Negative-ion mass spectra of some N-mesyl derivatives of o-(cycloalk-2-enyl)-, o-(cycloalk-1-enyl)-, o-(pent-2-enyl)-, o-dibromopentylanilines and (α-bromoalkyl)indolines

Article abstract of DOI:10.1023/A:1022108023832

The formation and fragmentation of negative ions of some N-(methylsulfonyl)anilines upon resonance electron capture have been studied. The formation of long-living molecular ions is due to the presence of the mesyl groups in the molecules. The difference

Full text of DOI:10.1023/A:1022108023832

Russian Chemical Bulletin, International Edition, Vol. 51, No. 12, pp. 2299—2302, December, 2002
2299
Brief Communications
Negativeꢀion mass spectra of some Nꢀmesyl derivatives of
oꢀ(cycloalkꢀ2ꢀenyl)ꢀ, oꢀ(cycloalkꢀ1ꢀenyl)ꢀ, oꢀ(pentꢀ2ꢀenyl)ꢀ,
oꢀdibromopentylanilines and (αꢀbromoalkyl)indolines
ꢀ
S. V. Pikhtovnikov, I. I. Furlei, V. K. Mavrodiev, R. R. Gataullin and I. B. Abdrakhmanov
Institute of Organic Chemistry, Ufa Research Center of the Russian Academy of Sciences,
71 prosp. Oktyabrya, 450054 Ufa, Russian Federation.
Fax: +7 (347 2) 35 6066. Eꢀmail: chemorg@anrb.ru
The formation and fragmentation of negative ions of some Nꢀ(methylsulfonyl)anilines
upon resonance electron capture have been studied. The formation of longꢀliving molecular
ions is due to the presence of the mesyl groups in the molecules. The difference in negativeꢀion
mass spectra of isomeric Nꢀ(methylsulfonyl)anilines has been revealed.
Key words: negative molecular ion, resonance electron capture, alkenylanilines, indolines.
The behavior of sulfoxides, sulfides,1 and cyclic sulꢀ
fones2 upon resonance electron capture has previously
been studied. It was found that negative molecular ions
(NMI) can be generated only in the case of cyclic sulꢀ
fones that contain double bonds or electronꢀwithdrawing
substituents.
(e.g., the number of degrees of freedom of the molꢀ
ecule,3,4 changes in the NMI geometry,5,6 etc.). The
search for such factors is a topical problem that can be
solved only in studies of compounds that form longꢀlivꢀ
ing NMI.
Here we report the results of the investigation of some
Nꢀ(methylsulfonyl)anilines to ascertain the influence of
the Ms group and other substituents on processes of negaꢀ
tive ion (NI) formation. To date, no common explanaꢀ
tion has been found for the relation between average NMI
lifetime relative to electron expulsion τe and properties of
the molecule. One of the main factors that affect τe is the
nature of LUMO, which usually bears an additional elecꢀ
tron. Naturally, there are other factors that influence τe
Experimental
The mass spectra and effective negative ion yield curves
were recorded on an MIꢀ1201 spectrometer adopted to record
negative ions. The electron energy scale was calibrated relative
from SF6. Halfꢀheight electron energy
distribution was 0.3—0.4 eV, electron current, 0.5 µA; measurꢀ
–•
to the yield of SF6
ing inaccuracy of maxima, 0.1 eV. Determination of the lifeꢀ
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2135—2138, December, 2002.
1066ꢀ5285/02/5112ꢀ2299 $27.00 © 2002 Plenum Publishing Corporation

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Russ.Chem.Bull., Int.Ed., Vol. 51, No. 12, December, 2002
Pikhtovnikov et al.
time τ relative to electron expulsion was carried out according
to the eknown method.7
Quantumꢀchemical calculations were carried out by semiꢀ
empirical MNDO/d method, geometry optimization was carꢀ
ried out using the HyperChem program package.
Nꢀ(Methylsulfonyl)anilines 1—4 were synthesized by the
reaction of 6ꢀmethylꢀ2ꢀ(cyclopentꢀ1ꢀenyl)aniline,8 6ꢀmethylꢀ
2ꢀ(cyclopentꢀ2ꢀenyl)aniline, 6ꢀmethylꢀ2ꢀ(cyclohexꢀ2ꢀenyl)aniꢀ
line9 and 2ꢀ(cyclohexꢀ2ꢀenyl)ꢀ4,5ꢀdifluoroaniline10 with
methanesulfonyl chloride (MsCl). The synthesis of comꢀ
pounds 5—7 will be published elsewhere. Compounds 8
and 9 were obtained by bromination of Nꢀmethylsulfonylꢀ
4,6ꢀdimethylꢀ2ꢀ(1ꢀmethylbutꢀ2ꢀenyl)aniline in CH2Cl2. Hexaꢀ
hydrocarbazole 10 was prepared by bromination of Nꢀmethylꢀ
sulfonylꢀ2ꢀ(cyclohexꢀ2ꢀenyl)aniline11 in CH2Cl2. The purity
and structures of the methanesulfonates obtained were proved
1
by TLC, data from elemental analysis and H and 13C NMR
spectroscopy, the spectra being recorded on a Bruker AMꢀ300
1
spectrometer (300.13 and 75.47 MHz for H and 13C, respecꢀ
tively).
Table 1. NI mass spectra of compounds 1—10
Compound
τ/ms
m/z (I (%))/E*
Compound
τ/ms
m/z (I (%))/E*
182 251 [M]– (38.5)/0.2; 250 [M – H]–
(1.4)/7.5; 172 [M – MeSO2]– (0.1)
0.2, (0.1)/3.5, (0.2)/7.6; 79
253 [M]– (70)/0.2; 252 [M – H]–
(1.4)/7.8; 238 [M – Me]– (0.4)/4.4;
224 [M – Et]– (1.8)/4.3, (2.1)/1.4;
174 [M – MeSO2]– (<0.1)/0.2, (0.1)
3.6, (0.2)/8.4; 79 [MeSO2]– (100)
0.4, (1.6)/4.4, (<0.1)/8.3; 64 [SO2]–
(<0.1)/0.2, (0.1)/3.4, (0.1)/7.5; 48
[SO]– (<0.1)/0.2, (0.3)/4.6
253 [M]– (12)/0.2; 252 [M – H]–
(1.4)/7.6; 238 [M – Me]– (0.6)/3.7;
224 [M – Et]– (1.6)/0.9, (1.3)/3.7;
174 [M – MeSO2]– (0.4)/0.2, (0.5)
2.7, (1.7)/7.2; 79 [MeSO2]– (100)
0.2, (3.5)/4, (<0.1)/8; 64 [SO2]–
(0.1)/0.2, (0.7)/3.5, (0.9)/7.9; 48
[SO]– (<0.1)/0.2, (0.9)/4.2
[MeSO2]– (100)/0.3, (3.2)/4.4, (1.3)
7.4; 64 [SO2]– (2)/0.2, (0.2)/3.6,
(0.5)/7.4; 48 [SO]– (<0.1)/0.2,
(0.2)/4.5
(1)
(6)
140 251 [M]– (97)/0.2; 250 [M – H]–
(2.7)/7.5; 210 [M – C3H4 – H]–
(11)/1.5, (0.7)/4.7; 184 [M – C5H7]–
(0.1)/8; 172 [M – MeSO2]– (1.3)/0.3,
(<0.1)/4, (<0.1)/8.2; 79 [MeSO2]–
(100)/0.3, (1)/4.4, (1.3)/8; 64 [SO2]–
(1.3)/0.1, (2.3)/3.9, (1.6)/7.6; 48
[SO]– (3.6)/0.2; (0.5)/3.4
56
(2)
(7)
167 265 [M]– (100)/0.1; 264 [M – H]–
(4.4)/7.1; 210 [M – C4H6 – H]–
(2.6)/1.4, (1)/4.6; 186 [M – MeSO2]–
(0.5)/0.1, (<0.1)/2.9, (0.1)/7.5; 184
[M – C6H9]– (<0.1)/7.7; 81 [C6H9]–
(0.6)/4; 79 [MeSO2]– (27.8)/0.2,
(0.8)/4.2, (0.4)/7.9; 64 [SO2]– (0.1)
0.1, (0.1)/3.6, (0.1)/7.5; 48 [SO]–
(<0.1)/0.2, (0.2)/4.4
82
425, 427, 429 [M]– (0.7)/0.3, (1.3)
0.3, (0.6)/0.3; 345, 347 [M – HBr]–
(50)/0.1, (48.9)/0.1; 226
(3)
[M – C3H5Br2]– (0.2)/1.1; 198
[M – C5H9Br2]– (8)/1.3; 158, 160,
162 [Br2]– (33.4)/0.1, (65.3)/0.1,
(31.9)/0.1; 79 [MeSO2]– (73)/0.2,
(<0.1)/4.3, (<0.1)/8.3; 79, 81 [Br]–
(100)/0.1, (97.8)/0.1, 64 [SO2]– (0.6)
0.2, (31.4)/3.7; 48 [SO]– (0.1)/4.4,
(0.1)/0.4
(8)
237 287 [M]– (100)/0.1; 268 [M – H]–
(0.4)/0.3, (<0.1)/7.8; 232
[M – C4H6 – H]– (<0.1)/4.3;
208 [M – MeSO2]– (0.2)/0.2, (<0.1)
3.7, (<0.1)/8; 206 [M – C6H8]–
(<0.1)/7.7; 81 [C6H8]– (<0.1)/8; 79
[MeSO2]– (5.7)/0.2, (0.2)/4.5, (<0.1)
8; 64 [SO2]– (<0.1)/0.2, (<0.1)/3.4,
(<0.1)/7.7; 48 [SO]– (<0.1)/0.2,
(<0.1)/4.5
113 345, 347 [M]– (31.1)/0.1, (30.4)/0.1;
265 [M – HBr]– (7.3)/0.1; 79
(4)
[MeSO2]– (42)/0.2, (1.5)/4.4, (0.2)
8.2; 79, 81 [Br]– (100)/0.1, (97.8)
0.1; 64 [SO2]– (<0.1)/0.2, (40)/3.8,
(9)/6.9; 48 [SO]– (0.2)/0.2, (0.1)/4.7
292 329, 327 [M]– (2.4)/0.3, (2.3)/0.3;
249 [M – HBr]– (17.6)/0.1; 79
[MeSO2]– (21.5)/0.2, (<0.1)/4.4,
(<0.1)/8.1; 79, 81 [Br]– (100)/0.1,
(97.8)/0.1; 64 [SO2]– (0.1)/0.3, (0.6)
3.9, (0.2)/7.4; 48 [SO]– (<0.1)/0.3,
(0.1)/4.7
(9)
236 265 [M]– (26.3)/0.2; 264 [M – H]–
(0.2)/7.4; 236 [M – CO – H]– (0.1)
7.9; 186 [M – MeSO2]– (0.2)/0.2,
(0.1)/4, (0.1)/8; 184 [M – C5H5O]–
(2.4)/0.3, (0.6)/4.2, (0.5)/8.5; 159
[M – C2HC5H5O]– (0.5)/3.1; 79
[MeSO2]– (100)/0.2, (0.2)/4.2, (<0.1)
7; 64 [SO2]– (0.4)/0.2, (9)/3.7; 48
[SO]– (1.7)/0.4, (0.1)/4.5
(10)
(5)
* Electron energy values (eV) in the maxima of the resonance curve.

Negativeꢀion mass spectra of Nꢀmesylanilines
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 12, December, 2002 2301
Results and Discussion
The sensitivity to the structure of compounds is maniꢀ
fested in the upfield resonances (at 1.5—4.5 eV). Thus
alkenylaniline 2 gives an additional ion with m/z 210,
which is absent in the spectrum of compound 1. The
formation of this ion can be explained by the fragmentaꢀ
tion of the cyclopentenyl group with subsequent intramoꢀ
lecular cyclization (Scheme 1).
Table 1 lists relative intensities of the NI lines
and electron energies in the maxima of the resonance
curves.
The NMI, [MeSO2]–, and Br– peaks are the most
intense peaks in the region of thermal energies of elecꢀ
trons. The presence of NMI and [MeSO2]– signals in the
mass spectra of compounds studied suggests that the elecꢀ
tron capture occurs on the vacant MO with the major
contribution of the Ms group. Benzene and its derivatives
(except for nitrobenzene) do not produce longꢀliving
NMI, which confirms indirectly this conclusion.12,13
Moreover, quantumꢀchemical calculations of the molꢀ
ecules studied and their NMI showed that the orbital with
the major contribution of MeSO2NH group (∼80%) and
the contribution of the benzene ring (∼20%) is the LUMO
in compounds 1—7. The low yield of NMI in the case of
compounds 8 and 10 is evidently related to the low σ*ꢀMO
of C—Br, so that the competitive formation of Br– leads
to the reduction of peak intensities in the mass spectra. At
the same time, the relative intensity of the NMI peak
in the spectrum of compound 9, which also contains
σ*ꢀMO of C—Br, is ∼31%. Quantumꢀchemical calculaꢀ
tion showed that the repulsion of atoms of the Ms group
and Br atom in NMI of this compound takes place, in
contrast to 8 and 10. Probably, such intramolecular interꢀ
action stabilizes NMI with an additional electron on
the vacant orbital with the major contribution of the Ms
group.
Scheme 1
The similar process is also typical of cyclohexenyl deꢀ
rivatives 3 and 4, but not of compound 1. This is due to
the conjugation of the double bond of the substituent with
the πꢀelectrons of the benzene ring, which inhibits such
process. The conjugation also favors stabilization of NMI
because the mean lifetime τe of compound 1 is larger than
that of alkenylaniline 2.
The presence of an O atom in the cyclopentenyl group
of compound 5 favors the appearance of new states of
NMI and hence the appearance of new pathways of fragꢀ
mentation, which lead to ions [M – H]–, [М – HCO]–
and [M – C5H5O]– in the region of energies of 8 eV (see
Table 1).
Thus, based on the results of this study and the literaꢀ
ture data for the generation of NI in substituted benzenes,
a conclusion can be made that the ability of this class of
compound for thermal energy electron capture is govꢀ
erned by the presence of the MeSO2NH group, which
interacts with the πꢀsystem of the benzene ring, though
the nature of some other substituents has also noticeable
effect.
An interesting tendency is observed as regards generaꢀ
tion of [MeSO2]– in the region of thermal energies of
electrons. The preponderant formation of such ions for
compounds 1, 5, 6, and 7 where the substituent is conjuꢀ
gated with the benzene ring can be explained by the higher
stability of the neutral radical due to the delocalization of
the radical center. On the contrary, for compounds 2—4
where the substituent is not conjugated with the benzene
ring relative yield of NMI is higher. The presence of
F atoms in compound 4 favors the stabilization of
NMI14,15 and thus the formation of [MeSO2]– becomes
less probable.
Noteworthy is the sensitivity of mass spectra of NI to
the structure of compounds studied. Thus the average
lifetime τe of the cisꢀisomer 6 is more than twice as high as
that for transꢀisomer 7. The probable reason for the enꢀ
hanced stability of NMI is the intramolecular interaction
of the Ms group and an alkenyl substituent. The similar
effect was observed earlier in nitrotoluenes.12 The quanꢀ
tumꢀchemical calculations of the geometry of these isoꢀ
mers and their NMI showed that the Ms group in comꢀ
pound 6 is turned in such a way that the O atom is arꢀ
ranged close to the alkenyl substituent, while in molecule
7 it is remote from the substituent.
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Received January 21, 2002;
In revised form July 24, 2002