Transition-Metal-Free Stereospecific Oxidative Annulative Coupling of Indolines with Aziridines

Article abstract of DOI:10.1021/acs.joc.0c00899

Tandem C-N bond formation for the oxidative annulation of indolines with aziridines is accomplished employing the combination of DDQ and NaOCl at ambient conditions. Optically active aziridine can be coupled with high enantiomeric purity (>99% ee). The substrate scope, stereocontrol with the enantioenriched substrate, and scale-up are the important practical advantages.

Full text of DOI:10.1021/acs.joc.0c00899

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Note
Transition-Metal-Free Stereospecific Oxidative
Annulative Coupling of Indolines with Aziridines
PALLAB KARJEE, TANUMAY SARKAR, Subhradeep Kar, and Tharmalingam Punniyamurthy
J. Org. Chem., Just Accepted Manuscript • Publication Date (Web): 29 May 2020
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Transition-Metal-Free Stereospecific Oxidative Annulative Coupling of Indolines with
Aziridines
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Pallab Karjee, Tanumay Sarkar, Subhradeep Kar and Tharmalingam Punniyamurthy*
Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati-781039, India.
*E-mail: tpunni@iitg.ac.in
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SO2Ar
tandem
C-N/C-N
N
N
N
N
H
R
R
Aryl
SO2Ar
TM
N
SO2Ar
Alkyl
N
Aryl/Alkyl
R
28 examples
3 examples, >99% ee
Stereospecific Metal-free C-N bond formation
ABSTRACT: Tandem C-N bond formation for the oxidative annulation of indolines with
aziridines is accomplished employing the combination of DDQ and NaOCl at ambient
conditions. Optically active aziridine can be coupled with high enantiomeric purity (>99% ee).
The substrate scope, stereocontrol with the enantioenriched substrate and scale up are the
important practical advantages.
C-N bond formation1 has attracted considerable attention due to the ubiquity of the aza-
heterocycles in a broad spectrum of pharmaceuticals, functional materials and natural
products.2 In this realm, C-H functionalization of indoles3 has witnessed impeccable growth,
owing to the profuse prominence of the indole frameworks in myriads of bio-active molecules.
Among them, imidazoindolines represent privileged structures due to their interesting
biological properties.4 Stereospecific syntheses of these fused structural frameworks in an atom
and step-economical approach5 would thus be valuable. While small ring heterocycles, due to
their staple architecture and intrinsic ring strain, have propensity to undergo easy ring
scissoring, and are thereby useful for the construction of diverse heterocycles.6 Contextually,
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aziridines are versatile building blocks for the contemporary synthesis of N-heterocycles via a
tandem C-N bond formation.7,8 Consequently, development of synthetic strategies with these
two heterocyclic units can lead a potential route to access fused structural scaffolds. Recently,
NaOCl has been explored as an effective reagent for the oxidation for organic substrates,9a
amidation of amines9b and C-N coupling of 3-alkylindoles with amino esters.9c-d Herein we
report a stereospecific oxidative annulative coupling of indoles with N-sulfonyl aziridines
using the combination of DDQ and NaOCl to furnish imidazoindoles at ambient conditions via
a tandem C-N bond formation. The substrate scope, selectivity and transition-metal-free C-N
bond formation10 are the important features.
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Scheme 1. Optimization of the Reaction Conditions
Ts
Ts
neat, rt, 4 h
N
N
+
+
N
N
NHTs
N
then oxidant, additive,
solvent, rt, 8 h
Ph
H
Ph
4aa
Ph
3aa
2a
1a
We began our optimization studies employing indoline 1a and 2-phenyl-1-tosylaziridine 2a
as the test substrates using a series of oxidants, additives and solvents (see Scheme 1 and Table
S1 in the SI). The heterocycle 4aa was formed in 10% along with the ring opening 3aa in 62%,
when the neat substrates were stirred for 4 h at ambient conditions, and then 8 h with PhI(OAc)2
as an oxidant and aqueous NaOCl solution as an additive in 1,4-dioxane. Subsequent screening
of the oxidants led to an increase in the yield of 4aa to 75% using DDQ, whereas p-
benzoquinone produced inferior results. In contrast, O2, TBHP and DTBP were not effective.
In a set of additives studied, aqueous NaOCl, t-BuOCl and iodine, the former produced the best
results. 1,4-Dioxane was found to be the solvent of choice, whereas THF, DMF, MeOH, 1,2-
dichloroethane, toluene and CH3CN produced <57% yield. Control experiments confirmed that
the combination of DDQ and NaOCl is essential to furnish the annulated 4aa. Recrystallization
of 4aa gave single crystal, whose structure was determined using X-ray analysis (see SI).
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Scheme 2. Substrate Scope of Aziridinesa-c
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6
O
Ar
S
neat, rt, 4 h
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8
9
O
SO2Ar
SO2Ar
+
N
N
N
N
N
then DDQ/NaOCl (1:6)
1,4-dioxane, rt, 8 h
R = alkyl, aryl
N
H
R
Alkyl
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Aryl
4as-at
4ab-ar
1a
2b-t
Ts
N
Ts
Ts
N
N
N
N
N
4ab
4ac
4ad
X = Br,
= Cl,
= F,
= CH3,
, 73%
, 66%
, 63%
4ah
X = Br,
= Cl,
= CH3,
, 71%
4ai
, 69%
X
4af
X = Br,
, 68%
4aj
4ak
, 64%
, 68%
4ag
= CH3,
, 64%
4ae
, 67%
= Ph,
X
X
Ts
Ts
Ts
N
N
N
N
N
N
H3C
CH3
CH3
H3C
H3C
4an
4am
, 67%
, 63%
Ts
4al
, 65%
O
O
S
Ts
N
N
N
N
N
N
CH3
CH3
R
5
7
Ph
4ao
R = H,
= Cl,
, 71%
4at
, 68%
4as
, 66%
4ap
, 72%
4aq
= NO2,
= t-Bu,
, 62%
, 67%
4ar
aReaction conditions: 1a (0.2 mmol), 2b-t (0.24 mmol), neat, room temperature, 4 h;
then DDQ (0.2 mmol), aq. NaOCl (4.2%, 2.1 mL), 1,4-dioxane (2 mL), room
temperature, 8 h. bIsolated yield. cAccompanied a trace amount of 3 (see scheme 5 for a
structure).
Having the optimized reaction conditions, we investigated the scope of the procedure for a
series of aziridines 2b-t with indoline 1a as a standard substrate (Scheme 2). Aziridines having
substitution at the 2-position of the aryl ring with bromo 2b, chloro 2c, fluoro 2d and methyl
2e groups gave the target heterocycles 4ab-ae in 63-73% yields. Similar results observed with
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aziridines bearing substitution at the 3-position of the aryl ring with bromo 2f and methyl 2g
functionalities, giving 4af and 4ag in 68 and 64% yields, respectively. The reaction of
aziridines containing substituents at the 4-position of the aryl ring with bromo 2h, chloro 2i,
methyl 2j and phenyl 2k groups produced 4ah-ak in 64-71% yields. Furthermore, di- and
trimethyl substituted aziridines 2l-m in the aryl ring participated to deliver 4al and 4am in 65
and 63% yields, respectively. In addition, 2-naphthyl aziridine 2n was amenable to furnish 4an
in 67% yield. The reaction condition was extended to the coupling of aziridines bearing a varied
N-sulfonyl aryl substituent. Aziridine having N-sulfonylphenyl 2o produced 4ao in 71% yield,
whereas the reaction of aziridines having substitution at the 4-position of the N-sulfonyl aryl
Scheme 3. Substrate Scope of Indolinesa-c
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Ts
Ts
neat, rt, 4 h
R'
N
R'
+
N
N
N
then DDQ/NaOCl (1:6)
1,4-dioxane, rt, 8 h
H
Ph
Ph
2a
4ba-ia
1b-i
Br
CH3
Ph
O
Br
Ts
Ts
Ts
Ts
Ts
N
N
N
N
N
N
N
N
N
Ph
Ph
Ph
Ph
4ca
4ea
, 58%
4da
, 71%
4ba
4fa
, 67%
,64%
Ts
Ts
Ts
N
N
N
N
N
N
N
Cl
F
CH3
Cl
Ph
Ph
Ph
Ph
4ia
4ga
, 73%
, 66%
4ha
, 63%
, 69%
aReaction conditions: 1b-i (0.2 mmol), 2a (0.24 mmol), neat, room temperature, 4 h;
then DDQ (0.2 mmol), aq. NaOCl (4.2%, 2.1 mL), 1,4-dioxane (2 mL), room
temperature, 8 h. bIsolated yield. cAccompanied a trace amount of 3 (see scheme 5 for a
structure).
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ring with chloro 2p, nitro 2q and tert-butyl 2r functionalities, afforded 4ap-ar in 62-72%
yields. In addition, the reaction of 2-alkyl aziridines could be pursued and the ring opening
occurred at the sterically less hindered C-3 position.11 For examples, aziridines with hexyl 2s
and octyl 2t substituents participated to produce 4as and 4at in 66 and 68% yields, respectively.
The scope of the procedure was further extended to the annulation of a series of substituted
indolines 1b-i with aziridine 2a as a standard substrate (Scheme 3). The substrates bearing 3-
methyl 1b, 4-bromo 1c, 5-benzyloxy 1d and 5-bromo 1e substituents delivered the target
heterocycles 4ba-ea in 58-71% yields, whereas the reaction of the substrates bearing 6-chloro
1f, 6-fluoro 1g, 7-chloro 1h and 7-methyl 1i functionalities afforded 4fa-ia in 63-73% yields.
These results suggest that the procedure can be employed for the annulative coupling of the
broad range of indolines and aziridines.
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Scheme 4. Enantiospecific Synthesisa-c
Ts
Ts
neat, rt., 4 h
N
R
R
N
+
Ph
N
N
then DDQ/NaOCl (1:6)
1,4-dioxane, rt, 8 h
H
1a,e,g
4'
2a
(R)-
'
Ph
Br
Ts
Ts
Ts
N
N
N
N
N
N
F
Ph
Ph
Ph
4aa
', 73%,
>99% ee
4ea
', 70%,
>99% ee
4ga
', 68%,
>99% ee
aReaction conditions: 1a,e,g (0.2 mmol), (R)-2aʹ (0.24 mmol), neat, room temperature,
4 h; then DDQ (0.2 mmol), aq. NaOCl (4.2%, 2.1 mL), 1,4-dioxane (2 mL), room
temperature, 6 h. bIsolated yield. cAccompanied a trace amount of 3 (see scheme 5 for a
structure).
To understand the stereochemical aspects, the reaction of 1a, 1e and 1g studied using (R)-2-
phenyl-1-tosylaziridine 2aʹ as the representative substrates (Scheme 4). The reaction occurred
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with high enantiomeric purity (>99% ee). For examples, the reaction of 1a furnished 4aaʹ in
73% yield and 99% ee. Similar enantiomeric purity (>99% ee) observed with indolines having
5-bromo 1e and 6-fluoro 1g substituents, providing 4eaʹ and 4gaʹ in 70% and 68% yields,
respectively. The absolute configuration of 4aaʹ was determined using a single crystal X-ray
analysis (see SI). These results suggest that the ring opening of aziridine is stereospecific (SN2)
and the annulation can be realized in high enantiomeric purity.
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Scheme 5. Plausible Reaction Pathway
SN2
DDQ
[O]
N
N
N
NHTs
NHTs
N
H
1
Ts
Ph
Ph
Ph
2
a
3
NaOCl
H
:B
Cl
Cl
H
Ts
:B
Ts
- HCl
N
H
N
+
N
N
N
NTs
Ph
4
Ph
c
Ph
b
To get insight into the reaction pathway, the coupling of 1a with 2a was performed as the
representative substrates in the presence of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) as
well as 2,6-di-tert-butyl-4-methylphenol (BHT) (see Scheme S1a). As above, the reaction
occurred, which suggests that a radical pathway is not likely. In addition, 1a with 2a under neat
conditions for 4 h, followed by treatment with DDQ for 2 h in 1,4-dioxane, produced 3aa in
81% yield (see Scheme S1b). The latter with NaOCl underwent annulation to produce 4aa in
77% yield. These experimental results suggest that the stereospecific ring opening (SN2) of
aziridines with indolines can deliver a (Scheme 5).12 The latter can oxidize using DDQ to
furnish 3, which can undergo an electrophilic chlorination using NaOCl9 to give the iminium
ion b that can lead to an intramolecular cyclization to furnish c. Base promoted
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dehydrochlorination of c can furnish the target heterocycle 4, which can be reduced using
NaBH3CN to yield imidazoindolines that are privileged structural scaffold with broad bio-
active spectrum.4 Scheme S2a presents some post synthetic applications for C-C coupling of 4
with organoboranes. The Pd-catalyzed Suzuki-coupling of 4ea with 1-pyreneboronic acid
produced 5 in 85% yield, while the borylation employing B2pin2 gave 6 in 73% yield. In
addition, to reveal the scale up synthesis (3 mmol), the coupling of 1a and 2a was examined as
the representative substrates. The reaction was effective to furnish the annulated target product
in 66% yield (see Scheme S2b).
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In conclusion, the stereospecific oxidative annulative coupling of indolines with aziridines is
described employing DDQ as the oxidant and NaOCl as the electrophilic chlorinating reagent
at ambient conditions. Enantiomeric purity, transition-metal-free tandem C-N bond formation
and substrate scope are the important practical features.
EXPERIMENTAL SECTION
General Information. Alkenes, (R)-(-)-2-phenylglycinol (99%), DDQ (98%),
Pd(dppf)Cl2•CH2Cl2 (>99%) and Pd(PPh3)4 (99%) of Aldrich, and NaOCl (4.2% w/v available
chlorine) and chloramine-T hydrate (95%) of Merck were used as received. Indolines13 and
aziridines14 were prepared according to reported procedure. SRL silica gel G/GF 254 plates
were used for analytical TLC and SRL silica gel (60-120 mesh) was used for column
chromatography. NMR spectra were recorded with Bruker Avance III 600 MHz and Ascend
400 MHz spectrometers using CDCl3 as solvent and Me4Si as an internal standard. Chemical
shifts (δ) and spin-spin coupling constant (J) are reported in ppm and in Hz, respectively, and
other data are reported as follows: s = singlet, d = doublet, t = triplet, m = multiplet, q = quartet,
dd = doublet of doublets. Melting points were determined using a Büchi B-540 apparatus and
are uncorrected. FT-IR spectra were collected on Perkin Elmer IR spectrometer. Q-Tof ESI-
MS instrument (model HAB 273) was used for recording mass spectra. Optical rotations were
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determined by using Rudolph autopol I automatic polarimeter. HPLC analysis was carried out
using Waters-2489 with Daicel Chiralcel OD-H column using iso-propanol and hexane as an
eluent. Single crystal X-ray data were collected on a Bruker SMART APEX equipped with a
CCD area detector using Mo/Kα radiation and the structure was solved by direct method using
SHELXL-16 (Göttingen, Germany).
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General Procedure for the Preparation of Indolines.13 To a solution of indole (3.0 mmol)
in AcOH (15 mL) at 0 °C was added NaBH3CN (756 mg, 12.0 mmol) in portion-wise. The
reaction was allowed to stir at room temperature for 8 h. After completion, aqueous NaOH
(250 L) was added slowly to the mixture at 0 °C and extracted with ethyl acetate (3  20 mL).
The combined organic layer was washed successively with brine (10 mL) and water (10 mL).
Drying (Na2SO4) and evaporation of the solvent produced a residue that was purified on silica
gel column chromatography using ethyl acetate and hexane as an eluent.
Indolines 1a-b,13a 1c,13b 1d,13a 1e,13b 1f -g,13c 1h13d and 1i13e are known compounds and were
1
synthesized according to the reported procedure. To show the purity, H NMR spectra are
provided.
4-Bromoindoline 1c.13b Analytical TLC on silica gel, 1:9 ethyl acetate/hexane; Rf = 0.49;
purification on silica gel column chromatography using 1:19 ethyl acetate/hexane as eluent;
thick liquid; yield 81% (478 mg); 1H NMR (400 MHz, CDCl3) δ 6.88-6.79 (m, 2H), 6.53 (d, J
= 7.6 Hz, 1H), 3.88 (s, 1H), 3.59 (t, J = 8.4 Hz, 2H), 3.05 (t, J = 8.4 Hz, 2H).
6-Chloroindoline 1f.13c Analytical TLC on silica gel, 1:9 ethyl acetate/hexane; Rf = 0.51;
purification on silica gel column chromatography using 1:19 ethyl acetate/hexane as eluent;
thick liquid; yield 76% (348 mg); 1H NMR (400 MHz, CDCl3) δ 7.19 (s, 1H), 7.10 (dd, J = 8.4
Hz, 2.0 Hz, 1H), 6.50 (d, J = 8.0 Hz, 1H), 3.75 (s, 1H), 3.55 (t, J = 8.0 Hz, 2H), 3.01 (t, J = 8.4
Hz, 2H).
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6-Fluoroindoline 1g.13c Analytical TLC on silica gel, 1:9 ethyl acetate/hexane; Rf = 0.48;
purification on silica gel column chromatography using 1:16 ethyl acetate/hexane as eluent;
thick liquid; yield 73% (301 mg); 1H NMR (400 MHz, CDCl3) δ 6.98 (t, J = 6.8 Hz, 1H), 6.37-
6.30 (m, 2H), 3.82 (s, 1H), 3.59 (t, J = 8.4 Hz, 2H), 2.97 (t, J = 8.4 Hz, 2H).
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7-Chloroindoline 1h.13d Analytical TLC on silica gel, 1:9 ethyl acetate/hexane; Rf = 0.49;
purification on silica gel column chromatography using 1:16 ethyl acetate/hexane as eluent;
thick liquid; yield 84% (385 mg); 1H NMR (400 MHz, CDCl3) δ 7.00 (t, J = 7.6 Hz, 2H), 6.62
(t, J = 7.6 Hz, 1H), 3.97 (s, 1H), 3.62 (t, J = 8.4 Hz, 2H), 3.11 (t, J = 8.4 Hz, 2H).
7-Methylindoline 1i.13e Analytical TLC on silica gel, 1:9 ethyl acetate/hexane; Rf = 0.52;
purification on silica gel column chromatography using 1:19 ethyl acetate/hexane as eluent;
thick liquid; yield 79% (315 mg); 1H NMR (400 MHz, CDCl3) δ 7.00 (d, J = 7.2 Hz, 1H), 6.87
(d, J = 7.2 Hz, 1H), 6.66 (t, J = 7.2 Hz, 1H), 3.57 (t, J = 8.4 Hz, 2H), 3.06 (t, J = 8.4 Hz, 2H),
2.14 (s, 3H).
General Procedure for Preparation of Aziridines.14 To a stirred solution of alkene (1.0
mmol) and benzyltriethylammonium chloride (0.05 mmol, 11.4 mg) in CH2Cl2/H2O (2:1, 15
mL) were added chloramine-T (1.1 mmol, 250.8 mg) and iodine (0.1 mmol, 25.4 mg) at room
temperature. The stirring was continued for 24 h, and then treated with a saturated Na2S2O3 (5
mL) and extracted with CH2Cl2 (3 × 10 mL). Drying (Na2SO4) and evaporation of the solvent
gave a residue that was purified on a silica gel column chromatography using hexane and ethyl
acetate as an eluent.
Aziridines 2a-b,14e 2c,14c 2d,14e 2e,14c 2f,14e 2g,14b 2h,14a 2i-j,14b 2k,14d 2l,14c 2m-n,14e 2o-r,14a
and 2s-t14c are known compounds and were synthesized according to the reported procedure.
To show the purity, 1H NMR spectra are provided.
2-Phenyl-1-tosylaziridine 2a.14e Analytical TLC on silica gel, 1:9 ethyl acetate/hexane; Rf =
0.41; purification on silica gel column chromatography using 1:12 ethyl acetate/hexane as
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eluent; colorless solid; yield 73% (199 mg); 1H NMR (400 MHz, CDCl3) δ 7.88 (d, J = 8.4 Hz,
2H), 7.34 (d, J = 8.0 Hz, 2H), 7.30-7.27 (m, 3H), 7.22-7.20 (m, 2H), 3.79-3.76 (m, 1H), 2.99
(d, J = 7.2 Hz, 1H), 2.43 (s, 3H), 2.39 (d, J = 4.4 Hz, 1H).
2-(2-Bromophenyl)-1-tosylaziridine 2b.14e Analytical TLC on silica gel, 1:9 ethyl
acetate/hexane; Rf = 0.38; purification on silica gel column chromatography using 1:12 ethyl
acetate/hexane as eluent; colorless solid; yield 65% (227 mg); 1H NMR (400 MHz, CDCl3) δ
7.91 (d, J = 8.0 Hz, 2H), 7.52 (dd, J = 7.6, 1.2 Hz, 1H), 7.36 (d, J = 8.0 Hz, 2H), 7.23-7.11 (m,
3H), 4.00-3.97 (m, 1H), 3.04 (d, J = 7.2 Hz, 1H), 2.45 (s, 3H), 2.27 (d, J = 4.4 Hz, 1H).
2-(2-Chlorophenyl)-1-tosylaziridine 2c.14c Analytical TLC on silica gel, 1:9 ethyl
acetate/hexane; Rf = 0.39; purification on silica gel column chromatography using 1:12 ethyl
acetate/hexane as eluent; colorless solid; yield 68% (208 mg); 1H NMR (400 MHz, CDCl3) δ
7.90 (d, J = 8.0 Hz, 2H), 7.36-7.31 (m, 3H), 7.23-7.16 (m, 3H), 4.05-4.02 (m, 1H), 3.04 (d, J
= 7.6 Hz, 1H), 2.44 (s, 3H), 2.29 (d, J = 4.4 Hz, 1H).
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2-(2-Fluorophenyl)-1-tosylaziridine 2d.14e Analytical TLC on silica gel, 1:9 ethyl
acetate/hexane; Rf = 0.36; purification on silica gel column chromatography using 1:12 ethyl
acetate/hexane as eluent; colorless solid; yield 63% (183 mg); 1H NMR (400 MHz, CDCl3) δ
7.88 (d, J = 8.4 Hz, 2H), 7.35 (d, J = 8.0 Hz, 2H), 7.25-7.21 (m, 1H), 7.15-7.11 (m, 1H), 7.07-
6.98 (m, 2H), 3.98-3.96 (m, 1H), 3.01 (d, J = 7.2 Hz, 1H), 2.44 (s, 3H), 2.40 (d, J = 4.4 Hz,
1H).
2-(o-Tolyl)-1-tosylaziridine 2e.14c Analytical TLC on silica gel, 1:9 ethyl acetate/hexane; Rf =
0.42; purification on silica gel column chromatography using 1:12 ethyl acetate/hexane as
eluent; colorless solid; yield 71% (203 mg); 1H NMR (400 MHz, CDCl3) δ 7.91 (d, J = 8.4 Hz,
2H), 7.35 (d, J = 8.0 Hz, 2H), 7.19-7.09 (m, 4H), 3.88-3.85 (m, 1H), 2.99 (d, J = 7.2 Hz, 1H),
2.44 (s, 3H), 2.38 (s, 3H), 2.32 (d, J = 4.4 Hz, 1H).
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2-(3-Bromophenyl)-1-tosylaziridine 2f.14e Analytical TLC on silica gel, 1:9 ethyl
acetate/hexane; Rf = 0.35; purification on silica gel column chromatography using 1:12 ethyl
acetate/hexane as eluent; colorless solid; yield 61% (213 mg); 1H NMR (400 MHz, CDCl3) δ
7.87 (d, J = 8.4 Hz, 2H), 7.41-7.38 (m, 1H), 7.35-7.33 (m, 3H), 7.16-7.15 (m, 2H), 3.73-3.70
(m, 1H), 2.97 (d, J = 7.2 Hz, 1H), 2.44 (s, 3H), 2.34 (d, J = 4.4 Hz, 1H).
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2-(m-Tolyl)-1-tosylaziridine 2g.14b Analytical TLC on silica gel, 1:9 ethyl acetate/hexane; Rf
= 0.40; purification on silica gel column chromatography using 1:12 ethyl acetate/hexane as
eluent; colorless solid; yield 69% (198 mg); 1H NMR (400 MHz, CDCl3) δ 7.88 (d, J = 8.4 Hz,
2H), 7.34 (d, J = 8.0 Hz, 2H), 7.17 (t, J = 7.6 Hz, 1H), 7.09 (d, J = 7.6 Hz, 1H), 7.02-7.00 (m,
2H), 3.75-3.72 (m, 1H), 2.96 (d, J = 7.2 Hz, 1H), 2.43 (s, 3H), 2.38 (d, J = 4.8 Hz, 1H), 2.30
(s, 3H).
2-(4-Bromophenyl)-1-tosylaziridine 2h.14a Analytical TLC on silica gel, 1:9 ethyl
acetate/hexane; Rf = 0.38; purification on silica gel column chromatography using 1:12 ethyl
acetate/hexane as eluent; colorless solid; yield 72% (252 mg); 1H NMR (400 MHz, CDCl3) δ
7.86 (d, J = 8.4 Hz, 2H), 7.42 (d, J = 8.8 Hz, 2H), 7.34 (d, J = 8.0 Hz, 2H), 7.09 (d, J = 8.4 Hz,
2H), 3.73-3.70 (m, 1H), 2.98 (d, J = 7.2 Hz, 1H), 2.43 (s, 3H), 2.34 (d, J = 4.4 Hz, 1H).
2-(4-Chlorophenyl)-1-tosylaziridine 2i.14b Analytical TLC on silica gel, 1:9 ethyl
acetate/hexane; Rf = 0.37; purification on silica gel column chromatography using 1:12 ethyl
acetate/hexane as eluent; colorless solid; yield 65% (199 mg); 1H NMR (400 MHz, CDCl3) δ
7.86 (d, J = 8.0 Hz, 2H), 7.34 (d, J = 8.0 Hz, 2H), 7.27-7.26 (m, 1H), 7.25-7.24 (m, 1H), 7.15
(d, J = 8.4 Hz, 2H), 3.74-3.71 (m, 1H), 2.98 (d, J = 7.2 Hz, 1H), 2.44 (s, 3H), 2.34 (d, J = 4.4
Hz, 1H).
2-(p-Tolyl)-1-tosylaziridine 2j.14b Analytical TLC on silica gel, 1:9 ethyl acetate/hexane; Rf =
0.41; purification on silica gel column chromatography using 1:12 ethyl acetate/hexane as
eluent; colorless solid; yield 74% (212 mg); 1H NMR (400 MHz, CDCl3) δ 7.86 (d, J = 8.4 Hz,
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2H), 7.33 (d, J = 8.0 Hz, 2H), 7.09 (s, 3H), 3.75-3.72 (m, 1H), 2.97 (d, J = 7.2 Hz, 1H), 2.42
(s, 3H), 2.38 (d, J = 4.4 Hz, 1H), 2.30 (s, 3H).
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2-([1,1'-Biphenyl]-4-yl)-1-tosylaziridine 2k.14d Analytical TLC on silica gel, 1:9 ethyl
acetate/hexane; Rf = 0.38; purification on silica gel column chromatography using 1:9 ethyl
acetate/hexane as eluent; colorless solid; yield 59% (205 mg); 1H NMR (400 MHz, CDCl3) δ
7.89 (d, J = 8.0 Hz, 2H), 7.55-7.50 (m, 4H), 7.42 (t, J = 7.2 Hz, 2H), 7.36-7.33 (m, 3H), 7.29
(d, J = 8.4 Hz, 2H), 3.83-3.80 (m, 1H), 3.02 (d, J = 7.2 Hz, 1H), 2.44-2.42 (m, 4H).
2-(2,4-Dimethylphenyl)-1-tosylaziridine 2l.14c Analytical TLC on silica gel, 1:9 ethyl
acetate/hexane; Rf = 0.35; purification on silica gel column chromatography using 1:9 ethyl
acetate/hexane as eluent; colorless solid; yield 64% (192 mg); 1H NMR (400 MHz, CDCl3) δ
7.90 (d, J = 8.4 Hz, 2H), 7.34 (d, J = 8.0 Hz, 2H), 6.98-6.95 (m, 2H), 6.91 (d, J = 8.0 Hz, 1H),
3.84-3.81 (m, 1H), 2.97 (d, J = 7.2 Hz, 1H), 2.44 (s, 3H), 2.34 (s, 3H), 2.31 (d, J = 4.4 Hz, 1H),
2.27 (s, 3H).
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2-Mesityl-1-tosylaziridine 2m.14e Analytical TLC on silica gel, 1:9 ethyl acetate/hexane; Rf =
0.32; purification on silica gel column chromatography using 1:9 ethyl acetate/hexane as
eluent; colorless solid; yield 67% (211 mg); 1H NMR (400 MHz, CDCl3) δ 7.89 (d, J = 8.4 Hz,
2H), 7.36 (d, J = 8.0 Hz, 2H), 6.78 (s, 2H), 3.87-3.84 (m, 1H), 2.94 (d, J = 7.2 Hz, 1H), 2.45
(s, 3H), 2.30 (s, 6H), 2.23 (s, 3H), 2.17 (d, J = 4.8 Hz, 1H).
2-(Naphthalen-2-yl)-1-tosylaziridine 2n.14e Analytical TLC on silica gel, 1:9 ethyl
acetate/hexane; Rf = 0.37; purification on silica gel column chromatography using 1:12 ethyl
acetate/hexane as eluent; colorless solid; yield 61% (197 mg); 1H NMR (400 MHz, CDCl3) δ
7.90 (d, J = 8.3 Hz, 2H), 7.80-7.72 (m, 4H), 7.48-7.45 (m, 2H), 7.34 (d, J = 8.0 Hz, 2H), 7.28
(d, J = 1.7 Hz, 1H), 3.94-3.91 (m, 1H), 3.07 (d, J = 7.2 Hz, 1H), 2.50 (d, J = 4.4 Hz, 1H), 2.42
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2-Phenyl-1-(phenylsulfonyl)aziridine 2o.14a Analytical TLC on silica gel, 1:9 ethyl
acetate/hexane; Rf = 0.36; purification on silica gel column chromatography using 1:12 ethyl
acetate and hexane as eluent; colorless solid; yield 63% (163 mg); 1H NMR (400 MHz, CDCl3)
δ 8.01-7.98 (m, 2H), 7.66-7.61 (m, 1H), 7.56-7.52 (m, 2H), 7.30-7.27 (m, 3H), 7.22-7.20 (m,
2H), 3.82-3.79 (m, 1H), 3.02 (d, J = 7.2 Hz, 1H), 2.42 (d, J = 4.4 Hz, 1H).
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1-((4-Nitrophenyl)sulfonyl)-2-phenylaziridine 2q.14a Analytical TLC on silica gel, 1:9 ethyl
acetate/hexane; Rf = 0.29; purification on silica gel column chromatography using 1:9 ethyl
1
acetate/hexane as eluent; orange solid; yield 51% (155 mg); H NMR (400 MHz, CDCl3) δ
8.39 (d, J = 9.2 Hz, 2H), 8.20 (d, J = 8.8 Hz, 2H), 7.32-7.30 (m, 3H), 7.22-7.20 (m, 2H), 3.90-
3.88 (m, 1H), 3.12 (d, J = 7.2 Hz, 1H), 2.51 (d, J = 4.8 Hz, 1H).
1-((4-tert-Butyl)phenyl)sulfonyl)-2-phenylaziridine 2r.14a Analytical TLC on silica gel, 1:9
ethyl acetate/hexane; Rf = 0.32; purification on silica gel column chromatography using 1:9
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ethyl acetate/hexane as eluent; colorless solid; yield 56% (176 mg); H NMR (600 MHz,
CDCl3) δ 7.91 (d, J = 8.6 Hz, 2H), 7.55 (d, J = 8.6 Hz, 2H), 7.30-7.27 (m, 3H), 7.23-7.22 (m,
2H), 3.81-3.79 (m, 1H), 2.99 (d, J = 7.2 Hz, 1H), 2.40 (d, J = 4.8 Hz, 1H), 1.34 (s, 9H).
2-Hexyl-1-tosylaziridine 2s.14c Analytical TLC on silica gel, 1:9 ethyl acetate/hexane; Rf =
0.36; purification on silica gel column chromatography using 1:12 ethyl acetate/hexane as
eluent; thick liquid; yield 62% (174 mg); 1H NMR (400 MHz, CDCl3), δ 7.83 (d, J = 8.4 Hz,
2H), 7.34 (d, J = 8.0 Hz, 2H), 2.74-2.68 (m, 1H), 2.64 (d, J = 7.2 Hz, 1H), 2.44 (s, 3H), 2.06
(d, J = 4.8 Hz, 1H), 1.55-1.50 (m, 1H), 1.34-1.30 (m, 1H), 1.24-1.17 (m, 8H), 0.84 (t, J = 6.8
Hz, 3H).
2-Octyl-1-tosylaziridine 2t.14c Analytical TLC on silica gel, 1:9 ethyl acetate/hexane; Rf =
0.36; purification on silica gel column chromatography using 1:12 ethyl acetate/hexane as
eluent; thick liquid; yield 59% (182 mg); 1H NMR (400 MHz, CDCl3) δ 7.83 (d, J = 8.4 Hz,
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2H), 7.34 (d, J = 8.0 Hz, 2H), 2.74-2.68 (m, 1H), 2.64 (d, J = 6.8 Hz, 1H), 2.44 (s, 3H), 2.06
(d, J = 4.8 Hz, 1H), 1.57-1.50 (m, 2H), 1.34-1.20 (m, 12H), 0.87 (t, J = 6.8 Hz, 3H).
Procedure for the Preparation of Chiral Aziridine.14e To a stirred solution of (R)-(-)-2-
phenylglycinol (1.0 mmol, 137 mg), TsCl (2.2 mmol, 420 mg) and DMAP (0.05 mmol, 6 mg)
in dry CH2Cl2 (25 mL) at 0 °C was added Et3N (3.0 mmol). The resultant mixture was allowed
to warm to room temperature and the stirring was continued for 24 h. The mixture was then
treated with a saturated NH4Cl (20 mL) and extracted with CH2Cl2 (3 × 10 mL). Drying
(Na2SO4) and evaporation of the solvent gave a residue that was purified on a silica gel column
chromatography using hexane and ethyl acetate (9:1) as the eluent.
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General Procedure for the Coupling of Indolines with Aziridines. A mixture of indoline 1
(0.2 mmol) and aziridine 2 (0.24 mmol) was stirred for 4 h at room temperature. The resultant
mixture was treated with 1,4-dioxane (2.0 mL), DDQ (45 mg, 0.2 mmol) and aq. NaOCl (4.2%,
2.1 mL, 1.2 mmol), and the stirring was continued for an additional 8 h. The reaction mixture
was then diluted with ethyl acetate (10 mL) and the organic layer was separated. The aqueous
phase was extracted with ethyl acetate (2 ×10 mL). Drying (Na2SO4) and evaporation of the
solvent gave a residue that was purified on silica gel column chromatography using ethyl
acetate and hexane as an eluent.
General Procedure for the Enantiospecific Annulative Coupling. Indoline 1 (0.2 mmol)
and (R)-2-phenyl-1-tosylaziridine 2aʹ (0.24 mmol) were subjected to the above described
reaction conditions. The enantiomeric purity was determined using chiral HPLC analysis.
Scale-up Synthesis of 4aa: Indoline 1a (357 mg, 3 mmol) and 2-phenyl-1-tosylaziridine 2a
(983 mg, 3.6 mmol) were subjected to the reaction condition described in the general procedure
to produce 4aa in 66% yield (768 mg).
N-(2-(1H-Indol-1-yl)-2-phenylethyl)-4-methylbenzenesulfonamide 3aa. Analytical TLC on
silica gel, 1:6 ethyl acetate/hexane; Rf = 0.49; purification on silica gel column chromatography
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using 1:9 ethyl acetate/hexane as eluent; colorless solid; mp 127-128 C; yield 81% (63 mg);
1H NMR (400 MHz, CDCl3) δ 7.67 (d, J = 8.4 Hz, 2H), 7.63-7.61 (m, 1H), 7.30-7.26 (m, 5H),
7.13-7.06 (m, 6H), 6.57 (d, J = 3.2 Hz, 1H), 5.59-5.56 (m, 1H), 4.49-4.45 (m, 1H), 3.89-3.83
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(m, 1H), 3.76-3.69 (m, 1H), 2.44 (s, 3H); C{1H} NMR (100 MHz, CDCl3) δ 143.9, 137.6,
136.7, 136.3, 130.0, 129.1, 128.8, 128.5, 127.1, 126.6, 124.5, 122.2, 121.2, 120.2, 109.9, 103.2,
59.0, 46.3, 21.7; FT-IR (KBr) 3283, 2922, 1598, 1493, 1458, 1326, 1308, 1158, 1092 cm-1;
HRMS (ESI) m/z [M+H]+ calcd for C23H23N2O2S: 391.1475, found: 391.1486.
3-Phenyl-1-tosyl-2,3-dihydro-1H-imidazo[1,2-a]indole 4aa'. Analytical TLC on silica gel,
1:9 ethyl acetate/hexane; Rf = 0.45; purification on silica gel column chromatography using

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1:14 ethyl acetate/hexane as eluent; colorless solid; mp 169-170 C; yield 73% (56 mg); H
NMR (400 MHz, CDCl3) δ 7.71 (d, J = 8.0 Hz, 2H), 7.45 (d, J = 8.0 Hz, 1H), 7.22-7.18 (m,
1H), 7.15-7.11 (m, 4H), 6.98-6.94 (m, 1H), 6.82-6.78 (m, 3H), 6.50 (d, J = 8.0 Hz, 1H), 6.23
(s, 1H), 5.25-5.21 (m, 1H), 4.57-4.52 (m, 1H), 3.93-3.88 (m, 1H), 2.31 (s, 3H); 13C{1H} NMR
(100 MHz, CDCl3) δ 145.0, 141.8, 137.8, 133.3, 132.6, 130.5, 130.0, 129.2, 128.8, 127.8,
126.3, 120.56, 120.52, 109.5, 83.4, 61.2, 58.2, 21.7; FT-IR (KBr) 3053, 2918, 1616, 1597,
1566, 1493, 1454, 1422, 1361, 1306, 1168, 1106 cm-1; HRMS (ESI) m/z [M+H]+ calcd for
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C23H21N2O2S: 389.1318, found: 389.1318; [α]D = +54.00 (c= 0.01, CHCl3); HPLC: >99%
ee [CHIRALCEL OD-H, hexane/iPrOH = 90:10, flow rate: 1 mL /min, λ = 254 nm, tR = 23.67
min (minor), 31.97 min (major)].
3-(2-Bromophenyl)-1-tosyl-2,3-dihydro-1H-imidazo[1,2-a]indole 4ab. Analytical TLC on
silica gel, 1:9 ethyl acetate/hexane; Rf = 0.42; purification on silica gel column chromatography
using 1:14 ethyl acetate/hexane as eluent; colorless solid; mp 175-176 C; yield 73% (68 mg);
1H NMR (400 MHz, CDCl3) δ 7.72 (d, J = 8.4 Hz, 2H), 7.57-7.53 (m, 2H), 7.15-7.06 (m, 4H),
6.97-6.93 (m, 1H), 6.88 (t, J = 7.2 Hz, 1H), 6.70 (d, J = 8.0 Hz, 1H), 6.34 (s, 1H), 6.11-6.03
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(m, 1H), 5.72-5.69 (m, 1H), 4.73-4.68 (m, 1H), 4.10-4.06 (m, 1H), 2.34 (s, 3H); 13C{1H} NMR
(150 MHz, CDCl3) δ 144.9, 141.8, 137.2, 133.1, 132.6, 130.3, 129.9, 129.7, 128.1, 127.7,
126.8, 122.6, 121.6, 120.8, 120.72, 120.70, 109.7, 83.8, 60.2, 57.2, 21.7; FT-IR (KBr) 3054,
2918, 1617, 1567, 1477, 1455, 1421, 1362, 1306, 1167, 1106 cm-1; HRMS (ESI) m/z [M+H]+
calcd for C23H20BrN2O2S: 467.0423, found: 467.0426.
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3-(2-Chlorophenyl)-1-tosyl-2,3-dihydro-1H-imidazo[1,2-a]indole 4ac. Analytical TLC on
silica gel, 1:9 ethyl acetate/hexane, Rf = 0.43; purification on silica gel column chromatography
using 1:14 ethyl acetate/hexane as eluent; colorless solid; mp 172-173 C; yield 66% (55 mg);
1H NMR (400 MHz, CDCl3) δ 7.72 (d, J = 8.4 Hz, 2H), 7.56 (d, J = 8.0 Hz, 1H), 7.39 (d, J =
9.2 Hz, 1H), 7.19-7.12 (m, 3H), 7.08(t, J = 7.6 Hz, 1H), 6.95 (t, J = 8.0 Hz, 1H), 6.84 (t, J =
7.6 Hz, 1H), 6.71 (d, J = 8.0 Hz, 1H), 6.34 (s, 1H), 6.13 (d, J = 6.8 Hz, 1H), 5.76-5.73 (m, 1H),
4.72-4.67 (m, 1H), 4.11-4.08 (m, 1H), 2.34 (s, 3H); 13C{1H} NMR (100 MHz, CDCl3) δ 144.9,
141.8, 135.7, 133.1, 132.6, 131.8, 130.3, 129.9, 129.8, 129.4, 127.7, 127.4, 126.6, 120.8, 120.7,
120.6, 109.6, 83.8, 60.1, 54.9, 21.7; FT-IR (KBr) 3054, 2917, 1617, 1595, 1566, 1476, 1455,
1421, 1361, 1305, 1166, 1106 cm-1; HRMS (ESI) m/z [M+H]+ calcd for C23H20ClN2O2S:
423.0929, found: 423.0929.
3-(2-Fluorophenyl)-1-tosyl-2,3-dihydro-1H-imidazo[1,2-a]indole 4ad. Analytical TLC on
silica gel, 1:9 ethyl acetate/hexane; Rf = 0.41; purification on silica gel column chromatography
using 1:11 ethyl acetate/hexane as eluent; colorless solid; mp 176-177 C; yield 63% (51 mg);
1H NMR (400 MHz, CDCl3) δ 7.75 (d, J = 8.4 Hz, 2H), 7.54 (d, J = 8.0 Hz, 1H), 7.24-7.20 (m,
1H), 7.18 (d, J = 8.0 Hz, 2H), 7.09-7.04 (m, 2H), 6.96-6.91 (m, 1H), 6.79 (t, J = 7.6 Hz, 1H),
6.71 (d, J = 8.0 Hz, 1H), 6.34-6.30 (m, 2H), 5.69-5.65 (m, 1H), 4.66-4.61(m, 1H), 4.13-4.09
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(m, 1H), 2.36 (s, 3H); C{1H} NMR (100 MHz, CDCl3) δ 161.0 (JC-F = 245.3 Hz), 144.9,
141.7, 133.3, 132.7, 130.4, 130.1 (JC-F = 8.2 Hz), 129.9, 127.8, 127.0 (JC-F = 3.4 Hz), 125.4
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(JC-F = 12.8 Hz), 124.8 (JC-F = 3.6 Hz), 120.76, 120.71, 120.6, 115.8 (JC-F = 20.8 Hz), 109.4,
83.7, 60.2, 51.6 (JC-F = 4.8 Hz), 21.7; FT-IR (KBr) 3052, 2924, 1616, 1567, 1490, 1455, 1422,
1362, 1306, 1168, 1108 cm-1; HRMS (ESI) m/z [M+H]+ calcd for C23H20FN2O2S: 407.1224,
found: 407.1226.
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3-(o-Tolyl)-1-tosyl-2,3-dihydro-1H-imidazo[1,2-a]indole 4ae. Analytical TLC on silica gel,
1:9 ethyl acetate/hexane; Rf = 0.45; purification on silica gel column chromatography using

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1:14 ethyl acetate/hexane as eluent; colorless solid; mp 176-177 C; yield 67% (53 mg); H
NMR (400 MHz, CDCl3) δ 7.75 (d, J = 8.0 Hz, 2H), 7.54 (d, J = 8.0 Hz, 1H), 7.19-7.15 (m,
4H), 7.07-7.03 (m, 1H), 6.91-6.87 (m, 2H), 6.57 (d, J = 8.0 Hz, 1H), 6.329-6.327 (m, 2H),
5.54-5.51 (m, 1H), 4.68-4.63 (m, 1H), 3.93-3.89 (m, 1H), 2.37 (s, 3H), 2.28 (s, 3H); 13C{1H}
NMR (100 MHz, CDCl3) δ 144.9, 141.9, 135.5, 134.7, 133.3, 132.6, 131.0, 130.9, 130.6, 129.9,
128.3, 127.8, 126.8, 125.6, 120.58, 120.54, 120.50, 109.6, 83.5, 60.1, 55.1, 21.7, 19.2; FT-IR
(KBr) 3052, 2921, 1616, 1597, 1566, 1477, 1455, 1425, 1361, 1306, 1168, 1089 cm-1; HRMS
(ESI) m/z [M+H]+ calcd for C24H23N2O2S: 403.1475, found: 403.1479.
3-(3-Bromophenyl)-1-tosyl-2,3-dihydro-1H-imidazo[1,2-a]indole 4af. Analytical TLC on
silica gel, 1:9 ethyl acetate/hexane; Rf = 0.43; purification on silica gel column chromatography
using 1:14 ethyl acetate/hexane as eluent; colorless solid; mp 95-96 C; yield 68% (63 mg); 1H
NMR (400 MHz, CDCl3) δ 7.77 (d, J = 8.4 Hz, 2H), 7.53 (d, J = 7.6 Hz, 1H), 7.42 (d, J = 8.0
Hz, 1H), 7.24 (d, J = 8.0 Hz, 2H), 7.09-7.00 (m, 3H), 6.91 (t, J = 8.0 Hz, 1H), 6.78 (d, J = 7.6
Hz, 1H), 6.59 (d, J = 8.0 Hz, 1H), 6.31 (s, 1H), 5.28-5.24 (m, 1H), 4.65-4.61 (m, 1H), 3.99-
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3.95 (m, 1H), 2.39 (s, 3H); C{1H} NMR (100 MHz, CDCl3) δ 145.2, 141.8, 140.3, 133.4,
132.5, 132.0, 130.8, 130.4, 130.0, 129.3, 127.8, 124.9, 123.3, 120.78, 120.71, 109.4, 83.8, 61.0,
57.5, 21.8; FT-IR (KBr) 3052, 2918, 1616, 1596, 1568, 1476, 1455, 1420, 1362, 1306, 1185,
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1167, 1107, 1089 cm-1; HRMS (ESI) m/z [M+H]+ calcd for C23H20BrN2O2S: 467.0423, found:
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3-(m-Tolyl)-1-tosyl-2,3-dihydro-1H-imidazo[1,2-a]indole 4ag. Analytical TLC on silica gel,
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1:9 ethyl acetate/hexane; Rf = 0.44; purification on silica gel column chromatography using

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1:14 ethyl acetate/hexane as eluent; colorless solid; mp 143-144 C; yield 64% (51 mg); H
NMR (400 MHz, CDCl3) δ 7.80 (d, J = 8.4 Hz, 2H), 7.52 (d, J = 8.0 Hz, 1H), 7.24 (d, J = 8.0
Hz, 2H), 7.12-7.09 (m, 2H), 7.05-7.01 (m, 1H), 6.89-6.85 (m, 1H), 6.70-6.68 (m, 2H), 6.58 (d,
J = 8.0 Hz, 1H), 6.30 (s, 1H), 5.27-5.23 (m, 1H), 4.63-4.59 (m, 1H), 3.99-3.94 (m, 1H), 2.39
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(s, 3H), 2.22 (s, 3H); C{1H} NMR (100 MHz, CDCl3) δ 144.9, 141.9, 139.0, 137.7, 133.3,
132.5, 130.6, 129.9, 129.6, 129.0, 127.94, 126.96, 123.5, 120.49, 120.45, 109.6, 83.3, 61.2,
58.2, 21.7, 21.4; FT-IR (KBr) 3051, 2921, 1615, 1596, 1566, 1477, 1456, 1421, 1362, 1306,
1185, 1168, 1107, 1089 cm-1; HRMS (ESI) m/z [M+H]+ calcd for C24H23N2O2S: 403.1475,
found: 403.1478.
3-(4-Bromophenyl)-1-tosyl-2,3-dihydro-1H-imidazo[1,2-a]indole 4ah. Analytical TLC on
silica gel, 1:9 ethyl acetate/hexane; Rf = 0.42; purification on silica gel column chromatography
using 1:14 ethyl acetate/hexane as eluent; colorless solid; mp 171-172 C; yield 71% (66 mg);
1H NMR (400 MHz, CDCl3) δ 7.74 (d, J = 8.4 Hz, 2H), 7.53 (d, J = 7.6 Hz, 1H), 7.31-7.29 (m,
2H), 7.21 (d, J = 8.0 Hz, 2H), 7.08-7.04 (m, 1H), 6.93-6.89 (m, 1H), 6.68-6.66 (m, 2H), 6.60
(d, J = 8.0 Hz, 1H), 6.31 (s, 1H), 5.30-5.27 (m, 1H), 4.65-5.61 (m, 1H), 3.98-3.94 (m, 1H),
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2.40 (s, 3H); C{1H} NMR (100 MHz, CDCl3) δ 145.1, 141.6, 137.0, 133.3, 132.6, 132.3,
130.4, 129.9, 127.9, 127.8, 127.7, 122.7, 120.74, 120.71, 109.4, 83.7, 61.0, 57.5, 21.7; FT-IR
(KBr) 3051, 2922, 1617, 1596, 1566, 1477, 1455, 1421, 1361, 1306, 1185, 1166, 1071 cm-1;
HRMS (ESI) m/z [M+H]+ calcd for C23H20BrN2O2S: 467.0423, found: 467.0423.
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3-(4-Chlorophenyl)-1-tosyl-2,3-dihydro-1H-imidazo[1,2-a]indole 4ai. Analytical TLC on
silica gel, 1:9 ethyl acetate/hexane; Rf = 0.41; purification on silica gel column chromatography
using 1:14 ethyl acetate/hexane as eluent; colorless solid; mp 142-143 C; yield 69% (58 mg);
1H NMR (400 MHz, CDCl3) δ 7.75 (d, J = 8.4 Hz, 2H), 7.53 (d, J = 8.0 Hz, 1H), 7.21 (d, J =
8.0 Hz, 2H), 7.17-7.14 (m, 2H), 7.07-7.03 (m, 1H), 6.92-6.88 (m, 1H), 6.75-6.73 (m, 2H), 6.59
(d, J = 8.0 Hz, 1H), 6.31 (s, 1H), 5.32-5.28 (m, 1H), 4.65-4.60 (m, 1H), 3.98-3.94 (m, 1H),
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2.39 (s, 3H); C{1H} NMR (100 MHz, CDCl3) δ 145.1, 141.7, 136.5, 134.6, 133.3, 132.7,
130.4, 129.9, 129.4, 128.6, 127.8, 127.5, 126.8, 120.75, 120.73, 109.4, 83.7, 61.1, 57.5, 21.7;
FT-IR (KBr) 3063, 2922, 1708, 1567, 1492, 1456, 1362, 1306, 1168, 1090 cm-1; HRMS (ESI)
m/z [M+H]+ calcd for C23H20ClN2O2S: 423.0929, found: 423.0927.
3-(p-Tolyl)-1-tosyl-2,3-dihydro-1H-imidazo[1,2-a]indole 4aj. Analytical TLC on silica gel,
1:9 ethyl acetate/hexane; Rf = 0.44; purification on silica gel column chromatography using

1
1:14 ethyl acetate/hexane as eluent; colorless solid; mp 135-136 C; yield 64% (51 mg); H
NMR (400 MHz, CDCl3) δ 7.78 (d, J = 8.4 Hz, 2H), 7.51 (d, J = 7.6 Hz, 1H), 7.23 (d, J = 8.0
Hz, 2H), 7.04-7.01 (m, 3H), 6.89-6.85 (m, 1H), 6.79 (d, J = 8.0 Hz, 2H), 6.57 (d, J = 8.0 Hz,
1H), 6.29 (s, 1H), 5.28-5.25 (m, 1H), 4.62-4.57 (m, 1H), 3.97-3.93 (m, 1H), 2.39 (s, 3H), 2.31
(s, 3H); 13C{1H} NMR (100 MHz, CDCl3) δ 144.9, 141.8, 138.7, 134.7, 133.3, 132.7, 130.6,
129.9, 129.86, 129.81, 127.8, 126.3, 120.5, 120.4, 109.6, 83.3, 61.2, 58.1, 21.7, 21.2; FT-IR
(KBr) 3051, 2922, 1693, 1597, 1566, 1477, 1455, 1360, 1306, 1185, 1168, 1105 cm-1; HRMS
(ESI) m/z [M+H]+ calcd for C24H23N2O2S: 403.1475, found: 403.1480.
3-([1,1'-Biphenyl]-4-yl)-1-tosyl-2,3-dihydro-1H-imidazo[1,2-a]indole 4ak. Analytical TLC
on silica gel, 1:9 ethyl acetate/hexane; Rf = 0.46; purification on silica gel column

chromatography using 1:14 ethyl acetate/hexane as eluent; colorless solid; mp 198-199 C;
yield 68% (63 mg); 1H NMR (400 MHz, CDCl3) δ 7.79 (d, J = 8.0 Hz, 2H), 7.54-7.51 (m, 3H),
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7.45-7.42 (m, 4H), 7.35 (t, J = 7.2 Hz, 1H), 7.23 (d, J = 7.6 Hz, 2H), 7.05 (t, J = 7.2 Hz, 1H),
6.94-6.88 (m, 3H), 6.65 (d, J = 8.0 Hz, 1H), 6.33(s, 1H), 5.38-5.34 (m, 1H), 4.68-4.63 (m, 1H),
4.05-4.00 (m, 1H), 2.35 (s, 3H); 13C{1H} NMR (150 MHz, CDCl3) δ 145.0, 141.8, 141.7, 140.2,
136.7, 133.3, 132.6, 130.5, 129.9, 129.0, 127.9, 127.89, 127.81, 127.1, 126.7, 120.59, 120.56,
109.6, 83.4, 61.2, 58.0, 21.7; FT-IR (KBr) 3030, 2925, 1616, 1597, 1566, 1487, 1456, 1362,
1306, 1260, 1168, 1089 cm-1; HRMS (ESI) m/z [M+H]+ calcd for C29H25N2O2S: 465.1631,
found: 465.1631.
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3-(2,4-Dimethylphenyl)-1-tosyl-2,3-dihydro-1H-imidazo[1,2-a]indole 4al. Analytical TLC
on silica gel, 1:9 ethyl acetate/hexane; Rf = 0.44; purification on silica gel column

chromatography using 1:14 ethyl acetate/hexane as eluent; colorless solid; mp 146-147 C;
yield 65% (54 mg); 1H NMR (400 MHz, CDCl3) δ 7.76 (d, J = 8.4 Hz, 2H), 7.53 (d, J = 8.0
Hz, 1H), 7.20 (d, J = 8.4 Hz, 2H), 7.06-7.02 (m, 1H), 6.98 (s, 1H), 6.91-6.86 (m, 1H), 6.70 (d,
J = 8.0 Hz, 1H), 6.57 (d, J = 8.0 Hz, 1H), 6.31(s, 1H), 6.27 (s, 1H), 5.51-5.47 (m, 1H), 4.65-
4.60 (m, 1H), 3.89-3.85 (m, 1H), 2.37 (s, 3H), 2.26-2.22 (m, 6H); 13C{1H} NMR (100 MHz,
CDCl3) δ 144.9, 141.9, 138.1, 134.5, 133.2, 132.6, 132.4, 131.8, 130.6, 129.9, 127.8, 127.5,
120.5, 120.47, 120.44, 109.7, 83.4, 60.2, 55.3, 21.7, 21.1, 19.0; FT-IR (KBr) 3052, 2922, 1615,
1596, 1565, 1477, 1455, 1361, 1306, 1185, 1168, 1103, 1089 cm-1; HRMS (ESI) m/z [M+H]+
calcd for C25H25N2O2S: 417.1631, found: 417.1632.
3-Mesityl-1-tosyl-2,3-dihydro-1H-imidazo[1,2-a]indole 4am. Analytical TLC on silica gel,
1:9 ethyl acetate/hexane; Rf = 0.43; purification on silica gel column chromatography using

1
1:14 ethyl acetate/hexane as eluent; colorless solid; mp 196-197 C; yield 63% (54 mg); H
NMR (400 MHz, CDCl3) δ 7.86 (d, J = 8.4 Hz, 2H), 7.49 (d, J = 7.6 Hz, 1H), 7.27-7.25 (m,
2H), 7.02-6.98 (m, 1H), 6.90 (s, 1H), 6.84-6.80 (m, 1H), 6.67 (s, 1H), 6.39 (d, J = 8.0 Hz, 1H),
6.28 (s, 1H), 5.80 (t, J = 9.2 Hz, 1H), 4.58-4.53 (m, 1H), 4.01-3.96 (m, 1H), 2.39 (d, J = 2.4
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Hz, 6H), 2.24 (s, 3H), 1.22 (s, 3H); 13C{1H} NMR (100 MHz, CDCl3) δ 145.1, 141.4, 138.5,
137.3, 136.7, 132.9, 132.7, 131.9, 130.6, 129.9, 127.9, 120.4, 120.3, 108.6, 83.1, 57.3, 53.8,
21.7, 20.9, 20.8, 18.2; FT-IR (KBr) 2922, 1615, 1457, 1425, 1363, 1306, 1170, 1090 cm-1;
HRMS (ESI) m/z [M+H]+ calcd for C26H27N2O2S: 431.1788, found: 431.1790.
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3-(Naphthalen-2-yl)-1-tosyl-2,3-dihydro-1H-imidazo[1,2-a]indole 4an. Analytical TLC on
silica gel, 1:9 ethyl acetate/hexane; Rf = 0.47; purification on silica gel column chromatography
using 1:14 ethyl acetate/hexane as eluent; colorless solid; mp 183-184 C; yield 67% (58 mg);
1H NMR (400 MHz, CDCl3) δ 7.80-7.76 (m, 3H), 7.68-7.64 (m, 2H), 7.54 (d, J = 8.0 Hz, 1H),
7.49-7.47 (m, 2H), 7.39 (s, 1H), 7.19 (d, J = 8.4 Hz, 2H), 7.03 (t, J = 8.0 Hz, 1H), 6.89-6.81
(m, 2H), 6.57 (d, J = 8.0 Hz, 1H), 6.35 (s, 1H), 5.50-5.46 (m, 1H), 4.74-4.69 (m, 1H), 4.09-
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4.05 (m, 1H), 2.34 (s, 3H); C{1H} NMR (100 MHz, CDCl3) δ 145.0, 141.9, 135.2, 133.3,
133.1, 132.6, 130.6, 129.9, 129.4, 128.1, 127.8, 126.8, 126.7, 125.8, 123.2, 120.6, 120.58,
120.56, 109.6, 83.6, 61.1, 58.4, 21.7; FT-IR (KBr) 3053, 2923, 1616, 1597, 1566, 1477, 1456,
1361, 1306, 1185, 1168, 1106, 1089 cm-1; HRMS (ESI) m/z [M+H]+ calcd for C27H23N2O2S:
439.1475, found: 439.1478.
3-Phenyl-1-(phenylsulfonyl)-2,3-dihydro-1H-imidazo[1,2-a]indole 4ao. Analytical TLC on
silica gel, 1:9 ethyl acetate/hexane; Rf = 0.44; purification on silica gel column chromatography
using 1:14 ethyl acetate/hexane as eluent; colorless solid; mp 174-175 C; yield 71% (53 mg);
1H NMR (400 MHz, CDCl3) δ 7.91 (d, J = 7.2 Hz, 2H), 7.62-7.58 (m, 1H), 7.53 (d, J = 8.0 Hz,
1H), 7.47-7.43 (m, 2H), 7.29-7.19 (m, 3H), 7.06-7.02 (m, 1H), 6.90-6.85 (m, 3H), 6.57 (d, J =
8.0 Hz, 1H), 6.33 (s, 1H), 5.33-5.29 (m, 1H), 4.66-4.61 (m, 1H), 4.00-3.96 (m, 1H); 13C{1H}
NMR (150 MHz, CDCl3) δ 141.7, 137.6, 135.5, 134.0, 133.3, 130.5, 129.4, 129.2, 128.9, 127.8,
126.3, 120.58, 120.56, 109.6, 83.4, 61.2, 58.2; FT-IR (KBr) 3060, 2924, 1616, 1566, 1477,
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1454, 1362, 1307, 1220, 1171, 1090 cm-1; HRMS (ESI) m/z [M+H]+ calcd for C22H18N2O2S:
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4ap.
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Analytical TLC on silica gel, 1:9 ethyl acetate/hexane; Rf = 0.42; purification on silica gel
column chromatography using 1:11 ethyl acetate/hexane as eluent; colorless solid; mp 192-193
C; yield 72% (58 mg); 1H NMR (400 MHz, CDCl3) δ 7.81 (d, J = 8.8 Hz, 2H), 7.53 (d, J =
7.6 Hz, 1H), 7.38-7.36 (m, 2H), 7.31-7.27 (m, 1H), 7.23-7.19 (m, 2H), 7.08-7.04 (m, 1H), 6.93-
6.89 (m, 1H), 6.81-6.79 (m, 2H), 6.61 (d, J = 8.0 Hz, 1H), 6.32 (s, 1H), 5.37-5.33 (m, 1H),
4.69-4.64 (m, 1H), 4.02-3.97 (m, 1H); 13C{1H} NMR (150 MHz, CDCl3) δ 141.2, 140.7, 137.7,
134.0, 133.1, 130.5, 129.6, 129.3, 129.1, 128.8, 126.0, 120.8, 120.6, 109.7, 83.6, 61.3, 58.1;
FT-IR (KBr) 3060, 2925, 1616, 1573, 1475, 1454, 1366, 1307, 1281, 1171, 1092 cm-1; HRMS
(ESI) m/z [M+H]+ calcd for C22H17ClN2O2S: 409.0772, found: 409.0777.
1-((4-Nitrophenyl)sulfonyl)-3-phenyl-2,3-dihydro-1H-imidazo[1,2-a]indole
4aq.
Analytical TLC on silica gel, 1:9 ethyl acetate/hexane; Rf = 0.40; purification on silica gel
column chromatography using 1:11 ethyl acetate/hexane as eluent; orange solid; mp 194-195
C; yield 62% (51 mg); 1H NMR (400 MHz, CDCl3) δ 8.20 (d, J = 8.8 Hz, 2H), 8.03 (d, J =
8.8 Hz, 2H), 7.55 (d, J = 8.0 Hz, 1H), 7.27-7.23 (m, 1H), 7.16 (t, J = 7.6 Hz, 2H), 7.08 (t, J =
8.0 Hz, 1H), 6.96-6.92 (m, 1H), 6.77 (d, J = 7.2 Hz, 2H), 6.64 (d, J = 8.0 Hz, 1H), 6.36 (s, 1H),
5.40-5.37 (m, 1H), 4.75-4.70 (m, 1H), 4.09-4.05 (m, 1H); 13C{1H} NMR (150 MHz, CDCl3) δ
150.8, 141.2, 140.4, 137.6, 132.8, 130.7, 129.2, 128.9, 128.8, 125.8, 124.4, 121.2, 120.9, 120.8,
109.8, 83.9, 61.5, 58.0; FT-IR (KBr) 3104, 2924, 1606, 1595, 1567, 1477, 1454, 1370, 1309,
1256, 1173, 1089 cm-1; HRMS (ESI) m/z [M+H]+ calcd for C22H18N3O4S: 420.1013, found:
420.1012.
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1-((4-(tert-Butyl)phenyl)sulfonyl)-3-phenyl-2,3-dihydro-1H-imidazo[1,2-a]indole
4ar.
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Analytical TLC on silica gel, 1:9 ethyl acetate/hexane; Rf = 0.44; purification on silica gel
column chromatography using 1:14 ethyl acetate/hexane as eluent; colorless solid; mp 193-194
C; yield 67% (57 mg); 1H NMR (400 MHz, CDCl3) δ 7.83 (d, J = 8.4 Hz, 2H), 7.53 (d, J =
8.0 Hz, 1H), 7.46 (d, J = 8.4 Hz, 2H), 7.21 (t, J = 7.6 Hz, 2H), 7.04 (t, J = 8.0 Hz, 1H), 6.89-
6.86 (m, 3H), 6.58 (d, J = 8.0 Hz, 1H), 6.32 (s, 1H), 5.35-5.31 (m, 1H), 4.65-4.60 (m, 1H),
3.99-3.95 (m, 1H), 1.30 (s, 9H); 13C{1H} NMR (100 MHz, CDCl3) δ 157.9, 141.9, 137.8, 133.4,
132.4, 130.5, 129.2, 128.9, 127.8, 126.39, 126.38, 120.52, 120.52, 120.4, 109.5, 83.2, 61.1,
58.2, 35.4, 31.1; FT-IR (KBr) 3057, 2963, 1617, 1593, 1566, 1476, 1455, 1361, 1307, 1266,
1131, 1085 cm-1; HRMS (ESI) m/z [M+H]+ calcd for C26H27N2O2S: 431.1788, found: 431.1791.
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2-Hexyl-1-tosyl-2,3-dihydro-1H-imidazo[1,2-a]indole 4as. Analytical TLC on silica gel, 1:9
ethyl acetate/hexane; Rf = 0.43; purification on silica gel column chromatography using 1:14
ethyl acetate/hexane as eluent; colorless solid; mp 113-114 C; yield 66% (52 mg); 1H NMR
(400 MHz, CDCl3) δ 7.69 (d, J = 8.4 Hz, 2H), 7.53-7.50 (m, 1H), 7.18 (d, J = 8.0 Hz, 2H),
7.08-7.05 (m, 2H), 7.01-6.99 (m, 1H), 6.27 (s, 1H), 4.50-4.44 (m, 1H), 3.81-3.77 (m, 1H), 3.70-
3.67 (m, 1H), 2.34 (s, 3H), 2.06-1.98 (m, 1H), 1.90-1.81 (m, 1H), 1.44-1.25 (m, 8H), 0.88 (t, J
= 6.8 Hz, 3H); 13C{1H} NMR (150 MHz, CDCl3) δ 144.7, 141.3, 133.9, 132.8, 130.8, 129.9,
127.5, 120.6, 120.5, 120.1, 108.7, 84.8, 66.2, 46.5, 35.8, 31.80, 29.1, 24.8, 22.7, 21.7, 14.2;
FT-IR (KBr) 2922, 2859, 1562, 1457, 1428, 1306, 1185, 1167, 1090, 1008 cm-1; HRMS (ESI)
m/z [M+H]+ calcd for C23H29N2O2S: 397.1944, found: 397.1951.
2-Octyl-1-tosyl-2,3-dihydro-1H-imidazo[1,2-a]indole 4at. Analytical TLC on silica gel, 1:9
ethyl acetate/hexane; Rf = 0.42; purification on silica gel column chromatography using 1:11
ethyl acetate/hexane as eluent; colorless solid; mp 90-91 C; yield 68% (57 mg); 1H NMR (400
MHz, CDCl3)δ 7.69 (d, J = 8.4 Hz, 2H), 7.53-7.50 (m, 1H), 7.18 (d, J = 8.0 Hz, 2H), 7.09-7.04
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(m, 2H), 7.02-6.99 (m, 1H), 6.27 (s, 1H), 4.50-4.44 (m, 1H), 3.81-3.77 (m, 1H), 3.70-3.67 (m,
1H), 2.34 (s, 3H), 2.06 – 1.98 (m, 1H), 1.90-1.81 (m, 1H), 1.45-1.27 (m, 12H), 0.88 (t, J = 6.4
Hz, 3H); 13C{1H} NMR (100 MHz, CDCl3) δ 144.7, 141.3, 134.0, 132.8, 130.8, 129.9, 127.5,
120.6, 120.5, 120.1, 108.7, 84.8, 66.2, 46.5, 35.8, 31.9, 29.57, 29.51, 29.3, 24.9, 22.7, 21.7,
14.2; FT-IR (KBr) 3051, 2924, 1618, 1597, 1562, 1478, 1457, 1361, 1306, 1276, 1167, 1089
cm-1; HRMS (ESI) m/z [M+H]+ calcd for C25H33N2O2S: 425.2257, found: 425.2260.
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9-Methyl-3-phenyl-1-tosyl-2,3-dihydro-1H-imidazo[1,2-a]indole 4ba. Analytical TLC on
silica gel, 1:9 ethyl acetate/hexane; Rf = 0.51; purification on silica gel column chromatography
using 1:16 ethyl acetate/hexane as eluent; colorless solid; mp 130-131 C; yield 64% (53 mg);
1H NMR (400 MHz, CDCl3) δ 7.54 (d, J = 8.4 Hz, 3H), 7.279-7.277 (m, 1H), 7.18 (t, J = 7.6
Hz, 2H), 7.13 (d, J = 8.0 Hz, 2H), 7.09-7.05 (m, 1H), 6.93-6.89 (m, 1H), 6.80 (d, J = 7.2 Hz,
2H), 6.45 (d, J = 8.0 Hz, 1H), 4.87 (t, J = 7.6 Hz, 1H), 4.78-4.73 (m, 1H), 4.15-4.10 (m, 1H),
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2.55 (s, 3H), 2.36 (s, 3H); C{1H} NMR (100 MHz, CDCl3) δ 144.6, 137.8, 137.2, 133.8,
133.3, 130.4, 130.0, 129.0, 128.4, 127.8, 126.3, 121.2, 119.8, 119.1, 109.6, 96.2, 63.3, 57.2,
21.7, 8.9; FT-IR (KBr) 2922, 1596, 1457, 1361, 1275, 1168, 1090, 1006 cm-1; HRMS (ESI)
m/z [M+H]+ calcd for C24H23N2O2S: 403.1475, found: 403.1477.
8-Bromo-3-phenyl-1-tosyl-2,3-dihydro-1H-imidazo[1,2-a]indole 4ca. Analytical TLC on
silica gel, 1:9 ethyl acetate/hexane; Rf = 0.46; purification on silica gel column chromatography

using 1:14 ethyl acetate/hexane as eluent; solid; colorless solid; mp 192-193 C; yield 58%
(54 mg); 1H NMR (400 MHz, CDCl3) δ 7.73 (d, J = 8.4 Hz, 2H), 7.24-7.16 (m, 4H), 7.15-7.11
(m, 2H), 6.77 (d, J = 7.2 Hz 2H), 6.66 (t, J = 8 Hz, 1H), 6.44 (d, J = 8.4 Hz, 1H), 6.31 (s, 1H),
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5.28-5.25 (m, 1H), 4.58-4.53 (m, 1H), 3.94-3.90 (m, 1H), 2.33 (s, 3H); C{1H} NMR (100
MHz, CDCl3) δ 145.2, 142.2, 137.4, 133.7, 132.5, 130.6, 130.1, 129.3, 129.0, 127.8, 126.2,
123.5, 121.4, 113.8, 108.5, 83.6, 61.0, 58.4, 21.7; FT-IR (KBr) 3066, 2923, 1611, 1597, 1566,
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1493, 1456, 1428, 1363, 1167 cm-1; HRMS (ESI) m/z [M+H]+ calcd for C23H20BrN2O2S:
467.0423, found: 467.0426.
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7-(Benzyloxy)-3-phenyl-1-tosyl-2,3-dihydro-1H-imidazo[1,2-a]indole 4da. Analytical TLC
on silica gel, 1:9 ethyl acetate/hexane; Rf = 0.42; purification on silica gel column
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chromatography using 1:11 ethyl acetate/hexane as eluent; colorless solid; mp 150-151 C;
yield 67% (66 mg); 1H NMR (400 MHz, CDCl3) δ 7.71 (d, J = 8.4 Hz, 2H), 7.38-7.36 (m, 2H),
7.32-7.28 (m, 2H), 7.26 – 7.20 (m, 2H), 7.17-7.12 (m, 4H), 7.02 (d, J = 2.4 Hz, 1H), 6.80-6.78
(m, 2H), 6.54 (dd, J = 8.8, 2.4 Hz, 1H), 6.39 (d, J = 8.8 Hz, 1H), 6.17 (s, 1H), 5.20-5.17 (m,
1H), 4.98 (s, 2H), 4.55-4.50 (m, 1H), 3.89-3.85 (m, 1H), 2.32 (s, 3H); C{1H} NMR (150
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MHz, CDCl3) δ 154.0, 145.0, 142.5, 137.76, 137.72, 134.0, 132.5, 130.0, 129.2, 128.8, 128.6,
127.9, 127.8, 127.6, 126.3, 125.8, 110.4, 110.2, 104.8, 83.5, 70.8, 61.1, 58.4, 21.7; FT-IR (KBr)
3063, 2921, 1621, 1576, 1494, 1478, 1451, 1363, 1289, 1168 cm-1; HRMS (ESI) m/z [M+H]+
calcd for C30H27N2O3S: 495.1737, found: 495.1737.
7-Bromo-3-phenyl-1-tosyl-2,3-dihydro-1H-imidazo[1,2-a]indole 4eaʹ. Analytical TLC on
silica gel, 1:9 ethyl acetate/hexane; Rf = 0.45; purification on silica gel column chromatography
using 1:14 ethyl acetate/hexane as eluent; colorless solid; mp 186-187 C; 70% (65 mg); 1H
NMR (400 MHz, CDCl3) δ 7.69 (d, J = 8.0 Hz, 2H), 7.55 (d, J = 1.6 Hz, 1H), 7.23-7.12 (m,
5H), 6.89 (dd, J = 8.4, 2.0 Hz, 1H), 6.75-6.73 (m, 2H), 6.35 (d, J = 8.4 Hz, 1H), 6.17 (s, 1H),
5.24-5.21 (m, 1H), 4.58-4.53 (m, 1H), 3.93-3.88 (m, 1H), 2.32 (s, 3H); C{1H} NMR (100
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MHz, CDCl3) δ 145.2, 142.8, 137.3, 134.9, 132.5, 130.0, 129.2, 129.1, 128.9, 127.8, 126.2,
123.2, 122.9, 113.8, 110.8, 82.8, 61.1, 58.3, 21.7; FT-IR (KBr) 3063, 2923, 1612, 1595, 1565,
1459, 1364, 1275, 1168 cm-1; HRMS (ESI) m/z [M+H]+ calcd for C23H20BrN2O2S: 467.0423,
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found: 467.0427; [α]D = +24.00 (c= 0.01, CHCl3); HPLC: >99% ee [CHIRALCEL OD-H,
hexane/iPrOH = 90:10, flow rate: 1 mL /min, λ = 254 nm, tR = 18.56 min (minor), 25.91 min
(major)].
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6-Chloro-3-phenyl-1-tosyl-2,3-dihydro-1H-imidazo[1,2-a]indole 4fa. Analytical TLC on
silica gel, 1:9 ethyl acetate/hexane; Rf = 0.44; purification on silica gel column chromatography
using 1:14 ethyl acetate/hexane as eluent; colorless solid; mp >200 C; yield 63% (53 mg); 1H
NMR (400 MHz, CDCl3) δ 7.76 (d, J = 8.4 Hz, 2H), 7.41 (d, J = 8.4 Hz, 1H), 7.32-7.28 (m,
1H), 7.25-7.21 (m, 4H), 7.01 (dd, J = 8.4, 1.6 Hz, 1H), 6.84-6.82 (m, 2H), 6.54 (d, J = 2.0 Hz,
1H), 6.27 (s, 1H), 5.29-5.25 (m, 1H), 4.64-4.59 (m, 1H), 3.99-3.95 (m, 1H), 2.40 (s, 3H);
13C{1H} NMR (100 MHz, CDCl3) δ 145.2, 142.3, 137.3, 132.5, 131.8, 130.8, 130.0, 129.3,
129.0, 127.8, 126.1, 121.2, 121.1, 109.5, 83.3, 61.1, 58.3, 21.7; FT-IR (KBr) 3063, 2923, 1611,
1597, 1572, 1493, 1456, 1419, 1363, 1279, 1167 cm-1; HRMS (ESI) m/z [M+H]+ calcd for
C23H20ClN2O2S: 423.0929, found: 423.0928.
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6-Fluoro-3-phenyl-1-tosyl-2,3-dihydro-1H-imidazo[1,2-a]indole 4gaʹ. Analytical TLC on
silica gel, 1:9 ethyl acetate/hexane; Rf = 0.42; purification on silica gel column chromatography
using 1:11 ethyl acetate/hexane as eluent; colorless solid; mp 188-189 C; yield 68% (55 mg);
1H NMR (400 MHz, CDCl3) δ 7.77 (d, J = 8.4 Hz, 2H), 7.41-7.38 (m, 1H), 7.32-7.27 (m, 1H),
7.24-7.21 (m, 4H), 6.85- 6.83 (m, 2H), 6.81-6.76 (m, 1H), 6.27 (s, 1H), 6.26-6.23 (m, 1H),
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5.27-5.23 (m, 1H), 4.64-4.59 (m, 1H), 3.99-3.95 (m, 1H), 2.40 (s, 3H). C{1H} NMR (150
MHz, CDCl3) δ 159.4 (JC-F = 235.65 Hz), 145.1, 142.05 (JC-F = 3.15 Hz), 137.2, 132.5, 130.3
(JC-F = 12.45 Hz), 130.0, 129.5, 129.3, 129.0, 127.8, 126.2, 121.0 (JC-F = 9.75 Hz), 108.7 (JC-F
= 24 Hz), 96.6 (JC-F = 2.67 Hz), 83.2, 61.1, 58.2, 21.7; FT-IR (KBr) 3063, 2923, 1622, 1575,
1484, 1421, 1358, 1279 1167 cm-1; HRMS (ESI) m/z [M+H]+ calcd for C23H20FN2O2S:
407.1224, found: 407.1228; [α]D27 = +22.00 (c= 0.01, CHCl3); HPLC: >99% ee [CHIRALCEL
OD-H, hexane/iPrOH = 90:10, flow rate: 1 mL /min, λ = 254 nm, tR = 17.63 min (minor), 28.30
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5-Chloro-3-phenyl-1-tosyl-2,3-dihydro-1H-imidazo[1,2-a]indole 4ha. Analytical TLC on
silica gel, 1:9 ethyl acetate/hexane; Rf = 0.43; purification on silica gel column chromatography
using 1:11 ethyl acetate/hexane as eluent; colorless solid; mp 164-165 C; yield 69% (58 mg);
1H NMR (400 MHz, CDCl3) δ 7.73 (d, J = 8.4 Hz, 2H), 7.41 (d, J = 7.6 Hz, 1H), 7.18-7.14 (m,
3H), 7.09-7.05 (m, 2H), 6.96 (t, J = 8.0 Hz, 1H), 6.89 (d, J = 7.2 Hz, 1H), 6.55 (d, J = 7.6 Hz,
2H), 6.33 (s, 1H), 5.87-5.85 (m, 1H), 4.50-4.46 (m, 1H), 4.18-4.15 (m, 1H), 2.37 (s, 3H);
13C{1H} NMR (100 MHz, CDCl3) δ 145.0, 142.7, 141.0, 135.3, 132.5, 130.0, 128.9, 128.0,
127.7, 127.4, 124.6, 121.5, 121.1, 118.9, 116.1, 83.2, 60.8, 59.4, 21.7; FT-IR (KBr) 3063, 2924,
1616, 1597, 1575, 1485, 1455, 1429, 1362, 1276, 1167 cm-1; HRMS (ESI) m/z [M+H]+ calcd
for C23H20ClN2O2S: 423.0929, found: 423.0931.
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5-Methyl-3-phenyl-1-tosyl-2,3-dihydro-1H-imidazo[1,2-a]indole 4ia. Analytical TLC on
silica gel, 1:9 ethyl acetate/hexane; Rf = 0.46; purification on silica gel column chromatography
using 1:14 ethyl acetate/hexane as eluent; colorless solid; mp 174-175 C; yield 73% (58 mg);
1H NMR (400 MHz, CDCl3) δ 7.72 (d, J = 8.4 Hz, 2H), 7.38 (d, J = 7.6 Hz, 1H), 7.17-7.13 (m,
3H), 7.09-7.05 (m, 2H), 6.96 (t, J = 7.2 Hz, 1H), 6.70 (d, J = 7.2 Hz, 1H), 6.53-6.50 (m, 2H),
6.32 (s, 1H), 5.67-5.64 (m, 1H), 4.53-4.49 (m, 1H), 4.16-4.13 (m, 1H), 2.36 (s, 3H), 2.06 (s,
3H); 13C{1H} NMR (150 MHz, CDCl3) δ 144.8, 141.8, 141.3, 133.4, 132.6, 129.9, 129.8,
129.1, 128.0, 127.7, 124.6, 122.4, 120.9, 120.3, 118.2, 83.1, 60.9, 59.5, 21.7, 17.7; FT-IR (KBr)
3049, 2925, 1607, 1597, 1572, 1492, 1455, 1416, 1358, 1263, 1165, 1090 cm-1; HRMS (ESI)
m/z [M+H]+ calcd for C24H23N2O2S: 403.1475, found: 403.1477.
3-Phenyl-7-(pyren-2-yl)-1-tosyl-2,3-dihydro-1H-imidazo[1,2-a]indole 5. Compound 4ea
(46 mg, 0.1 mmol), boronic acid (25 mg, 0.1 mmol), Pd(PPh3)4 (2.3 mg, 0.002 mmol), Na2CO3
(22 mg, 0.2 mmol) and H2O (50 mL) were stirred in toluene: EtOH (1:1, 2 mL) at 100 C in an
oil bath for 12 h under nitrogen atmosphere. After completion, the reaction mixture was cooled
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to room temperature and passed through a short pad of celite using CH2Cl2 (10 ml).
Evaporation of the solvent gave a residue that was purified on silica gel column
chromatography using 1:14 ethyl acetate/hexane as eluent to give 5. Analytical TLC on silica
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gel, 1:9 ethyl acetate/hexane; Rf = 0.46; grey solid; mp 151-152 C; yield 85% (50 mg); H
NMR (400 MHz, CDCl3) δ 8.23-8.17 (m, 3H), 8.15 (d, J = 7.6 Hz, 1H), 8.10-8.05 (m, 2H),
8.01-7.97 (m, 3H), 7.85 (d, J = 8.4 Hz, 2H), 7.76-7.75(m 1H), 7.36-7.29 (m, 5H), 7.16 (dd, J
= 8.0, 1.6 Hz, 1H), 7.01 (d, J = 6.8 Hz, 2H), 6.74 (d, J = 8.4 Hz, 1H), 6.40 (s, 1H), 5.43-5.39
(m, 1H), 4.71-4.67 (m, 1H), 4.07-4.03 (m, 1H), 2.43 (s, 3H); 13C{1H} NMR (100 MHz, CDCl3)
δ 145.1, 142.4, 138.9, 137.7, 133.6, 133.5, 132.6, 131.6, 131.1, 130.3, 130.1, 129.9, 129.3,
128.9, 128.8, 128.2, 127.9, 127.5, 127.25, 127.23, 126.4, 126.0, 125.9, 125.1, 125.0, 124.7,
124.6, 123.5, 122.5, 109.2, 83.5, 61.2, 58.4, 21.8; FT-IR (KBr) 2977, 2926, 1613, 1567, 1435,
1351, 1168, 1143, 1074 cm-1; HRMS (ESI) m/z [M+H]+ calcd for C39H29N2O2S: 589.1944,
found: 589.1946.
3-Phenyl-7-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1-tosyl-2,3-dihydro-1H-imida-
zo[1,2-a]indole 6. Compound 4ea (46 mg, 0.1 mmol), diboron (25 mg, 0.1 mmol), KOAc (20
mg, 0.2 mmol) and Pd(dppf)Cl2•CH2Cl2(4 mg, 0.005 mmol) were stirred in THF (2 mL) at 100
C in an oil bath for 12 h under nitrogen atmosphere. The reaction mixture was cooled to room
temperature and passed through a short pad of celite using CH2Cl2 (15 ml). Evaporation of the
solvent gave a residue that was purified on silica gel column chromatography using 1:14 ethyl
acetate/hexane as eluent to give 6. Analytical TLC on silica gel, 1:9 ethyl acetate/hexane, Rf =
0.48; colorless solid; mp 95-96 C; yield 73% (37 mg); 1H NMR (400 MHz, CDCl3) δ 8.03 (s,
1H), 7.75 (d, J = 8.0 Hz, 2H), 7.35 (dd, J = 8.0, 0.8 Hz, 1H), 7.24 (t, J = 1.6 Hz, 1H), 7.19-7.16
(m, 4H), 6.80 – 6.78 (m, 2H), 6.58 (d, J = 8.0 Hz, 1H), 6.31 (s, 1H), 5.35-5.31 (m, 1H), 4.65-
4.61 (m, 1H), 4.02-3.98 (m, 1H), 2.37 (s, 3H), 1.32 (s, 12H); 13C{1H} NMR (150 MHz, CDCl3)
δ 145.0, 141.7, 137.8, 132.9, 132.4, 131.2, 129.9, 129.2, 128.7, 128.0, 127.8, 126.9, 126.1,
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The Journal of Organic Chemistry
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109.0, 83.7, 83.6, 61.3, 58.0, 25.0, 24.9, 21.7; FT-IR (KBr) 3039, 2924, 1739, 1573, 1470,
1456, 1432, 1364, 1311, 1168, 1090 cm-1; HRMS (ESI) m/z [M+H]+ calcd for C29H32BN2O4S:
515.2170, found: 515.2184.
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ASSOCIATED CONTENT
Supporting Information
The Supporting Information having Table S1, Scheme S1-S2, crystallographic data for 4aa-
4aaʹ, HPLC chromatograms and NMR spectra of the starting materials and products are
available free of charge on the ACS Publications website at DOI:
■ AUTHOR INFORMATION
Corresponding Author
*E-mail: tpunni@iitg.ac.in
Notes
The author declares no competing financial interest.
■ ACKNOWLEDGMENTS
We thank the Science and Engineering Research Board (CRG/2018/000406) for the financial
supports. We are grateful to the Department of Chemistry (COE-FAST and FIST) and Central
Instrumentation Facility, Indian Institute of Technology Guwahati for NMR and HRMS
facilities.
REFERENCES
1. For recent reviews on C-N bond formation, see: (a) Thirunavukkarasu, V. S.; Kozhushkov,
S. I.; Ackermann, L. C-H Nitrogenation and Oxygenation by Ruthenium Catalysis. Chem.
Commun. 2014, 50, 29. (b) Louillat, M.-L.; Patureau, F. W. Oxidative C-H Amination
Reactions. Chem. Soc. Rev. 2014, 43, 901. (c) Park, Y.; Kim, Y.; Chang, S. Transition
Metal-Catalyzed C-H Amination: Scope, Mechanism, and Applications. Chem. Rev. 2017,
117, 9247. For some recent examples, see: (d) Sibi, M. P.; Soeta, T. Enantioselective
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