Intramolecular Acylation of Unactivated Pyridines or Arenes via Multiple C-H Functionalizations: Synthesis of All Four Azafluorenones and Fluorenones

Article abstract of DOI:10.1021/acs.joc.6b02065

An unprecedented intramolecular acylation of unactivated pyridines via multiple C(sp³/sp²)-H functionalizations of a methyl, hydroxymethyl, or aldehyde group has been developed providing a general access to all four azafluorenones. The application of this protocol is further demonstrated to the synthesis of azafluorenone related fused nitrogen heterocycles and fluorenones. In addition, design and synthesis of a novel fluorene based organic emitter for potential use in organic light emitting devices (OLEDs) is also reported.

Full text of DOI:10.1021/acs.joc.6b02065

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Article
Intramolecular Acylation of Unactivated Pyridines
or Arenes via Multiple C-H Functionalizations:
Synthesis of all Four Azafluorenones and Fluorenones
Joydev K. Laha, Krupal P. Jethava, Sagarkumar Patel, and Ketul V. Patel
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.6b02065 • Publication Date (Web): 30 Nov 2016
Downloaded from http://pubs.acs.org on December 1, 2016
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Intramolecular Acylation of Unactivated Pyridines or Arenes via Multiple C−H
Functionalizations: Synthesis of all Four Azafluorenones and Fluorenones
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Joydev K. Laha,* Krupal P. Jethava, Sagarkumar Patel, and Ketul V. Patel
Department of Pharmaceutical Technology (Process Chemistry)
National Institute of Pharmaceutical Education and Research
S. A. S. Nagar, Punjab 160062, India
E-mail: jlaha@niper.ac.in
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ABSTRACT
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Abstract: An unprecedented intramolecular acylation of unactivated pyridines via multiple
C(sp3/sp2)
−
H functionalizations of a methyl, hydroxymethyl, or aldehyde group has been developed
providing a general access to all four azafluorenones. The application of this protocol is further
demonstrated to the synthesis of azafluorenone related fused nitrogen heterocycles and fluorenones. In
addition, design and synthesis of a novel fluorene based organic emitter for potential use in organic light
emitting devices (OLEDs) is also reported.
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INTRODUCTION
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Azafluorenones and related heterocycles are privileged fused heterocycles ubiquitously
found in natural products and pharmaceuticals showcasing diverse pharmacological and
biological activities.1 In addition, single fluorene molecule based fluorescent organic
emissive materials are available as electron-transporting host material capable of being
fabricated into the efficient organic light emitting devices (OLED).2 Despite their diverse
applications, the chemistry of azafluorenones has been least investigated. Among the various
synthetic approaches reported for the synthesis of azafluorenones3 and fluorenones,4
intramolecular acylation reactions have been identified as a major contributor to the synthesis
of these heterocycles. The classical Friedel-Crafts acylation approach to the synthesis of
azafluorenones (and fluorenones) include intramolecular acylation in 2-arylpyridines or
biaryls containing an acyl source appropriately placed in on one of the two rings (Scheme
1).3a-c,4c Remarkably, Glorius5 and Studer6a independently reported intramolecular acylation
of arenes using an aldehyde group as acylating agent yielding fluorenones in good to
excellent yields.
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Scheme 1. Synthetic Approaches to Azafluorenones or Fluorenones from Biaryls
O
O
H
R
H
oxidant5,6
Lewis acid
Ar
X
X
X = N or C
R= -COOCH3,3a,3c
-COOH,3a
if, A = N (Azafluorenone)
C (fluorenone)
X = C
-CONEt2,3b
-COCl4c
T his
work
T ransition metal f ree!
H
R
X = N or C
Ar
X
R = CH3, CH2OH, CHO
Despite significant advances realized in azafluorenone synthesis largely using classical
chemistry, a general strategy which could lead to the synthesis of all four azafluorenones via
multiple C−H functionalizations has not been realized. Previously, we reported the synthesis
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of 4-azafluorenones via intramolecular acylation of arenes using a methyl or hydroxymethyl
group as latent acylating agent present on pyridine ring.7 However, other azafluorenones
were inaccessible by this protocol. Inspired by our recent success, and based on previous
experiences on multiple C−H functionalizations in the synthesis of biaryl sultams,8
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heterobiaryl sultams,9 carbazoles and α-carbolines,10we surmised that an intramolecular
acylation of unactivated pyridines in arylpyridines containing a latent carbonyl source while
an ambitious objective would be a distinct, straightforward gateway to the general synthesis
of azafluorenones. Perhaps most importantly, acylation of pyridines using aryl aldehydes or
methylarenes as acylating agents is an unsolved problem and remains unexplored, although
intermolecular acylation of activated pyridines, such as pyridine-N-oxides via
decarboxylative acylations has been achieved.11 However, they suffer from using additional
steps including preparation of pyridine N-oxides and deoxygenation of N-oxides. Therefore,
intramolecular acylation of unactivated pyridines, especially under transition-metal-free
conditions, to the general synthesis of azafluorenones while attractive would be an elusive
problem. Herein, we unveil a first report on intramolecular acylation of unactivated pyridines
at 2, 3, or 4-positions via successive C-H functionalizations of a methyl, hydroxymethyl, or
aldehyde group present in arylpyridines. The optimized condition in our study is quite
resourceful warranting broad applications to the synthesis of all four azafluorenones,
fluorenones, and related heterocycles. A key feature of this work includes demonstration, for
the first time, of an intramolecular acylation of unactivated pyridines via multiple
C(sp3/sp2)−H bond functionalizations and subsequent preparation of all four azafluorenones
that are otherwise accessible by classical acylation with difficulty. Based on a novel synthetic
design, a single fluorene molecule coupled with an azafluorenone was also prepared for
potential use in OLEDs.
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RESULTS AND DISCUSSION
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Our initial investigation was largely focused on finding a condition that could effect
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intramolecular acylation in 2-arylpyridine via C−H functionalizations of a hydroxymethyl
group. We started our optimization study with a model substrate 2-arylpyridine 1 containing
a hydroxymethyl group on the phenyl ring. The reaction of 1 in the presence of 8 equiv t-
BuOOH in DCE at 100 °C for 24 h gave 4-azafluorenone 2 in 42% yield (Table 1, entry1).
Distinct from our previous report,7 intramolecular acylation of pyridine at the 3-position
using a hydroxymethyl group as acyl surrogate via multiple C−H functionalizations yielded
4-azafluorenone 2. The yield of 2 was improved by lowering the stoichiometric ratios of t-
BuOOH to 4 equiv, which led to the isolation of 2 in 60% yield (entry 2). In addition to t-
BuOOH, the presence of a catalytic amount (5 mol%) of TBAI, known to act as an initiator
for radical reactions,12 proved effective providing 2 in 76% isolated yield (entry 3). The
higher catalytic loading of TBAI resulted in a reaction of a complex mixture of products
(entry 4). Interestingly, a catalytic amount of KI or I2 completely diminishes the formation of
product (entry 5). Further decrease of molar ratios of t-BuOOH or temperature did not offer
any improvement in the formation of 2 (entries 6−7). The substrate remains unreacted in both
protic and aprotic polar solvents (entry 8). The presence of TEMPO could largely suppress
the formation of 2 revealing the formation of a radical intermediate in the reaction (entry 9).
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Table 1. Optimization Study of Intramolecular Acylationa
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OH
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O
H
t-BuOOH
additive
solvent
time, temp.
N
N
1
2
TBAI
(mol %)
temp
(ºC)
100
100
100
yield of 2b
t-BuOOH
entry
(equiv)
(%)
1
2
3
8
4
4
-
42
-
60
5
76
Complex
4
4
10
100
mixture
5c
6
4
2
4
4
4
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5
100
100
80
0
38
45
0
7
8d
9e
100
100
0
aSubstrate (0.2 mmol), t-BuOOH (2 to 8 equiv), TBAI (5 to 10 mol%), DCE (0.5 mL), 100 C, 24 h.
bisolated yield. cKI or I2 as an additive. dMeOH/DMF/DMSO as a solvent. eTEMPO (10 equiv) added as
a radical quencher.
°
The optimized conditions were utilized to investigate the substrate scope not only for 4-
azafluorenones, but also for the synthesis of other azafluorenones (Scheme 2). The
preparation of starting arylpyridines 3−17 was achieved from the commercially available
materials. When 2-arylpyridine 3 was exposed to the standard conditions, intramolecular
acylation occurred at the 3-position yielding 4-azafluorenone 18 in 45% yield (entry 1). The
incomplete conversion of 3 to the product 18 could largely account for the observed
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moderate yield. Under the optimized conditions, each of 3-arylpyridine 4 and 5 bearing a
hydroxymethyl or aldehyde group on arene is intramolecularly acylated at the 2- and 4-
positions yielding a 1:1 mixture of 1-azafluorenone (19) and 3-azafluorenone (20) in
comparable combined yields (entries 2-3). More importantly, 3-arylpyridine 6 with a methyl
group on arene ring also underwent intramolecular cyclization to give a 1:1 mixture of 19
and 20 in a combined 62% yield (entry 4). The difficulty of C-H functionalizations of a
methyl group compared to a hydroxymethyl or aldehyde group could apparently explain the
somewhat reduced yield. Evidently, 3-arylpyridine 7 worked eventfully under the optimized
conditions, wherein a methyl group remains unaffected (entry 5). When two methyl groups,
each on pyridine and phenyl rings are present as in 3-arylpyridine 8, a competitive C-H
functionalization is anticipated between the two methyl groups. However, the methyl group
on phenyl ring undergoes C-H functionalizations, and the cyclization occurs regioselectively
on the pyridine ring along with a minor product 22 (entry 6). The compound 22 could form
by the intramolecular trapping of acyl radical with the hydroxymethyl group, generated in
situ from the methyl group. Remarkably, an excellent regiocontrol (1-: 3-azafluorenone = 9:1
ratio) to the formation of 3-azafluorenone 19 was observed when 5 was subjected to the
optimized conditions in the absence of TBAI (entry 7). The reasonable explanation for this
excellent regioselectivity requires further investigation. However, a moderate regiocontrol
(3:1) was observed in the formation of azafluorenones 23 and 24 (entry 8). In addition,
reverse regiocontrol (1:3) was observed with trifluoromethyl group at 2-position gave
azafluorenones 25 and 26 (entry 9). Nonetheless, strong electron withdrawing group at 2-
position in 11 formed only one regioisomer 28 in 87% yield (entry 10). The presence of a
chloro substituent at the 2-position of 3-arylpyridine 12 gave 3-azafluorenone 29 in 90%
yield under the optimized conditions (entry 11). Similarly, 2-ethoxy-3-arylpyridine 13 also
reacted under the optimized conditions resulting in the formation of 3-azafluorenone 30 in
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70% yield (entry 12). Attempted preparation of 2-azafluorenone 31 from 4-arylpyridine 14
under the optimized conditions was not successful. However, a tert-butyl ester 32 was
isolated in this reaction. This suggests that an acyl radical was generated from 14, which
upon subsequent trapping with t-butanol gave 32 (entry 13). The poor reactivity at the C-3
position in the 4-arylpyridine ring towards acyl radical was largely circumvented by the
presence of an electron-withdrawing group at 2-position. Thus, 4-arylpyridine 15 under the
optimized conditions yielded 2-azafluorenone 33 regioselectively in 53% isolated yield
(entry 14). This observation indicated that 4-arylpyridine 15 undergoes regioselective
cyclization at the more electron-deficient C-3 position. Similarly, 4-arylpyridine 16
undergoes cyclization at 2-position afforded azafluorenone 34 in 42% yield (entry 15). Under
the optimized conditions, 2-arylpyridine 17 was less viable for cyclization and gave 4-
azafluorenone (2) only in trace amount (entry 16). Central to this investigation was an
unprecedented intramolecular acylation of unactivated pyridines at 2, 3, and 4-positions
occurred under transition-metal-free conditions via multiple C-H functionalizations. The
intramolecular acylation of pyridines reported herein is clearly distinct from our previous
report and the classical acylation approaches currently available in the literature.
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Scheme 2. Scope of Azafluorenone Synthesis
H
X
N
O
t-BuOOH (4 equiv)
TBAI (5 mol%)
O
t
BuO
N
DCE (0.5 mL)
100 °C, 6-30 h
N
N
3-17
,
O
X= CH3, CH2OH, CHO
2, 18-21, 23-31, 33-34
O
32
22
Product
Yield (%)a
Yield (%)a
Entry
Substrate
O
Time (h)
Product
Entry
1
Time (h)
24
Substrate
OH
O
N
O
9b
F3C
+
45
N
N
N
6
F3C
F3C
74 (1:3)
O
N
N
10
25
26
H3C
N
18
H3C
3
O
O
OH
O
O
N
N
10b
O2N
+
N
N
N
6
82 (1:1)
O2N
O2N
87 (0:1)
24
2
3
+
N
11
27
28
O
20
20
19
19
4
O
O
O
11b
90
12
85 (1:1)
+
12
30
N
N
Cl 12
Cl 29
5
O
O
H3C
4
12b
13b
14b
15b
16
62 (1:1)
+
19
20
70
12
N
N
N
6
OEt
13
OEt
30
O
O
O
N
O
5b
N
70
12
24
0 [88]
32
6
+
N
CH3
CH3 21
7
14
31
H3C
O
N
O
45 [20]
F
F
22
6
21
+
+
24
53
42
N
N
CH3
8
15
33
O
O
7b
88 (9:1)
78 (3:1)
19
20
12
Cl
Cl
N
5
24
N
O
N
16
O
34
8b
MeO
+
N
O
H3C
N
MeO
MeO
12
30
O
<5
9
24
23
N
N
2
17
aisolated yields of products.breaction without TBAI, DCE (0.2 mL).
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The scope of aryl quinoline, aryl isoquinoline, aryl pyrimidine and bipyridine as substrates
was also examined (Scheme 3). Under the standard conditions, 3-arylquinoline 35,
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underwent regioselective intramolecular acylation at the 4-position affording 39 in 90%
yield. However, aryl isoquinoline 36 failed to undergo intramolecular acylation on the
pyridine ring to give compound 40, Instead, an intramolecular acylation on the arene ring
afforded 41 in 93% yield. The aryl pyrimidine 37 was also found useful for cyclization
forming 42 in 88% yield. We also prepared a bipyridine compound 38, which upon attempted
cyclization under the standard reaction condition did not give the cyclized product 43.
Nevertheless, our protocol is quite resourceful for the synthesis of azafluorenone related
compounds.
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Scheme 3. Synthesis of Azafluorenone Related Compounds
A
O
t-BuOOH (4 equiv)
X
Y
Y
N
X
DCE (0.5 mL)
100 °C, 6-24 h
N
35-38
X = C, N
Y = C, N
A= CHO, CH3
39, 40, 42, 43
Entry
1
Substrate
O
Product
O
Time
Yield(%)
90
6
N
N
39
35
2
6
0 [93]
O
O
O
N
N
N
40
41
36
O
3
4
O
8
88
0
N
N
Cl
Cl
N
N
37
42
24
H3C
O
N
N
N
38
N
43
The application of our protocol was further extended to the synthesis of fluorenones with a
methyl or hydroxymethyl group as the acylating agent (Scheme 4). To our delight,
intramolecular acylation of 2-phenylbenzylalcohol 44 in the presence of 2 equiv. t-BuOOH
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and 1 mol% TBAI in DCE at 90 °C gave fluorenone 52 in 70% yield. Various other 2-
arylbenzylalcohols 45-49 with an ortho, meta, or para-substituent on the aryl ring reacted
eventfully affording good to excellent yields (43−72%) of fluorenones 53-57. Interestingly, a
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substrate 48 containing both -CH2OH and -CH3 functional groups when exposed to the
optimized conditions, the intramolecular acylation occurred involving -CH2OH group
affording 4-methyl fluorenone (56) in 65% yield (entry 5). While an unsymmetrically
substituted biaryl could give two different regioisomers, the biaryl 49 regioselectively
cyclized at electron-deficient 2-position of aryl rings yielding 57 in 43% yield (entry 6).
Furthermore, a substrate 50 with one methyl group cyclized to give fluorenone 52, while
substrate 51 containing two methyl groups, each on a phenyl ring, intramolecular acylation
occurred involving one methyl group (entry 7-8).
Scheme 4. Synthesis of Fluorenones from 2-Arylbenzylalcohols and 2-Methylbiaryls
aisolated yields of products. bt-BuOOH (8 equiv), TBAI (10 mol%), DCE (0.5 mL), 100 ºC, 24 h.
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To understand the mechanism for intramolecular acylation, we performed some control
experiments (Scheme 5). As stated in optimization study, use of a radical quencher TEMPO
(10 equiv) largely inhibits the formation of the desired product, suggesting a free radical
pathway is involved in this reaction (Eq 1). Reaction of substrate 6 and TBHP (4 equiv) in
DCE in the presence of AIBN (10 mol%) at 40 °C did not give any product. However, the
corresponding intramolecular cyclization products 19 and 20 were obtained at elevated
temperature (100 °C) albeit in low yield (23%) (Eq 2). An experiment with compound 6 was
performed under the standard condition in an inert atmosphere. Compound 6 did not yield
any cyclized product. This observation reveals that oxygen is indeed required as the O source
or as an oxidant (Eq 3). Under the standard condition, however, at a lower temperature (at 40
°C), compound 6 did not give any cyclized compound (Eq 4). Interestingly, we also observed
that substrate 2-methylbiaryl 50 formed fluorenone 52 along with a minor product 52a
containing an aldehyde group (Eq 5).
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Scheme 5. Control Experiments
Based on these observations and our previous experiences,7 we propose a plausible
mechanism for this intramolecular acylation as depicted in Scheme 6. As the reaction is
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radical in nature, two different pathways could be operative. In Path A, TBAI could promote
radical generation12 from TBHP, which upon H· abstraction from substrate A could form
benzyl radical. Subsequent oxidation could give a hydroxymethyl containing intermediate B.
The oxidation of hydroxymethyl could afford intermediate C with an aldehyde functionality.
Subsequently, a C-centered radical could easily be formed from C, which could undergo
substitution on the pyridine ring to give heterohexadienyl radical intermediate D. The H·
abstraction either by TBHP or iodine species would deliver azafluorenone. In Path B, the C-
centered radical could undergo direct substitution13 on the pyridine ring to form intermediate
E, which upon proton abstraction by excess TBHP or iodine species could deliver
azafluorene F. Oxidation of F could give azafluorenone. Based on our experiments, Path A is
more likely in this reaction. However, occurrence of Path B or concurrence of both path ways
is not ruled out.
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60
Scheme 6. Plausible Mechanism
t-BuOO + H2O
t-BuOOH + OH
(I)
1/2 I
I
t-BuOOH
t-BuO
+
OH
(II)
[O]
(I)/(II)
N
(I)/(II)
O
N
A
A
A
HO
t-BuOOH
or t-BuOH
t-BuOOH or
t-BuOH
N
N
N
B
H
(I)/(II) or
(1/2 I + OH)
E
Path B
Path A
(I)/(II)
X
O
O
H
OO
(I)/(II) or
(I + H2O)
N
N
N
F
O
C
H
D
X = C
(I)/(II)
[O]
(I)/(II)
N
N
tBu
O
52a
(Isolated)
G
O
t-BuO
N
32 (Isolated)
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The design of single fluorene molecule based fluorescent organic emissive materials for
potential use in organic light emitting devices (OLEDs) is one of the emerging technologies
in the field of organic electronics.14 The currently available single fluorene emitters suffer
from many desirable properties, namely, a specific emission, high charge-carrier mobility,
good thermal and electrochemical stability, high photoluminescence quantum yield, and
facile chemical modification.15 A chromophoric group incorporated into the fluorene
backbone could lead to extensive designing of new OLEDs. A 9,9-dialkylfluorene backbone
tethered with azafluorenone has never been explored in OLED preparation despite their
potential electron injection properties (Scheme 7). To demonstrate a translational application
of our newly developed protocol for the synthesis of azafluorenones, we prepared a fluorene
based butterfly shaped molecule 59 tethered with 3-azafluorenone 29. When 3-azafluorenone
29 was reacted with 9,9-dioctyl-9H-fluorene-2,7-diboronic acid bis(pinacol) ester (58) under
Suzuki cross-coupling reaction conditions, a novel fluorene-azafluorenone coupled product
59 was obtained. The absorption spectra displayed λmax at 326 nm while the
photoluminescence spectra of 59 displayed λemission = 515 nm in toluene and 498 nm in
cyclohexane, and λexcitation = 445 nm in toluene and 442 nm in cyclohexane (see the
Supporting Information). The detailed photophysical properties of 59 will be described
elsewhere. This preliminary study could open a new avenue for the preparation of single
fluorene based fluorescent organic materials for potential use in OLEDs.
10
11
12
13
14
15
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17
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20
21
22
23
24
25
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40
41
42
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44
45
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49
50
51
52
53
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59
60
Scheme 7. Synthesis of Fluorene Based Organic Fluorescent Tethered with 3-Azafluorenone
Back-bone
O
C8H17C8H17
O
O
C8H17C8H17
Bpin
Bpin
+
N
N
N
X
Commercially
available
X = Halogen
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Pd(OAc)2 (2 mol%)
5
6
7
8
S-Phos (4 mol%)
O
K2CO3 (2.5 equiv)
C8H17 C8H17
O
O
O
29
C8H17C8H17
+
B
B
MeCN (1.5 mL)
Water (1 mL)
N2, 100 oC, 6 h
O
O
N
N
58
9
(40%)
59
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59
60
In conclusion, we have developed a general strategy to the synthesis of all four
azafluorenones. Unlike classical approaches reported for acylations of pyridines, the current
study describes intramolecular acylation of unactivated pyridines using a methyl,
hydroxymethyl, or aldehyde groups as acylating agent under transition-metal-free conditions.
The protocol is extended to the synthesis of fluorenones and related fused heterocycles. Also,
we have designed and synthesized a single fluorene molecule based organic materials
incorporated with azafluorenone.
EXPERIMENTAL SECTION
General Methods
Unless noted otherwise, all reagents and solvents were purchased from commercial sources and used as
received. All reactions were performed in a screw-capped vial. The proton (1H) and carbon (13C) NMR
spectra were obtained using a 400 MHz using Me4Si as an internal standard and are reported in δ units.
Coupling constants (J values) are reported in Hz. Column chromatography was performed on silica gel
(60−120#, 100−200#). High resolution mass spectra (HRMS) were obtained using the electron spray
ionization (ESI) technique and as TOF mass analyzer. IR spectra are reported in cm−1 units. All melting
points were taken using a melting point apparatus equipped with a calibrated thermometer and are
uncorrected. 2-Bromo-3-methyl pyridine, arylboronic acid derivatives, t-butyl hydroperoxide (TBHP,
5.5 M in decane), and tetra-butyl ammonium iodide (TBAI), Azobisisobutyronitrile (AIBN) and
solvents were purchased and used as received.
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General procedure for the Suzuki coupling of bromoheteroarenes with 2-formyl benzeneboronic acid
6
7
(for compounds 5, 7, 9−16, 35-37)
8
9
Following a literature procedure,16 a solution of bromoheteroarene (e.g. bromopyridine or 3-
bromoquinoline or 4-bromoisoquinolineor 5-bromo 2-chloro pyrimidine) (1 equiv, 0.5 mmol), 2-formyl
benzeneboronic acid (1.2 equiv, 0.6 mmol), Pd(PPh3)4 (5 mol %) and sodium carbonate (2 equiv, 1
mmol) in THF:Water (4:1, 3 mL), was heated at 70 oC for 12 h. THF was evaporated in vacuuo. Water
(20 mL) was added, and the reaction mixture was extracted with ethyl acetate (2×10 mL). The organic
layers were combined, dried (Na2SO4), concentrated under reduced pressure, and purified by column
chromatography (100−200# silica, ethyl acetate/hexane = 3:7) to give the desired product.
10
11
12
13
14
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16
17
18
19
20
21
22
23
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25
26
27
28
29
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31
32
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39
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41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
General procedure for the synthesis of compounds 1, 3 and 4
Following a literature procedure,17 a suspension of 2-bromobenzyl alcohol (0.7 mmol),
bispinacolato diboron (1.1 equiv, 0.77 mmol), 1,1'-Bis(diphenylphosphino)ferrocene dichloride
[Pd(dppf)Cl2, 3 mol %], and KOAc (3 equiv, 1.5 mmol) in anhydrous DMF (2 mL) was purged twice
with nitrogen balloon and heated at 80 oC for 9 h. After complete consumption of 2-bromobenzylalcohol
(monitored by TLC), the reaction mixture was added to the ice cooled water (10 mL) and extracted with
ethyl acetate (2×10 mL) and water (2×20 mL), dried (Na2SO4), and concentrated in vacuuo. The crude
was directly used for the next step without purification. A stirred solution of the crude product,
bromopyridine (0.5 mmol), Pd(PPh3)4 (5 mol %) and sodium carbonate (2 equiv, 1 mmol) in THF:Water
o
(4:1, 3 mL) was stirred at 70 C for 12 h. THF was evaporated in vacuuo. Water (20 mL) was added,
and the reaction mixture was extracted with ethyl acetate (2×10 mL). The organic layers were
combined, dried (Na2SO4), concentrated under reduced pressure, and purified by column
chromatography (100−200# silica, ethyl acetate /hexane = 2:8) to give the desired product.
General procedure for the synthesis of (o-tolyl)pyridines (compounds 6, 8, 17)
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Following a literature procedure,16 a solution of bromopyridine (1 equiv, 0.5 mmol), 2-methyl
benzeneboronic acid (1.2 equiv, 0.6 mmol), Pd(PPh3)4 (5 mol %) and sodium carbonate (2 equiv, 1
mmol) in THF:Water (4:1, 3 mL), was heated at 70 oC for 12 h. THF was evaporated in vacuuo. Water
(20 mL) was added, and the reaction mixture was extracted with ethyl acetate (2×10 mL). The organic
layers were combined, dried (Na2SO4), concentrated under reduced pressure, and purified by column
chromatography (100-200# silica, ethyl acetate/hexane = 1:9) to give the desired product.
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11
12
13
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51
52
53
54
55
56
57
58
59
60
General procedure for the Suzuki coupling of 2-bromobenzyl alcohols with benzeneboronic acids
(compounds 44, 45, 47-49)
Following a literature procedure,16 a solution of any 2-bromobenzylalcohol (1 equiv, 0.5 mmol),
benzene boronic acid (1.2 equiv, 0.6 mmol), Pd(PPh3)4 (5 mol %) and sodium carbonate (2 equiv, 1
mmol) in THF:Water (4:1, 3 mL), was heated at 70 oC for 12 h. THF was evaporated in vacuuo. Water
(20 mL) was added, and the reaction mixture was extracted with ethyl acetate (2×10 mL). The organic
layers were combined, dried (Na2SO4), concentrated under reduced pressure, and purified by column
chromatography (100−200# silica, ethyl acetate/hexane = 2:8) to give the desired product.
Procedure for the synthesis of 46
Following a literature procedure,17 a suspension of 4-chloro bromobenzene (0.7 mmol),
bispinacolato diboron (1.1 equiv, 0.77 mmol), 1,1'-Bis(diphenylphosphino)ferrocene dichloride
(Pd(dppf)Cl2, 3 mol %), and KOAc (3 equiv, 1.5 mmol) in anhydrous DMF (2 mL) was heated at 80 oC
for 5 h under nitrogen atmosphere. After complete consumption of 4-chloro bromobenzene (monitored
by TLC), the reaction mixture was added to the ice cooled water (10 mL) and extracted with ethyl
acetate (2×10 mL) and water (2×20 mL), dried (Na2SO4), and concentrated in vacuuo. The crude was
directly used for the next step without purification. A stirred solution of the crude product, 2-
bromobenzyl alcohol (0.5 mmol), Pd(PPh3)4 (5 mol %) and sodium carbonate (2 equiv, 1 mmol) in
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9
o
THF:Water (4:1, 3 mL) was stirred at 70 C for 12 h. THF was evaporated in vacuuo. Water (20 mL)
was added, and the reaction mixture was extracted with ethyl acetate (2×10 mL). The organic layers
were combined, dried (Na2SO4), concentrated under reduced pressure, and purified by column
chromatography (100−200# silica, ethyl acetate /hexane = 1:9) to give the desired product.
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56
57
58
59
60
General procedure for the synthesis of 2-methyl biaryls (50, 51)
Following a literature procedure,16 a solution of 2-bromotoluene (1 equiv, 0.5 mmol), benzene
boronic acid (1.2 equiv, 0.6 mmol), Pd(PPh3)4 (5 mol %) and sodium carbonate (2 equiv, 1 mmol) in
o
THF:Water (4:1, 3 mL), was heated at 70 C for 12 h. THF was evaporated in vacuuo. Water (20 mL)
was added, and the reaction mixture was extracted with ethyl acetate (2×10 mL). The organic layers
were combined, dried (Na2SO4), concentrated under reduced pressure, and purified by column
chromatography (100−200# silica, ethyl acetate/hexane = 0.1:99.9) to give the desired product.
General procedure for the azafluorenones (2, 18, 19−20, 21) [from the substrates containing -CH2OH
and CH3]
In an oven-dried screw capped vial equipped with a magnetic stir bar, a solution of (2-(pyridin-
3-yl)phenyl)methanol or 3-(o-tolyl)pyridine (0.15 mmol), TBHP (4 equiv), TBAI (5 mol%) and DCE
(0.5 mL) was heated at 100 oC for 12-30 h. Silica gel was added to the reaction mixture and the excess
solvent was evaporated. The silica gel mixed with the crude product was loaded on the column, which
upon chromatography (ethyl acetate /hexane = 1:9 − 3:7) afforded desired product.
General procedure for the azafluorenones (19−20, 21, 23-26, 28-34) or azafluorenone related
compounds (39, 41, 42) [from the substrates containing –CHO group]
In an oven-dried screw capped vial equipped with a magnetic stir bar, a solution of 2-(2-pyridin-
o
3-yl)benzaldehyde (0.15 mmol), TBHP (4 equiv) and DCE (0.2 mL) was heated at 100 C for 6−24 h.
Silica gel was added to the reaction mixture and the excess solvent was evaporated. The silica gel mixed
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with the crude product was loaded on the column, which upon chromatography (ethyl acetate /hexane =
1:9 − 3:7) afforded desired product.
7
8
9
General procedure for the synthesis of fluorenones (52−57) [from the substrates containing –CH2OH]
10
11
12
13
14
15
16
17
18
19
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22
23
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60
In an oven-dried screw capped vial equipped with a magnetic stir bar, a solution of 2−arylbenzyl
o
alcohol (0.2 mmol), TBHP (2 equiv), TBAI (1 mol%) and DCE (0.5 mL) was heated at 90 C for 16 h.
Silica gel was added to the reaction mixture and the excess solvent was evaporated. The silica gel mixed
with the crude product was loaded on the column, which upon chromatography (ethyl acetate /hexane =
0.5:9.5 − 1:9) afforded desired product.
General procedure for the synthesis of fluorenones (52, 56) [from the substrates containing –CH2OH]
In an oven-dried screw capped vial equipped with a magnetic stir bar, a solution of 2-
o
methylbiaryls (0.2 mmol), TBHP (8 equiv), TBAI (10 mol%) and DCE (0.5 mL) was heated at 100 C
for 24 h. Silica gel was added to the reaction mixture and the excess solvent was evaporated. The silica
gel mixed with the crude product was loaded on the column, which upon chromatography (ethyl acetate
/hexane = 0.5:9.5 − 1:9) afforded desired product.
(2-(Pyridin-2-yl)phenyl)methanol (1)
Pale yellow oil; Yield 65% (60 mg); 1H NMR (400 MHz, CDCl3): δ 8.64 (ddd, J = 5.0,1.8, 1.0 Hz, 1H),
7.89−7.83 (m, 1H), 7.63 (td, J = 8.0, 1.0 Hz, 1H), 7.57−7.54 (m, 1H), 7.52−7.48 (m, 1H), 7.45−7.41 (m,
2H), 7.33 (ddd, J = 7.5, 5.0, 1.0 Hz, 1H), 4.48 (s, 2H); 13C NMR (100 MHz, CDCl3): δ 159.4, 148.2,
140.4, 140.0, 137.8, 131.3, 130.3, 129.5, 128.4, 124.0, 122.4, 64.8; HRMS: calcd for C12H12NO [M+H]+
186.0919, found 186.0920; IR (neat): 3304, 3062, 2925 cm−1.
5H-Indeno[1,2-b]pyridin-5-one (2)7
The spectral data were consistent with previous report.7
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(2-(6-Methylpyridin-2-yl)phenyl)methanol (3)
6
7
8
9
Pale yellow oil; Yield 55% (55 mg); 1H NMR (400 MHz, CDCl3): δ 7.73−7.79 (m, 1H), 7.54−7.56 (m,
1H), 7.49−7.51 (m, 1H), 7.41−7.46 (m, 3H), 7.20 (d, J = 8.0 Hz, 1H), 4.48 (s, 2H), 2.64 (s, 3H); 13C
NMR (100 MHz, CDCl3): δ 158.6, 157.0, 140.3, 137.7, 131.1, 130.1, 129.2, 128.1, 121.9, 120.9, 64.7,
24.9; HRMS: calcd for C13H14NO [M+H]+ 200.1075, found 200.1079; IR (neat): 3327, 3053, 2974 cm−1.
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14
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16
17
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19
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59
60
(2-(Pyridin-3-yl)phenyl)methanol (4)
Pale yellow oil; Yield 70% (65 mg); 1H NMR (400 MHz, CDCl3): δ 8.51−8.58 (m, 2H), 7.76 (d, J = 7.8
13
Hz, 1H), 7.62 (d, J = 7.5 Hz, 1H), 7.31−7.48 (m, 3H), 7.25 (d, J = 7.5 Hz, 1H), 4.57 (s, 2H); C NMR
(100 MHz, CDCl3): δ 149.5, 148.1, 138.6, 137.4, 136.9, 136.6, 130.1, 129.0, 128.6, 127.8, 123.2, 62.5;
HRMS: calcd for C12H12NO [M+H]+ 186.0919, found 186.0925; IR (neat): 3310, 3048, 2933 cm−1.
2-(Pyridin-3-yl)benzaldehyde (5)
o
Off-white solid; Yield 73% (67 mg); mp 65-67 C;1H NMR (400 MHz, CDCl3): δ 9.99 (s, 1H),
13
8.67−8.71 (m, 2H), 8.06−8.10 (m, 1H), 7.71−7.74 (m, 2H), 7.56−7.59 (m, 1H), 7.42−7.45 (m, 2H); C
NMR (100 MHz, CDCl3): δ 191.3, 150.1, 149.3, 141.8, 137.2, 133.9, 133.8, 133.7, 131.0, 128.7, 128.5,
123.2; HRMS-ESI m/z calcd for C12H10NO [M+H]+ 184.0762, found 184.0769; IR (KBr): 3067, 2825,
1692 cm−1.
3-(o-Tolyl)pyridine (6)18
Colorless oil; 1H NMR (400 MHz, CDCl3): δ 8.60−8.63 (m, 2H) 7.66−7.70 (m, 1H) 7.38 (ddd, J = 7.78,
4.89, 0.88 Hz, 1H), 7.28−7.35 (m, 3H), 7.22−7.26 (m, 1H), 2.30 (s, 3H).
2-(4-Methylpyridin-3-yl)benzaldehyde (7)
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1
Pale yellow oil; Yield 85% (83 mg); H NMR (400 MHz, CDCl3): δ 9.79 (s, 1H), 8.56 (d, J = 5.0 Hz,
1H), 8.44 (s, 1H), 8.07 (d, J = 7.8 Hz, 1H), 7.70 (t, J = 7.5 Hz, 1H), 7.60 (t, J = 7.5 Hz, 1H), 7.32 (d, J =
7.5 Hz, 1H), 7.27 (d, J = 5.0 Hz, 1H), 2.15 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 191.2, 149.8, 149.3,
145.6, 141.0, 134.2, 134.1, 134.0, 131.1, 128.7, 128.3, 124.9, 19.8; HRMS: calcd for C13H12NO [M+H]+
198.0919, found 198.0910; IR (neat): 3072, 2829, 1695 cm−1.
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59
60
4-Methyl-3-(o-tolyl)pyridine (8)
1
Pale yellow oil; Yield 60% (55 mg); H NMR (400 MHz, CDCl3): δ 8.48 (d, J = 5.0 Hz, 1H), 8.35 (s,
1H), 7.25–7.33 (m, 3H), 7.21 (d, J = 5.0 Hz, 1H), 7.11 (d, J = 7.3 Hz, 1H), 2.1 (s, 3H), 2.0 (s, 3H);13C
NMR (100 MHz, CDCl3): δ 149.7, 148.4, 145.2, 137.5, 137.4, 136.2, 130.1, 129.54, 128.0, 125.8,
124.8, 19.8, 19.3; HRMS: calcd for C13H14N [M+H]+ 184.1126, found 184.1121; IR (neat): 3029, 2941
cm−1.
2-(6-Methoxypyridin-3-yl)benzaldehyde (9)
Light yellow oil; Yield 92% (98 mg); 1H NMR (400 MHz, CDCl3): δ 10.02 (s, 1H), 8.19 (dd, J = 2.6,
0.6 Hz, 1H), 8.03−8.07 (m, 1H), 7.67 (td, J = 7.5, 1.5 Hz, 1H), 7.63 (dd, J = 8.5, 2.5 Hz, 1H), 7.50−7.56
(m, 1H), 7.40−7.45 (m, 1H), 6.88 (dd, J = 8.53, 0.75 Hz, 1H), 4.02 (s, 3H); 13C NMR (100 MHz,
CDCl3): δ 191.7, 164.1, 147.3, 142.1, 140.0, 133.9, 133.8, 131.0, 128.3, 128.1, 126.6, 110.7, 53.7;
HRMS: calcd for C13H12NO2 [M+H]+ 214.0868, found 214.0870; IR (neat): 3062, 2947, 1693 cm−1.
2-(6-(trifluoromethyl)pyridin-3-yl)benzaldehyde (10)
Off-white solid: Yield 82% (102 mg); mp 100−101 oC; 1H NMR (400 MHz, CDCl3): δ 10.00 (d, J = 0.5
Hz, 1H), 8.78 (d, J = 2.0 Hz, 1H), 8.10 (dd, J = 7.7, 1.2 Hz, 1H), 7.92 (ddt, J = 8.0, 1.4, 0.6 Hz, 1H),
7.83 (dd, J = 8.0, 0.7 Hz, 1H), 7.73−7.78 (m, 1H), 7.64−7.70 (m, 1H), 7.42−7.48 (m, 1H); 13C NMR
(100 MHz, CDCl3): δ 190.8, 150.2, 147.8 (J = 34 Hz), 139.8, 138.4, 137.1, 134.1, 133.8, 131.1, 129.8,
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129.5, 122.9 (J = 273 Hz), 120.1 (J = 3 Hz); HRMS: calcd for C13H9F3NO [M+H]+ 252.0636, found
6
7
252.0643; IR (KBr): 2920, 2077, 1729 cm−1.
8
9
2-(6-Nitropyridin-3-yl)benzaldehyde (11)
10
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12
13
14
15
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17
18
19
20
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Light yellow solid; Yield 90% (103 mg): mp 122-124 oC; 1H NMR (400 MHz , CDCl3): δ 10.01 (s, 1H),
8.66 (dd, J = 2.3, 0.8 Hz, 1H), 8.39 (dd, J = 8.3, 0.5 Hz, 1H), 8.09 (dd, J = 7.7, 1.4 Hz, 1H), 8.06 (dd, J
= 8.3, 2.3 Hz, 1H), 7.78 (dt, J = 7.5, 1.5 Hz, 1H), 7.72 (dt, J = 7.5, 1.0 Hz, 1H), 7.45 (dd, J = 7.4, 1.1
Hz, 1H); 13C NMR (100 MHz, CDCl3): δ 190.6, 156.0, 148.9. 140.6, 140.5, 138.2, 134.2, 133.7, 131.2,
130.0, 117.5; HRMS: calcd for C12H9N2O3 [M+H]+ 229.0613, found 229.0609; IR (KBr): 3063, 2887,
1695 cm−1.
2-(2-Chloropyridin-3-yl)benzaldehyde (12)
1
Yellow solid; Yield 83% (90 mg); mp 176-178oC; H NMR (400 MHz, CDCl3): δ 9.87 (s, 1H), 8.51
(dd, J = 4.8, 2.0 Hz, 1H), 8.06 (dd, J = 7.8, 1.0 Hz, 1H), 7.66−7.76 (m, 2H), 7.58−7.66 (m, 1H), 7.40
13
(dd, J = 7.5, 5.0 Hz, 1H), 7.35 (dd, J = 7.7, 0.9 Hz, 1H); C NMR (100 MHz, CDCl3): δ 190.7, 150.3,
149.5, 139.9, 139.9, 133.9, 133.7, 131.0, 129.3, 129.0, 122.4; HRMS: calcd for C12H9ClNO [M+H]+
218.0372, found 218.0379; IR (KBr): 2924, 2085, 1735, 772 cm−1.
2-(2-Ethoxypyridin-3-yl)benzaldehyde (13)
1
Brown oil; Yield 80% (91 mg); H NMR (400 MHz, CDCl3): δ 9.93 (d, J = 0.7 Hz, 1H), 7.99 (dd, J =
7.9, 1.3 Hz, 1H), 7.60−7.66 (m, 1H), 7.47−7.53 (m, 1H), 7.41−7.46 (m, 2H), 7.36−7.40 (m, 1H), 6.36 (t,
J = 6.7 Hz, 1H), 4.08 (q, J = 7.1 Hz, 2H), 1.41 (t, J = 7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3): δ
191.6, 161.4, 139.6, 139.5, 137.6, 134.6, 133.6, 131.0, 130.0, 128.3, 127.9, 106.1, 45.7, 14.6; HRMS:
calcd for C14H13NO2 [M]+ 227.0946, found 227.0950; IR (neat): 2929, 2081, 1734 cm−1.
2-(Pyridin-4-yl)benzaldehyde (14)
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9
Light yellow solid; Yield 81% (74 mg); mp 79-81oC;1H NMR (400 MHz, CDCl3): δ 9.96 (s, 1H), 8.71
(d, J = 5.8 Hz, 2H), 8.04 (dd, J = 7.8, 1.3 Hz, 1H), 7.63−7.70 (m, 2H), 7.40−7.42 (m, 1H), 7.30−7.32
(m, 2H); 13C NMR (100 MHz, CDCl3): δ 191.2, 149.8, 133.9, 133.5, 132.1, 130.4, 129.1, 128.6, 128.4,
124.8; HRMS: calcd for C12H10NO [M+H]+ 184.0762, found 184.0775; IR (KBr): 3080, 2832, 1696
cm−1.
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2-(2-Fluoropyridin-4-yl)benzaldehyde (15)
Light yellow solid; Yield 62% (62 mg); mp 104-106 oC; 1H NMR (400 MHz, CDCl3): δ 9.99 (d, J = 0.8
Hz, 1H), 8.07 (dd, J = 4.5 Hz, 1H), 7.74−7.78 (m, 1H), 7.77−7.64 (m, 2H), 7.40−7.44 (m, 1H), 7.30 (d,
J = 5.5 Hz, 2H); 13C NMR (100 MHz, CDCl3): δ 190.8, 164.2, 161.6 (J = 261 Hz), 142.0, 134.0, 133.5,
130.4, 129.4, 129.3, 126.5, 117.7 (J = 21 Hz), 113.6; HRMS: calcd for C12H9FNO [M+H]+ 202.0668,
found 202.0670; IR (KBr): 3066, 2933, 1692 cm−1.
2-(2-Chloropyridin-4-yl)benzaldehyde (16)
o
Off-white solid; Yield 87% (94 mg); mp 100-102 C; 1H NMR (400 MHz, CDCl3): δ 10.00 (d, J = 0.7
Hz, 1H), 8.51 (dd, J = 5.0, 0.7 Hz, 1H), 8.05−8.11 (m, 1H), 7.70−7.76 (m, 1H), 7.60−7.67 (m, 1H),
7.38−7.45 (m, 2H), 7.26 (dd, J = 5.1, 1.6 Hz, 1H); 13C NMR (100 MHz, CDCl3): δ 190.6, 151.9, 149.5,
149.2, 141.0, 134.0, 133.4, 130.0, 129.6, 129.0, 124.9, 123.5; HRMS: calcd for C12H9ClNO [M + H]+
218.0373, found 218.0380; IR (KBr): 3060, 2895, 1698 cm−1.
2-(o-Tolyl)pyridine (17)19
1
Colorless oil; H NMR (400 MHz, CDCl3): δ 8.66−8.72 (m, 1H), 7.74 (td, J = 7.7, 1.9 Hz, 1H),
7.37−7.42 (m, 2H), 7.21−7.31 (m, 4H), 2.36 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 160.0, 149.2,
140.4, 136.2, 135.8, 130.7, 129.6, 128.3, 125.9, 124.1, 121.7, 20.3.
2-Methyl-5H-indeno[1,2-b]pyridin-5-one (18)
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o
1
Light yellow solid; Yield 45% (13 mg); mp 142−143 C; H NMR (400 MHz, CDCl3): δ 8.71(dd, J =
6
7
8.0, 0.6 Hz, 1H), 8.38 (dd, J = 7.9, 0.8 Hz, 1H), 7.88 (td, J = 8.0, 1.3 Hz, 1H), 7.68 (td, J = 8.4, 1.0 Hz,
8
9
13
1H), 7.56 (d, J = 8.4 Hz, 1H), 7.28–7.30 (m, 1H), 2.68 (s, 3H); C NMR (100 MHz, CDCl3): δ 196.4,
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160.5, 155.0, 146.0, 135.8, 135.0, 130.3, 130.0, 125.0, 124.7, 123.3, 122.4, 24.22; HRMS: calcd for
C13H10NO [M+H]+ 196.0762, found 196.0772; IR (KBr): 2924, 1734 cm−1.
9H-Indeno[2,1-b]pyridin-9-one (19)20
1
Yellow solid; H NMR (400 MHz, CDCl3):
δ 8.60 (dd, J = 4.8, 1.3 Hz, 1H), 7.86 (dd, J = 7.5, 1.3 Hz,
1H), 7.75 (d, J = 7.5 Hz, 1H), 7.55−7.57 (m, 2H), 7.31–7.38 (m, 2H).
9H-Indeno[2,1-c]pyridin-9-one (20)20
1
Yellow solid; H NMR (400 MHz, CDCl3):
δ 8.92 (s, 1H), 8.22 (dd, J = 4.5 Hz, 1H), 7.75 (d, J = 7.4
Hz, 1H), 7.66 (d, J = 7.4 Hz, 1H), 7.58 (td, J = 7.5 Hz, 1H), 7.52 (t, J = 4.6 Hz, 1H), 7.38 (t, J = 7.4 Hz,
1H).
4-Methyl-9H-indeno[2,1-b]pyridin-9-one (21)
Yellow solid; Yield 70% (20 mg); mp 150−152 oC; 1H NMR (400 MHz, CDCl3):
δ 8.45 (d, J = 5.0 Hz,
1H), 7.77 (d, J = 7.4 Hz, 1H), 7.64 (d, J = 7.5 Hz, 1H), 7.57 (td, J = 7.5, 1.2 Hz, 1H), 7.39 (td, J = 7.4,
13
0.8 Hz, 1H), 7.14 (d, J = 5.0, 0.6 Hz, 1H), 2.66 (s, 3H); C NMR (100 MHz, CDCl3): δ191.9, 151.8,
148.8, 141.6, 141.2, 137.6, 134.4, 131.2, 128.4, 128.3, 123.8, 122.8, 18.7; HRMS: calcd for C13H10NO
[M+H]+ 196.0762, found 196.0764; IR (KBr): 3065, 2927, 1730 cm−1.
Benzo[5,6]oxepino[4,3-c]pyridin-7(5H)-one (22)
Pale yellow solid; Yield 20% (8 mg); mp 132−134 oC; 1H NMR (400 MHz, CDCl3):
δ 8.94 (s, 1H), 8.72
(d, J = 5.0 Hz, 1H), 8.04−8.09 (m, 1H), 7.72−7.79 (m, 1H), 7.64−7.70 (m, 1H), 7.59−7.64 (m, 1H), 7.42
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(d, J = 5.0 Hz, 1H), 5.03 (s, 2H); 13C NMR (100 MHz, CDCl3):
δ 169.3, 149.9, 149.0, 142.5, 134.3,
5
6
7
8
9
133.8, 133.1, 132.7, 130.8, 129.5, 128.4, 122.4, 67.7; HRMS: calcd for C13H10NO2 [M+H]+ 212.0712,
found 212.0719; IR (KBr): 3043, 2912, 1745 cm−1.
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3-Methoxy-5H-indeno[2,1-b]pyridin-5-one (23)
o
Yellow solid; Yield 62% (19 mg); mp 134-136 C; 1H NMR (400 MHz, CDCl3): δ 7.76 (d, J = 8.5 Hz,
1H), 7.65 (dd, J = 7.2, 0.5 Hz, 1H), 7.48 (td, J = 7.5, 1.0 Hz, 1H), 7.38 (d, J = 7.2 Hz, 1H), 7.24−7.30
13
(m, 1H), 6.84 (d, J = 8.2 Hz, 1H); C NMR (100 MHz, CDCl3): δ 192.9, 165.9, 150.6, 142.0, 135.3,
134.9, 131.9, 130.6, 128.6, 124.6, 119.8, 115.6, 54.3; HRMS: calcd for C13H10NO2 [M + H]+ 212.0712,
found 212.0710; IR (KBr): 2922, 2857, 1728 cm−1.
2-Methoxy-9H-indeno[1,2-c]pyridin-9-one (24)
Light yellow solid; Yield 16% (5 mg); mp 158-160 C; 1H NMR (400 MHz, CDCl3): δ 8.42 (s, 1H),
o
8.29 (s, 1H), 8.00 (d, J = 8.0 Hz, 1H) 7.84 (td, J = 7.6, 1.5 Hz, 1H), 7.55−7.61 (m, 1H), 6.84 (d, J = 8.5
Hz, 1H); 13C NMR (100 MHz, CDCl3): δ 194.7, 164.1, 155.4, 135.1, 134.7, 134.3, 130.8, 128.2, 121.2,
120.1, 108.7, 105.9, 54.4; HRMS: calcd for C13H10NO2 [M + H]+ 212.0712, found 212.0715; IR (KBr):
2922, 2857, 1728 cm−1.
2-(Trifluoromethyl)-5H-indeno[1,2-b]pyridin-5-one (25)
Yellow solid; Yield 19% (7 mg); mp 165−166 oC; 1H NMR (400 MHz, CDCl3):
δ 8.05 (dd, J = 8.0, 0.5
Hz, 1H), 7.82 (dt, J = 7.4, 0.9 Hz, 1H), 7.77 (d, J = 7.7 Hz, 1H), 7.62−7.69 (m, 2H), 7.49 (ddd, J = 7.4,
13
6.2, 2.3 Hz, 1H); C NMR (100 MHz, CDCl3):
δ 190.7, 153.4, 148.6 (J = 35 Hz), 142.2, 136.1, 132.8,
131.2, 128.8, 125.3, 124.3 (J = 3 Hz), 124.2, 122.6 (J = 274 Hz), 122.0; HRMS: calcd for C13H7F3NO
[M+H]+ 250.0480, found 250.0476; IR (KBr): 3052, 2917, 1735 cm−1.
3-(Trifluoromethyl)-5H-indeno[1,2-c]pyridin-5-one (26)
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Yellow solid; Yield 55% (21 mg); mp 153−155 oC; 1H NMR (400 MHz, CDCl3):
δ 9.00 (s, 1H), 7.89 (s,
6
7
8
9
1H), 7.81 (d, J = 7.5 Hz, 1H), 7.75 (d, J = 7.5 Hz, 1H), 7.66 (t, J = 7.4 Hz, 1H), 7.51−7.46 (m, 1H); 13C
NMR (100 MHz, CDCl3): 191.2, 150.0, 145.2 (J = 36 Hz), 142.1, 141.7, 140.5, 136.0, 133.6, 131.0,
δ
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125.8, 122.5 (J = 273 Hz), 122.0, 114.6; HRMS: calcd for C13H7F3NO [M+H]+ 250.0480, found
250.0490; IR (KBr): 3055, 2910, 1735 cm−1.
3-Nitro-5H-indeno[1,2-c]pyridin-5-one (28)
Yellow solid; Yield 87% (29 mg); mp 208-210 oC: 1H NMR (400 MHz, CDCl3): δ 8.79 (d, J = 0.8 Hz,
1H), 8.35 (d, J = 1.0 Hz, 1H), 7.76−7.81 (m, 1H), 7.74 (d, J = 7.5 Hz, 1H), 7.59−7.66 (m, 1H),
7.43−7.49
(m,
1H);
13C
NMR
(100
MHz,
CDCl3):
δ
189.5, 144.3, 143.3, 140.7, 140.5, 136.3, 134.5, 131.7, 126.1,122.7, 112.7; HRMS: calcd for C12H7N2O3
[M + H]+ 227.0457, found 227.0454; IR (KBr): 3043, 2925, 1725 cm−1.
1-Chloro-5H-indeno[1,2-c]pyridin-5-one (29)
1
Yellow solid; Yield 90% (29 mg); mp 181−182 oC; H NMR (400 MHz, CDCl3):
δ
8.48 (d, J = 4.5 Hz,
1H), 8.19 (d, J = 7.5 Hz, 1H), 7.78 (d, J = 7.2 Hz, 1H), 7.63 (td, J = 7.6, 1.2 Hz, 1H) 7.51 (d, J = 4.5 Hz,
1H), 7.44−7.45 (m, 1H); 13C NMR (100 MHz, CDCl3):
191.6, 151.3, 145.6, 143.5, 142.0, 135.9,
δ
133.2, 130.3, 130.1, 125.3, 124.3, 116.5; HRMS: calcd for C12H7ClNO [M+H]+ 216.0216, found
216.0227; IR (KBr): 3067, 2920, 1726, 1262, 681 cm−1.
1-Ethoxy-5H-indeno[1,2-c]pyridin-5-one (30)
Yellow solid; Yield 70% (24 mg); mp 148−150 oC; 1H NMR (400 MHz, CDCl3):
δ 8.01−8.05 (m, 1H),
7.73 (td, J = 7.5, 1.2 Hz, 1H), 7.67 (td, J = 7.4, 1.1 Hz, 1H), 7.27−7.30 (m, 1H), 6.70 (d, J = 9.7 Hz,
1H), 6.52 (d, J = 9.7 Hz, 1H), 3.83−4.02 (m, 2H), 1.17 (t, J = 7.1 Hz, 3H); 13C NMR (100 MHz,
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CDCl3):
δ
168.8, 166.9, 162.8, 146.0, 140.1, 135.2, 131.2, 128.0, 125.2, 124.8, 121.1, 35.8, 12.9;
5
6
7
HRMS: calcd for C14H12NO2 [M+H]+ 226.0868, found 226.0880; IR (KBr): 3055, 2933, 1730 cm−1.
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tert-Butyl 2-(pyridin-4-yl)benzoate (32)
Off-white solid, Yield 88% (34 mg); mp 98−99 oC;1H NMR (400 MHz, CDCl3):
2H), 7.75 (d, J = 7.7 Hz, 1H), 7.54 (t, J = 7.5 Hz, 1H), 7.44 (t, J = 7.5 Hz, 1H), 7.29 (d, J = 7.3 Hz, 1H),
7.22 (d, J = 6.0 Hz, 2H) 1.0 (s, 9H); 13C NMR (100 MHz, CDCl3):
192.8, 165.7, 149.7, 148.5, 139.5,
δ 8.57 (d, J = 5.8 Hz,
δ
132.1, 130.3, 130.2, 128.6, 128.0, 123.4, 83.7, 25.9; HRMS: calcd for C16H18NO2 [M+H]+ 256.1338,
found 256.1348; IR (KBr): 3021, 2926, 1755, 1262 cm−1.
1-Fluoro-9H-indeno[2,1-c]pyridin-9-one (33)
Light yellow solid; Yield 53% (15 mg); mp 159−161 oC; 1H NMR (400 MHz, CDCl3):
Hz, 1H), 7.79 (dd, J = 7.8, 1.1 Hz, 1H), 7.68 (td, J = 7.6, 1.3 Hz, 1H), 7.52 (td, J = 7.7, 1.2 Hz, 1H),
7.32 (dd, J = 7.7, 0.9 Hz, 1H), 7.13 (dd, J = 5.7, 1.0 Hz, 1H); 13C NMR (100 MHz, CDCl3):
196.7,
δ 8.54 (d, J = 5.8
δ
164.0 (J = 260 Hz), 161.9, 148.0, 141.1, 133.8, 131.5, 129.0, 127.4, 125.3, 116.8, 113.7, 100.5; HRMS:
calcd for C12H7FNO [M+H]+ 200.0512, found 200.0518; IR (KBr): 3067, 2930, 1725, 1260 cm−1.
1-Chloro-9H-indeno[2,1-c]pyridin-9-one (34)
o
1
Light yellow solid; Yield 42% (13 mg); mp 212−214 C; H NMR (400 MHz, CDCl3): δ 8.52 (dt, J =
7.9, 0.6 Hz, 1H), 8.38 (d, J = 5.2 Hz, 1H), 8.21 (d, J = 8.0 Hz, 1H), 7.94−8.00 (m, 1H), 7.90 (d, J = 5.2
Hz, 1H), 7.78−7.84 (m, 1H); 13C NMR (100 MHz, CDCl3): δ 192.8, 158.9, 143.8, 135.5, 131.7, 130.9,
128.8, 128.1, 127.6, 125.6, 122.9, 115.6; HRMS: calcd for C12H7ClNO [M + H]+ 216.0216, found
216.0214; IR (KBr): 3053, 2910, 1733 cm−1.
2-(Quinolin-3-yl)benzaldehyde (35)
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9
Off-white solid; Yield 85% (99 mg); mp 70−72 oC; 1H NMR (400 MHz, CDCl3): δ 10.06 (s, 1H), 9.00
(d, J = 2.2 Hz, 1H), 8.21 (d, J = 9.0 Hz, 1H), 8.17 (d, J = 2.0 Hz, 1H), 8.13 (dd, J = 7.7, 1.0 Hz, 1H),
7.88−7.94 (m, 1H), 7.82 (ddd, J = 8.4, 6.9, 1.5 Hz, 1H), 7.73−7.79 (m, 1H), 7.60−7.69 (m, 2H),
7.53−7.59 (m, 1H); 13C NMR (100 MHz, CDCl3): δ 191.4, 150.9, 147.5, 141.9, 136.7, 134.1, 134.0,
131.4, 130.9, 130.2, 129.4, 128.7, 128.0, 127.6, 127.3; HRMS: calcd for C16H12NO [M + H]+ 234.0919,
found 234.0912; IR (KBr): 3066, 2960, 2873, 1723, 1695 cm−1.
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2-(Isoquinolin-4-yl)benzaldehyde (36)
Pale yellow oil; Yield 90% (104 mg); 1H NMR (400 MHz, CDCl3): δ 9.69 (s, 1H), 9.36 (s, 1H), 8.50 (s,
1H), 8.16 (dt, J = 7.7, 0.7 Hz, 1H), 8.08−8.13 (m, 1H), 7.73−7.80 (m, 1H), 7.65−7.70 (m, 3H),
7.50−7.54 (m, 1H), 7.46−7.50 (m, 1H); 13C NMR (100 MHz, CDCl3): δ 191.3, 153.1, 143.5, 140.2,
135.3, 135.0, 134.9, 134.0, 132.0, 131.4, 131.0, 129.0, 128.1, 127.9, 127.7, 124.5; HRMS: calcd for
C16H12NO [M + H]+ 234.0919, found 234.0910; IR (neat): 2926, 2873, 1725, 1694 cm−1.
2-(2-Chloropyrimidin-5-yl)benzaldehyde (37)
o
1
Off-white solid; Yield 88% (96 mg); mp 131−133 C; H NMR (400 MHz, CDCl3): δ 10.04 (s, 1H),
8.66 (s, 2H), 8.07 (dd, J = 7.7, 1.4 Hz, 1H), 7.77 (dt, J = 7.5, 1.6 Hz, 1H), 7.71 (dt, J = 7.5, 1.3 Hz, 1H),
7.40 (dd, J = 7.5, 1.3 Hz, 1H); 13C NMR (100 MHz, CDCl3): δ 190.6, 160.9, 159.0, 135.4, 134.2, 133.7,
131.9, 131.4, 131.1, 129.9; HRMS: calcd for C11H8ClN2O [M + H]+ 219.0325, found 219.0322; IR
(KBr): 3068, 2894, 1698 cm−1.
3-Methyl-2,3'-bipyridine (38)
A solution of 2-bromo 3-methylpyridine (1 equiv, 0.5 mmol), 3-pyridylboronic acid (1.2 equiv, 0.6
mmol), Pd2(dba)3 (1 mol %), PCy3 (2.4 mol %) and potassium phosphate (1.7 equiv, 0.85 mmol) in
o
dioxane:water (4:1, 3 mL), was heated at 100 C for 18 h. Then, water (20 mL) was added, and the
reaction mixture was extracted with ethyl acetate (2×10 mL). The organic layers were combined, dried
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The Journal of Organic Chemistry
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(Na2SO4), concentrated under reduced pressure, and purified by column chromatography (100-200#
silica, ethyl acetate/hexane = 1:1) to give the desired product. Pale yellow oil; Yield 70% (60 mg); 1H
NMR (400 MHz, CDCl3): δ 8.76−8.84 (m, 1H), 8.66 (dd, J = 4.7, 1.5 Hz, 1H), 8.57 (d, J = 4.5 Hz, 1H),
7.90 (dt, J = 7.7, 2.0 Hz, 1H), 7.62−7.66 (m, 1H), 7.42 (ddd, J = 7.8, 4.8, 0.8 Hz, 1H), 7.25 (dd, J = 7.7,
4.7 Hz, 1H), 2.40 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 155.5, 149.9, 149.0, 147.4, 138.8, 136.5,
136.2, 131.3, 123.2, 122.8, 19.9; HRMS: calcd for C11H10N2 [M]+ 170.0844, found 170.0848; IR (neat):
3044, 2954 cm−1.
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11H-Indeno[1,2-c]quinolin-11-one (39)
o
Yellow solid; Yield 90% (31 mg); mp 198−200 C;1H NMR (400 MHz, CDCl3): δ 9.23 (s, 1H), 8.80
(dq, J = 8.2, 0.7 Hz, 1H), 8.09 (dt, J = 8.7, 0.7 Hz, 1H), 7.69−7.73 (m, 1H), 7.66−7.69 (m, 1H),
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7.62−7.66 (m, 2H), 7.53 (td, J = 7.4, 1.1 Hz, 1H), 7.35 (td, J = 7.4, 1.0 Hz, 1H); C NMR (100 MHz,
CDCl3): δ 195.1, 150.4, 143.4, 142.7, 137.5, 135.1, 133.4, 133.3, 130.0, 129.8, 129.7, 129.7, 125.1,
124.2, 123.3, 120.8; HRMS: calcd for C16H10NO [M + H]+ 232.0762, found 232.0757; IR (KBr): 3047,
2924, 1711 cm−1.
7H-Dibenzo[de,h]isoquinolin-7-one (41)
Yellow solid; Yield 93% (32 mg); mp 218−220 oC: 1H NMR (400 MHz, CDCl3): δ 9.49 (s, 1H), 9.40 (s,
1H), 8.87−8.94 (m, 1H), 8.54 (d, J = 8.0 Hz, 1H), 8.39 (d, J = 8.0 Hz, 1H), 8.42 (d, J = 8.0 Hz, 1H),
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7.94 (t, J = 7.7 Hz, 1H), 7.78−7.85 (m, 1H), 7.64 (t, J = 7.5 Hz, 1H); C NMR (100 MHz, CDCl3): δ
193.0, 153.9, 146.1, 142.1, 136.8, 134.9, 132.5, 132.1, 131.0, 130.9, 129.7, 129.5, 129.3, 124.3, 123.9,
123.6; HRMS: calcd for C16H10NO [M + H]+ 232.0762, found 232.0754; IR (KBr): 2925, 2853, 1722
cm−1.
2-Chloro-9H-indeno[2,1-d]pyrimidin-9-one (42)
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