Copper-Catalyzed One-Pot Cross-Dehydrogenative Thienannulation: Chemoselective Access to Naphtho[2,1-b]thiophene-4,5-diones and Subsequent Transformation to Benzo[a]thieno[3,2-c]phenazines

Article abstract of DOI:10.1021/acs.joc.7b03092

A facile, cost-effective, and highly efficient copper-catalyzed, TEMPO-mediated straightforward synthesis of 2,3-disubstituted naphtho[2,1-b]thiophene-4,5-diones has been achieved via cross-dehydrogenative thienannulation. The reaction proceeded via in situ generated naphthalene-1,2-diones by dearomatization of β-naphthols, followed by oxidative heteroannulation with α-enolic dithioesters chemoselectively in an open flask. Further, the naphtho[2,1-b]thiophene-4,5-diones undergo l-proline-catalyzed cross-dehydrative coupling with ortho-phenylenediamine enabling pentacyclic benzo[a]thieno[3,2-c]phenazines in good yields under solvent-free conditions. A mechanistic rationale for this cascade reaction sequence is well supported by the control experiments.

Full text of DOI:10.1021/acs.joc.7b03092

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Article
Copper-Catalyzed One-Pot Cross-Dehydrogenative Thienannulation:
Chemoselective Access to Naphtho[2,1-b]thiophene-4,5-diones and
Subsequent Transformation to Benzo[a]thieno[3,2-c]phenazines
Gaurav Shukla, Abhijeet Srivastava, Dhananjay Yadav, and Maya Shankar Singh
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.7b03092 • Publication Date (Web): 18 Jan 2018
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Copper-Catalyzed One-Pot Cross-Dehydrogenative Thienannulation: Chemoselective Access
to Naphtho[2,1-b]thiophene-4,5-diones and Subsequent Transformation to Benzo[a]thieno[3,2-
c]phenazines
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Gaurav Shukla†, Abhijeet Srivastava†, Dhananjay Yadav, and Maya Shankar Singh*
Department of Chemistry, Institute of Science, Banaras Hindu University, Varanasi 221005, India
ABSTRACT: A facile, cost-effective and highly efficient copper-catalyzed, TEMPO-mediated
straightforward synthesis of 2,3-disubstituted naphtho[2,1-b]thiophene-4,5-diones has been achieved
via Cross-Dehydrogenative Thienannulation (CDT). The reaction proceeded via in situ generated
naphthalene-1,2-diones by dearomatization of β-naphthols, followed by oxidative heteroannulation
with -enolic dithioesters chemoselectively in an open-flask. Further, the naphtho[2,1-b]thiophene-
4,5-diones undergo L-Proline-catalyzed cross-dehydrative coupling with ortho-phenylenediamine
enabling pentacyclic benzo[a]thieno[3,2-c]phenazines in good yields under solvent-free conditions.
A mechanistic rationale for this cascade reaction sequence is well supported by the control
experiments.
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INTRODUCTION
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Polycyclic molecules are important skeletal units that are widely distributed in a number of natural
products and biologically active compounds.1 Sulfur and its compounds have been used extensively
for centuries and are important to our daily lives. In particular, fused sulfur heterocycles are key
structural motifs of many active pharmaceutical ingredients and material science.2 Among them,
naphtho fused thiophenes such as naphtho[2,1-b]thiophene-4,5-diones, naphtho[1,2-b]thiophene-4,5-
diones and naphtho[2,3-b]thiophene-4,9-diones are notable due to their massive applications in
various fields. Some of their derivatives show antitumor, antibacterial or antimicrobial activities, and
high efficacy toward the cell lines that were highly resistant to treatment with doxorubicin such as
MDA-MB435 (melanoma), IGROV (ovarian) and SF-295 (glioblastoma) human cell lines.3
Moreover, naphthothiophene derivatives possess unique semi-conducting properties that not only
could be used in solar cells, but also exploited in the preparation of organic nanotubes. Some of them
have been utilized for the preparation of dyes, which are further employed in dye-sensitized solar
cells.4 Hence, significant interest has been directed toward the development of efficient and concise
methods for the synthesis of naphtho-fused thiophene derivatives.
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Literature reports5 for the construction of naphtho[1,2-b]thiophene-4,5-diones and naphtho[2,3-
b]thiophene-4,9-diones involve C–H activation of thiophene derivatives employing different metallic
reagents followed by oxidation of corresponding naphthothiophenes. Yoshida and co-workers6a
reported the synthesis of 1,2-naphthoquinone fused thiophene derivatives via oxidative cyclization of
Folin's reagent or sodium 1,2-naphthoquinone-4-sulfonate with diaryl disulfide in the presence of
o
nickel salt at 80 C. Snieckus and coworkers6b disclosed the synthesis of 1,2-naphthoquinone fused
thiophene by intramolecular oxidative coupling of suitably substituted thiophene derivative (Scheme
1a and 1b). However, the reported strategies suffer from significant limitations such as poor yields,
lack of generality and pre-functionalization of starting materials. The direct methods for the synthesis
of naphtho[2,1-b]thiophene-4,5-diones are rather limited. Therefore, it is still challenging and highly
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desirable to explore operationally simple, efficient and widely applicable general approach for the
construction of structurally diverse naphtho-fused thiophene derivatives.
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To the best of our knowledge, no report is known to date on the synthesis of naphtho[2,1-
b]thiophene-4,5-diones utilizing -enolic dithioesters (EDTEs). With this in mind, we envisioned the
viability of annulation between readily available and inexpensive β-naphthols and -enolic
dithioesters for the direct construction of naphtho[2,1-b]thiophene-4,5-dione scaffolds. With the aim
of triggering annulation, we performed different experiments employing β-naphthols and -enolic
dithioesters modifying the variables, which enabled the optimized reaction conditions for the
formation of naphtho[2,1-b]thiophene-4,5-diones in high yield (Scheme 1c).
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Scheme 1. Strategies for Naphtho[2,1-b]thiophene-4,5-diones
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RESULTS AND DISCUSSION
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The development of metal-catalyzed cross-coupling reactions over the past 30 years has
revolutionized the way, carboncarbon bonds are formed. The development of this chemistry is
highly important because it offers a great opportunity to diminish the dependence of synthetic
chemistry on traditional cross-coupling reactions, which heavily rely on prefunctionalization of the
coupling partners and precious metals. These methods have profoundly changed the protocols for the
construction of simple/complex molecules for organic materials, polymers, and lead compounds in
medicinal chemistry from simpler entities.7a-e In view of green and economical synthesis, coupling
between two partners under oxidative conditions has been developed recently for the formation of
chemical bonds and revolutionized the classical coupling technology. Oxidative cross-coupling7f-i
(OCC) is a hot research topic that covers aspects of classical coupling, C-H functionalization,
oxidation reactions, and radical chemistry for chemical, materials, and biological synthesis. Cascade
processes have received tremendous development over the past decades, and remain one of the most
powerful tools to create carboncarbon or carbonheteroatom bonds in one-pot due to their ecologic
and economic competence.8 These strategies are not only limited to the synthesis of simple
molecules (carbocycles/heterocycles), but also have been utilized for biomimetic synthesis of several
natural products,9 thus revolutionized the field dramatically. Utilizing these tools, chemists improved
their skills in communicating chemistry to non-experts, thereby also reflecting their perceptions on
research. Therefore, one of the important frontiers of modern synthesis is the development of cascade
processes incorporating the chemoselective intramolecular reaction.
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The demand for better synthetic methods towards bioactive heterocyclic scaffolds and their
derivatives is high and continuous. -Oxodithioesters exert diverse and amazing reactivity as novel
multi-role-synthons, and have been widely utilized as a practical key intermediate for the
construction of diverse important heterocyclic frameworks.10 As part of an on-going study into the
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design and development of operationally simple and efficient methodologies for the construction of
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valuable heterocycles utilizing -oxo/-enolic dithioesters,11 we envisioned to employ inexpensive
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and easily viable β-naphthols as one of the reaction partner for annulation with -enolic dithioesters
with the aim to trigger new naphtho fused sulfur heterocycles. During the recent past, β-naphthol has
been employed as a reaction partner in various organic transformations.12 Herein, we report the first
concise example of a copper-catalyzed, TEMPO-mediated cross-dehydrogenative annulation of β-
naphthols with -enolic dithioesters in open air, which enabled 2,3-disubstituted naphtho[2,1-
b]thiophene-4,5-diones in good yields (Scheme 1c). Of particular interest is the chemoselectivity of
the reactions, consistent with a cascade process.
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Initially, we performed the reaction of β-naphthol 1a (1 mmol) with -enolic dithioesters 2d (1
mmol) in AcOH (3 mL) in the absence of catalyst, and with 10 mol% of CuCl separately at room
temperature. Under both conditions, we did not observe the trace of the desired product 3ad, even
after 12 h of stirring, and the starting materials remained completely unreacted (Table 1, entries 1
and 2). In an effort to trigger the reaction, we carried out the model reaction in the presence of 2
equiv of TEMPO at room temperature. TEMPO triggered the reaction producing the desired product
3ad, albeit in only 10% isolated yield (Table 1, entry 3). The above observation was encouraging
enough to optimize the reaction conditions. To improve the efficiency of the reaction, the test
reaction was carried out at higher temperatures (Table 1, entries 4 and 5). It has been found that
maximum conversion occurred at 100 °C, providing the desired product 3ad in 40% yield after 10 h
(Table 1, entry 5). The improvement in the result of the protocol prompted us to investigate some
other copper salts such as CuBr2, Cu(OAc)2 and Cu(OTf)2 (Table 1, entries 6-8). To our satisfaction,
10 mol% of Cu(OTf)2 provided the best result affording the desired product 3ad in 75% yield (Table
1, entry 8).
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Table 1. Optimization of Reaction Conditionsa
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entry catalyst (mol%)
oxidant (equiv)
temp (oC) time (h)
yield (%)b
ND
ND
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none
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CuCl (10)
none
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CuCl (10)
TEMPO (2)
TEMPO (2)
TEMPO (2)
TEMPO (2)
TEMPO (2)
TEMPO (2)
TEMPO (2)
TEMPO (2)
TEMPO (3)
TEMPO (4)
TEMPO (3)
TBHP (4)
rt
CuCl (10)
80
20
CuCl (10)
CuBr2 (10)
Cu(OAc)2 (10)
Cu(OTf)2 (10)
Cu(OTf)2 (20)
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120
100
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60
65
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80
10 Cu(OTf)2 (30)
11 Cu(OTf)2 (20)
12 Cu(OTf)2 (20)
13 Cu(OTf)2 (20)
14 Cu(OTf)2 (20)
7
80
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85
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85
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65
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aReaction conditions: All the reactions were performed with 1a (1 mmol), 2d (1 mmol), Cu(OTf)2
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(20 mol%), TEMPO (3 equiv) in 3 mL of AcOH at 100 C in open air. Isolated yield. ND = Not
Detected.
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Encouraged by the efficacy of Cu(OTf)2, next we optimized its loading. It was found that 20
mol% of Cu(OTf)2 furnished the desired product 3ad in 80% isolated yield within 7 h (Table 1, entry
9). Further increasing the amount of Cu(OTf)2 could not improve the result (Table 1, entry 10).
Finally, we screened the loading of TEMPO, and it was observed that 3 equiv of TEMPO afforded
maximum conversion in minimum time providing the desired product 3ad in 85% yield (Table 1,
entries 11 and 12). Further elevating the reaction temperature (120 oC) was found to be detrimental to
the reaction (Table 1, entry 13) that could be due to decomposition of dithioester at higher
temperature. Use of other oxidant TBHP did mediate the reaction, but could not provide the better
result (Table 1, entry 14). Thus, the optimum condition for the synthesis of 3ad was achieved by
employing 1a (1 mmol), 2d (1 mmol), 20 mol% of Cu(OTf)2, TEMPO (3 equiv) in 3 mL of AcOH at
100 °C in open flask (Table 1, entry 11).
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With the established optimal conditions in hand, we then set out to explore the generality and the
scope of the protocol by using a variety of structurally diverse -enolic dithioesters 2, and the results
are summarized in Scheme 2. -Enolic dithioesters (EDTEs) bearing an electron-donating or
electron-withdrawing group on the phenyl ring (R2 moiety) could tolerate well the reaction
conditions forming the target product 3 in good yield, revealing no obvious electronic impact from
the substituents. The variants of the substituents like Me, OMe, OCH2O, Cl, Br, and strong electron-
withdrawing CF3 group on the phenyl ring (R2 moiety) were found to be compatible well and did not
hamper the reaction process. Importantly, EDTEs bearing heteroaromatic groups such as 2-thienyl
and 2-furyl at R2 moiety were also well tolerated furnishing the corresponding products 3 up to 85%
yields (Scheme 2, 3ag, 3ak, 3al, 3ap, and 3as). It is noteworthy that -enolic dithioesters bearing not
only aromatic and heteroaromatic groups at R2 moiety, but extended aromatics such as biphenyl and
2-naphthyl groups also found to be compatible well under the optimized conditions (Scheme 2, 3aj
and 3ar). Halo-substituted derivatives could be potential precursors for further synthetic
manipulations to access useful compounds.
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Scheme 2. Substrate Scope with different EDTEs to Access Products 3
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Notably, aliphatic based cyclopropyl and methyl substituted dithioesters 2m and 2t also
underwent the reaction smoothly to give the products 3am and 3at in 85% and 65% yield,
respectively. Next, in order to probe the effect of R3 substituent of dithioester, we evaluated the
substrate 2 bearing different substituents at R3. Replacing the R3 thiomethyl with groups such as
thioethyl, thiopropyl, thiobutyl and thiobenzyl were successfully amenable to this protocol affording
the corresponding naphtho[2,1-b]thiophene-4,5-diones 3 in high yields (Scheme 2, 3ah-3at),
revealing the broad adaptability of this method. The consecutive formation of CC and CS bonds
enabled a thiophene ring over naphthoquinone moiety, and made this strategy an excellent tool
toward molecular diversity. It is worthy to note that the excellent regio-selectivity profile was
observed for this cascade heterocyclization. The chemoselective strategy reported herein allows a
novel entry to naphtho[2,1-b]thiophene-4,5-diones with full control over substitution at the various
ring positions, which would otherwise be more difficult to prepare by alternative routes.
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To further extend the utility of this reaction, we also investigated four -naphthol derivatives
having different substituents (1b-1e) with a view to add further diversity to naphtho[2,1-b]thiophene-
4,5-dione frameworks. Subsequently, 6-cyano-2-naphthol 1b, 6-bromo-2-naphthol 1c, 6-
carbomethoxy-2-naphthol 1d and 6-(p-methoxyphenylethynyl)-2-naphthol 1e upon treatment with
dithioesters (2c, 2e) separately under the previously described one-pot standard conditions afforded
8-substituted naphtho[2,1-b]thiophene-4,5-diones in 76-92% yields (Scheme 3, 3bc, 3be, 3cc, 3dc,
3ee).
Scheme 3. Use of Various -Naphthol Derivatives toward the Synthesis of Naphtho[2,1-
b]thiophene-4,5-diones
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Since the naphtho[2,1-b]thiophene-4,5-diones 3 bear adjacent keto groups, we considered
evaluating their scope with 1,2-diaminobenzene13 with the vision to get phenazine derivatives, which
have immense applications in various fields such as dyes, pharmaceuticals and antibiotics.14
Subsequently, we treated compound 3 with 1,2-diaminobenzene 4 in the presence of 10 mol% of L-
o
proline at 100 C under solvent-free conditions (for detail optimization refer to Supporting
Information, Table S1). The reaction proceeded well affording the corresponding pentacyclic
phenazine derivatives 5 in good yields (Scheme 4). Differently decorated naphtho[2,1-b]thiophene-
4,5-diones could be successfully employed.
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Scheme 4. Construction of Pentacyclic Phenazine Derivatives 5
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The structures of all the newly synthesized naphtho[2,1-b]thiophene-4,5-diones 3 and their
corresponding phenazine derivatives 5aa, 5ai, 5al and 5aq were fully characterized by their
satisfactory spectral (1H, 13C, and HRMS) studies. Further, the structure of one of the representative
naphtho[2,1-b]thiophene-4,5-dione 3ap was unambiguously established by the single crystal X-ray
diffraction analysis (see Supporting Information for X-ray structure and other details).15
To gain some insights into the mechanism of the reaction, we conducted a series of control
experiments. The standard reaction without TEMPO was unsuccessful even after 24 h (Scheme 5,
Eq. 1). Similarly, another standard experiment without Cu(II) provided 3aa in only 30% isolated
yield along with the formation of several undesired overlapping spots on TLC plate, which could not
be isolated, indicating crucial role of Cu(II) for successful clean transformation (Scheme 5, Eq. 2).
To prove the intermediacy of naphthalene-1,2-dione 6, we conducted two different sets of reaction.
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First the oxidation of β-naphthol under our optimized reaction conditions and next the reaction of
isolated naphthalene-1,2-dione intermediate with -enolic dithioester. When β-naphthol 1a was
treated with 20 mol% of Cu(II) and 1 equiv of TEMPO in AcOH at 100 oC in open flask, to our great
pleasure, the corresponding intermediate 6 was obtained in 80% yield within 0.5 h (Scheme 5, Eq.
3). Further treatment of 6 with 2a under the standard reaction conditions without TEMPO and with 2
equiv of TEMPO furnished the desired product 3aa in 40% and 75% yield, respectively (compare
with Scheme 2, entry 3aa) validating the intermediacy of compound 6 and the key role of TEMPO in
oxidative cyclization (Scheme 5, Eqs. 4 and 5). To ascertain the role of the atmospheric oxygen
during the transformation, we performed the standard reaction of 1a with 2a under the argon
atmosphere. The desired product 3aa was obtained only in 15% yield even after 24 h of heating at
100 oC. The above observation indicates that molecular oxygen is necessary for the oxidation of 1 to
intermediate 6 (Scheme 5, Eq. 6).
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Scheme 5. Control Experiments
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On the basis of our experimental observations and control experiment studies, a plausible
mechanistic proposal is depicted in Scheme 6. The first step is believed to be the copper-catalyzed,
TEMPO mediated oxidation of β-naphthol to naphthalene-1,2-dione intermediate 6 that has been
isolated and fully characterized. Oxidative addition of -naphthol 1 to Cu(II) catalyst would lead to
species A, which undergoes tautomerization to more favoured form B. Species B on reaction with
atmospheric oxygen could produce a copper stabilized peroxide intermediate C, which reacts with
TEMPOH to generate another peroxide intermediate D. Intermediate D upon reaction with TEMPO
generates a radical intermediate E, which upon oxidation produces naphthalene-1,2-dione
intermediate 6 that acts as Michael acceptor. Subsequent a Michael-type attack of -enolic
dithioester 2 via its α-C atom to intermediate 6 provided open chain intermediate F. Intermediate F
may undergo intramolecular cyclization via its two possible rotamers F1 and F2 through pathways I
and II to furnish tricyclic naphtho[2,1-b]thiophene-4,5-dione 3 and naphtho[2,1-b]furan-4,5-dione 7,
respectively. Rotamer F1 undergoes chemoselective S-cyclization via route I followed by oxidation
to give the desired compound 3. The alternative O-cyclization of rotamer F2 could lead to naphtho
fused furan derivative 7 via route II. During the course of our present investigation, we did not
observe a trace of compound 7, and compound 3 was obtained exclusively. It should be emphasized
that under the present conditions only S-cyclization took place making the protocol highly
chemoselective (Scheme 6). It could be due to the thioalkyl group attached to the thiocarbonyl
carbon, which increases the nucleophilicity of thiocarbonyl sulfur making it more efficient toward
nucleophilic attack than carbonyl oxygen. Moreover, the aromatic ring attached to the carbonyl
carbon further decreases the nucleophilicity of carbonyl oxygen making it almost inefficient toward
nucleophilic attack.
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Scheme 6. Proposed Mechanism for the Formation of Naphtho[2,1-b]thiophene-4,5-dione 3
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CONCLUSION
In summary, we have developed a new cascade C-O/C-C/C-S bonds formation via synergistic Cu-
catalyzed TEMPO-mediated cross-dehydrogenative annulation (CDA) of β-naphthols with -enolic
dithioesters that enabled efficient construction of tricyclic 2,3-disubstituted naphtho[2,1-b]thiophene-
4,5-diones 3. The reaction involved in situ formation of naphthalene-1,2-diones 6 from
dearomatization of -naphthols 1 followed by thienannulation with -enolic dithioesters via Michael-
type addition/oxidation/cyclization/oxidation cascade sequence. Non-toxic conditions, flexible
structural modification, broad substrate scope, excellent chemoselectivity, and good functional group
tolerance are the practical advantages of this new domino protocol. Further transformation of
compound 3 to pentacyclic fused phenazine derivatives 5 makes this strategy highly viable for future
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applications. It is worth to note that the described cascade chemistry is general, eco-compatible and
low cost, making this protocol a good alternative to existing ones.
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EXPERIMENTAL SECTION
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General: Chemicals were purchased from commercial suppliers and used without further purification.
1
-Enolic dithioesters could be easily prepared by reported procedure.16 All the H and 13C NMR
spectra if not mentioned otherwise, have been recorded at room temperature on JEOL AL 500 FT-
NMR spectrometer. Chemical shifts are given as δ value (in parts per million, ppm) with reference to
tetramethylsilane (TMS) as the internal standard, and the coupling constants (J) were given in Hz.
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Proton-decoupled C{1H} NMR spectra were recorded at 125 MHz. Mass spectra were recorded on
Agilent 6530 Accurate-Mass Q-TOF and Thermo Exactive orbitrap instruments. Melting points were
determined with Büchi B-540 melting point apparatus and are uncorrected. All the reactions were
monitored by TLC using pre-coated sheets of silica gel G/UV-254 plates of 0.25 mm thickness (Merck
60F254) using different organic solvent mixtures.
General Experimental Procedures for the Synthesis of Compounds 3 and 5
Typical procedure for the synthesis of compound 3 (Schemes 2 and 3). A dry 25 mL round-bottomed
flask equipped with a magnetic stir bar was charged with a solution of β-naphthol 1 (1.0 mmol) and
TEMPO (3.0 equiv) in 3 mL acetic acid followed by addition of 20 mol% of Cu(OTf)2. The reaction
mixture was stirred at 100 oC for 10 min, then -enolic dithioester 2 (1.0 mmol) was added to this. The
resulting mixture was then allowed to stir at 100 oC for the stipulated period of time (Scheme 2). After
completion of the reaction (monitored by TLC), the reaction mixture was diluted with 30 mL of ethyl
acetate followed by washing with aqueous NaHCO3 (2 x 10 mL) to neutralize excess of acetic acid.
The organic layer was dried over anhydrous Na2SO4, and solvent was evaporated under reduced
pressure. The crude residue thus obtained was purified by column chromatography over silica gel
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(100-200 mesh) using increasing percentage of ethyl acetate in hexane as eluent to afford the pure
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products 3.
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Typical procedure for the synthesis of 5 (Scheme 4). A mixture of compound 3 (0.5 mmol), ortho-
phenylenediamine 4 (0.5 mmol), and L-Proline (10 mol%) was taken in 10 mL oven dried round
bottom flask and stirred at 100 oC for the stipulated period of time (Scheme 3). After completion of the
reaction (monitored by TLC), the mixture was diluted with 20 mL of CHCl3 followed by washing with
aqueous NH4Cl (2 x 10 mL). The organic layer was dried over anhydrous Na2SO4, and solvent was
evaporated under reduced pressure. The crude residue thus obtained was purified by column
chromatography over silica gel (100-200 mesh) using increasing percentage of ethyl acetate in hexane
as eluent to afford the pure phenazine derivative 5.
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1-Benzoyl-2-(methylthio)naphtho[2,1-b]thiophene-4,5-dione (3aa): (yield 80%, 291 mg); Red solid;
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m. p. = 148-150 C; H NMR (500 MHz, CDCl3) δ 8.08 (d, J = 9.00 Hz, 1H), 7.93 (d, J = 7.00 Hz,
2H), 7.64 (t, J = 8.00 Hz, 1H), 7.49 (t, J = 8.00 Hz, 2H), 7.33-7.27 (m, 2H), 7.17 (d, J = 7.50 Hz, 1H),
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2.61 (s, 3H); C NMR (125 MHz, CDCl3) δ 193.4, 180.6, 171.1, 157.7, 144.9, 136.1, 135.9, 135.5,
135.1, 134.7, 132.0, 131.2, 130.9, 130.1, 130.0, 129.5, 128.9, 126.9, 124.2, 19.3; HRMS [ESI,
(M+Na)+]: C20H12NaO3S2, Calcd.: 387.0126, Found: 387.0137.
1-(4-Methylbenzoyl)-2-(methylthio)naphtho[2,1-b]thiophene-4,5-dione (3ab): (yield 85%, 321 mg);
Red solid; m. p. = 155-157 oC; 1H NMR (500 MHz, CDCl3) δ 8.11 (d, J = 6.50 Hz, 1H), 7.86 (d, J =
8.00 Hz, 2H), 7.34-7.22 (m, 5H), 2.62 (s, 3H), 2.44 (s, 3H); 13C NMR (125 MHz, CDCl3) δ 192.8,
180.6, 170.9, 157.0, 146.4, 144.7, 136.1, 135.9, 135.4, 134.6, 133.6, 132.7, 132.2, 131.9, 131.1, 130.8,
130.1, 129.8, 126.7, 21.6, 19.0; HRMS [ESI, (M+Na)+]: C21H14NaO3S2, Calcd.: 401.0282, Found:
401.0291.
1-(4-Methoxybenzoyl)-2-(methylthio)naphtho[2,1-b]thiophene-4,5-dione (3ad): (yield 85%, 335 mg);
Red solid; m. p. = 197-199 oC; 1H NMR (500 MHz, CDCl3) δ 8.02-8.01 (m, 1H), 7.85 (d, J = 8.50 Hz,
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2H), 7.26-7.25 (m, 2H), 7.19-7.17 (m, 1H), 6.89 (d, J = 9.00 Hz, 2H), 3.80 (s, 3H), 2.54 (s, 3H); C
NMR (125 MHz, CDCl3) δ 191.6, 180.6, 170.9, 165.1, 156.9, 144.6, 136.2, 135.5, 134.6, 132.5, 131.9,
131.0, 130.8, 129.8, 129.0, 126.6, 114.7, 113.9, 55.5, 19.1; HRMS [ESI, (M+Na)+]: C21H14NaO4S2,
Calcd.: 417.0231, Found: 417.0240.
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1-(3-Bromobenzoyl)-2-(methylthio)naphtho[2,1-b]thiophene-4,5-dione (3ae): (yield 80%, 354 mg);
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Gummy red; H NMR (500 MHz, CDCl3) δ 8.08 (d, J = 7.25 Hz, 1H), 7.71-7.69 (m, 1H), 7.61-7.59
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(m, 1H), 7.41-7.34 (m, 5H), 2.63 (s, 3H); C NMR (125 MHz, CDCl3) δ 191.2, 180.5, 171.1, 161.0,
145.8, 138.0, 134.9, 133.9, 132.3, 131.7, 130.9, 130.7, 129.8, 127.8, 127.4, 122.3, 19.0; HRMS [ESI,
(M+Na)+]: C20H11BrNaO3S2, Calcd.: 466.9210, Found: 466.9218.
2-(Methylthio)-1-(4-(trifluoromethyl)benzoyl)naphtho[2,1-b]thiophene-4,5-dione (3af): (yield 75%,
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324 mg); Red solid; m. p. = 186-188 C; H NMR (500 MHz, CDCl3) δ 8.12 (d, J = 7.30 Hz, 1H),
8.06 (d, J = 8.05 Hz, 2H), 7.77 (d, J = 8.15 Hz, 2H), 7.38-7.31 (m, 2H), 7.10 (d, J = 7.60 Hz, 1H), 2.64
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(s, 3H); C NMR (125 MHz, CDCl3) δ 192.1, 180.2, 170.8, 157.9, 144.6, 138.5, 135.7, 135.3, 134.7,
134.5, 131.5, 131.2, 130.7, 130.1, 130.0, 126.5, 126.3, 126.3, 19.1; HRMS [ESI, (M+Na)+]:
C21H11F3NaO3S2, Calcd.: 454.9999, Found: 454.9998.
2-(Methylthio)-1-(thiophene-2-carbonyl)naphtho[2,1-b]thiophene-4,5-dione (3ag): (yield 85%, 314
1
mg); Gummy red; H NMR (500 MHz, CDCl3) δ 8.13-8.11 (m, 1H), 7.83 (d, J = 4.95 Hz, 1H), 7.59
(d, J = 3.40 Hz, 1H), 7.38-7.36 (m, 3H), 7.13 (d, J = 4.25 Hz, 1H), 2.65 (s, 3H); 13C NMR (125 MHz,
CDCl3) δ 184.9, 180.5, 170.9, 157.8, 144.3, 143.3, 137.2, 136.2, 135.5, 134.6, 131.8, 131.1, 130.8,
129.9, 129.0, 126.6, 19.2; HRMS [ESI, (M+Na)+]: C18H10NaO3S3, Calcd.: 392.9690, Found: 392.9699.
2-(Ethylthio)-1-(4-methoxybenzoyl)naphtho[2,1-b]thiophene-4,5-dione (3ah): (yield 85%, 347 mg);
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Gummy red; H NMR (500 MHz, CDCl3) δ 8.11-8.10 (m, 1H), 7.92 (d, J = 8.00 Hz, 2H), 7.34-7.33
(m, 2H), 7.27-7.26 (m, 1H), 6.97 (d, J = 9.00 Hz, 2H), 3.88 (s, 3H), 3.06 (q, J = 7.50 Hz, 2H), 1.37 (t,
J = 7.50 Hz, 3H); 13C NMR (125 MHz, CDCl3) δ 191.5, 180.5, 170.8, 165.1, 156.8, 144.5, 136.2,
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135.4, 132.5, 131.9, 131.0, 130.7, 129.7, 129.0, 126.6, 114.6, 55.6, 29.7, 19.0; HRMS [ESI, (M+Na)+]:
C22H16NaO4S2, Calcd.: 431.0388, Found: 431.0410.
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1-(4-Chlorobenzoyl)-2-(ethylthio)naphtho[2,1-b]thiophene-4,5-dione (3ai): (yield 75%, 309 mg); Red
solid; m. p. = 147-149 oC; 1H NMR (500 MHz, CDCl3) δ 8.11 (d, J = 8.35 Hz, 1H), 7.89 (d, J = 8.20
Hz, 2H), 7.48 (d, J = 8.40 Hz, 2H), 7.36-7.34 (m, 2H), 7.15 (d, J = 8.00 Hz, 11H), 3.07 (q, J = 7.33
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Hz, 2H), 1.37 (t, J = 7.27 Hz, 3H); C NMR (125 MHz, CDCl3) δ 192.2, 180.3, 171.1, 155.0, 144.3,
141.7, 136.7, 135.5, 135.4, 134.4, 131.7, 131.2, 130.7, 129.9, 129.8, 126.4, 31.3, 14.0; HRMS [ESI,
(M+Na)+]: C21H13ClNaO3S2, Calcd.: 434.9892, Found: 434.9897.
1-([1,1'-Biphenyl]-4-carbonyl)-2-(ethylthio)naphtho[2,1-b]thiophene-4,5-dione (3aj): (yield 85%, 386
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mg); Red solid; m. p. = 146-148 C; H NMR (500 MHz, CDCl3) δ 8.13-8.11 (m, 1H), 8.02 (d, J =
8.00 Hz, 2H), 7.73 (d, J = 8.00 Hz, 2H), 7.63 (d, J = 7.50 Hz, 2H), 7.49-7.40 (m, 3H), 7.35-7.34 (m,
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2H), 7.27-7.25 (m, 1H), 3.08 (q, J = 7.50 Hz, 2H), 1.38 (t, J = 7.50 Hz, 3H); C NMR (125 MHz,
CDCl3) δ 193.0, 180.5, 171.1, 154.7, 147.6, 144.4, 139.3, 137.5, 135.6, 134.8, 131.9, 131.2, 130.6,
129.9, 129.1, 128.8, 127.9, 127.4, 126.6, 31.4, 14.1; HRMS [ESI, (M+Na)+]: C27H18NaO3S2, Calcd.:
477.0595, Found: 477.0599.
2-(Ethylthio)-1-(thiophene-2-carbonyl)naphtho[2,1-b]thiophene-4,5-dione (3ak): (yield 85%, 326
mg); Gummy red; 1H NMR (500 MHz, CDCl3) δ 8.10 (d, J = 6.50 Hz, 1H), 7.84 (d, J = 5.00 Hz, 1H),
7.59 (d, J = 3.50 Hz, 1H), 7.40-7.36 (m, 3H), 7.14 (t, J = 4.50 Hz, 1H), 3.09 (q, J = 7.20 Hz, 2H), 1.40
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(t, J = 7.70 Hz, 3H); C NMR (125 MHz, CDCl3) δ 185.1, 180.4, 171.1, 155.3, 144.0, 143.5, 137.2,
137.1, 136.2, 135.6, 135.3, 131.8, 131.1, 130.7, 129.9, 129.1, 126.5, 31.4, 14.0; HRMS [ESI,
(M+Na)+]: C19H12NaO3S3, Calcd.: 406.9846, Found: 406.9838.
2-(Ethylthio)-1-(furan-2-carbonyl)naphtho[2,1-b]thiophene-4,5-dione (3al): (yield 85%, 313 mg); Red
solid; m. p. = 111-113 oC; 1H NMR (500 MHz, CDCl3) δ 8.12 (d, J = 6.65 Hz, 1H), 7.67 (s, 1H), 7.41-
7.36 (m, 2H), 7.29 (d, J = 7.30 Hz, 1H), 6.59 (s, 1H), 3.10 (q, J = 7.26 Hz, 2H), 1.40 (t, J = 7.32 Hz,
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3H); 13C NMR (125 MHz, CDCl3) δ 180.5, 179.6, 171.1, 156.4, 152.2, 148.8, 144.4, 135.5, 132.0,
131.1, 130.7, 129.8, 126.4, 113.3, 31.3, 14.0; HRMS [ESI, (M+Na)+]: C19H12NaO4S2, Calcd.:
391.0075, Found: 391.0083.
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1-(Cyclopropanecarbonyl)-2-(ethylthio)naphtho[2,1-b]thiophene-4,5-dione (3am): (yield 85%, 291
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mg); Red solid; m. p. = 120-122 C; H NMR (500 MHz, CDCl3) δ 8.10 (d, J = 7.50 Hz, 1H), 7.56-
7.55 (m, 2H), 7.44-7.41 (m, 1H), 3.10 (q, J = 7.50 Hz, 2H, -SCH2), 2.29-2.24 (m, 1H), 1.47-1.42 (m,
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5H, 1 X –CH3, 1 X -CH2-), 1.18-1.14 (m, 2H); C NMR (125 MHz, CDCl3) δ 201.9, 180.6, 171.0,
156.4, 144.0, 138.3, 135.2, 134.6, 132.0, 131.2, 131.1, 130.8, 127.1, 30.8, 29.7, 24.1, 14.5, 13.8;
HRMS [ESI, (M+Na)+]: C18H14NaO3S2, Calcd.: 365.0282, Found: 365.0289.
1-(4-Methoxybenzoyl)-2-(propylthio)naphtho[2,1-b]thiophene-4,5-dione (3an): (yield 70%, 295 mg);
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Gummy red; H NMR (500 MHz, CDCl3) δ 8.12-8.10 (m, 1H), 7.92 (d, J = 7.25 Hz, 2H), 7.35-7.33
(m, 3H), 6.97 (d, J = 8.50 Hz, 2H), 3.88 (s, 3H), 3.01 (t, J = 7.27 Hz, 2H), 1.78-1.70 (m, 2H), 0.99 (t, J
= 7.27 Hz, 3H); 13C NMR (125 MHz, CDCl3) δ 191.7, 180.5, 171.0, 165.0, 154.8, 144.2, 137.6, 135.4,
132.4, 131.9, 131.0, 130.7, 129.7, 129.1, 126.5, 114.5, 55.6, 38.9, 22.2, 13.2; HRMS [ESI, (M+Na)+]:
C23H18NaO4S2, Calcd.: 445.0544, Found: 445.0546.
1-(Benzo[d][1,3]dioxole-5-carbonyl)-2-(propylthio)naphtho[2,1-b]thiophene-4,5-dione (3ao): (yield
85%, 371 mg); Red solid; m. p. = 110-112 oC; 1H NMR (500 MHz, CDCl3) δ 8.12-8.10 (m, 1H), 7.51
(br s, 1H), 7.43 (br s, 1H), 7.37-7.35 (m, 2H), 7.26-7.23 (m, 1H), 6.84(d, J = 8.00 Hz, 1H), 6.10 (s,
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2H), 3.01 (t, J = 7.00 Hz, 2H), 1.77-1.72 (m, 2H), 1.00 (t, J = 7.50 Hz, 3H); C NMR (125 MHz,
CDCl3) δ 191.3, 180.4, 171.0, 154.7, 153.5, 148.9, 144.2, 137.4, 135.4, 135.1, 131.8, 131.0, 130.6,
129.7, 127.7, 126.3, 108.5, 102.3, 39.0, 22.2, 13.2; HRMS [ESI, (M+Na)+]: C23H16NaO5S2, Calcd.:
459.0337, Found: 459.0325.
1-(Furan-2-carbonyl)-2-(propylthio)naphtho[2,1-b]thiophene-4,5-dione (3ap): (yield 85%, 325 mg);
Red solid; m. p. = 144-146 oC; 1H NMR (500 MHz, CDCl3) δ 8.12 (d, J = 6.50 Hz, 1H), 7.67 (s, 1H),
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(m, 2H), 1.02 (t, J = 7.42 Hz, 3H); C NMR (125 MHz, CDCl3) δ 180.4, 179.6, 171.0, 156.9, 152.1,
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148.7, 144.4, 135.7, 135.4, 134.9, 131.9, 131.0, 130.6, 129.7, 126.3, 113.2, 39.0, 22.2, 13.2; HRMS
[ESI, (M+Na)+]: C20H14NaO4S2, Calcd.: 405.0231, Found: 405.0252.
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2-(Butylthio)-1-(4-methoxybenzoyl)naphtho[2,1-b]thiophene-4,5-dione (3aq): (yield 90%, 392 mg);
Red solid; m. p. = 130-132 oC; 1H NMR (500 MHz, CDCl3) δ 8.10-8.08 (m, 1H), 7.91 (d, J = 8.00 Hz,
2H), 7.33-7.31 (m, 2H), 7.26-7.25 (m, 1H), 6.95 (d, J = 9.00 Hz, 2H), 3.87 (s, 3H), 3.02 (t, J = 7.70
Hz, 2H), 1.70-1.64 (m, 2H), 1.40-1.36 (m, 2H), 0.89 (t, J = 7.50 Hz, 3H); 13C NMR (125 MHz,
CDCl3) δ 191.8, 180.6, 171.1, 165.1, 155.0, 144.3, 137.6, 135.5, 135.1, 132.5, 132.0, 131.1, 130.7,
129.7, 129.2, 126.5, 114.6, 55.7, 36.8, 30.8, 21.8, 13.5; HRMS [ESI, (M+Na)+]: C24H20NaO4S2,
Calcd.: 459.0701, Found: 459.0691.
1-(2-Naphthoyl)-2-(butylthio)naphtho[2,1-b]thiophene-4,5-dione (3ar): (yield 90%, 392 mg); Red
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solid; m. p. = 140-142 C; H NMR (500 MHz, CDCl3) δ 8.34 (br s, 1H), 8.11 (t, J = 8.50 Hz, 1H),
7.98 (t, J = 8.50 Hz, 1H), 7.92-7.90 (m, 2H), 7.66-7.63 (m, 1H), 7.55 (t, J = 8.00 Hz, 1H), 7.30-7.26
(m, 3H + 1H in CDCl3), 3.03 (t, J = 7.50 Hz, 2H), 1.68-1.62 (m, 2H), 1.38-1.35 (m, 2H), 0.86 (t, J =
13
7.50 Hz, 3H); C NMR (125 MHz, CDCl3) δ 193.5, 180.5, 171.1, 155.4, 144.5, 137.4, 136.5, 135.5,
135.3, 133.6, 133.1, 132.6, 131.9, 131.2, 130.7, 130.1, 129.8, 129.6, 129.5, 128.0, 127.3, 126.5, 124.1,
36.9, 30.8, 21.8, 13.4; HRMS [ESI, (M+Na)+]: C27H20NaO3S2, Calcd.: 479.0752, Found: 479.0740.
2-(Benzylthio)-1-(furan-2-carbonyl)naphtho[2,1-b]thiophene-4,5-dione (3as): (yield 80%, 344 mg);
Red solid; m. p. = 152-154 oC; 1H NMR (500 MHz, CDCl3) δ 8.08 (dd, J = 7.70 and 2.0 Hz, 1H), 7.64
(br s, 1H), 7.38-7.33 (m, 2H), 7.29-7.24 (m, 7H), 6.52 (dd, J = 4.00 and 2.0 Hz, 1H), 4.21 (s, 2H); 13C
NMR (125 MHz, CDCl3) δ 180.3, 179.6, 171.3, 153.9, 152.2, 148.9, 144.0, 137.5, 136.0, 135.6, 134.7,
132.0, 131.1, 130.6, 129.8, 129.1, 128.9, 128.3, 126.3, 122.2, 113.3, 41.7; HRMS [ESI, (M+Na)+]:
C24H14NaO4S2, Calcd.: 453.0231, Found: 453.0229.
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= 80-82 oC; H NMR (500 MHz) δ 8.16 (d, J = 7.55 Hz, 1H), 7.61-7.58 (m, 1H), 7.49-7.46 (m, 1H),
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7.33 (d, J = 7.80 Hz, 1H), 2.68 (s, 3H), 2.60 (s, 3H); 13C NMR (125 MHz) δ 199.7, 180.5, 170.9,
157.2, 146.9, 143.9, 135.4, 132.0, 131.3, 130.9, 130.1, 126.5, 32.0, 19.1; HRMS [ESI, (M+Na)+]:
C15H10NaO3S2, Calcd.: 324.9964, Found: 324.9964.
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2-(Ethylthio)-1-(4-methylbenzoyl)-4,5-dioxo-4,5-dihydronaphtho[2,1-b]thiophene-8-carbonitrile
(3bc): (yield 85%, 177 mg); Brown solid; m. p. = 188-190 oC; 1H NMR (500 MHz) δ 8.15 (d, J = 7.80
Hz, 1H), 7.85 (d, J = 7.85 Hz, 2H), 7.76 (d, J = 7.60 Hz, 1H), 7.57 (s, 1H), 7.30 (d, J = 8.15 Hz, 2H),
3.09 (q, J = 7.46 Hz, 2H), 2.42 (s, 3H), 1.39 (t, J = 7.47 Hz, 3H); 13C NMR (125 MHz) δ 192.7, 179.9,
170.5, 167.0, 146.7, 143.3, 139.2, 137.1, 135.5, 133.6, 132.6, 132.0, 131.3, 130.3, 130.0, 129.1, 128.7,
127.8, 125.4, 31.3, 22.0, 13.9; HRMS [ESI, (M+Na)+]: C23H15NNaO3S2, Calcd.: 440.0386, Found:
440.0386.
1-(3-Bromobenzoyl)-2-(methylthio)-4,5-dioxo-4,5-dihydronaphtho[2,1-b]thiophene-8-carbonitrile
o
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(3be): (yield 92%, 215 mg); Red solid; m. p. = 201-203 C; H NMR (500 MHz) δ 8.19 (d, J = 7.95
Hz, 1H), 8.09 (s, 1H), 7.84 (d, J = 7.60 Hz, 1H), 7.78-7.74 (m, 2H), 7.56 (s, 1H), 7.40-7.36 (m, 1H),
2.68 (s, 3H); 13C NMR (125 MHz) δ 191.6, 179.8, 170.3, 166.8, 159.5, 143.7, 139.2, 137.9, 132.7,
132.4, 131.8, 131.4, 131.0, 128.5, 125.9, 123.8, 19.2; HRMS [ESI, (M+Na)+]: C21H10BrNNaO3S2,
Calcd.: 489.9178, Found: 489.9178.
8-Bromo-2-(ethylthio)-1-(4-methylbenzoyl)naphtho[2,1-b]thiophene-4,5-dione (3cc): (yield 76%, 179
o
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mg); Red solid; m. p. = 232-234 C; H NMR (500 MHz) δ 7.87 (d, J = 8.45 Hz, 1H), 7.75 (d, J =
7.75 Hz, 2H), 7.40 (dd, J1 = 1.72 Hz, J2 = 8.52 Hz, 1H), 7.29 (s, 1H), 7.24 (d, J = 8.15 Hz, 2H), 3.01
13
(q, J = 7.10 Hz, 2H), 2.37 (s, 3H), 1.32 (t, J = 7.35 Hz, 3H); C NMR (125 MHz) δ 192.5, 179.7,
170.6, 155.3, 146.5, 142.6, 137.4, 135.9, 133.7, 133.1, 132.8, 132.2, 131.1, 130.2, 130.0, 129.8, 129.3,
31.3, 22.0, 14.0; HRMS [ESI, (M+Na)+]: C22H15BrNaO3S2, Calcd.: 492.9538, Found: 492.9538.
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1-(3-Bromobenzoyl)-8-((4-methoxyphenyl)ethynyl)-2-(methylthio)naphtho[2,1-b]thiophene-4,5-dione
(3ee): (yield 80%, 229 mg); Red solid; m. p. = 195-197 oC; 1H NMR (500 MHz) δ 8.18 (s, 1H), 8.07
(d, J = 7.80 Hz, 1H), 7.78-7.75 (m, 2H), 7.41 (m, 3H), 7.37-7.34 (m, 1H), 7.17 (s, 1H), 7.39 (d, J =
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8.70 Hz, 2H), 3.84 (s, 3H), 2.66 (s, 3H); C NMR (125 MHz) δ 191.5, 179.6, 170.9, 160.6, 158.5,
143.9, 138.1, 137.7, 135.1, 134.6, 133.6, 132.2, 132.0, 131.5, 131.2, 131.1, 130.8, 129.7, 129.1, 128.6,
123.8, 114.2, 96.2, 87.0, 55.4, 19.2; HRMS [ESI, (M+Na)+]: C29H17BrNaO4S2, Calcd.: 594.9644,
Found: 594.9644.
Methyl
2-(ethylthio)-1-(4-methylbenzoyl)-4,5-dioxo-4,5-dihydronaphtho[2,1-b]thiophene-8-
o
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carboxylate (3dc): (yield 65%, 146 mg); Red solid; m. p. = 202-204 C; H NMR (500 MHz) δ 8.16
(d, J = 8.00 Hz, 1H), 7.96-7.95 (m, 1H), 7.90-7.86 (m, 2H), 7.30 (d, J = 5.40 Hz, 2H), 7.27 (s, 1H),
3.80 (s, 3H), 3.11 (q, J = 7.11 Hz, 2H), 2.43 (s, 3H), 1.40 (t, J = 7.40 Hz, 3H); 13C NMR (125 MHz) δ
192.5, 180.2, 170.5, 164.9, 155.5, 146.3, 143.5, 137.6, 135.7, 135.5, 133.7, 133.2, 131.9, 130.9, 130.4,
130.0, 130.0, 127.8, 52.6, 31.3, 22.0, 14.0; HRMS [ESI, (M+Na)+]: C24H18NaO5S2, Calcd.: 473.0488,
Found: 473.0488.
(2-(Methylthio)benzo[a]thieno[3,2-c]phenazin-3-yl)(phenyl)methanone (5aa): (yield 85%, 185 mg);
Orange solid; m. p. = 200-202 oC; 1H NMR (500 MHz, CDCl3) δ 9.43 (d, J = 8.00 Hz, 1H), 8.35 (d, J
= 7.00 Hz, 1H), 8.30 (d, J = 7.30 Hz, 1H), 8.01 (d, J = 7.65 Hz, 2H), 7.88-7.87 (m, 2H), 7.77 (d, J =
8.05 Hz, 1H), 7.66-7.60 (m, 2H), 7.50-7.46 (m, 3H), 2.62 (s, 3H); 13C NMR (125 MHz, CDCl3) δ
195.1, 143.4, 142.3, 142.2, 141.4, 139.6, 138.8, 137.2, 137.0, 136.9, 134.3, 130.4, 130.1, 130.0, 129.8,
129.7, 129.0, 128.8, 127.2, 126.5, 125.1, 20.8; HRMS [ESI, (M+H)+]: C26H17N2OS2, Calcd.: 437.0782,
Found: 437.0779.
(4-Chlorophenyl)(2-(ethylthio)benzo[a]thieno[3,2-c]phenazin-3-yl)methanone (5ai): (yield 80%, 194
mg); Orange solid; m. p. = 206-208 oC; 1H NMR (500 MHz, CDCl3) δ 9.44 (d, J = 8.00 Hz, 1H), 8.36
(d, J = 7.05 Hz, 1H), 8.30 (d, J = 9.10 Hz, 1H), 7.94 (d, J = 8.10 Hz, 2H), 7.89-7.88 (m, 2H), 7.73 (d, J
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= 8.10 Hz, 1H), 7.68-7.65 (m, 1H), 7.53-7.50 (m, 1H), 7.44 (d, J = 8.30 Hz, 2H), 3.02 (q, J = 7.30 Hz,
2H), 1.34 (t, J = 7.37 Hz, 3H); 13C NMR (125 MHz, CDCl3) δ 194.1, 142.3, 141.4, 140.9, 140.1,
139.5, 138.1, 136.5, 135.5, 131.3, 130.5, 130.2, 129.8, 129.8, 129.4, 129.1, 128.8, 127.3, 126.6, 124.8,
32.5, 14.7; HRMS [ESI, (M+H)+]: C27H18ClN2OS2, Calcd.: 485.0549, Found: 485.0552.
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(2-(Ethylthio)benzo[a]thieno[3,2-c]phenazin-3-yl)(furan-2-yl)methanone (5al): (yield 85%, 176 mg);
Yellow solid; m. p. = 183-185 oC; 1H NMR (500 MHz, CDCl3) δ 9.43 (d, J = 8.65 Hz, 1H), 8.35-8.33
(m, 1H), 8.30-8.28 (m, 1H), 7.89-7.86 (m, 3H), 7.70-7.66 (m, 2H), 7.59-7.55 (m, 1H), 7.13 (s, 1H),
13
3.07 (q, J = 7.15 Hz, 2H), 1.37 (t, J = 7.27 Hz, 3H); C NMR (125 MHz, CDCl3) δ 181.8, 153.0,
148.4, 142.3, 142.2, 141.4, 139.5, 136.5, 130.4, 130.3, 130.2, 129.7, 129.3, 128.8, 127.2, 126.5, 124.8,
112.9, 32.6, 14.7; HRMS [ESI, (M+H)+]: C25H17N2O2S2, Calcd.: 441.0731, Found: 441.0735.
(2-(Butylthio)benzo[a]thieno[3,2-c]phenazin-3-yl)(4-methoxyphenyl)methanone (5aq): (yield 80%,
203 mg); Yellow solid; m. p. = 138-140 oC; 1H NMR (500 MHz, CDCl3) δ 9.29 (d, J = 9.50 Hz, 1H),
8.22-8.15 (m, 2H), 7.91 (d, J = 9.00 Hz, 2H), 7.77-7.73 (m, 3H), 7.53 (t, J = 7.50 Hz, 1H), 7.43-7.39
(m, 1H), 6.86 (d, J = 9.50 Hz, 2H), 3.76 (s, 3H), 2.91 (t, J = 7.20 Hz, 2H), 1.58-1.17 (m, 4H), 0.79 (t, J
= 7.50 Hz, 3H); 13C NMR (125 MHz, CDCl3) δ 193.8, 164.4, 142.1, 142.0, 141.3, 140.8, 140.5, 139.5,
137.7, 136.6, 132.4, 130.3, 130.2, 130.1, 129.6, 129.5, 129.3, 128.7, 127.0, 126.4, 124.8, 114.2, 55.5,
38.0, 31.4, 21.6, 13.5; HRMS [ESI, (M+H)+]: C30H25N2O2S2, Calcd.: 509.1357, Found: 509.1367.
ASSOCIATED CONTENT
Supporting Information
1
Optimization of reaction condition for compound 5, copies of H and 13C NMR spectra of all
compounds and X-ray crystallography data for compound 3ap. The Supporting Information is
available free of charge on the ACS Publications website.
AUTHOR INFORMATION
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Corresponding Author
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*E-mail: mayashankarbhu@gmail.com; Fax: +91-542-2368127
†Gaurav Shukla and Abhijeet Srivastava contributed equally.
ORCID ID:
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Maya Shankar Singh: 0000-0002-3199-0823
Abhijeet Srivastava: 0000-0001-5118-7539
Gaurav Shukla: 0000-0002-1927-2095
Dhananjay Yadav: 0000-0003-1649-8926
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
We acknowledge the financial support from the Science and Engineering Research Board
(SERB/EMR/2015/002482), New Delhi and the Council of Scientific and Industrial Research
(02(0263)/16/EMR-II), New Delhi, India. The authors (G.S., A.S. & D.Y.) are thankful to CSIR and
UGC, New Delhi for research fellowship.
REFERENCES
(1) (a) Marco-Contelles, J.; Carreiras, M. C.; Rodríguez, C.; Villarroya, M.; García, A. G. Chem.
Rev. 2006, 106, 116. (b) Martins P.; Jesus, J.; Santos, S.; Raposo, L. R.; Roma-Rodrigues, C.;
Baptista, P. V.; Fernandes A. R. Molecules 2015, 20, 16852. (c) Han, D.; Chen, J.; He, Q.; Fan, R.
Org. Lett. 2016, 18, 4690. (d) Roncali, J. Chem. Rev. 1992, 92, 711. (e) Katz, H. E.; Bao, Z.; Gilat, S.
L. Acc. Chem. Res. 2001, 34, 359.
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(2) (a) Irgashev, R. A.; Karmatsky, A. A.; Rusinov, G. L.; Charushin, V. N. Org. Lett. 2016, 18, 804.
(b) Baumann, M.; Steven, I. R., Ley, V.; Nikbi, N. Beilstein J. Org. Chem. 2011, 7, 442. (c)
Mushrush, M.; Facchetti, A.; Lefenfeld, M.; Katz, H. E.; Marks, T. J. J. Am. Chem. Soc. 2003, 125,
9414. (d) Osaka, I.; Abe, T.; Shinamura, S.; Takimiya, K. J. Am. Chem. Soc. 2011, 133, 6852.
10
11
12
13
14
15
16
17
18
19
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25
26
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55
56
57
58
59
60
(3) (a) Shinamura, S.; Osaka, I.; Miyazaki, E.; Nakao, A.; Yamagishi, M.; Takeya, J.; Takimiya, K.
J. Am. Chem. Soc. 2011, 133, 5024. (b) Shinamura, S.; Miyazaki, E.; Takimiya, K. J. Org. Chem.
2010, 75, 1228. (c) Dutta, P.; Yang, W.; Lee, W.-H.; Kang, I. N.; Lee, S.-H. J. Mat. Chem. 2012, 22,
10840. (d) Gomez-Monterrey, I.; Campiglia, P.; Aquino, C.; Bertamino, A.; Maresca, B.; Novellino,
E. J. Med. Chem. 2011, 54, 4077.
(4) (a) Gao, J. H.; Li, R. J.; Li, L. Q.; Ming, Q.; Jiang, H.; Li, H. X.; Hu, W. P. Adv. Mater. 2007, 19,
3008. (b) Bren, V. A.; Dubonosov, A. D.; Minkin, V. I.; Tsukanov, A. V.; Gribanova, T. N.;
Shepelenko, E. N.; Revinsky, Y. V.; Rybalkin, V. P. J. Phys. Org. Chem. 2007, 20, 917. (c) Ferrara,
G.; Jin, T.; Akhtaruzzaman, M.; Islam, A.; Han, L.; Jiang, H.; Yamamoto, Y. Tetrahedron Lett.
2012, 53, 1946. (d) Yanai, N.; Mori, T.; Shinamura, S.; Osaka, I.; Takimiya, K. Org. Lett. 2014, 16,
240.
(5) (a) Cote, B.; Ducharme, Y.; Frenette, R.; Friesen, R.; Giroux, A.; Martins, E.; Hamel, P.
Phenanthrene derivatives as mPGES-1 inhibitors and their preparation, pharmaceutical compositions
and use in the treatment of pain and inflammation. PCT Int. Appl., 2007134434, 29 Nov., 2007. (b)
Tominaga, Y.; Tedjamulia, M. L.; Castle, R. N.; Lee, M. L. J. Heterocycl. Chem. 1983, 20, 487. (c)
Moritz, S.; Simon, T.; Lara, S.; Carolin, B.; Dieter, S.; Siegfried, R. W. Eur. J. Org. Chem. 2014, 32,
7091. (d) Acosta, A.; De la Cruz, P.; De Miguel, P.; Diez-Barra, E.; De la Hoz, A.; Langa, F.; Loupy,
A.; Majdoub, M.; Martin, N. Tetrahedron Lett. 1995, 36, 2165. (e) Croisy, A.; Mispelter, J.; Lhoste,
J. M.; Zajdela, F.; Jacquignon, P. J. Heterocycl. Chem. 1984, 21, 353.
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7
8
9
(6) (a) Yoshida, K.; Hayashi, A.; Mamura, T. Heteropolycyclic phenazine compounds and
fluorescent dyes containing them. Jpn. Kokai Tokkyo Koho 2008195749, 28 Aug., 2008. (b)
Brandao, M. A. F.; Braga de Oliveira, A.; Snieckus, V. Tetrahedron Lett. 1993, 34, 2437.
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(7) (a) Meijere, A. D.; Diederich, F. Metal-Catalyzed Cross-Coupling Reactions, 2nd Edn., Wiley-
VCH: Weinheim, Germany, 2008. (b) Meijere, A. D.; Bräse, S.; Oestreich, M. Metal-Catalyzed
Cross-Coupling Reactions and More, Wiley-VCH: Weinheim, Germany, 2013. (c) Zhao, K.; Shen,
L.; Shen, Z-L.; Loh, T-P. Chem. Soc. Rev. 2017, 46, 586. (d) Evano, G.; Blanchard, N.; Toumi, M.
Chem. Rev. 2008, 108, 3054. (e) Lei, A.; Shi, W.; Liu, C.; Liu, W.; Zhang, H.; He, C. Oxidative
Cross-Coupling Reactions, Wiley-VCH, Weinheim, 2016, pp. 229. (f) Jiang, B.; Ning, Y.; Fan, W.;
Tu, S.-J.; Li, G. J. Org. Chem. 2014, 79, 4018. (g) Wang, N.-N.; Hao, W.-J.; Zhang, T.-S.; Li, G.;
Wu, Y.-N.; Tu, S.-J.; Jiang, B. Chem. Commun. 2016, 52, 5144. (h) Qiu, J.-K.; Hao, W.-J.; Wang,
D.-C.; Wei, P.; Sun, J.; Jiang, B.; Tu, S.-J. Chem. Commun. 2014, 50, 14782. (i) Sun, J.; Qiu, J.-K.;
Wu, Y.-N.; Hao, W.-J.; Guo, C.; Li, G.; Tu, S.-J.; Jiang, B. Org. Lett. 2017, 19, 754.
(8) (a) Tietze, L. F.; Brasche, G.; Gericke, K. M. Domino Reactions in Organic Synthesis, Wiley-
VCH: Weinheim, Germany, 2006. (b) Pellissier, H. Chem. Rev. 2013, 113, 442. (c) Tietze, L. F.
Domino Reactions: Concepts for Efficient Organic Synthesis, Wiley-VCH: Weinheim, Germany,
2014. (d) Hayashi, Y. Chem. Sci. 2016, 7, 866.
(9) (a) Johnson, W. S.; Gravestock, M. B.; McCarry, B. E. J. Am. Chem. Soc. 1971, 93, 4332. (b)
Nicolaou, K. C.; Petasis, N. A.; Zipkin, R. E.; Uenishi, J. J. Am. Chem. Soc. 1982, 104, 5555. (c)
Nicolaou, K. C.; Petasis N. A.; Zipkin, R. E.; J. Am. Chem. Soc. 1982, 104, 5560. (d) Piettre, S.;
Heathcock, C. H. Science 1990, 248, 1532.
(10) (a) Wen, L.-R.; Li, Z.-R.; Li, M.; Cao, H. Green Chem. 2012, 14, 707. (b) Wen, L.-R.; Yuan,
W.-K.; Li, M. J. Org. Chem. 2015, 80, 4942. (c) Singh, O. M.; Devi, N. S. J. Org. Chem. 2009, 74,
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3141. (d) Li, M.; Cao, H.; Wang, Y.; Lv, X.-L.; Wen, L. R. Org. Lett. 2012, 14, 3470. (e) Wang, S.-
W.; Guo, W.-S.; Wen, L.-R.; Li, M. RSC Adv. 2015, 5, 47418.
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7
8
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(11) (a) Nandi, G. C.; Singh, M. S.; Ila, H.; Junjappa, H. Eur. J. Org. Chem. 2012, 967. (b)
Chowdhury, S.; Chanda, T.; Koley, S.; Anand, N.; Singh, M. S. Org. Lett. 2014, 16, 5536. (c)
Chowdhury, S.; Chanda, T.; Koley, S.; Ramulu, B. J.; Jones, R. C. F.; Singh, M. S. Org. Lett. 2013,
15, 5386. (d) Singh, M. S.; Nagaraju, A.; Verma, G. K.; Shukla, G.; Verma, R. K.; Srivastava, A.;
Raghuvanshi, K. Green Chem. 2013, 15, 954. (e) Shukla, G.; Srivastava, A.; Singh, M. S. Org. Lett.
2016, 18, 2451.
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(12) (a) Samai, S.; Nandi, G. C.; Singh, M. S. Tetrahedron 2012, 68, 1247. (b) Nandi, G. C.; Samai,
S.; Kumar, R.; Singh, M. S. Tetrahedron 2009, 65, 7129. (c) Kumar, R.; Nandi, G. C.; Verma, R. K.;
Singh, M. S. Tetrahedron Lett. 2010, 51, 442. (d) Singh, M. S.; Nagaraju, A.; Anand, N.;
Chowdhury, S. RSC Adv. 2014, 4, 55924. (e) Narute, S.; Pappo, D. Org. Lett. 2017, 19, 2917.
(13) (a) Cheng, C.; Jiang, B.; Tu, S.-J.; Li, G. Green Chem. 2011, 13, 2107. (b) Jiang, B.; Zhang, G.;
Ma, N.; Shi, F.; Tu, S.-J.; Kaur, P.; Li, G. Org. Biomol. Chem. 2011, 9, 3834. (c) Wang, S.-L.;
Zhang, G.; Jie, D.; Jiang, B.; Wang, X.-H.; Tu, S.-J. Comb. Chem. High Throughput Screening 2012,
15, 400.
(14) (a) Berridge, M. V.; Herst, P. M.; Tan, A. S. Biotechnol. Annu. Rev. 2005, 11, 127. (b) Gao, .
ua, . ing, . Ma, . u, J. ao, W. Wang, . i, T. Microbiol. Res. 2012, 167, 616. (c)
Pierson, L. S.; Pierson, E. A. Appl. Microbiol. Biotechnol. 2010, 86, 1659. (d) Borrero, N. V.; Bai,
F.; Perez, C.; Duong, B. Q.; Rocca, J. R.; Jin, S.; Huigens, R. W. Org. Biomol. Chem. 2014, 12, 881.
(15) Monocrystal of 3ap was obtained after recrystallization in methanol (see the SI for details
Figure S1). The crystallographic coordinates have been deposited with the Cambridge
Crystallographic Data Centre; Deposition no. CCDC 1535633 (3ap). These data can be obtained free
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of charge from the Cambridge Crystallographic Data Centre, 12 Union Rd., Cambridge CB2 1EZ,
UK.
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(16) Samuel, R.; Asokan, C. V.; Suma, S.; Chandran, P.; Retnamma, S.; Anabha, E. R. Tetrahedron
Lett. 2007, 48, 8376.
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