Diversity-oriented approach to natural product inspired pyrano-carbazole derivatives: strategic utilization of hetero-Diels-Alder reaction, Fischer indolization and the Suzuki-Miyaura cross-coupling reaction

Article abstract of DOI:10.1016/j.tet.2015.09.044

A variety of natural products inspired pyrano-carbazole derivatives have been assembled via hetero-Diels-Alder reaction and Fischer indolization (FI) under operationally simple reaction conditions. Later, the scope of this methodology has been expanded th

Full text of DOI:10.1016/j.tet.2015.09.044

Accepted Manuscript
Diversity-oriented approach to natural product inspired pyrano-carbazole derivatives:
Strategic utilization of hetero-Diels‒Alder reaction, Fischer indolization and the
Suzuki–Miyaura cross-coupling reaction
Sambasivarao Kotha, Rashid Ali, Mohammad Saifuddin
PII:
S0040-4020(15)30072-7
10.1016/j.tet.2015.09.044
TET 27141
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 1 July 2015
Revised Date: 1 September 2015
Accepted Date: 21 September 2015
Please cite this article as: Kotha S, Ali R, Saifuddin M, Diversity-oriented approach to natural product
inspired pyrano-carbazole derivatives: Strategic utilization of hetero-Diels‒Alder reaction, Fischer
indolization and the Suzuki–Miyaura cross-coupling reaction, Tetrahedron (2015), doi: 10.1016/
j.tet.2015.09.044.
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to
our customers we are providing this early version of the manuscript. The manuscript will undergo
copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please
note that during the production process errors may be discovered which could affect the content, and all
legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT
Diversity-oriented approach to natural product inspired pyrano-carbazole derivatives:
Strategic utilization of hetero-Diels‒Alder reaction, Fischer indolization and the
Suzuki–Miyaura cross-coupling reaction
Sambasivarao Kotha,* Rashid Ali and Mohammad Saifuddin
Department of Chemistry, Indian Institute of Technology-Bombay, Powai, Mumbai-400076
India, Phone: +91-22-2576 7160, Fax: +91(22)-2572 7152; E-mail: srk@chem.iitb.ac.in
Keywords: 1,3-Diketones, Fischer indolization, Hetero-Diels‒Alder reaction, Pyrano-
carbazoles, Styrenes, Suzuki–Miyaura cross-coupling reaction
ABSTRACT: A variety of natural products inspired pyrano-carbazole derivatives have been
assembled via hetero-Diels‒Alder reaction and Fischer indolization (FI) under operationally
simple reaction conditions. Later, the scope of this methodology has been expanded through
Suzuki–Miyaura cross-coupling reaction involving different boronic acids. This simple
strategy can be useful to generate a variety of medicinally important carbazole derivatives.
Graphical abstract
1. Introduction
Generating a library of architecturally complex frameworks with minimum number of steps
in a diversity-oriented fashion1 is an important tactic for assembling “drug-like” small
molecules.2 The pioneering work in this area has been done by Schreiber and co-workers to
establish a diverse collection of nitrogen-containing small molecules with the applications in
drug discovery and chemical genetics.3 Among the heterocycles, nitrogen containing
compounds are considered as privileged core structural units present in many natural
products,4 medicinally relevant substances5 and organic materials.6 Amongst these nitrogen
containing compounds, carbazoles, isolated first from coal tar in 1872 by Graebe and Glazer7
are important class of hetero-aromatics and are embedded in several pharmaceuticals8 as well
as materials9 with broad range of activities.10 Therefore, in recent years synthesis of
1

ACCEPTED MANUSCRIPT
carbazoles has remained as an active area of research. Alternatively, a variety of natural and
non-natural products contain the pyran ring system in their structures.11 To this end, a number
of synthetic strategies to these targets have been reported.12 In view of the various aplications
of carbazoles as well as pyran-ring containing natural products, we are interested in
assembling diverse and intricate hybrid molecules containing both of these subunits in a
diversity-oriented manner under operationally simple reaction conditions involving minimum
number of steps. The structures of some natural products containing pyrano-carbazole
scaffold are shown in Fig. 1.13
Me
CHO
CHO
Me
Me
O
Me
Me
O
Me
Me
O
N
N
N
H
H
H
OH
1
2
3
Murrayacine
Heptazolicine
Girinimbine
Me
O
CHO
Me
Me
Me
Me
Me
O
Me
Me
HO
O
N
H
N
N
H
MeO
MeO
H
5
6
4
Koenine
Mupamine
7-methoxyMurrayacine
Fig. 1. List of diverse bio-active pyrano-carbazole natural products
The retrosynthetic approach towards the synthesis of diverse pyrano-carbazole derivatives is
shown in the Fig. 2. To this end, the target carbazole derivative 9 can be obtained from the
enones 8 by employing FI followed by the Suzuki–Miyaura cross-coupling reaction. The
enone derivatives 8 could be obtained from the cyclohaxane-1,3-dione derivatives 7a-c via
hetero-Diels‒Alder reaction with different styrenes and paraformaldehyde under mild
reaction conditions.
Fig. 2. Retrosynthetic analysis for pyrano-carbazoles
2

ACCEPTED MANUSCRIPT
2. Results and discussion
A general outline for the synthesis of diverse carbazole derivatives is shown in Scheme 1 and
the structures of 1,3-diones as well as styrenes used in our study are shown in Fig. 3.
Our journey towards the synthesis of diverse and intricate pyrano-carbazole derivatives began
with the preparation of the pyran derivative 8a through the hetero-Diels‒Alder reaction of
styrene 11a and paraformaldehyde 12 in glycerol by following the known procedure.14 Here,
we found that formation of the side product 14 (Scheme 2) was unavoidable and also we were
unable to obtain the expected product in good yield (Table 1 and Entry 1). Therefore, we
investigated various reaction conditions to avoid the formation of the side product 14 and to
improve the yield of the desired product 8a (Table 1). Later, the optimized reaction
conditions were employed to other diones and styrenes to assemble a variety of pyrano-
intermediates 8b-i and 15a-c in fair to excellent yields (Fig. 4).
Scheme 1. General scheme for the formation of pyrano-carbazoles
Fig. 3. List of 1,3-diones and styrene derivatives used in our study
Scheme 2. Synthesis of pyrano-enone intermediate 8a
Table 1: Optimization studies for the synthesis of compound 8a
Entry
1
Solvent
glycerol
Temp.
120 °C
Time
16 h
8a (%yield)a
14 (%yield)
57
14
3

ACCEPTED MANUSCRIPT
2
3
benzene
toluene
80 °C
110 °C
120 °C
100 °C
110 °C
90 °C
24 h
24 h
<5
13
25
28
46
-
4
xylene
24 h
<10
82
5
1,4-dioxane
DMSO
15 h
6
16 h
59
<10
<10
15
-
7
Et3N
18 h
66
8
triethylaminoethanol
DMF
110 °C
110 °C
66 °C
30 h
30
9
12 h
88
10
11
12
THF
30 h
12
33
-
DMU:L-(+)TA (70:30)
DMU:L-(+)TA (50:50)
80 °C
24 h/40 h
24 h
trace
trace
80 °C
-
a= Isolated yields after column chromatography technique, DMU = 1,3-dimethyl urea, TA = tartaric acid
Fig. 4. List of pyrano-ketone intermediates assembled in our strategy
Having the ketone precursors 8a-f in hand, our next target was to generate diverse pyrano-
carbazole derivatives via FI. To this end, survey of the literature indicated that the FI of α, β-
unsaturated carbonyl compounds via conventional protocol is not explored. Therefore, it
remained a challenge to perform the FI of α,β-unsaturated carbonyl compounds by using
conventional conditions. In this regard, the keto derivative 8a was subjected to the FI with
phenylhydrazine hydrochloride under different reaction conditions but in most of the cases,
we realized low yield of the desired product (Table 2). The low yield and longer reaction time
for the FI may be because of the reduction of electrophilicity of the carbonyl carbon due to
4

ACCEPTED MANUSCRIPT
the conjugation of lone pair of the oxygen atom present in the ring system (Fig. 5). Therefore,
the tendency of phenylhydrazine to attack the carbonyl group is decreased. After screening
various reaction conditions to FI of 8a, we observed that p-toluene sulfonic acid (p-TSA) in
refluxing toluene gave the expected product in a respectable yield (Table 2 and Entry 2).
Later, the optimized reaction conditions were applied to other substrates to generate the
desired products 13b-13k in moderate to good yields (Fig. 6).
Fig. 5. Resonating structures of keto precursor 8
Scheme 3. Synthesis of pyrano-carbazole 13a via FI
Table 2: Optimization for the synthesis of pyrano-carbazole derivative 13a
Entry
1
Solvent
Acid
Temp.
75-80 °C
110 °C
110 °C
120 °C
110 oC
110 °C
Time
24 h
13a (% yield)a
DMU:L-(+)-TA (70:30)
30
69
2
toluene
toluene
DMF
p-TSA
CH3SO3H
CH3SO3H
HCl
3 days
24 h
3
38
4
24 h
53
5
toluene
EtOH
3 days
3 days
4 h
33
6
SOCl2
<5
21
7
DMF
CH3SO3H 120 °C/MW
8
CH3COOH
110 °C
110 °C
120 °C*
120 °C*
120 °C
5 days
3 days
36 h
<10
18
9
CH3COOH
DMF
TFA
CH3SO3H
PTSA
10
11
12
46
toluene
toluene
36 h
25
PPA
24 h
NR
5

ACCEPTED MANUSCRIPT
a = yields are based on starting material recovery; *= Sealed tube; NR = no reaction, MW = microwave
N
H
N
N
H
N
O
O
O
O
13d (61%)
13b (57%)
13c (43%)
13a (69%)
F
F
N
N
N
H
N
O
O
O
O
H
13h (48%)
13f (50%)
13g (63%)
13e (42%)
Br
Br
N
N
N
O
O
O
H
13i (68%)
13j (63%)
13k (55%)
Br
Br
F
Fig. 6. List of highly diversified pyrano-carbazole derivatives
To further expand the substrate scope of this methodology, the Suzuki–Miyaura cross-
coupling reaction was employed with different boronic acids to generate diverse and highly
functionalized pyrano-carbazole derivatives. In this context, we first performed the Suzuki-
Miyaura cross-coupling reaction of compound 13f with phenyl boronic acid to furnish the
cross-coupling product 9a in 94% yield (Scheme 4 and Fig. 7). Later, the coupling products
9b-d were also prepared by using different boronic acid in good to excellent yields (Fig. 7).
Scheme 4. Synthesis of highly diversified pyrano-carbazole derivatives
6

ACCEPTED MANUSCRIPT
Fig. 7. List of highly diversified pyrano-carbazole derivatives via Suzuki coupling
3. Conclusions
In summary, we have demonstrated a very simple strategy to diverse and intricate pyrano-
carbazole derivatives under simple reaction conditions with minimum number of steps and
without the involvement of protecting groups.15 Here, we have used readily available starting
1,3-diones and styrenes to generate architecturally complex carbazoles which otherwise
would be difficult to synthesize. The carbazole derivatives synthesized here resembles with
natural products (Fig. 1) and this strategy may be useful for the construction of diverse
natural products as well as boiactive targets.
4. Experimental section
All commercially accessible reagents were used without further purification and the reactions
involving air sensitive catalysts or reagents were performed in degassed solvents. Moisture
sensitive materials were transferred by using syringe-septum techniques and the reactions
were maintained under nitrogen atmosphere. Analytical thin layer chromatography (TLC)
was performed on (7.5×2.5 cm) glass plates coated with Acme’s silica gel GF 254
(containing 13% calcium sulfate as a binder) by using a suitable mixture of EtOAc and
petroleum ether for development. Column chromatography was performed by using Acme’s
silica gel (100-200 mesh) with an appropriate mixture of EtOAc and petroleum ether. The
coupling constants (J) are given in hertz (Hz) and chemical shifts are denoted in parts per
million (ppm) downfield from internal standard, tetramethylsilane (TMS). The abbreviations,
s, d, t, q, m, dd and td, refer to singlet, doublet, triplet, quartet, multiplet, doublet of doublets,
and triplet of doublets respectively. Infrared (IR) spectra were recorded on Nicolet Impact-
400 FT IR spectrometer. Proton nuclear magnetic resonance (1H NMR, 400 MHz and 500
MHz) spectra and carbon nuclear magnetic resonance (13C NMR, 100 MHz and 125 MHz)
spectra were recorded on a Bruker spectrometer. The high-resolution mass measurements
7

ACCEPTED MANUSCRIPT
were carried out by using electrospray ionization (ESI, Q-ToF) spectrometer. Melting points
were recorded on a Veego melting point apparatus.
General procedure for the synthesis of 8a-i and 15a-c: The solution of compounds 7a-c or
10, formaldehyde 12 (2 equiv) and styrenes 11 (1.2 equiv) in DMF was heated at 110 °C for
10-18 h. At the conclusion of the reaction (TLC monitoring), the reaction mixture was diluted
with water and the organic layer was extracted with EtOAc. Later, the organic layer was
washed with water (4×50 mL) to remove the excess amount of DMF and the solvent was
removed under reduced pressure. The crude products were purified by silica gel column
chromatography (25% EtOAc-petroleum ether) to afford the desired products (Fig. 4).
General procedure for the synthesis of 13a-k: The solution of compounds 8a-f and p-TSA
(5 equiv) in toluene was heated at 110 °C for 3-5 days. At the conclusion of the reaction
(TLC monitoring), the reaction mixture was diluted with saturated aq. NaHCO3 (10 mL)
solution and the compounds were extracted with EtOAc. Solvent was removed under reduced
pressure and the crude products were purified by silica gel column chromatography by using
appropriate mixtures of EtOAc-petroleum ether to afford the expected products (Fig. 6).
General procedure for the Suzuki–Miyaura cross-coupling of 13f and 13k: To a solution
of bromo derivatives 13f or 13k in THF/toluene/water (1:1:1, each 10 mL), were added
Na2CO3 (3.0 equiv) and arylboronic acid (2.0 equiv). The reaction mixture was degassed with
nitrogen for 15 min. Later, Pd(PPh3)4 (5 mol%) was added and the reaction mixture was
o
heated at 100 C. At the conclusion of the reaction (TLC monitoring), the reaction mixture
was diluted with water and the organic layer was extracted with CH2Cl2. The solvent was
removed under reduced pressure and the crude products were purified by silica gel column
chromatography by using appropriate mixtures of EtOAc-petroleum ether to afford the
desired cross-coupling products (Fig. 7).
2-Phenyl-2,3,4,6,7,8-hexahydro-5H-chromen-5-one 8a: Thick colourless liquid; yield =
88% (896 mg, starting from 500 mg of 7a); reaction time = 10 h; Rf = 0.40 (silica gel, 25%
1
EtOAc-petroleum ether); H NMR (400 MHz, CDCl3): δ = 1.84-1.96 (m, 3H), 2.09-2.15 (m,
1H), 2.20-2.31 (m, 1H), 2.34-2.44 (m, 5H), 4.90 (dd, J1 = 2.40 Hz, J2 = 10.40 Hz, 1H), 7.27-
7.37 (m, 5H); 13C NMR (100 MHz, CDCl3):
δ = 18.1, 20.9, 28.6, 29.1, 36.6, 78.9, 111.6,
125.8, 128.1, 128.5, 140.2, 171.4, 198.1; IR (neat): υmax = 1266, 1602, 1659, 2855, 2926,
3074 cm-1; HRMS (ESI, Q-ToF) m/z: calculated for C15H17O2 [M+H]+ 229.1223, found:
229.1222.
8

ACCEPTED MANUSCRIPT
2-(4-Fluorophenyl)-2,3,4,6,7,8-hexahydro-5H-chromen-5-one 8b: White solid; yield =
81% (889 mg, starting from 500 mg of 7a); reaction time = 16 h; mp 69-71 °C; Rf = 0.41
1
(silica gel, 25% EtOAc-petroleum ether); H NMR (400 MHz, CDCl3): δ = 1.80-1.91 (m,
2H), 1.97-2.03 (m, 2H), 2.12-2.17 (m, 1H), 2.23-2.31 (m, 1H), 2.39-2.47 (m, 4H), 4.91 (dd,
J1 = 1.96 Hz, J2 = 10.48 Hz, 1H), 7.05-7.09 (m, 2H), 7.30-7.34 (m, 2H); 13C NMR (100 MHz,
CDCl3): δ = 18.4, 21.1, 28.8, 29.4, 36.8, 78.6, 111.8, 115.6, 115.8, 127.8, 127.9, 136.2, 136.3,
162.7 (d, J = 245.0 Hz), 171.6, 198.4; IR (neat): υmax = 1647, 2867, 2949, 3054 cm-1; HRMS
(ESI, Q-ToF) m/z: calculated for C15H15FNaO2 [M+Na]+ 269.0948, found: 269.0948.
2-(4-Bromophenyl)-2,3,4,6,7,8-hexahydro-5H-chromen-5-one 8c: White solid; yield =
80% (1.13 g, starting from 500 mg of 7a); reaction time = 16 h; mp 94-97 °C; Rf = 0.38
1
(silica gel, 25% EtOAc-petroleum ether); H NMR (400 MHz, CDCl3): δ = 1.77-1.89 (m,
2H), 1.96-2.03 (m, 2H), 2.11-2.17 (m, 1H), 2.22-2.31 (m, 1H), 2.38-2.47 (m, 4H), 4.89 (dd,
13
J1 = 2.22 Hz, J2 = 10.44 Hz, 1H), 7.22 (d, J = 8.44 Hz, 2H), 7.49-7.53 (m, 2H); C NMR
(100 MHz, CDCl3):
δ = 18.2, 21.0, 28.8, 29.3, 36.8, 78.5, 111.9, 122.2, 127.8, 131.9, 139.5,
171.3, 198.3; IR (neat): υmax = 1394, 1489, 1620, 1644, 2945, 3052 cm-1; HRMS (ESI, Q-
ToF) m/z: calculated for C15H1579BrNaO2 [M+Na]+ 329.0148, found: 329.0156.
2,7-Diphenyl-2,3,4,6,7,8-hexahydro-5H-chromen-5-one 8d: Thick yellow liquid of an
inseparable mixture of diastereomers (0.5:1); yield = 82% (663 mg, starting from 500 mg of
7b); reaction time = 15 h; Rf = 0.46 (silica gel, 25% EtOAc-petroleum ether); 1H NMR (500
MHz, CDCl3) for major diastereomer with some peaks overlapping: δ = 1.90-1.98 (m, 1H),
2.17-2.23 (m, 1H), 2.29-2.37 (m, 1H), 2.42-2.48 (m, 1H), 2.60-2.84 (m, 4H), 3.38-3.46 (m,
13
1H), 5.10 (dd, J1 = 2.70 Hz, J2 = 9.50 Hz, 1H), 7.31-7.40 (m, 10H); C NMR (125 MHz,
CDCl3) for both diastereomers:
δ = 17.5, 18.6, 28.7, 29.4, 36.2, 36.3, 39.0, 39.1, 43.8, 43.9,
79.2, 79.6, 111.4, 111.6, 125.9, 126.1, 126.7, 126.8, 127.0, 127.1, 128.3, 128.4, 128.7, 128.8,
128.9, 140.2, 140.3, 143.0, 143.1, 170.5, 170.8, 197.1, 197.4; IR (neat): υmax = 1399, 1496,
1623, 1652, 2942, 3064 cm-1; HRMS (ESI, Q-ToF) m/z: calculated for C21H21O2 [M+H]+
305.1536, found: 305.1539.
2-(4-Fluorophenyl)-7-phenyl-2,3,4,6,7,8-hexahydro-5H-chromen-5-one 8e: Thick yellow
liquid of an inseparable mixture of diastereomers; yield = 73% (625 mg, starting from 500
mg of 7b); reaction time = 18 h; Rf = 0.45 (silica gel, 25% EtOAc-petroleum ether); 1H NMR
(500 MHz, CDCl3) for major diastereomer with some peaks overlapping: δ = 1.86-1.91 (m,
1H), 2.14-2.18 (m, 1H), 2.29-2.33 (m, 1H), 2.43-57 (m, 1H), 2.60-2.80 (m, 4H), 3.36-3.43
(m, 1H), 5.04 (dd, J1 = 2.40 Hz, J2 = 9.65 Hz, 1H), 7.02-7.08 (m, 2H), 7.23-7.34 (m, 7H); 13C
9

ACCEPTED MANUSCRIPT
NMR (125 MHz, CDCl3) for both diastereomers:
δ
= 17.5, 18.6, 28.7, 29.4, 36.2, 36.3, 38.9,
39.1, 43.7, 43.8, 78.6, 78.9, 111.4, 111.6, 115.5, 115.7, 126.7, 126.8, 127.0, 127.1, 127.6,
127.7, 127.8, 127.9, 128.8, 128.9, 136.0, 136.0, 136.1, 142.9, 143.0, 162.6 (d, J = 196.0 Hz)
162.7 (d, J = 196.0 Hz), 170.4, 170.6, 197.1, 197.3; IR (neat): υmax = 1394, 1512, 1624, 1652,
2857, 2947, 3030 cm-1; HRMS (ESI, Q-ToF) m/z: calculated for C21H19FNaO2 [M+Na]+
345.1261, found: 345.1264.
2-(4-Bromophenyl)-7-phenyl-2,3,4,6,7,8-hexahydro-5H-chromen-5-one 8f: White solid of
an inseparable mixture of diastereomers; yield = 72% (1.46 g, starting from 500 mg of 7b);
reaction time = 16 h; mp 147-150 °C; Rf = 0.45 (silica gel, 25% EtOAc-petroleum ether); 1H
NMR (500 MHz, CDCl3) for major diastereomer with some peaks overlapping: δ = 1.83-1.91
(m, 1H), 2.13-2.19 (m, 1H), 2.26-2.33 (m, 1H), 2.40-58 (m, 1H), 2.60-2.81 (m, 4H), 3.36-
3.44 (m, 1H), 5.03 (dd, J1 = 2.55 Hz, J2 = 9.50 Hz, 1H), 7.17 (d, J = 10.00 Hz, 1H), 7.22-7.25
(m, 4H), 7.33 (t, J = 7.85 Hz, 2H), 7.48-7.52 (m, 2H); 13C NMR (125 MHz, CDCl3) for both
diastereomers:
δ = 17.5, 18.6, 28.7, 29.5, 36.3, 36.3, 39.0, 39.2, 43.8, 43.9, 78.5, 78.8, 111.5,
111.7, 122.2, 122.3, 126.8, 126.9, 127.1, 127.2, 127.6, 127.8, 128.9, 129.0, 131.9, 139.3,
139.3, 142.9, 143.0, 170.3, 170.5, 197.1, 197.4; IR (neat): υmax = 1266, 1393, 1491, 1625,
1649, 2955, 3055 cm-1; HRMS (ESI, Q-ToF) m/z: calculated for C21H1979BrNaO2 [M+Na]+
405.0461, found: 405.0461.
7,7-Dimethyl-2-phenyl-2,3,4,6,7,8-hexahydro-5H-chromen-5-one 8g: Creamy solid; yield
= 93% (850 mg, starting from 500 mg of 7c); reaction time = 12 h; mp 99-101 °C; Rf = 0.43
(silica gel, 25% EtOAc-petroleum ether); 1H NMR (400 MHz, CDCl3): δ = 1.07 (d, J = 7.28
Hz, 6H), 1.84-1.90 (m, 1H), 2.13-2.17 (m, 1H), 2.22-2.34 (m, 5H), 2.43 (d, J = 16.48 Hz,
13
1H), 4.94 (dd, J1 = 1.92 Hz, J2 = 10.12 Hz, 1H), 7.27-7.39 (m, 5H); C NMR (100 MHz,
CDCl3):
δ = 17.8, 27.7, 29.1, 29.2, 32.1, 42.4, 50.6, 79.0, 110.3, 125.9, 126.09, 128.2, 128.4,
128.6, 140.3, 169.7, 197.9; IR (neat): υmax = 1451, 1630, 1647, 2954, 3027 cm-1; HRMS (ESI,
Q-ToF) m/z: calculated for C17H20NaO2 [M+Na]+ 279.1356, found: 279.1355.
2-(4-Fluorophenyl)-7,7-dimethyl-2,3,4,6,7,8-hexahydro-5H-chromen-5-one 8h: Creamy
solid; yield = 85% (832 mg, starting from 500 mg of 7c); reaction time = 12 h; mp 101-106
°C; Rf = 0.43 (silica gel, 25% EtOAc-petroleum ether); 1H NMR (500 MHz, CDCl3): δ = 1.09
(d, J = 7.20 Hz, 6H), 1.83-1.92 (m, 1H), 2.11-2.22 (m, 1H), 2.24-2.36 (m, 5H), 2.46 (d, J =
13
16.60 Hz, 1H), 4.94 (d, J = 10.35 Hz, 1H), 7.05-7.08 (m, 2H), 7.29-7.33 (m, 2H); C NMR
(125 MHz, CDCl3):
δ = 17.9, 27.7, 29.1, 29.2, 32.1, 42.4, 50.6, 78.4, 110.3, 115.4, 115.6,
127.7, 127.8, 136.1, 136.2, 162.5 (d, J = 196.0 Hz), 169.6, 197.9; IR (neat): υmax = 1268,
10

ACCEPTED MANUSCRIPT
1350, 1649, 2953, 3020 cm-1; HRMS (ESI, Q-ToF) m/z: calculated for C17H19FNaO2
[M+Na]+ 297.1261, found: 297.1264.
2-(4-Bromophenyl)-7,7-dimethyl-2,3,4,6,7,8-hexahydro-5H-chromen-5-one 8i: Brown
solid; yield = 87% (1.03 g, starting from 500 mg of 7c); reaction time = 13 h; mp 144-145 °C;
Rf = 0.44 (silica gel, 25% EtOAc-petroleum ether); 1H NMR (400 MHz, CDCl3): δ = 1.08 (d,
J = 7.25 Hz, 6H), 1.78-1.88 (m, 1H), 2.11-2.18 (m, 1H), 2.21-2.33 (m, 5H), 2.41-2.47 (m,
13
1H), 4.92 (dd, J1 = 2.40 Hz, J2 = 10.24 Hz, 1H), 7.20-7.22 (m, 2H), 7.49-7.52 (m, 2H); C
NMR (100 MHz, CDCl3):
δ = 17.8, 27.8, 29.2, 29.3, 32.2, 42.5, 50.7, 78.4, 110.5, 122.2,
127.7, 131.9, 139.5, 169.6, 198.0; IR (neat): υmax = 1621, 1645, 2871, 2944, 3050 cm-1;
HRMS (ESI, Q-ToF) m/z: calculated for C17H1979BrNaO2 [M+Na]+ 357.0461, found:
357.0462.
2-Phenyl-3,4-dihydroindeno[1,2-b]pyran-5(2H)-one 15a: Sticky yellow liquid; yield =
42% (377 mg, starting from 500 mg of 10); reaction time = 12 h; Rf = 0.42 (silica gel, 25%
1
EtOAc-petroleum ether); H NMR (400 MHz, CDCl3): δ = 2.01-2.09 (m, 1H), 2.20-2.27 (m,
1H), 2.35-2.46 (m, 2H), 5.27 (dd, J1 = 2.48 Hz, J2 = 9.92 Hz, 1H), 7.12 (d, J = 7.08 Hz, 1H),
13
7.23-7.31 (m, 2H), 7.36-7.45 (m, 6H); C NMR (100 MHz, CDCl3):
δ = 16.4, 29.5, 81.7,
108.2, 117.7, 121.1, 126.1, 128.6, 128.8, 129.9, 132.0, 133.5, 138.2, 139.6, 174.5, 193.3; IR
(neat): υmax = 1283, 1594, 1631, 1695, 2851, 2927, 3063 cm-1; HRMS (ESI, Q-ToF) m/z:
calculated for C18H14NaO2 [M+Na]+ 285.0886, found: 285.0885.
2-(4-Fluorophenyl)-3,4-dihydroindeno[1,2-b]pyran-5(2H)-oned 15b: Sticky yellow
liquid; yield = 34% (326 mg, starting from 500 mg of 10); reaction time = 15 h; Rf = 0.44
1
(silica gel, 25% EtOAc-petroleum ether); H NMR (400 MHz, CDCl3): δ = 1.96-2.06 (m,
1H), 2.19-2.25 (m, 1H), 2.36-2.46 (m, 2H), 5.25 (dd, J1 = 2.12 Hz, J2 = 10.08 Hz, 1H), 7.04-
7.14 (m, 3H), 7.23-7.31 (m, 2H), 7.37-7.41 (m, 3H); 13C NMR (100 MHz, CDCl3):
δ = 16.5,
29.5, 81.1, 108.2, 115.7, 115.9, 117.7, 121.2, 128.0, 128.1, 129.9, 132.0, 133.4, 135.5, 135.5,
138.1, 162.9 (d, J = 246.0 Hz), 174.4, 193.3; IR (neat): υmax = 1475, 2846, 2923, 3043 cm-1;
HRMS (ESI, Q-ToF) m/z: calculated for C18H14FO2 [M+H]+ 281.0972, found: 281.0974.
2-(4-Bromophenyl)-3,4-dihydroindeno[1,2-b]pyran-5(2H)-one 15c: Sticky yellow liquid;
yield = 33% (154 mg, starting from 200 mg of 10); reaction time = 12 h; Rf = 0.40 (silica gel,
25% EtOAc-petroleum ether); 1H NMR (500 MHz, CDCl3): δ = 1.93-2.01 (m, 1H), 2.17-2.22
(m, 1H), 2.37-2.41 (m, 2H), 5.20 (dd, J1 = 2.24 Hz, J2 = 10.05 Hz, 1H), 7.09 (d, J = 6.80 Hz,
13
1H), 7.22-7.29 (m, 4H), 7.37 (dd, J1 = 0.75 Hz, J2 = 6.35 Hz, 1H), 7.52-7.54 (m, 2H); C
NMR (125 MHz, CDCl3):
δ
= 16.3, 29.4, 80.9, 108.2, 117.7, 121.2, 122.5, 127.8, 129.9,
11

ACCEPTED MANUSCRIPT
131.9, 132.0, 133.3, 138.0, 138.6, 174.2, 193.2; IR (neat): υmax = 1394, 2829, 2955, 3020 cm-
1; HRMS (ESI, Q-ToF) m/z: calculated for C18H1479BrO2 [M+H]+ 341.0177, found: 341.0176.
3-Phenyl-1,2,3,11-tetrahydropyrano[3,2-a]carbazole 13a: White solid; yield = 69% (90
mg, starting from 100 mg of 8a); reaction time = 3 days; mp 216-217 °C; Rf = 0.52 (silica gel,
10% EtOAc-petroleum ether); 1H NMR (500 MHz, CDCl3): δ = 2.19-2.27 (m, 1H), 2.33-2.37
(m, 1H), 2.89 (d, J = 13.25 Hz, 1H), 3.01-3.07 (m, 1H), 5.12 (d, J = 10.10 Hz, 1H), 6.87 (d, J
= 8.45 Hz, 1H), 7.21 (t, J = 7.70 Hz, 1H), 2.24-2.35 (m, 2H), 7.39-7.42 (m, 3H), 7.47 (d, J =
13
7.30 Hz, 2H), 7.81 (d, J = 8.50 Hz, 2H), 7.97 (d, J = 7.70 Hz, 1H); C NMR (125 MHz,
CDCl3):
δ = 20.7, 29.4, 77.8, 104.1, 110.3, 110.6, 116.6, 119.1, 119.7, 119.8, 124.3, 124.4,
126.3, 128.1, 128.7, 139.2, 139.5, 141.7, 154.0; IR (neat): υmax = 1535, 2857, 2987, 3023,
3444 cm-1; HRMS (ESI, Q-ToF) m/z: calculated for C21H18NO [M+H]+ 300.1383, found:
300.1389.
11-Methyl-3-phenyl-1,2,3,11-tetrahydropyrano[3,2-a]carbazole 13b: White solid; yield =
57% (125 mg, starting from 200 mg of 8a, starting material recovered = 40 mg); reaction
time = 4 days; mp 193-195 °C; Rf = 0.63 (silica gel, 10% EtOAc-petroleum ether); 1H NMR
(400 MHz, CDCl3): δ = 2.05-2.15 (m, 1H), 2.26-2.30 (m, 1H), 3.36-3.43 (m, 2H), 3.98 (s,
3H), 5.06 (d, J = 8.36, 1H), 6.79 (d, J = 8.40, 1H), 7.13 (t, J = 7.36 Hz, 1H), 7.18-7.42 (m,
7H), 7.75 (d, J = 8.44 Hz, 1H), 7.89 (d, J = 7.64 Hz, 1H); 13C NMR (100 MHz, CDCl3):
δ =
23.1, 29.9, 32.8, 77.1, 105.1, 108.5, 110.6, 117.2, 119.2, 119.3, 123.4, 124.3, 126.2, 128.0,
128.7, 140.4, 141.8, 141.9, 154.6; IR (neat): υmax = 1463, 1592, 2920, 3040 cm-1; HRMS
(ESI, Q-ToF) m/z: calculated for C22H20NO [M+H]+ 314.1539, found: 314.1537.
3-(4-Fluorophenyl)-1,2,3,11-tetrahydropyrano[3,2-a]carbazole 13c: White solid; yield =
43% (40 mg, starting from 100 mg of 8b, starting material recovered = 28 mg); reaction time
= 3 days; mp 210-212 °C; Rf = 0.55 (silica gel, 10% EtOAc-petroleum ether); 1H NMR (500
MHz, CDCl3): δ = 2.16-2.24 (m, 1H), 2.30-2.35 (m, 1H), 2.88-2.92 (m, 1H), 30.1-3.07 (m,
1H), 5.10 (dd, J1 = 2.00 Hz, J2 = 10.25 Hz, 1H), 6.86 (d, J = 8.45 Hz, 1H), 7.08-7.12 (m, 2H),
7.21-7.24 (m, 1H), 7.32-7.35 (m, 1H), 7.40-7.47 (m, 3H), 7.82 (d, J = 8.45 Hz, 1H), 7.87
(brs, 1H), 7.98 (d, J = 7.70 Hz, 1H); 13C NMR (125 MHz, CDCl3):
δ = 20.7, 29.5, 77.4,
104.0, 110.3, 110.7, 115.5, 115.6, 116.7, 119.2, 119.7, 119.9, 124.2, 124.5, 127.9, 128.0,
137.5, 137.5, 139.2, 139.6, 153.9, 162.6 (d, J = 196.0 Hz); IR (neat): υmax = 1266, 1456,
1593, 1605, 2855, 2929, 3045, 3387 cm-1; HRMS (ESI, Q-ToF) m/z: calculated for
C21H16FNNaO [M+Na]+ 340.1108, found: 340.1108.
12

ACCEPTED MANUSCRIPT
3-(4-Fluorophenyl)-11-methyl-1,2,3,11-tetrahydropyrano[3,2-a]carbazole 13d: White
solid; yield = 61% (53 mg, starting from 100 mg of 8b, starting material recovered = 35 mg);
reaction time = 4 days; mp 190-192 °C; Rf = 0.53 (silica gel, 10% EtOAc-petroleum ether);
1H NMR (400 MHz, CDCl3): δ = 2.04-2.15 (m, 1H), 2.27-2.30 (m, 1H), 3.40-3.44 (m, 2H),
4.01 (s, 3H), 5.05 (d, J = 10.16 Hz, 1H), 6.82 (d, J = 8.44 Hz, 1H), 7.07 (t, J = 8.68 Hz, 2H),
7.18-7.24 (m, 1H), 7.28 (d, J = 8.12 Hz, 1H), 7.35-7.44 (m, 3H), 7.81 (d, J = 8.44 Hz, 1H),
13
7.95 (d, J = 7.68 Hz, 1H); C NMR (100 MHz, CDCl3):
δ = 23.1, 30.0, 32.7, 76.8, 105.0,
108.5, 110.5, 115.4, 115.6, 117.3, 119.2, 119.2, 119.3, 123.3, 124.3, 127.9, 128.0, 137.5,
137.6, 140.3, 141.9, 154.4, 162. 6 (d, J = 244.0 Hz); IR (neat): υmax = 1347, 1563, 1597,
2861, 3010 cm-1; HRMS (ESI, Q-ToF) m/z: calculated for C22H19FNO [M+H]+ 332.1445,
found: 332.1447.
3-(4-Bromophenyl)-1,2,3,11-tetrahydropyrano[3,2-a]carbazole 13e: White solid; yield =
42% (197 mg, starting from 500 mg of 8c, starting material recovered = 120 mg); reaction
time = 4 days; mp 235-237 °C; Rf = 0.50 (silica gel, 10% EtOAc-petroleum ether); 1H NMR
(500 MHz, CDCl3): δ = 2.05-2.25 (m, 1H), 2.32-2.38 (m, 1H), 2.89-2.95 (m, 1H), 3.02-3.11
(m, 1H), 5.10 (dd, J1 = 2.04 Hz, J2 = 10.12 Hz, 1H), 6.86 (d, J = 8.44 Hz, 1H), 7.07 (t, J =
8.68 Hz, 2H), 7.31-7.37 (m, 3H), 7.41 (d, J = 8.00 Hz, 1H), 7.53 (d, J = 8.40 Hz, 1H), 7.83
(d, J = 8.56 Hz, 2H), 7.97 (d, J = 7.68 Hz, 1H); 13C NMR (125 MHz, CDCl3):
δ = 20.6, 29.4,
77.0, 103.9, 110.2, 110.6, 116.7, 119.2, 119.7, 119.9, 121.9, 124.2, 124.5, 127.9, 131.8,
139.1, 139.5, 140.7, 153.7; IR (neat): υmax = 1070, 1266, 1459, 1608, 2928, 3057, 3447 cm-1;
HRMS (ESI, Q-ToF) m/z: calculated for C21H1779BrNO [M+H]+ 378.0488, found: 378.0483.
3-(4-Bromophenyl)-11-methyl-1,2,3,11-tetrahydropyrano[3,2-a]carbazole 13f: White
solid; yield = 50% (48 mg, starting from 100 mg of 8c, starting material recovered = 24 mg);
reaction time = 5 days; mp 222-225 °C; Rf = 0.53 (silica gel, 10% EtOAc-petroleum ether);
1H NMR (500 MHz, CDCl3): δ = 2.05-2.16 (m, 1H), 2.30-2.34 (m, 1H), 3.41-3.52 (m, 2H),
4.06 (s, 3H), 5.08 (dd, J1 = 1.80 Hz, J2 = 10.00 Hz, 1H), 6.84 (d, J = 8.40 Hz, 1H), 7.21 (t, J
= 7.60 Hz, 1H), 7.31-7.41 (m, 4H), 7.53 (d, J = 8.40 Hz, 2H), 7.83 (d, J = 8.45 Hz, 1H), 7.96
13
(d, J = 7.70 Hz, 1H); C NMR (125 MHz, CDCl3):
δ = 22.9, 29.9, 32.8, 76.9, 105.0, 108.6,
110.5, 117.3, 119.2, 119.3, 119.3, 121.8, 123.3, 124.4, 127.9, 131.8, 140.3, 140.8, 141.9,
154.2; IR (neat): υmax = 1247, 1443, 1593, 2855, 2929, 3025 cm-1; HRMS (ESI, Q-ToF) m/z:
calculated for C22H1979BrNO [M+H]+ 392.0649, found: 392.0656.
3,6-Diphenyl-1,2,3,11-tetrahydropyrano[3,2-a]carbazole 13g: Yellow solid; yield = 63%
(33 mg, starting from 100 mg of 8d, starting material recovered = 58 mg); reaction time = 4
13

ACCEPTED MANUSCRIPT
1
days; mp 201-203 °C; Rf = 0.50 (silica gel, 10% EtOAc-petroleum ether); H NMR (400
MHz, CDCl3): δ = 2.23-2.29 (m, 1H), 2.35-2.40 (m, 1H), 2.91-2.96 (m, 1H), 3.03-3.12 (m,
1H), 5.15 (dd, J1 = 2.08 Hz, J2 = 10.08 Hz, 1H), 6.81 (s, 1H), 6.97 (t, J = 7.88 Hz, 1H), 7.25-
13
7.29 (m, 2H), 7.33-7.53 (m, 10H), 7.63 (d, J = 7.15 Hz, 1H), 7.98 (brs, 1H); C NMR (100
MHz, CDCl3):
δ = 20.6, 29.5, 77.8, 102.9, 110.5, 111.6, 114.2, 119.4, 121.7, 123.9, 124.3,
126.2, 127.6, 128.0, 128.5, 128.7, 128.8, 129.3, 136.8, 139.5, 139.8, 141.0, 141.6, 153.6; IR
(neat): υmax = 1274, 1459, 1588, 1618, 2850, 2925, 3057, 3409 cm-1; HRMS (ESI, Q-ToF)
m/z: calculated for C27H22NO [M+H]+ 376.1696, found: 376.1695.
11-Methyl-3,6-diphenyl-1,2,3,11-tetrahydropyrano[3,2-a]carbazole 13h: Brown solid;
yield = 48% (162 mg, starting from 300 mg of 8d, starting material recovered = 36 mg);
reaction time = 3 days; mp 184-185 °C; Rf = 0.65 (silica gel, 10% EtOAc-petroleum ether);
1H NMR (400 MHz, CDCl3): δ = 2.17-2.25 (m, 1H), 2.36-2.41 (m, 1H), 3.51-3.56 (m, 2H),
4.10 (s, 3H), 5.17 (dd, J1 = 1.84 Hz, J2 = 10.00 Hz, 1H), 6.77 (s, 1H), 6.90-6.94 (m, 1H), 7.25
(t, J = 3.88 Hz, 2H), 7.31 (d, J = 3.80 Hz, 2H), 7.34 (d, J = 7.24 Hz, 1H), 7.41 (t, J = 7.12 Hz,
13
2H), 7.45-7.50 (m, 4H), 7.58 (d, J = 6.64 Hz, 2H); C NMR (100 MHz, CDCl3):
δ = 23.3,
30.1, 32.9, 77.1, 104.0, 108.4, 112.1, 114.9, 118.9, 121.5, 123.0, 124.2, 126.2, 127.6, 128.0,
128.5, 128.7, 129.3, 136.9, 140.9, 141.1, 141.8, 142.3, 154.1; IR (neat): υmax = 1266, 1568,
1584, 2854, 2924, 3050 cm-1; HRMS (ESI, Q-ToF) m/z: calculated for C28H24NO [M+H]+
390.1852, found: 390.1851.
3-(4-Fluorophenyl)-11-methyl-6-phenyl-1,2,3,11-tetrahydropyrano[3,2-a]carbazole 13i:
Yellow solid; yield = 68% (40 mg, starting from 100 mg of 8e, starting material recovered =
53 mg); reaction time = 4 days; mp 198-200 °C; Rf = 0.69 (silica gel, 10% EtOAc-petroleum
ether); 1H NMR (400 MHz, CDCl3): δ = 2.13-2.29 (m, 1H), 2.35-2.39 (m, 1H), 3.51-3.55 (m,
2H), 4.10 (s, 3H), 5.15 (d, J = 8.84 Hz, 1H), 6.79 (s, 1H), 6.95-6.99 (m, 1H), 7.14 (t, J = 8.64
13
Hz, 2H), 7.29-7.38 (m, 3H), 7.47-7.56 (m, 5H), 7.62 (d, J = 7.12 Hz, 2H); C NMR (100
MHz, CDCl3):
δ = 23.3, 30.1, 32.9, 76.8, 103.9, 108.4, 112.0, 114.9, 115.4, 115.6, 119.0,
121.4, 122.9, 124.2, 127.6, 127.8, 127.9, 128.5, 129.3, 136.9, 137.5, 137.5, 140.8, 141.1,
142.2, 153.9, 162.6 (d, J = 244.0 Hz); IR (neat): υmax = 1289, 1388, 1467, 1583, 2850, 2923,
3054 cm-1; HRMS (ESI, Q-ToF) m/z: calculated for C28H23FNO [M+H]+ 408.1758, found:
408.1757.
3-(4-Bromophenyl)-6-phenyl-1,2,3,11-tetrahydropyrano[3,2-a]carbazole 13j: White
solid; yield = 63% (149 mg, starting from 200 mg of 8f); reaction time = 3 days; mp 273-274
1
°C; Rf = 0.53 (silica gel, 10% EtOAc-petroleum ether); H NMR (500 MHz, CDCl3): δ =
14

ACCEPTED MANUSCRIPT
2.09-2.12 (m, 1H), 2.25-2.26 (m, 1H), 2.81-2.83 (m, 1H), 2.96-2.98 (m, 1H), 5.02 (d, J = 9.70
Hz, 1H), 6.72 (s, 1H), 6.90 (t, J = 7.40 Hz, 1H), 7.16-7.22 (m, 1H), 7.28-7.31 (m, 3H), 7.36-
13
7.51 (m, 6H), 7.56 (d, J = 7.10 Hz, 2H), 7.85 (brs, 1H); C NMR (125 MHz, CDCl3):
δ =
20.5, 29.4, 77.1, 102.8, 110.5, 111.5, 114.3, 119.5, 121.7, 121.9, 123.8, 124.4, 127.6, 127.9,
128.5, 129.3, 131.8, 136.9, 139.4, 139.8, 140.7, 140.9, 153.3; IR (neat): υmax = 1267, 1369,
1468, 1604, 2853, 2929, 3030, 3417 cm-1; HRMS (ESI, Q-ToF) m/z: calculated for
C27H2179BrNO [M+H]+ 454.0807, found: 454.0809.
3-(4-Bromophenyl)-11-methyl-6-phenyl-1,2,3,11-tetrahydropyrano[3,2-a]carbazole 13k:
White solid; yield = 55% (104 mg, starting from 200 mg of 8f, starting material recovered =
45 mg); reaction time = 5 days; mp 167-169 °C; Rf = 0.66 (silica gel, 10% EtOAc-petroleum
ether); 1H NMR (500 MHz, CDCl3): δ = 2.05-2.19 (m, 1H), 2.37 (d, J = 13.35 Hz, 1H), 3.48-
3.56 (m, 2H), 4.11 (s, 3H), 5.14 (d, J = 9.35 Hz, 1H), 6.75 (s, 1H), 6.91-6.94 (m, 1H), 7.27 (s,
2H), 7.32 (d, J = 3.75 Hz, 2H), 7.37 (d, J = 8.35 Hz, 2H), 7.46-7.58 (m, 6H); 13C NMR (125
MHz, CDCl3):
δ = 23.1, 30.0, 33.0, 76.9, 103.8, 108.4, 112.0, 115.1, 119.0, 121.5, 121.8,
123.0, 124.3, 127.6, 127.9, 128.5, 128.9, 129.3, 131.8, 137.0, 140.8, 141.1, 142.3, 153.8; IR
(neat): υmax = 1468, 1598, 2813, 2924, 3054 cm-1; HRMS (ESI, Q-ToF) m/z: calculated for
C28H2379BrNO [M+H]+ 468.0958, found: 468.0942.
3-([1,1'-Biphenyl]-4-yl)-11-methyl-1,2,3,11-tetrahydropyrano[3,2-a]carbazole 9a: White
solid; yield = 94% (23 mg, starting from 25 mg of 13f); reaction time = 15 h; mp 254-258 °C;
1
Rf = 0.55 (silica gel, 10% EtOAc-petroleum ether); H NMR (400 MHz, CDCl3): δ = 2.00-
2.25 (m, 1H), 2.39-2.43 (m, 1H), 3.52-3.56 (m, 2H), 4.08 (s, 3H), 5.19 (d, J = 9.92 Hz, 1H),
6.78 (s, 1H), 6.89-6.93 (m, 1H), 7.247.34- (m, 3H), 7.42-7.54 (m, 4H), 7.57-7.64 (m, 6H);
13C NMR (100 MHz, CDCl3):
δ = 23.3, 30.0, 32.9, 77.9, 104.0, 108.4, 112.1, 114.9, 119.0,
121.5, 123.0, 124.2, 126.7, 127.3, 127.5, 127.6, 128.5, 128.5, 129.3, 136.9, 140.8, 140.9,
141.0, 141.2, 142.3, 154.1; IR (neat): υmax = 1463, 1562, 2854, 2925, 3055 cm-1; HRMS (ESI,
Q-ToF) m/z: calculated for C28H24NO [M+H]+ 390.1852, found: 390.1855.
4'-(11-Methyl-1,2,3,11-tetrahydropyrano[3,2-a]carbazol-3-yl)-[1,1'-biphenyl]-4-
carbonitrile 9b: White solid; yield = 86% (46 mg, starting from 50 mg of 13f); reaction time
1
= 24 h; mp 170 °C (decomposed); Rf = 0.52 (silica gel, 10% EtOAc-petroleum ether); H
NMR (500 MHz, CDCl3): δ = 2.19-2.24 (m, 1H), 2.38-2.42 (m, 1H), 3.47-3.54 (m, 2H), 4.08
(s, 3H), 5.20 (dd, J1 = 2.00 Hz, J2 = 10.01 Hz, 1H), 6.87 (d, J = 8.45 Hz, 1H), 7.21 (dt, J1 =
0.85 Hz, J2 = 7.10 Hz, 1H), 7.33 (d, J = 8.15 Hz, 1H), 7.39 (dt, J1 = 1.15 Hz, J2 = 8.20 Hz,
1H), 7.59-7.64 (m, 4H), 7.69-7.75 (m, 4H), 7.85 (d, J = 8.45 Hz, 1H), 7.98 (d, J = 7.65 Hz,
15

ACCEPTED MANUSCRIPT
1H); 13C NMR (125 MHz, CDCl3):
δ
= 23.0, 29.9, 32.8, 76.9, 105.0, 108.6, 110.5, 111.1,
117.3, 119.1, 119.2, 119.3, 119.4, 123.3, 124.4, 127.0, 127.6, 127.8, 132.8, 138.8, 140.3,
141.9, 142.4, 145.4, 154.4; IR (neat): υmax = 1247, 1363, 1443, 1466, 1593, 1605, 2225, 2854,
2924, 3054 cm-1; HRMS (ESI, Q-ToF) m/z: calculated for C29H22N2NaO [M+Na]+ 437.1624,
found: 437.1623.
1-(4'-(11-Methyl-1,2,3,11-tetrahydropyrano[3,2-a]carbazol-3-yl)-[1,1'-biphenyl]-4-
yl)ethan-1-one 9c: White solid; yield = 90% (20 mg, starting from 20 mg of 13f); reaction
1
time = 12 h; mp 212-215 °C; Rf = 0.43 (silica gel, 10% EtOAc-petroleum ether); H NMR
(500 MHz, CDCl3): δ = 2.16-2.23 (m, 1H), 2.43-2.48 (m, 1H), 2.65 (s, 3H), 3.52-3.55 (m,
2H), 4.09 (s, 3H), 5.20 (d, J = 9.15 Hz, 1H), 6.87 (d, J = 8.35 Hz, 1H), 7.22 (t, J = 7.20 Hz,
1H), 7.33 (d, J = 8.05 Hz, 1H), 7.59 (t, J = 7.95 Hz, 1H), 7.59 (d, J = 8.07 Hz, 2H), 7.69 (dd,
J1 = 6.20 Hz, J2 = 14.20 Hz, 4H), 7.84 (d, J = 8.35 Hz, 1H), 7.97 (d, J = 7.45 Hz, 1H), 8.04
13
(d, J = 8.15 Hz, 2H); C NMR (125 MHz, CDCl3):
δ = 23.0, 26.8, 29.9, 32.8, 76.9, 105.1,
108.6, 110.6, 117.3, 119.2, 119.3, 119.3, 123.4, 124.4, 126.9, 127.4, 127.6, 129.1, 136.1,
139.6, 140.4, 141.9, 145.6, 154.4, 197.9; IR (neat): υmax = 1259, 1509, 1598, 1706, 2857,
2926, 3069 cm-1; HRMS (ESI, Q-ToF) m/z: calculated for C30H25NNaO2 [M+Na]+ 454.1777,
found: 454.1775.
3-(4'-Fluoro-[1,1'-biphenyl]-4-yl)-11-methyl-6-phenyl-1,2,3,11-tetrahydropyrano[3,2-
a]carbazole 9d: White solid; yield = 82% (21 mg, starting from 25 mg of 13k); reaction time
1
= 15 h; mp 265-266 °C; Rf = 0.57 (silica gel, 10% EtOAc-petroleum ether); H NMR (500
MHz, CDCl3): δ = 2.23-2.29 (m, 1H), 2.43-2.46 (m, 1H), 3.55-3.60 (m, 2H), 4.13 (s, 3H),
5.24 (dd, J1 = 1.55 Hz, J2 = 10.00 Hz, 1H), 6.81 (s, 1H), 6.94-6.98 (m, 1H), 7.14-7.18 (m,
2H), 7.30 (s, 1H), 7.34 (d, J = 3.20 Hz, 2H), 7.47-7.55 (m, 3H), 7.57-7.63 (m, 8H); 13C NMR
(125 MHz, CDCl3):
119.0, 121.5, 123.0, 124.2, 126.7, 127.3, 127.6, 128.5, 128.8, 128.8, 129.3, 136.9, 137.1,
137.1, 140.0, 140.8, 140.9, 141.1, 142.3, 154.0, 162.7 (d, J = 196.0 Hz); IR (neat): υmax
δ = 23.3, 30.0, 32.9, 76.9, 103.9, 108.4, 112.1, 114.9, 115.7, 115.9,
=
1571, 1600, 2861, 2925, 3054 cm-1; HRMS (ESI, Q-ToF) m/z: calculated for C34H27FNO
[M+H]+ 484.2071, found: 484.2076.
Acknowledgements
We are grateful to DST-New Delhi for the financial support. R. A. thanks University Grants
Commission, New Delhi for the award of research fellowship. M. S. thanks IIT Bombay for
financial support. S. K. thanks the Department of Science and Technology for the award of a
J. C. Bose fellowship. We also thank to IRCC (IITB) for financial support.
16

ACCEPTED MANUSCRIPT
Supplementary Information
The copies of 1H and 13C NMR for all the new compounds associated with this article can be
found at http://dx.doi.org/.............
References and Notes
(1)
(a) Burke, M. D.; Schreiber, S. L. Angew. Chem. Int. Ed. 2004, 116, 48; (b) Tejedor,
D.; Gonzalez-Cruz, D.; Santos-Exposito, A.; Marrero-Tellado, J. J.; de Armas, P.;
Garcia-Tellado, F. Chem. Eur. J. 2005, 11, 3502; (c) Tan, D. S. Nat. Chem. Biol.
2005, 1, 74; (d) Kotha, S.; Mandal, K. Tetrahedron Lett. 2004, 45, 1391; (e) Kotha,
S.; Mandal, K.; Tiwari, A.; Mobin, S. M. Chem. Eur. J. 2006, 12, 8024; (f) Liao, Y.;
Hu, Y.; Wu, J.; Zhu, Q.; Donovan, M.; Fathi, R.; Yang, Z. Curr. Med. Chem. 2003,
10, 2285; (g) Kotha, S.; Ali, R.; Chinnam, A. K. Tetrahedron Lett. 2014, 55, 4492; (h)
Kotha, S.; Mandal, K.; Tiwari, A.; Mobin, S. M. Chem. Eur. J. 2006, 12, 8024; (i)
Kotha, S.; Wagule. G. T. J. Org. Chem. 2012, 77, 6314; (j) Kotha, S.; Ali, R.; Tiwari,
A. Synlett 2013, 1921; (k) Kotha, S.; Khedkhar, P. Eur. J. Org. Chem. 2009, 730; (l)
Kotha, S.; Misra, S.; Srinivas, V. Eur. J. Org. Chem. 2012, 4052; (m) Kotha, S.; Ali,
R.; Srinivas, V.; Krishna, N. G. Tetrahedron 2015, 71, 129; (n) Kotha, S.; Goyal, D.;
Chavan, A. S. J. Org. Chem. 2013, 78, 12288; (o) Kotha, S.; Ghosh, A. K. Synthesis.
2004, 558; (p) Kotha, S.; Halder, S.; Lahiri, K. Synthesis 2002, 339; (q) Kotha, S.;
Lahiri, K. Bioorg. Med. Chem. Lett. 2001, 11, 2887.
(2)
(a) Smith, A. B., III; Han, H.; Kim, W. S. Org. Lett. 2011, 13, 3328; (b) Strausberg,
R. L.; Schreiber, S. L. Science 2003, 300, 294; (c) Burke, M. D.; Schreiber, S. L.
Angew Chem. Int. Ed. 2004, 43, 46; (d) Lee, D.; Sello, J. K.; Schreiber, S. L. Org.
Lett. 2000, 5, 709; (e) Lee, D.; Sello, J. K. Schreiber, S. L. J. Am. Chem. Soc. 1999,
121, 10648; (f) Spring, D. R. Org. Biomol. Chem. 2003, 1, 3867; (g) Sore, H. F.;
Blackwell, D. T.; MacDonald, S. J. F.; Spring, D. R. Org. Lett. 2010, 12, 2806; (h)
Ajish, K. R.; Joseph, N.; Rani, M. P.; Raghu, K. G.; Vineetha, V. P.; Radhakrishnan,
K. V. Tetrahedron Lett. 2013, 54, 5682.
(3) (a) Pizzirani, D.; Kaya, T.; Clemons, P. A.; Schreiber, S. L. Org. Lett. 2010, 12, 2822;
(b) Schreiber, S. L. Chem. Bio. Chem. 2009, 10, 26; (c) Schreiber, S. L. Science 2000,
287, 1964.
(4) (a) Kawasaki, T.; Higuchi, K. Nat. Prod. Rep. 2005, 22, 761; (b) Kawasaki, T.; Higuchi,
K. Nat. Prod. Rep. 2007, 24, 843; (c) Hibino, S.; Choshi, T. Nat. Prod. Rep. 2001, 18,
66; (d) Robinson, T. The Biochemistry of Alkaloids, Springer-Verlag, New York, 1981;
17

ACCEPTED MANUSCRIPT
(e) Katritzky, A. R.; Pozharskii, A. F. In Handbook of Heterocyclic Chemistry;
Pergamon: Oxford, 2000; (f) Humphrey, G. R.; Kuethe, J. T. Chem. Rev. 2006, 106,
2875; (g) Heinrich, T.; Bottcher, H. Bioorg. Med. Chem. Lett. 2004, 14, 2681; (h)
Horton, D. A.; Bourne, G. T.; Smythe, M. L. Chem. Rev. 2003, 103, 893; (i) Costantino,
L.; Barlocco, D. Curr. Med. Chem. 2006, 13, 65; (j) Mason, J. S.; Morize, I.; Menard, P.
R.; Cheney, D. L.; Hulme, C.; Labaudiniere, R. F. J. Med. Chem. 1999, 42, 3251; (k)
Patchett, A. A.; Nargund, R. P. Ann. Rep. Med. Chem. 2000, 35, 289; (l) Horton, D. A.;
Bourne, G. T.; Smythe, M. L. Chem. Rev. 2003, 103, 893.
(5) (a) González, J. F.; Ortín, I.; Cuesta, E. D. L.; Menéndez, J. C. Chem. Soc. Rev. 2012, 41,
6902; (b) Samala, S.; Mandadapu, A. K.; Saifuddin, M.; Kundu, B. J. Org. Chem. 2013,
78, 6769; (c) Saifuddin, M.; Samala, S.; Krishna, D. G. V.; Kundu, B. Synthesis 2013,
45, 1553; (d) Agarwal, P. K.; Dathi, M. D.; Saifuddin, M.; Kundu, B. Beilstein J. Org.
Chem. 2012, 8, 1901; (e) Sharma, S. K.; Gupta, S.; Saifuddin, M.; Mandadapu, A. K.;
Agarwal, P. K.; Gauniyal, H. M.; Kundu, B. Tetrahedron Lett. 2011, 52, 65; (f) Sharma,
S. K.; Mandadapu, A. K.; Saifuddin, M.; Gupta, S.; Agarwal, P. K.; Mandwal, A. K.;
Gauniyal, H. M.; Kundu, B. Tetrahedron Lett. 2010, 51, 6022.
(6) (a) Shirota, Y. J. Mater Chem. 2000, 10, 1; (b) Schulten, H. R.; Schnitzer, M. Biol.
Fertil. Soils 1998, 26, 1.
(7) Graebe, C.; Glazer, C. Ber. Dtsch. Chem. Ges. 1872, 5, 12.
(8) (a) Cheng, J.; Kamiya, K.; Kodama, I. Cardiovasc Drug Rev. 2001, 19, 152; (b)
Rosenbaum, D. M.; Cherezov, V.; Hanson, M. A.; Rasmussen, S. G. F.; Thian, F. S.;
Kobilka, T. S.; Choi, H.; Yao, X.; Weis, W. I.; Stevens, R. C.; Kobilka, B. K. Science
2007, 318, 1266.
(9) (a) Hudson, Z. M.; Lu, Z. H.; Wang, S. Adv. Mater 2012, 24, 2922; (b) Kim, D.;
Coropceanu, V.; Bredas, J. L. J. Am. Chem. Soc. 2011, 133, 17895.
(10) Knölker, H.-J.; Reddy, K. R. Chem. Rev. 2002, 102, 4303.
(11) (a) Faul, M. M.; Huff, B. E. Chem. Rev. 2000, 100, 2407; (b) Faulkner, D. J. Nat. Prod.
Rep. 2000, 17, 7; (c) Butler, M. S. Nat. Prod. Rep. 2008, 25, 475; (d) Ferrari, F. D.;
Pasqua, A. E.; Ledgard, A. J.; Marquez, R. Org. Biomol. Chem. 2013, 11, 3469; (e)
Ammann, S. E.; Rice, G. T.; White, M. C. J. Am. Chem. Soc. 2014, 136, 10834; (f) Xin,
Z.; Zhang, Y.; Tao, H.; Xue, J.; Li, Y. Synlett 2011, 1579; (g) Xu, J.-F.; Zhao, H.-J.;
Wang, X.-B.; Li, Z.-R.; Luo, J.; Yang, M.-H.; Yang, L.; Yu, W.-Y.; Yao, H.-Q.; Luo, J.-
18

ACCEPTED MANUSCRIPT
G.; Kong, L.-Y. Org. Lett. 2015, 17, 146; (h) Tambar, U. K.; Kano, T.; Zepernick, J. F.;
Stoltz, B. M. J. Org. Chem. 2006, 71, 8357.
(12) (a) Schmidt, B. Eur. J. Org. Chem. 2003, 816; (b) Rosenberg, S.; Leino, R. Tetrahedron
Lett. 2009, 50, 5305; (c) Steinhuebel, D. P.; Fleming, J. J.; Bois, J. D. Org. Lett. 2002, 4,
293; (d) Pfrengle, F.; Lentz, D.; Reissig, H.-U. Org. Lett. 2009, 11, 5534; (e) Zhao, W.;
Carreira, E. M. Org. Lett. 2005, 7, 1609; (f) Xin, Z.; Zhang, Y.; Tao, H.; Xue, J.; Li, Y.
Synthesis 2011, 1579.
(13) Schmidt, A. W.; Reddy, K. R.; Knölker, H.-J. Chem. Rev. 2012, 112, 3193.
(14) Li, M.; Chen, C.; He, F.; Gu, Y. Adv. Synth. Catal. 2010, 352, 519.
(15) Hoffmann, R. W. Synthesis 2006, 3531.
19

ACCEPTED MANUSCRIPT
Supporting Information
Diversity-oriented approach to natural product inspired pyrano-carbazole derivatives:
Strategic utilization of hetero-Diels‒Alder reaction, Fisher indolization and the Suzuki–
Miyaura cross-coupling reaction
Sambasivarao Kotha,* Rashid Ali and Mohammad Saifuddin
Department of Chemistry, Indian Institute of Technology-Bombay, Powai, Mumbai-400076
India, Phone: +91-22-2576 7160, Fax: +91(22)-2572 7152; E-mail: srk@chem.iitb.ac.in
Table of contents
1H and 13C NMR spectrum of compound 8a
1H and 13C NMR spectrum of compound 8b
1H and 13C NMR spectrum of compound 8c
1H and 13C NMR spectrum of compound 8d
1H and 13C NMR spectrum of compound 8e
1H and 13C NMR spectrum of compound 8f
1H and 13C NMR spectrum of compound 8g
1H and 13C NMR spectrum of compound 8h
1H and 13C NMR spectrum of compound 8i
1H and 13C NMR spectrum of compound 15a
1H and 13C NMR spectrum of compound 15b
1H and 13C NMR spectrum of compound 15c
1H and 13C NMR spectrum of compound 13a
1H and 13C NMR spectrum of compound 13b
1H and 13C NMR spectrum of compound 13c
1H and 13C NMR spectrum of compound 13d
S3
S4
S5
S6
S7
S8
S9
S10
S11
S12
S13
S14
S15
S16
S17
S18
S1

ACCEPTED MANUSCRIPT
1H and 13C NMR spectrum of compound 13e
S19
S20
S21
S22
S23
S24
S25
S26
S27
S28
S29
1H and 13C NMR spectrum of compound 13f
1H and 13C NMR spectrum of compound 13g
1H and 13C NMR spectrum of compound 13h
1H and 13C NMR spectrum of compound 13i
1H and 13C NMR spectrum of compound 13j
1H and 13C NMR spectrum of compound 13k
1H and 13C NMR spectrum of compound 9a
1H and 13C NMR spectrum of compound 9b
1H and 13C NMR spectrum of compound 9c
1H and 13C NMR spectrum of compound 9d
S2

ACCEPTED MANUSCRIPT
S3

ACCEPTED MANUSCRIPT
S4

ACCEPTED MANUSCRIPT
S5

ACCEPTED MANUSCRIPT
S6

ACCEPTED MANUSCRIPT
O
O
F
8e
O
O
F
8e
S7

ACCEPTED MANUSCRIPT
S8

ACCEPTED MANUSCRIPT
O
O
8g
O
O
8g
S9

ACCEPTED MANUSCRIPT
S10