).
242.1342.
1,2-Dimethyl-2-[4-(prop-1-en-2-yl)phenyl]indoline (17)
13C NMR (151 MHz, CDCl3):  = 151.80, 144.48, 128.15, 127.99,
Yield: 29.5 mg (56%); colorless oil.
1H NMR (600 MHz, CDCl3):  = 7.50 (s, 4 H), 7.17 (t, J = 7.6 Hz, 1 H),
7.06 (d, J = 7.1 Hz, 1 H), 6.69 (t, J = 7.3 Hz, 1 H), 6.45 (d, J = 7.8 Hz, 1 H),
5.43 (s, 1 H), 5.12 (s, 1 H), 3.19 (d, J = 15.7 Hz, 1 H), 3.08 (d, J = 15.7 Hz,
1 H), 2.63 (s, 3 H), 2.20 (s, 3 H), 1.60 (s, 3 H).
127.86, 127.57, 126.91, 122.96, 117.29, 106.43, 76.87, 47.65, 31.23.
HRMS (ESI): m/z calcd for C21H20N [M + H]+: 286.1590; found:
286.1593.
13C NMR (151 MHz, CDCl3):  = 151.72, 145.60, 142.73, 139.54,
127.65, 127.30, 126.03, 125.37, 124.06, 116.83, 112.20, 105.68, 70.06,
47.20, 29.24, 21.74, 20.69.
HRMS (ESI): m/z calcd for C19H22N [M + H]+: 264.1747; found:
264.1752.
1-Isopropyl-2-phenylindoline (22)
Yield: 27.0 mg (57%); colorless oil.
1H NMR (600 MHz, CDCl3):  = 7.43 (d, J = 7.6 Hz, 2 H), 7.32 (t, J = 7.4
Hz, 2 H), 7.25 (dd, J = 12.9, 5.3 Hz, 1 H), 7.08 (t, J = 7.7 Hz, 1 H), 7.01 (d,
J = 7.1 Hz, 1 H), 6.65 (t, J = 7.3 Hz, 1 H), 6.60 (d, J = 7.9 Hz, 1 H), 4.71 (t,
J = 9.6 Hz, 1 H), 3.55 (dt, J = 13.6, 6.8 Hz, 1 H), 3.40 (dd, J = 15.9, 9.7 Hz,
1 H), 2.86 (dd, J = 15.8, 9.6 Hz, 1 H), 1.23 (d, J = 6.8 Hz, 3 H), 0.99 (d, J =
6.8 Hz, 3 H).
2-Cyclopropyl-1-methyl-2-phenylindoline (18)
Yield: 15.9 mg (32%); colorless oil.
13C NMR (151 MHz, CDCl3):  = 151.15, 145.67, 128.64, 128.43,
127.32, 127.17, 126.96, 124.11, 117.10, 107.95, 65.96, 48.04, 40.22,
19.39, 18.66.
HRMS (ESI): m/z calcd for C17H20N [M + H]+: 238.1590; found:
238.1593.
1H NMR (600 MHz, CDCl3):  = 7.58 (d, J = 8.0 Hz, 2 H), 7.32 (t, J = 7.6
Hz, 2 H), 7.25 (d, J = 7.9 Hz, 1 H), 7.09 (t, J = 7.7 Hz, 1 H), 6.90 (d, J = 7.1
Hz, 1 H), 6.57 (t, J = 7.3 Hz, 1 H), 6.35 (d, J = 7.8 Hz, 1 H), 2.88 (s, 1 H),
2.82 (s, 1 H), 2.69 (s, 3 H), 1.45–1.38 (m, 1 H), 0.81–0.74 (m, 1 H), 0.61
(dd, J = 9.6, 5.0 Hz, 1 H), 0.51–0.43 (m, 1 H), 0.39 (dd, J = 9.4, 5.4 Hz, 1
H).
13C NMR (151 MHz, CDCl3):  = 152.42, 147.45, 128.24, 127.61,
126.76, 126.74, 126.49, 123.41, 116.18, 104.20, 72.32, 39.95, 29.69,
15.88, 2.63, 0.40.
HRMS (ESI): m/z calcd for C18H20N [M + H]+: 250.1590; found:
250.1594.
1-(2-Ethylbutyl)-2-phenylindoline (23)
Yield: 35.7 mg (64%); colorless oil.
1H NMR (600 MHz, CDCl3):  = 7.33 (dt, J = 14.9, 7.4 Hz, 4 H), 7.28 (d,
J = 6.4 Hz, 1 H), 7.10 (t, J = 7.6 Hz, 1 H), 7.03 (d, J = 7.1 Hz, 1 H), 6.64 (t,
J = 7.3 Hz, 1 H), 6.44 (d, J = 7.8 Hz, 1 H), 4.60 (t, J = 8.9 Hz, 1 H), 3.44
(dd, J = 15.8, 9.6 Hz, 1 H), 2.99 (dd, J = 15.8, 8.3 Hz, 1 H), 2.90 (dd, J =
14.2, 7.2 Hz, 1 H), 2.80 (dd, J = 14.2, 7.2 Hz, 1 H), 1.40 (dt, J = 12.7, 6.4
Hz, 1 H), 1.37–1.31 (m, 1 H), 1.25–1.14 (m, 3 H), 0.76 (t, J = 7.4 Hz, 3
H), 0.71 (t, J = 7.4 Hz, 3 H).
13C NMR (151 MHz, CDCl3):  = 153.10, 143.35, 128.41, 127.83,
127.55, 127.53, 127.44, 124.06, 116.67, 105.62, 69.85, 51.28, 39.39,
39.24, 23.82, 23.32, 10.83, 10.56.
2-Cyclohexyl-1-methyl-2-phenylindoline (19)
Yield: 29.7 mg (51%); colorless oil.
1H NMR (600 MHz, CDCl3):  = 7.35 (d, J = 7.7 Hz, 2 H), 7.27 (dd, J =
10.1, 5.2 Hz, 2 H), 7.21 (t, J = 7.2 Hz, 1 H), 7.04 (dd, J = 10.8, 7.5 Hz, 2
H), 6.57 (t, J = 7.3 Hz, 1 H), 6.17 (d, J = 7.7 Hz, 1 H), 3.42 (d, J = 16.6 Hz,
1 H), 3.27 (d, J = 16.6 Hz, 1 H), 2.47 (d, J = 20.6 Hz, 3 H), 2.35 (ddd, J =
11.7, 9.2, 2.7 Hz, 1 H), 1.85 (d, J = 13.0 Hz, 1 H), 1.76 (s, 3 H), 1.67 (d, J =
13.8 Hz, 1 H), 1.41–1.29 (m, 2 H), 1.23–1.11 (m, 2 H), 1.03 (ddd, J =
25.1, 12.8, 3.2 Hz, 1 H).
HRMS (ESI): m/z calcd for C20H26N [M + H]+: 280.2060; found:
280.2063.
13C NMR (151 MHz, CDCl3):  = 151.78, 143.15, 128.12, 127.84,
127.61, 126.77, 126.08, 123.07, 115.73, 104.14, 73.86, 41.71, 39.01,
28.94, 28.28, 27.78, 26.91, 26.85, 26.71.
HRMS (ESI): m/z calcd for C21H26N [M + H]+: 292.2060; found:
292.2065
2-Phenyl-1-(3-phenylpropyl)indoline (24)
Yield: 38.8 mg (62%); colorless oil.
1H NMR (600 MHz, CDCl3):  = 7.40 (d, J = 7.4 Hz, 2 H), 7.34 (t, J = 7.4
Hz, 2 H), 7.29 (t, J = 7.0 Hz, 1 H), 7.23 (t, J = 7.4 Hz, 2 H), 7.15 (t, J = 7.2
Hz, 1 H), 7.08 (dd, J = 11.6, 7.7 Hz, 3 H), 7.03 (d, J = 7.1 Hz, 1 H), 6.65 (t,
© 2020. Thieme. All rights reserved. Synthesis 2020, 52, A–H

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J = 7.3 Hz, 1 H), 6.38 (d, J = 7.8 Hz, 1 H), 4.62 (t, J = 9.6 Hz, 1 H), 3.36
(dd, J = 15.7, 9.2 Hz, 1 H), 3.10 (dt, J = 14.7, 7.5 Hz, 1 H), 2.95 (dt, J =
14.8, 9.0 Hz, 2 H), 2.52 (t, J = 7.7 Hz, 2 H), 1.87–1.70 (m, 2 H).
13C NMR (151 MHz, CDCl3):  = 152.17, 143.05, 141.79, 128.52,
128.26, 128.19, 127.59, 127.57, 127.40, 125.74, 124.05, 117.27,
106.33, 69.01, 46.25, 39.53, 33.33, 27.70.
1H NMR (600 MHz, CDCl3):  = 7.43 (d, J = 7.6 Hz, 1 H), 7.22–7.09 (m, 4
H), 7.02 (d, J = 7.0 Hz, 1 H), 6.62 (t, J = 7.3 Hz, 1 H), 6.44 (d, J = 7.8 Hz, 1
H), 3.66 (d, J = 15.8 Hz, 1 H), 2.95 (d, J = 15.9 Hz, 1 H), 2.90 (dd, J = 9.3,
4.1 Hz, 1 H), 2.85 (dd, J = 14.1, 6.9 Hz, 1 H), 2.79 (s, 3 H), 2.06–1.91 (m,
4 H), 1.91–1.84 (m, 1 H), 1.61–1.51 (m, 1 H).
13C NMR (151 MHz, CDCl3):  = 151.14, 145.77, 140.60, 131.24,
127.59, 127.55, 126.96, 126.56, 126.14, 124.07, 116.48, 105.10, 74.92,
39.97, 36.81, 33.64, 30.05, 27.44, 25.73.
HRMS (ESI): m/z calcd for C23H24N [M + H]+: 314.1903; found:
314.1903.
HRMS (ESI): m/z calcd for C19H22N [M + H]+: 264.1747; found:
264.1746.
2-Phenyl-1-(4-phenylbutan-2-yl)indoline (25)
Yield: 42.5 mg (65%); brown oil; mixture of two stereoisomers.
1′-Methylspiro[chroman-4,2′-indoline] (29)
1H NMR (600 MHz, CDCl3):  (mixture of two stereoisomers) = 7.44
(dd, J = 14.2, 7.2 Hz, 2 H), 7.33 (dd, J = 13.7, 7.2 Hz, 2 H), 7.29 (t, J = 7.7
Hz, 1 H), 7.22 (dt, J = 13.3, 7.5 Hz, 2 H), 7.15 (dd, J = 15.8, 7.5 Hz, 1 H),
7.11–7.00 (m, 3 H), 6.97 (d, J = 7.4 Hz, 1 H), 6.60 (ddd, J = 56.3, 31.9,
7.8 Hz, 2 H), 4.70 (dt, J = 38.8, 9.6 Hz, 1 H), 3.53–3.18 (m, 2 H), 3.05–
2.88 (m, 1 H), 2.67 (ddd, J = 13.8, 10.8, 5.8 Hz, 0.5 H), 2.53 (dd, J = 11.4,
4.5 Hz, 1 H), 2.44 (ddd, J = 13.9, 10.9, 5.4 Hz, 0.5 H), 2.24–2.08 (m, 0.5
H), 1.87–1.52 (m, 1.5 H), 1.13 (dd, J = 102.1, 6.8 Hz, 3 H).
Yield: 28.1 mg (56%); colorless oil.
1H NMR (600 MHz, CDCl3):  = 7.48 (dd, J = 7.8, 1.5 Hz, 1 H), 7.23–7.15
(m, 2 H), 7.07 (d, J = 7.1 Hz, 1 H), 6.92 (t, J = 7.5 Hz, 1 H), 6.87 (d, J = 8.2
Hz, 1 H), 6.70 (t, J = 7.3 Hz, 1 H), 6.43 (d, J = 7.8 Hz, 1 H), 4.41 (ddd, J =
11.4, 4.0, 2.7 Hz, 1 H), 4.34–4.21 (m, 1 H), 3.33 (d, J = 15.7 Hz, 1 H),
3.16 (d, J = 15.7 Hz, 1 H), 2.59 (s, 3 H), 2.31 (td, J = 13.2, 4.1 Hz, 1 H),
1.86 (dt, J = 13.5, 2.1 Hz, 1 H).
13C NMR (151 MHz, CDCl3):  (mixture of two stereoisomers) =
151.72, 150.68, 145.54, 144.67, 142.21, 142.12, 128.81, 128.48,
128.46, 128.42, 128.32, 128.28, 128.26, 128.17, 127.52, 127.46,
127.41, 127.35, 127.32, 127.23, 125.68, 125.61, 124.21, 124.10,
117.20, 117.14, 108.04, 107.68, 67.08, 65.32, 52.62, 52.08, 40.24,
39.85, 36.80, 35.78, 33.46, 33.26, 17.17, 15.33.
13C NMR (151 MHz, CDCl3):  = 155.44, 151.55, 128.54, 127.89,
127.30, 126.33, 125.79, 124.25, 120.74, 116.96, 116.75, 105.16, 66.43,
63.81, 46.65, 28.66, 27.96.
HRMS (ESI): m/z calcd for C17H18NO [M + H]+: 252.1383; found:
252.1383.
HRMS (ESI): m/z calcd for C24H26N [M + H]+: 328.2060; found:
328.2056.
1′-Methyl-1,2,3,4-tetrahydrospiro[benzo[b]azepin-5,2′-indoline]
(30)
Yield: 36.5 mg (69%); colorless oil.
1-Cyclopentyl-2-phenylindoline (26)
1H NMR (600 MHz, CDCl3):  = 7.42 (d, J = 7.9 Hz, 1 H), 7.13 (t, J = 7.6
Hz, 1 H), 7.06 (t, J = 7.4 Hz, 1 H), 7.02 (d, J = 7.0 Hz, 1 H), 6.85 (t, J = 7.5
Hz, 1 H), 6.70 (d, J = 7.8 Hz, 1 H), 6.62 (t, J = 7.3 Hz, 1 H), 6.41 (d, J = 7.7
Hz, 1 H), 3.80 (s, 1 H), 3.49 (d, J = 16.0 Hz, 1 H), 3.37–3.21 (m, 1 H),
3.16–2.99 (m, 2 H), 2.74 (s, 3 H), 2.27–2.10 (m, 1 H), 2.03–1.83 (m, 3
H).
13C NMR (151 MHz, CDCl3):  = 151.12, 149.26, 134.12, 129.23,
127.52, 127.16, 127.04, 124.09, 120.45, 119.84, 116.32, 104.66, 73.86,
47.45, 41.43, 31.32, 29.37, 25.96.
Yield: 37.4 mg (71%); brown oil.
1H NMR (400 MHz, CDCl3):  = 7.41–7.35 (m, 2 H), 7.31 (dd, J = 9.9, 4.8
Hz, 2 H), 7.25 (dd, J = 7.6, 5.2 Hz, 1 H), 7.07 (t, J = 7.7 Hz, 1 H), 6.99 (d,
J = 7.0 Hz, 1 H), 6.63 (t, J = 7.3 Hz, 1 H), 6.56 (d, J = 7.9 Hz, 1 H), 4.74 (t,
J = 9.2 Hz, 1 H), 3.66 (pent, J = 8.5 Hz, 1 H), 3.42 (dd, J = 15.9, 9.8 Hz, 1
H), 2.84 (dd, J = 15.9, 8.6 Hz, 1 H), 1.84–1.74 (m, 2 H), 1.71–1.55 (m, 4
H), 1.54–1.40 (m, 2 H).
13C NMR (151 MHz, CDCl3):  = 151.33, 145.53, 128.55, 128.49,
127.28, 127.09, 126.60, 124.14, 116.94, 107.60, 67.18, 58.89, 39.99,
27.63, 27.40, 24.25, 23.71.
HRMS (ESI): m/z calcd for C18H21N2 [M + H]+: 265.1699; found:
265.1702
HRMS (ESI): m/z calcd for C19H22N [M + H]+: 264.1747; found:
264.1750.
1′,3,3-Trimethyl-2,3-dihydrospiro[inden-1,3′-indoline] (31)
Yield: 30.5 mg (58%); colorless oil.
1-Methyl-3′,4′-dihydro-2′H-spiro[indoline-2,1′-naphthalene] (27)
1H NMR (600 MHz, CDCl3):  = 7.29 (t, J = 7.3 Hz, 1 H), 7.21 (d, J = 7.5
Hz, 1 H), 7.15 (dt, J = 15.8, 7.5 Hz, 3 H), 7.04 (d, J = 7.0 Hz, 1 H), 6.66 (t,
J = 7.3 Hz, 1 H), 6.40 (d, J = 7.7 Hz, 1 H), 3.28 (q, J = 15.4 Hz, 2 H), 2.55
(s, 3 H), 2.30 (d, J = 13.5 Hz, 1 H), 2.07 (d, J = 13.5 Hz, 1 H), 1.41 (s, 3 H),
1.34 (s, 3 H).
13C NMR (151 MHz, CDCl3):  = 152.26, 151.70, 144.14, 128.36,
127.66, 127.62, 126.82, 123.92, 123.23, 122.44, 116.78, 105.13, 77.95,
49.82, 46.43, 41.41, 31.62, 29.86, 29.07.
Yield: 35.9 mg (72%); colorless oil.
1H NMR (600 MHz, CDCl3):  = 7.57–7.48 (m, 1 H), 7.22–7.09 (m, 4 H),
7.03 (d, J = 7.1 Hz, 1 H), 6.65 (t, J = 7.3 Hz, 1 H), 6.38 (d, J = 7.7 Hz, 1 H),
3.24 (d, J = 15.8 Hz, 1 H), 3.14 (d, J = 15.8 Hz, 1 H), 2.90–2.77 (m, 2 H),
2.58 (s, 3 H), 2.06–1.83 (m, 4 H).
13C NMR (151 MHz, CDCl3):  = 151.87, 140.97, 137.81, 128.78,
127.66, 126.97, 126.70, 126.67, 126.17, 124.10, 116.27, 104.49, 70.30,
46.39, 29.59, 28.83, 20.11.
HRMS (ESI): m/z calcd for C19H22N [M + H]+: 264.1747; found:
264.1749.
HRMS (ESI): m/z calcd for C18H20N [M + H]+: 250.1590; found:
250.1595.
1′-Methylspiro[fluoren-9,2′-indoline] (32)
1′-Methyl-6,7,8,9-tetrahydrospiro[benzo[7]annulen-5,3′-indo-
line] (28)
Yield: 31.1 mg (55%); colorless oil.
Yield: 37.4 mg (71%); brown oil.
© 2020. Thieme. All rights reserved. Synthesis 2020, 52, A–H

H
X. Zhao et al.
Paper
Synthesis
1H NMR (600 MHz, CDCl3):  = 7.68 (d, J = 7.5 Hz, 2 H), 7.37 (t, J = 7.6
Hz, 4 H), 7.24–7.16 (m, 3 H), 7.13 (d, J = 7.1 Hz, 1 H), 6.74 (t, J = 7.3 Hz,
1 H), 6.48 (d, J = 7.7 Hz, 1 H), 3.46 (s, 2 H), 2.23 (s, 3 H).
13C NMR (151 MHz, CDCl3):  = 152.94, 147.30, 139.88, 128.70,
128.52, 127.81, 127.68, 124.18, 123.57, 119.89, 117.29, 106.36, 78.55,
42.02, 29.65.
(13) Qin, X. R.; Lee, M. W. Y.; Zhou, J. S. Angew. Chem. Int. Ed. 2017,
56, 12723.
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Chen, C.; Shang, Y. Chem. Commun. 2020, 56, 3249.
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Chem. Commun. 2017, 53, 11205.
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496.
HRMS (ESI): m/z calcd for C21H18N [M + H]+: 284.1434; found:
284.1434.
(18) Timsina, Y. N.; Gupton, B. F.; Ellis, K. C. ACS Catal. 2018, 8, 5732.
(19) Long, J.; Le, L.; Iwasaki, T.; Qiu, R.; Kambe, N. J. Org. Chem. 2020,
85, 482.
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Funding Information
We are grateful for the financial support from the National Natural
Science Foundation of China (No 21672047), State Key Laboratory of
Urban Water Resource and Environment (No. 2018DX02), The Science
and Technology Plan of Shenzhen (JCYJ20180306172044124) and
Natural Science Foundation of Guangdong (No. 2020A1515010564).
W. X. is grateful for the Talent Plan of the Pearl River in Guangdong,
Starting up fund from Shenzhen Government, and the financial sup-
port from Guangdong Province Covid-19 Pandemic Control Research
Fund (No. 2020KZDZX1218).Natio
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Supporting Information
(27) Manna, M. K.; Bhunia, S. K.; Jana, R. Chem. Commun. 2017, 53,
6906.
Supporting information for this article is available online at
https://doi.org/10.1055/s-0040-1705963. Included are experimental
procedures and compound characterization data. Su
(28) Manna, M. K.; Hossian, A.; Jana, R. Org. Lett. 2015, 17, 672.
(29) Houlden, C. E.; Bailey, C. D.; Ford, J. G.; Gagne, M. R.; Lloyd-Jones,
G. C.; Booker-Milburn, K. I. J. Am. Chem. Soc. 2008, 130, 10066.
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© 2020. Thieme. All rights reserved. Synthesis 2020, 52, A–H