Microwave-assisted coupling reaction of N-Aryl Sydnones with 2-nitromethylenethiazolidine: Unexpected formation of (Z)-2-(Nitro((E)- p -substitutedphenyldiazenyl)methylene)thiazolidines

Article abstract of DOI:10.1021/jo5010229

Reaction of N-aryl sydnones with 2-nitromethylenethiazolidine straightforwardly gives rise to the formation of (Z)-2-(nitro((E)-p- substitutedphenyldiazenyl)methylene)thiazolidines in xylene and dimethoxyethane under microwave irradiation. A meaningful and plausible mechanism for this transformation is proposed, which anticipates the extrusion of an aceto-lactone-like moiety before a coupling occurs. The structures of all the new compounds were identified on the basis of the data obtained from the NMR, IR, X-ray diffraction spectra, HRMS measurements, and physical characteristics.

Full text of DOI:10.1021/jo5010229

Note
pubs.acs.org/joc
Microwave-Assisted Coupling Reaction of N‑Aryl Sydnones with
2‑Nitromethylenethiazolidine: Unexpected Formation of (Z)‑2-
(Nitro((E)‑p‑substitutedphenyldiazenyl)methylene)thiazolidines
Yasa̧ r Durust* and Akın Sagırlı
̆
̈ ̈
̇
Department of Chemistry, Abant Izzet Baysal University, TR-14280, Bolu, Turkey
S
* Supporting Information
ABSTRACT: Reaction of N-aryl sydnones with 2-nitro-
methylenethiazolidine straightforwardly gives rise to the
formation of (Z)-2-(nitro((E)-p-substitutedphenyldiazenyl)-
methylene)thiazolidines in xylene and dimethoxyethane under
microwave irradiation. A meaningful and plausible mechanism
for this transformation is proposed, which anticipates the
extrusion of an aceto-lactone-like moiety before a coupling
occurs. The structures of all the new compounds were identified
on the basis of the data obtained from the NMR, IR, X-ray
diffraction spectra, HRMS measurements, and physical
characteristics.
Upon an initial examination of the structures of the reaction
ydnones constitute a well-defined class of mesoionic
Scompounds obtained by the action of acetic anhydride or products, basically, on the basis of NMR, IR and HRMS data,
1,3-dibromo-5,5-dimethylhydantoin on N-nitroso derivative.1,2
despite the expected spiro structures (Scheme 2) we concluded
that fused cyclic compounds (Scheme 3) might be formed. This
could be confirmed by the existing two triplets of the
methylene protons, which are originated from the 2-nitro-
methylenethiazolidine. In addition, NH proton, which is
located adjacent to nitro group, might arise quite much
deshielded at around 14.5 ppm in the proton NMR spectra and
exhibits a strong absorption at around 3300−3400 cm−1 in the
IR spectra. Also, LC−MS spectra and HRMS measurements
reveal that M + H values exactly coincide with the molecular
formulas of the structures. But, however, when we were able to
obtain a fine crystal of the compound 3b, X-ray diffraction
ORTEP view revealed the structures assigned as depicted in
Scheme 1. As for 13C NMR signals, the carbon resonance of the
one attached to nitro group appeared at around 162 ppm, and
the other exocyclic double bond carbon did at around 150 ppm
(in DMSO-d6). We have noticed that one carbon resonance is
missing for some samples recorded in CDCl3. For this reason,
we decided to record 13C NMR spectra in dimethyl sulfoxide-d6
instead of CDCl3 for those samples. In this regard, we observed
8 carbon signals for compound 3g and 9 carbons for 3b. NH
proton chemical shifts have arose at around 12.7 ppm in
DMSO-d6.
These compounds are of interest because of the varied types of
biological activity displayed by some of them, particularly
sydnone 4-heterocycles.3−5 On the other hand, thiazolidine ring
substituted heterocyclic scaffolds have been reported as
insecticide agent against Lepidoptera species.6−8 Diazenyl
substituted compounds have also been found to exhibit various
biological activities such as antifungal, antibacterial, and
anticancer activities.9−11
Taking account of the above considerations, plus our
continuous interest in 1,3-dipolar cycloaddition chemistry of
various ylides leading to pyrazoles, triazoles and spiropyr-
roles,12−15 and our recent interest in 2-nitromethylene
thiazolidine chemistry,16−19 we have focused herein on the
reaction of N-aryl sydnones as ylide generating precursor with
2-nitromethylenethiazolidine as dipolarophilic reagent.
Syndones are known to react with dipolarophiles in 1,3-
dipolar cycloaddition route.20,21 But, however, in our case,
mesoionic sydnones 1 underwent, unexpectedly, a coupling
reaction with the electron deficient dipolarophile, 2-nitro-
methylene thiazolidine 2, under microwave irradiation instead
of 1,3-dipolar cycloaddition and afforded 8 novel (Z)-2-
(nitro((E)-p-substitutedphenyldiazenyl)methylene)-
thiazolidines 3a−h (Scheme 1), and their structures were
identified by means of IR, NMR, mass spectra, X-ray diffraction
data and physical characteristics. We were able to crystallize one
of the compounds (3b) to obtain X-ray diffraction data leading
us to establish exact structures of the end products (see
Supporting Information).
A possible reaction mechanism for this transformation was
proposed below (Scheme 4). It seems to be most likely that a
structure resembling acetolactone or methylenedioxirane22−26
Received: May 11, 2014
© XXXX American Chemical Society
A
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Note
Scheme 1. Reaction between N-Aryl Sydnones 1 and 2-Nitromethylenethiazolidine 2
Scheme 2. Anticipated Reaction Products of Sydnone-2-nitromethylenethiazolidine 1,3-Dipolar Cycloaddition Leading to Spiro
Heterocycles 6 or 7
diazonium chlorides to form 1-nitro-1-arylazo-2,2-diamino
ethylene (Scheme 6).28
Scheme 3. Anticipated Reaction Products of Sydnone-2-
nitromethylenethiazolidine 1,3-Dipolar Cycloaddition
Leading to Fused Heterocycles 8
NH proton shifted up to 14.5 ppm was not frequently
encountered. Therefore, we may think about a tautomeric
equilibriation in NMR solvent (CDCl3) or a resonance form as
depicted in Scheme 7. In this way, due to being closer to quite
electron deficient nitrogens via a complete electron delocaliza-
tion, we can consider that OH proton arises at around 14.5
ppm which shifts to 12.7 in DMSO-d6. Another supporting
evidence might be our failed attempts of trying D2O exchange
of NH proton, caused by this fast equilibrium.
In conclusion, this work represents, to the best of our
knowledge, the first example of the N-aryl sydnone-2-
nitromethylenethiazolidine reaction resembling a diazo cou-
pling at which possibly an intermediate anticipated as
acetolactone (oxiranone) or methylenedioxirane is liberated
and so far not reported.
is released during the reaction but not isolated (Scheme 5). It
was reported that only in the case of trifluoromethyl
substitution, these structures are stable and can be isolated.
In addition, in a study it was reported that during the
nitrosation of amino acids, lactones have been formed as
alkylating agents.27
Schafer and Gewald reported that N,N′-disubstituted 1-nitro-
2,2-diamino ethylenes underwent an azo-coupling with benzene
B
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Note
Scheme 4. Proposed Mechanism for the Generation of 3a−h
Scheme 7. Nitro-aci-nitrolic Acid Type Tautomerization and
Resonance Form of (Z)-2-(Nitro((E)-p-
substitutedphenyldiazenyl)methylene) Thiazolidines
NMR chemical shifts are reported in parts per million from
tetramethylsilane (TMS) with the solvent resonance as the internal
standard (CDCl3 at 77.20 ppm, DMSO-d6 at 39.51 ppm). IR spectra
were recorded in KBr; v in cm−1. Mass spectra were run on an LC−
̃
MS instrument equipped with an ESI probe operating in positive or
negative ion mode, in m/z (rel. %). HRMS was performed on a TOF
LC−MS equipped with an ESI probe operating in positive or negative
ion mode.
General Procedure for Synthesis of (Z)-2-(Nitro((E)-p-
substitutedphenyldiazenyl)methylene)thiazolidines 3a−h. A
mixture of p-substitutedphenyl sydnone 1 (0.5 mmol) and 2-
nitromethylenethiazolidine 2 (0.5 mmol, 73 mg) in xylene (5 mL)
was irradiated by microwave (CEM Discover) at 125 °C, which was
measured by internal probe, for 15 min. The reaction was monitored
by TLC (n-hexane/EtOAc,1:1). After the completion of the reaction,
the solvent was removed under the reduced pressure and crude
product was chromatographed to give 3a−h.
Scheme 5. Resonance Forms of Acetolactone (Oxiranone)
Structure
(Z)-2-(Nitro((E)-phenyldiazenyl)methylene)thiazolidine (3a).
Yield: 28.7 mg, 52%. Yellow oil: Rf 0.38 (EtOAc:n-hexane, 1:1); IR
(KBr, cm−1) 3419 (NH), 2926, 1631, 1554, 1263, 1049, 794; 1H NMR
(400 MHz, CDCl3) δ 14.56 (s, 1H, NH), 7.51 (dd, J = 7.6, 1.2 Hz,
2H), 7.41 (t, J = 8.2 Hz, 2H), 7.25−7.21 (m, 1H), 4.46 (t, J = 8.6 Hz,
2H, NCH2), 3.24 (t, J = 8.8 Hz, 2H, SCH2); 13C NMR (126 MHz,
CDCl3) δ 162.6, 142.6, 129.8, 126.8, 117.7, 61.5 (NCH2), 29.8
(SCH2); LC−MS (AP-ESI) m/z (%) 251.7 [M+ + H]; HRMS m/z
(ESI-TOF, [M + H]+) calcd for C10H11N4O2S 251.0603, found
251.0589.
EXPERIMENTAL SECTION
■
General Methods. Reagents were purchased from commercial
sources and were used as received. CEM DISCOVER Microwave
Reactor was used and progress of the reactions were monitored by
TLC. 1H NMR and 13C NMR (400 and 100 MHz, respectively)
1
spectra were recorded in CDCl3 and DMSO-d6. H NMR chemical
shifts are reported in parts per million relative to tetramethylsilane
(TMS) with the solvent resonance employed as the internal standard
(CDCl3 at 7.26 ppm, DMSO-d6 at 2.50 ppm). Data are reported as
follows: chemical shift (multiplicity, coupling constant(s) in Hz,
integration). Multiplicities are abbreviated as follows: s = singlet, br s =
broad singlet, d = doublet, t = triplet, q = quartet, m = multiplet. 13C
(Z)-2-(Nitro((E)-p-tolyldiazenyl)methylene)thiazolidine (3b). Light
yellow needles (dichloromethane:n-hexane). Yield 26.4 mg, 20%: mp
135 °C (decomposed); Rf 0.38 (EtOAc:n-hexane, 1:1) IR (KBr, cm−1)
1
3356 (NH), 2920, 1653, 1548, 1421, 1276, 1053, 817, 734; H NMR
(400 MHz, CDCl3) δ 14.55 (s, 1H, NH), 7.42 (d, J = 8.0 Hz, 2H),
Scheme 6. Azo Coupling of 1-Nitro-2,2-diamino Ethylenes
C
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The Journal of Organic Chemistry
Note
7.21 (d, J = 8.4 Hz, 2H), 4.42 (t, J = 8.6 Hz, 2H, NCH2), 3.21 (t, J =
8.4 Hz, 2H, SCH2), 2.35 (s, 3H); H NMR (400 MHz, DMSO-d6) δ
CDCl3) δ 162.9 (CC-NO2), 149.1 (CC-NO2), 147.4, 140.9,
114.5, 108.3, 101.9, 98.9 (OCH2O), 57.8 (NCH2), 30.0 (SCH2); LC−
MS (AP-ESI) m/z (%) 295 [M + H]; HRMS m/z (ESI-TOF, [M +
H]+) calcd for C11H11N4O4S 295.0501, found 295.0490.
1
12.44 (br s, 1H, NH), 7.63 (d, J = 8.0 Hz, 2H), 7.24 (d, J = 8.4 Hz,
2H), 4.16 (t, J = 8.6 Hz, 2H, NCH2), 3.25 (t, J = 8.4 Hz, 2H, SCH2),
2.30 (s, 3H).13C NMR (100 MHz, CDCl3) δ 162.5 (CC-NO2),
140.6, 137.0, 130.2, 117.8, 60.8 (NCH2), 30.5 (SCH2), 21.2 (CH3);
13C NMR (100 MHz, DMSO-d6) δ 162.7 (CC-NO2), 148.1 (C
ASSOCIATED CONTENT
* Supporting Information
■
S
C-NO2), 138.7, 135.8, 130.3, 121.1, 53.9 (NCH2), 29.2 (SCH2), 21.3
(CH3).LC−MS (AP-ESI) m/z (%) 265.7 [M+ + H]; HRMS m/z
(ESI-TOF, [M + H]+) calcd for C11H13N4O2S 265.0759, found
265.0750.
X-ray ORTEP view of the compound 3b, 1H, 13C NMR, COSY
and NOESY of the compound 3h, HRMS spectra of all new
compounds. This material is available free of charge via the
Internet at http://pubs.acs.org. X-ray diffraction data of
compound 3b have been deposited at the Cambridge
Crystallographic Data Centre and assigned CCDC 996089
deposition number. It can be obtained free of charge from
http://www.ccdc.cam.ac.uk/data_request/cif.
(Z)-2-(((E)-(4-Methoxyphenyl)diazenyl)(nitro)methylene)-
thiazolidine (3c). Orange oil. Yield 32.2 mg, 23%: Rf 0.36 (EtOAc:n-
hexane, 1:1); IR (KBr, cm−1) 3423 (NH), 2916, 1664, 1514, 1467,
1
1379, 1263, 738; H NMR (400 MHz, CDCl3) δ 14.24 (s, 1H, NH),
7.52 (d, J = 8.8 Hz, 2H), 6.94 (d, J = 8.8 Hz, 2H), 4.38 (t, J = 8.6 Hz,
2H, NCH2), 3.84 (s, 3H, OCH3), 3.23 (t, J = 8.6 Hz, 2H, SCH2); 13
C
NMR (100 MHz, CDCl3) δ 162.7 (CC-NO2), 159.2 (C−OCHH3),
138.6, 135.2, 120.2, 114.8, 58.5 (NCH2), 55.6 (OCH3), 30.1 (SCH2);
LC−MS (AP-ESI) m/z (%) 281 [M+ + H]; HRMS m/z (ESI-TOF,
[M + H]+) calcd for C11H13N4O3S:281.0708, found 281.0701.
(Z)-2-(((E)-(4-Fluorophenyl)diazenyl)(nitro)methylene)-
thiazolidine (3d). Orange oil. Yield 26.8 mg, 20%: Rf 0.35 (EtOAc:n-
hexane, 1:1); IR (KBr, cm−1) 3437 (NH), 2916, 1637, 1548, 1483,
AUTHOR INFORMATION
Corresponding Author
*E-mail: yasardurust@ibu.edu.tr.
Notes
■
The authors declare no competing financial interest.
1
1427, 1267, 839, 734; H NMR (400 MHz, CDCl3) δ 14.24 (s, 1H,
ACKNOWLEDGMENTS
■
NH), 7.55−7.52 (m, 2H), 7.12 (t, J = 8.6 Hz, 2H), 4.41 (t, J = 8.8 Hz,
2H), 3.25 (t, J = 8.6 Hz, 2H); 13C NMR (126 MHz, CDCl3) δ 163.0
(CC-NO2), 161.6 (C−F, d, J = 245.8 Hz), 140.7, 134.8, 120.1,
116.8, 59.5 (NCH2), 30.5 (SCH2); LC−MS (AP-ESI) m/z (%) 269
[M+ + H]; HRMS m/z (ESI-TOF, [M + H]+) calcd for
C10H10N4O2FS 269.0509, found 269.0497.
̈
̇
TUBITAK (Turkish Scientific and Technological Research
̇
Council, Grant No. 211T037) and Abant Izzet Baysal
University, Directorate of Research Projects Commission
(BAP Grant No. 2011.03.03.377) are gratefully acknowledged
for financial support.
(Z)-2-(((E)-(4-Chlorophenyl)diazenyl)(nitro)methylene)-
thiazolidine (3e). Yellow oil. Yield 38.3 mg, 27%: Rf 0.35 (EtOAc:n-
hexane, 1:1); IR (KBr, cm−1) 3419 (NH), 2916, 1629, 1548, 1483,
REFERENCES
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1419, 1267, 835, 732; H NMR (400 MHz, CDCl3) δ 14.34 (s, 1H,
NH), 7.47 (d, J = 9.2 Hz, 2H), 7.38 (d, J = 8.4 Hz, 2H), 4.43 (t, J = 8.8
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1265, 1051, 829, 738; H NMR (400 MHz, CDCl3) δ 14.36 (s, 1H,
NH), 7.53 (d, J = 8.8 Hz, 2H), 7.41 (d, J = 8.8 Hz, 2H), 4.43 (t, J = 8.8
Hz, 2H, NCH2), 3.25 (t, J = 8.8 Hz, 2H, SCH2); 13C NMR (100 MHz,
CDCl3) δ 165.4 (CC-NO2), 150.5 (CC-NO2), 132.8, 129.9,
129.2, 125.3, 66.7 (NCH2), 33.1 (SCH2); LC−MS (AP-ESI) m/z (%)
329 [M+ + H]; HRMS m/z (ESI-TOF, [M + H]+) calcd for
C10H10N4O2S79Br 328.9708, found 328.9685.
(Z)-2-(((E)-(4-Iodophenyl)diazenyl)(nitro)methylene)thiazolidine
(3g). Yellow oil. Yield 50.6 mg, 27%: Rf 0.36 (EtOAc:n-hexane, 1:1);
IR (KBr, cm−1) 3323 (NH), 2924, 1663, 1546, 1485, 1267, 1051,
1
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1003, 823, 738; H NMR (400 MHz, CDCl3) δ 14.39 (s, 1H, NH),
7.72 (d, J = 8.8 Hz, 2H), 7.27 (d, J = 10.0 Hz, 2H), 4.43 (t, J = 8.6 Hz,
2H, NCH2), 3.25 (t, J = 8.6 Hz, 2H, SCH2); 13C NMR (100 MHz,
CDCl3) δ 162.8, 143.0, 138.6, 119.6, 90.9 (C−I), 60.4 (NCH2), 30.6
(SCH2); 13C NMR (100 MHz, DMSO-d6) δ 163.0 (CC-NO2),
150.2 (CC-NO2), 138.6, 136.1, 123.2, 94.9 (C−I), 53.7 (NCH2),
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(Z)-2-(((E)-Benzo[d][1,3]dioxol-5-yldiazenyl)(nitro)methylene)-
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