Substituent effect on the tautomerization of 1-arylazonaphthalen-2-ols by mass spectrometric analysis

Article abstract of DOI:10.1002/jccs.201400305

An electron-ionization (EI) mass spectra of a series of 1-arylazonaphthalen-2-ols was obtained for studying the substituent effect on the fragmentation. The correlation between the ratio, molecular ion and fragment ion, and Hammett's constants is applied to examine the effect of the substituent on the fragmentation. The negative correction between the ratio, I_{molecular ion}/(I_171amu + I_143amu + I_115amu), and Hammett's constants indicates an electron-withdrawing group destabilized the molecular ion. An unusual long-range hydrogen transfer demonstrates an important role in the fragmentation process Mass spectra of a series of 1-arylazonaphthalen-2-ols were obtained for studying the substituent effect on the fragmentation. The correlation between the ratio of molecular ion and fragment ion, and Hammett's constants is applied to examine the effect of substituent on the fragmentation. The negative correction indicates an electron-with-drawing group destabilized the molecular ion. An unusual long-range hydrogen transfer demonstrates an important role in the fragmentation process.

Full text of DOI:10.1002/jccs.201400305

JOURNAL OF THE CHINESE
CHEMICAL SOCIETY
Article
Substituent Effect on the Tautomerization of 1-Arylazonaphthalen-2-ols by Mass
Spectrometric Analysis
Shaw-Tao Lin,a,* Lee-Hui Lin,a,b Yi-Cang Lina and Mei-Fan Dinga
aDepartment of Applied Chemistry, Providence University, Sha-Lu, Taichung 43301, Taiwan
bDepartment of Cosmetic Science & Application, Lan Yang Institute of Technology, I-Lan, 261, Taiwan
(Received: Jul. 19, 2014; Accepted: Oct. 27, 2014; Published Online: ??; DOI: 10.1002/jccs.201400305)
An electron-ionization (EI) mass spectra of a series of 1-arylazonaphthalen-2-ols was obtained for study-
ing the substituent effect on the fragmentation. The correlation between the ratio, molecular ion and frag-
ment ion, and Hammett’s constants is applied to examine the effect of the substituent on the fragmentation.
The negative correction between the ratio, Imolecular ion/(I171amu + I143amu + I115amu), and Hammett’s constants
indicates an electron-withdrawing group destabilized the molecular ion. An unusual long-range hydrogen
transfer demonstrates an important role in the fragmentation process.
Keywords: Arylazonaphthalen-2-ols; Tautomers; MS; Substituent effect; Long-range hydrogen
transfer.
INTRODUCTION
Arylazonaphthalen-2-ols are well known compounds
in fragmentation upon the substituent and position in the
aryl group and an unusual long-range hydrogen transfer (or
two subsequent ortho effects).
as dyestuffs and can coexist in two tautomer forms, i.e. azo
and hydrazone. The tautomerization is quite interesting
from a theoretical standpoint because tautomers have dif-
ferent technical properties.1 From the IR and UV spectra
of the 1-phenylazonaphthalen-2-ols, it is possible to qual-
itatively follow changes in the proportions of the enol-
and keto-forms as substituents on the phenyl-ring are
changed.1f-1h Both techniques strongly indicate that in solu-
tion, there exists a true tautomeric mixture of enol- and
keto-forms, in proportions dependent upon the substituents
and upon the solvent. The NMR spectra demonstrate as a
single form due to the requirement of long time-scale for
spectra acquisition. The fragmentation of the molecular ion
in the mass spectrometer strongly depends on the nature of
the molecular structure for formation of stable fragments.
The molecular ions can also undergo isomerization via hy-
drogen migration. The proton of the hydroxyl group and
the N(b) hydrogen in the arylazonaphthanen-1-ol system
can form a hydrogen bond via a six-membered ring which
is ready for tautomerization. Both tautomers undergo dif-
ferent fragmentation patterns. The distribution of the
tautomers depends on the basicity of N(b), which strongly
depends on the nature of the substituent on the phenyl
ring.2 Although the tautomerisms in the gas phase have
been studied to some extent,3 based on our knowledge, no
systematic mass spectroscopic study on 1-arylazonaph-
thols is reported. Here, we would like to report the variation
RESULTS AND DISCUSSION
Preparation of 1-arylazonaphthalen-2-ols
1-Arylazonaphthalen-2-ols were prepared in good
yields from the coupling of aryldiazonium and naphtha-
len-2-ol in an ionic liquid, {[NMP]+[CH3SO3]-}. 1-(Ami-
nophenylazo)naphthalen-2-ol was only obtained as a sin-
gle product from reduction of its nitro-precursor using
Na2S as a reducing agent. Due to the high reactivity of the
azo group, other reducing agents would reduce azo to hy-
drazine along with the reduction of the nitro group.
General fragmentation
The protonated molecular ion and/or adduct of multi-
ple molecules were often observed in an ion trap mass spec-
trometer during the trapping process. To gain the spectra
from the molecular fragmentation without bimolecular re-
action, the concentration of the analyte for analysis was
carefully manipulated to minimize the protonation process
* Corresponding author. E-mail: sdlin@pu.edu.tw
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Lin et al.
Table 1. Mass spectra of 1-arylazonaphthalen-2-ols
as well as the adduct formation. The mass spectra of the se-
ries of 1-arylazonaphthalen-2-ols were summarized in Ta-
ble 1 and the typical spectrum is shown in Figure 1. The
[M]+., [M-CO]+.(G), [M-CHO]+ and the ions at m/z 171(D),
143 (A or F) and 115 (C) are the major fragment. Ions A (or
F), and C are derived from the naphthalen-2-ol skeleton for
this series. In general, the main fragmentation is initiated
by the cleavage of the aryl ring and N(b) bond. The forma-
tion of ion at m/z 171 (D) and lack of ion at m/z 105 indi-
cates that the diazonium unit remain preferably bound to
the naphthalene ring. The even-electron [M-CHO]+ peak,
which is usually accompanied by [M-CO]+., is a character-
istic fragment for phenols. The formation of [M-CHO]+
ions can be considered as a sequence of losing H followed
by CO due to the presence of moderate intensity of [M-
H]+.3a The possible fragmentation mechanism is proposed
as shown in Scheme 1.
1-(4-(N,N-dimethylamino)phenylazo)naphthalen-2-ol (1)
77(4), 115(4), 120(8), 121(4), 133(5), 135(62), 136 (20), 137(8),
165(5), 195(4), 264(7), 291(M+., 100), 292(20).
1-(4-aminophenyl)naphthalen-2-ol (2)
65(13), 80(8), 89(5), 92(23), 107(27), 108(18), 115(11), 120(14),
128(6), 143(4), 218(4), 234(7), 246(9), 262(12), 263(M+., 100),
264(18).
1-(4-methoxyphenylazo)naphthalen-2-ol (3)
77(12), 107(9), 115(21), 116(4), 122(8), 125(5), 128(5), 135(8),
143(13), 171(3), 235(10), 247(5), 261(7), 263(11), 277(21), 278
(M+., 100), 279(19).
1-(4-methylphenylazo)naphthalen-2-ol (4)
65(6), 91(12), 115(21), 117(10), 143(21), 171(6), 218(4), 219(6),
233(7), 247(6), 261(28), 262(M+., 100), 263(19).
1-(3-aminophenylazo)naphthalen-2-ol (5)
65(7), 89(5), 115(40), 116(6), 129(4), 143(23), 144(5), 171(5),
189(5), 206(6), 207(7), 217(5), 218(16), 219(6), 234(25),
235(16), 246(11), 262(11), 263(M+., 100), 264(19).
1-(4-(N-acetylamino)phenylazo)naphthalen-2-ol (6)
65(9), 115(16), 128(4), 143(12), 218(25), 219(10), 234(17),
235(21), 262(8), 276(42), 277(13), 291(4), 305(M+., 100),
306(20).
The possible fragmentation of parent 1-aryl-
Scheme 1
1-phenylazonaphthalen-2-ol (7)
azonaphthalen-2-ol (7)
63(4), 77(7), 83(5), 89(7), 101(6), 111(11), 115(66), 128(4),
129(14), 143(44), 171(10), 219(10), 220(9), 247(24), 248(M+.,
100), 249(18).
1-(4-chlorophenylazo)naphthalen-2-ol (8)
63(4), 74(4), 75(10), 89(9), 101(4), 111(11), 115(81), 128(6),
143(49), 144(6), 171(12), 218(5), 219(11), 246(5), 247(24),
265(6), 281(28), 282(M+., 100), 283(28), 284(35), 285(6).
1-(3-chlorophenylazo)naphthalen-2-ol (9)
75(5), 89(5), 111(5), 115(100), 129(5), 143(75), 144(5), 171(20),
189(5), 219(10), 247(15), 281(10), 282(M+., 80), 283(20),
284(25).
1-(3-nitrophenylazo)naphthalen-2-ol (10)
75(4), 89(7), 114(4), 115(60), 143(36), 171(13), 218(5), 246(6),
247(11), 248(5), 276(8), 292(29), 293(M+., 100), 294(18).
1-(4-nitrophenyl)naphthalen-2-ol (11)
75(4), 89(8), 115(54), 129(4), 143(27), 171(10), 218(5), 246(8),
247(9), 248(5), 265(5), 276(10), 292(32), 293(M+., 100), 294(18).
1-(2-nitrophenylazo)naphthalen-2-ol (12)
The accurate masses determined from high-resolu-
tion mass spectrometry were used for determining the ion
formula to ensure the fragmentation pathway. The mass of
ions G corresponding to [M-28]+ from compound 7 and 11
are 220.1007 (220.1001 calculated from C15H12N2) and
265.0847 (265.0846 calculated from C15H11N3O2), respec-
tively. The exact masses of ion Aare 143.0490 and 143.0492
compared to the value of 143.0497 calculated from C10H7O
for 7 and 11, respectively. There is no signal corresponding
to ion F (C9H7N2, 143.0610 amu) from the ion with 143
amu suggesting that the fission of dinitrogen is a very feasi-
ble process. Compound 12 containing an ortho-nitro group
form a fragment with 246 amu which is 18 amu less than
that of the molecular ion. The exact mass of ion with 246
89(6), 114(5), 115(54), 143(31), 171(6), 218(8), 245(4), 246(17),
247(5), 259(12), 276(100), 277(18), 293(M+., 41), 294(7).
1-(2-hydroxycarbonylphenylazo)naphthalen-2-ol (13)
65(4), 75(6), 89(11), 101(4), 113(4), 115(63), 116(10), 128(11),
129(4), 137(4), 143(26), 144(10), 156(4), 189(20), 190(9),
218(46), 219(13), 245(33), 246(51), 247(19), 248(6), 274(100),
275(20), 292(M+., 64), 293(13).
1-(2-methoxycarbonylphenylazo)naphthalen-2-ol (14)
77(5), 89(5), 115(27), 116(16), 143(21), 189(14), 190(8),
218(35), 220(11), 245(23), 246(22), 247(11), 274(100), 275(19),
306(M+., 56), 307(14).
amu is 246.0796, which corresponds to C16H10N2O (calc.
246.0794) and indicated the loss of an H2O unit. The fol-
2
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Tautomerization of Arylazonaphthols in MS Analysis
Fig. 1. The mass spectra of compound 7.
and of a neutral NO molecule with rearrangement to form
the phenoxy cation [M-30]+ are the good diagnostic peaks
for the nitroarenes.5 However, the former is weak and the
latter is absent from compounds 10, 11, and 12. This is evi-
dence of a stronger C=N bond due to a high degree of reso-
nance, even for the formation of hydrazine type structure
H.
lowing fragment ion resulted from the loss of a CO mole-
cule is confirmed by comparing its exact mass of 218.0853
(218.0845 for C15H10N2).
Substituent effect
Ions A (143 amu), C (171 amu) and D (115 amu) are
the common fragments for this series of compounds. The
intensities of the ions, 171, 143 and 115 amu, functions of
the substituents were examined. The correlation between
the log[Imolecular ion/(I171amu + I143amu + I115amu)] and Hammett’s
constants (s)4 are shown in Fig. 2. If the nitro substituted
derivatives 10, 11 are excluded, good correlations are ob-
tained with a r and R2 of -0.801 and 0.965, respectively.
The negative value might be attributed to aryl radicals be-
ing destabilized by the phenyl ring containing the elec-
tron-withdrawing group. On the other hand, the nitro group
processes strong electron-withdrawing, resonance and la-
bile characteristics. Under this circumstance, the diazo
form can be converted to the hydrazone form (H). With the
presence of C=N in hydrazone, the formation of ion with
171 amu becomes less favorable. Normally, prominent
peaks resulting from elimination of an NO2 radical [M-46]+
Fragments at m/z 135 (62%) and m/z 107 (27%) are
observed in the spectra from 4-amino derivative 1, 2, re-
spectively. The exact mass of both ions are 135.0923,
107.0611 corresponding to ion I (135.0923 calculated from
C8H11N2 and 107.0610 calculated from C6H7N2). The frag-
ment with 122 amu (8%) from 4-methoxy derivative 3 can
be assumed to possess a similar structure. The formation of
ion I suggests the formation of hydrazone tautomer is rela-
tively pronounced for the compounds containing the ami-
no, and methoxy group at the para position (i.e. 1, 2, 3),
while, the fission of an N-N single bond required relatively
low energy and the positive charge located at the hetero-
atom is also a stable system.
Ortho effect
The proximity effect for the ortho disubstituted aro-
matic ionic structures is very pronounced in the fragmenta-
tion of molecules in the mass spectrometer.6 In general, the
Fig. 2. The correlation between the log[Imolecular ion
/
(I171amu + I143amu + I115amu)] and Hammett’s con-
stant s.
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Article
Lin et al.
Table 2. The Hammett’s constants4 and the fragment intensities
ratios for arylazonaphthalen-2-olsa
The possible fragmentation of losing a water
molecule from the ortho-substituent deriva-
tive 13
Scheme 2
Compds
ó
s+
ratioa
log ratio
4-N(CH3)2 (1)
4-NH2 (2)
4-OCH3 (3)
4-NHAc (6)
4-CH3 (4)
3-NH2 (5)
H (7)
-0.63
-0.57
-0.28
0.00
-0.06
-0.09
0
-1.70
-1.30
-0.78
-0.60
-0.31
-0.16
25
1.39
0.84
0.43
0.55
0.03
0.13
-0.09
6.92
2.69
3.57
1.07
1.34
0.82
ortho effect occurs when two substituents are located on
the same benzene ring. However, two substituents can be
eliminated during fragmentation, even if they are not in the
same ring for these series compounds. Compounds 12, 13,
and 14 showed the [M-17]+, [M-18]+. and [M-32]+., respec-
tively, as the base peaks. In the case of compounds 13 and
14, the ions of [M-H2O]+. and [M-CH3OH]+. appear as the
base peak, which undergoes substantial further fragmenta-
tion, resulting in a rather complicated spectrum. By in-
specting the spectrum of 13, we can conclude the fragments
resulted from two main parallel fragmentation pathways,
i.e. cleavage of the aryl ring and N(b) bond and fragmenta-
tion from [M-18]+.. From the intensities of the fragments,
the process from the latter is more important than the for-
mer. The disubstituents presence as an ortho-form are fa-
vorable for a five- or six-membered ring transition state for
elimination and left a fragment with a high degree of the
conjugation system, as shown in Scheme 2.6 The elimina-
tion process can be either a single process or a two-step
process. We are unable to judge which one is a possible
pathway. However, this pronounced long-range hydrogen
transfer is an unusual example.
EXPERIMENTAL
The mass spectra of fourteen 1-arylazonaphthalene-2-ols
Fig. 3. The spectrum of compound 10, where the [M-H2O]+. appears as a base peak.
4
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Tautomerization of Arylazonaphthols in MS Analysis
was obtained under electron impact with an ionization potential
of 70 eV on a mass spectrometer (Thermo PolarisQ) via a direct
insertion probe. The relative abundances were the averages of
three consecutive measurements. The high-resolution mass spec-
tra were obtained on a JEOL HX110 Double Focusing Magnetic
Sector Mass Spectrometer at National Chung Hsien University.
Preparation: 1-Methylpyrrolidonium hydrogen sulfate
{[NMP]+[CH3SO3]-}, solvent for coupling of diazonium ion and
naphthalen-2-ol, was prepared according to the literature.7
128.8, 129.9, 130.3, 133.6, 140.2, 145.3, 147.7, 173.1; Anal.
calcd. for C16H13N3O: C, 72.99; H, 4.98; N, 15.96. Found: C,
72.87; H, 4.97; N, 16.07.
Preparation of 1-(4-acetylaminophenylazo)-naphtha-
len-2-ol (6): Under N2 atmosphere the solution of 1-(4-amino-
phenylazo)naphthalen-2-ol (2, 26 mg, 0.1 mmol) in acetic anhy-
dride (1.0 mL) was heated at 100 °C in an for 1 h, the mixture was
poured onto ice-water (5.0 mL) to give a dark brown solid.
Recrystallization from ethanol gave 28 mg (92% yield) of com-
pound 6, mp. 259-260 °C, 1H NMR d 2.23 (s, 3H), 6.95 (d, 1H, J
9.2 Hz), 7.39 (t, 1H, J 7.6 Hz), 7.56(t, 1H, J 7.2 Hz), 7.63 (m, 2H),
7.68 (m, 2H), 7.74 (d, 1H, J 7.6 Hz), 7.77 (d, 1H, J 8.4 Hz), 8.62
(d,1H, J 8.4 Hz); 13C NMR d 24.8, 120.3, 120.6, 121.7,123.5,
125.3, 125.9, 128.1, 128.5, 129.9, 133.4, 138.6, 142.6, 167.0,
168.2; Anal. calcd. for C18H15N3O2: C, 70.81; H, 4.95; N, 13.76.
Found: C, 70.79; H, 4.97; N, 13.80.
Synthesis of 1-(4-methyphenylazo)naphthalene-2-ol (4):
The mixture of sodium nitrite (0.69 g, 10 mmol) and
[NMP]+[CH3SO3]- (5.0 g) was stirred in an ice-bath for 10 minute
and then 4-methylaniline (1.07 g, 10 mmol) in 37% HCl (5 mL)
was added to the mixture for formation of diazonium salt which is
allowed to react with naphthalen-2-ol (1.30 g, 9 mmol) in 10%
NaOH (24 mL) solution. The reaction mixture was stirred under
an ambient temperature for 10 min. The reaction progress was
monitored by thin-layer chromatography (TLC) using a mixture
of EtOAc and n-hexane (1:1; V/V) as solvent. Following the dis-
appearance of the starting materials, the reaction mixture was fil-
trated and washed with water. The aqueous layer was further ex-
tracted with ethyl acetate (3 ´ 10 mL). The combined organic
layer was dried with MgSO4 and filtration, and the solvent was
evaporated by a rotary evaporator at reduced pressure to dry. The
crude product was purified by passing through a short silica col-
umn. By this procedure, 2.1 g (80% yield) azo product 4 was ob-
tained with 74% isolated yield, mp.127-129 °C (lit mp. 129 °C).8
The same procedure was used to prepare the other compounds.
The products were confirmed by comparing the mp and NMR
spectra with literatures: Compounds (1, 3, 4, 7~12)9, 210 and 13.11
Preparation of 1-(4-aminophenylazo)naphthalen-2-ol
(2) from reduction of 1-(4-nitrophenylazo)-naphthalen-2-ol
(11)11: The solution of 11 (3.51 g, 12.5 mmol) was dissolved in
H2O (100 mL) and the pH of the solution was adjusted to 9~10 by
adding 10% NaOH. After the mixture was heated and maintained
at a temperature of 75~80 °C, Na2S (12.5 g, 50 mmol) was added
as a reducing agent. The progress of the reaction was monitored
by TLC analysis (eluent: EtOAc/hexane = 1:1 (vol)). When com-
pound 11 had disappeared, the precipitates were filtrated and
recrystallized from EtOH to give 3.02 g of compound 2 in 92%
yield, mp. 148-149 °C.(lit. 148 °C).10 Same procedure was used to
prepare 1-(3-aminophenylazo)naphthalen-2-ol (5), mp. 176-178
°C (lit. 179 °C),11 82% yield. 1H NMR d 6.60 (d, 1H, J 7.6 Hz),
6.86 (d, 1H, J 9.2 Hz), 7.07 (d, 1H, J 8.0 Hz), 7.10 (s, 1H), 7.20 (t,
1H, J 8.0 Hz), 7.37 (t, 1H, J 7.2 Hz), 7.54 (t, 1H, J 7.6 Hz), 7.60 (d,
Preparation of 1-(2-methoxycarbonylphenyl)-phtha-
len-2-ol (14) from methylation of 1-(2-hydroxycarbonyl)-
phthalene-2-ol (13): After the mixture of 13 (0.50 g, 1.7 mmol)
and LiOH.2H2O (0.10, 1.7 mmol) in THF (10 mL) was stirred for
30 min, dimethyl sulfate (0.11 g, 0.85 mmol) was added and
refluxed. The progress of the reaction was monitored by TLC
analysis using EtOAc: hexane as an eluent. The duration of the re-
action was about 1 h. Following completion of the reaction, THF
was removed using a rotor evaporator. The resulting mixture was
mixed with 20% NaHCO3 (20 mL) and extracted with EtOAc (3 ´
20 mL). The combined organic layer was dried (MgSO4), fil-
trated, and evaporated to give crude product 14. After recrys-
tallizing from EtOH to give 0.48g, 92% yield, mp. 261-263 °C; 1H
NMR d 4.05 (s, 1H), 6.70 (d, 1H, J 9.6 Hz), 7.18 (t, 1H, J 7.6 Hz),
7.36 (t, 1H, J 7.6 Hz), 7.48 (t, 1H, J 8.4 Hz), 7.53 (t, 2H, J 8.4 Hz),
7.61 (d, 1H, J 9.6 Hz), 7.67 (t, 1H, J 7.6 Hz), 8.08 (d, 1H, J 7.6
Hz), 8.33 (d, 1H, J 8.8 Hz), 8.42 (d, 1H, J 8.0 Hz); 13C NMR 52.6,
116.2, 116.4, 122.4, 124, 126.9, 127.3, 128.6, 128.9, 129.2, 131.4,
133.9, 134.2, 142.4, 144.5, 166.7, 180.2; Anal. calcd. for
C18H14N2O3: C, 70.58; H, 4.61; N, 9.15. Found: C, 70.61; H, 4.55;
N, 9.12.
CONCLUSIONS
The fragmentation patterns strongly depend on the
nature of the substituent on the phenyl ring. Substituent
containing an electron-withdrawing group leads to more
intense fragmentation. Although the elimination of a frag-
ment via the ortho effect often occurs in the disubstituted
arenes, the unusual ortho effect from the different rings in
this series demonstrates the role of fragmentation, which is
an important character for the differentiation of the iso-
1H, J 8.0 Hz), 7.68 (d, 1H, J 9.2 Hz), 8.52 (d, 1H, J 8.4 Hz); 13
NMR d 103.7, 109.6, 114.3, 121.7, 125.2, 125.7, 128.0, 128.6,
C
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I. Rapid Commun. Mass Spectrom. 2010, 24, 714-20.
mers.
4. Hansch, C.; Leo, A.; Taft, R. W. Chem. Rev. 1991, 91, 165-
195.
REFERENCES
5. Silverstein, R. M.; Webster, F. X.; Kiemle, D. J. Spectromet-
ric Identification of Organic Compounds, 7th ed.; John Wiley
& Sons, Inc.: New York, 2005; p 33.
1. (a) Cheon, K. S.; Park, Y. S.; Kazmaier, P. M.; Buncel, E.
Dyes and Pigments 2002, 53, 3-14; (b) Gilli, P.; Bertolasi, V.;
Pretto, L.; Antonov, L.; Gilli, G. J. Am. Chem. Soc. 2005,
127, 4943-4953; (c) Olivieri, A. C.; Wilson, R. B.; Paul, I.
C.; Curtin, D. Y. J. Am. Chem. Soc. 1989, 111, 5525-5532;
(d) Antonov, L.; Stoyanov, S.; Stoyanova, T. Dyes and Pig-
ments 1995, 27, 133-142.; (e) Lycka, A. Dyes and Pigments
1999, 43, 27-32; (e) Hihara, T.; Okada, Y.; Morita, Z. Dyes
and Pigments 2003, 59, 25-41; (f) Reeves, R. L.; Kaiser, R.
S. J. Org. Chem. 1970, 35, 3670-5; (g) Hadi, D. J. Chem. Soc.
1956, 2143; (h) Burawoy, A.; Salem, A. G.; Thompson, A. R.
J. Am. Chem. Soc. 1952, 74, 4793-4997.
6. (a) Lin, S. T.; Lee, C. C.; Chen, L. C.; Huang, K. F. Rapid
Commun. Mass Spectrom. 2004, 18, 935-938; (b) Schwarz,
H. Topic Curr. Chem. 1978, 73, 231-263; (c) Benoit, F.;
Holmes, J. L. Org. Mass Spectrom. 1970, 3, 993-1007.
7. Tong, X.; Li, Y. ChemSusChem 2010, 3, 350-355.
8. Prajapati, H. R.; Doshi, A. V. J. Indian Chem. Soc. 2009, 86,
470-474.
9. Barbero, M.; Crisma, M.; Degani, I.; Fochi, R.; Perracino, P.
Synthesis 1998, 1171 – 1175.
10. Paebumrung, P.; Petsom, A.; Thamyongkit, P. J. Am. Oil.
Chem. Soc. 2012, 89, 321-328.
2. Lee, C. C.; Yang, Y. C.; Lia, H. J.; Lin, S. T. J. Mass Spec-
trom. 2011, 46, 1131-1134.
11. Mohammad, M.; Fatemeh, Z.; Alireza, H. E.-J. Chem. 2012,
9, 1042-46.
3. (a) Nedeltcheva, D.; Kurteva, V.; Damyanova, B.; Popov, S.
Rapid Commun. Mass Spectrom. 2009, 23, 1724-34; (b)
Martiskainen, O.; Gawinecki, R.; OÑmia»owski, B.;
Wiinamäki, K.; Pihlaja, K. Rapid Commun. Mass Spectrom.
2009, 23, 1075-84; (c) Nedeltcheva, D.; Kurteva, V.; Topalova,
12. Maity, S. K.; Pradhan, N. C.; Patwardhan, A. V. Appl. Catal.
A: Gen. 2006, 301, 251–258.
6
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