ˇ
P. S im u˚ nek, V. Bertolasi, V. Machá cˇ ek
FULL PAPER
of the reaction mixtures, solution-state structures of the ary external standard (δ = –113.1 ppm against CFCl
3
as the pri-
[21]
1
19
mary standard ). H– F HETCOR measurement was optimized
products, and dynamic processes were studied by means of
1
9
1
1
13
to J( F, H) = 20 Hz under proton decoupling. 16 Scans per t1
increment, time-domain 2kϫ128 zero-filled to 2kϫ1k, sine-bell
multiplication in both dimensions, relaxation delay was set to 2 s.
H and C NMR spectroscopic analysis or by taking ad-
1
9
vantage of the far less complex proton-decoupled F NMR
spectra. The phenyl group adjacent to the pivaloyl group
has limited mobility, which is exhibited by anisochronism 2D EXSY spectra were measured in States-TPPI acquisition mode
by using the standard 2D NOESY pulse sequence supplied by
of the 2,2Ј and 3,3Ј proton and carbon atoms in the NMR
Bruker, time-domain 2kϫ128 zero-filled to 2kϫ1k, sine-bell
spectra of p-disubstituted benzene rings. The chemical ex-
squared in both dimensions. The phasing was carried giving posi-
change proceeds through a low energy barrier with a co-
tive diagonal peaks. Relaxation delay 2 s, 80 scans per t1 increment.
alescence temperature of about 320 K [for bis(4-fluoro-
phenyl) derivative in [D ]toluene]. In the case of the 3-tri- X-ray Structure Determination: X-ray diffraction data for 9a were
8
fluoromethylphenyl derivative, two conformers exist that collected with a Nonius Kappa CCD diffractometer, at room tem-
α
perature (T = 295 K), with graphite monochromated Mo-K radia-
differ in the orientation of the CF group, which exchange
3
tion (λ = 0.7107 Å). The data sets were integrated with the Denzo-
with each other. The relative abundance of the conformers
was almost equimolar. From MALDI HRMS analysis in
the positive mode it is clear that a diazonium ion splits off
during the ionization.
SMN package[ and corrected for Lorentz and polarization ef-
22]
[
23]
fects. The structure was solved by direct methods (SIR97)
and
refined (SHELXL-97)[ by full-matrix least-squares with aniso-
tropic non-hydrogen atoms and hydrogens included on calculated
positions, riding on their carrier atoms. ORTEP[ view of the mo-
lecule is shown in Figure 1. Selected structural parameters are re-
ported in Table S1 (see the Supporting Information).
24]
25]
Experimental Section
General Remarks: All the solvents and reagents were obtained from
commercial sources and were used without further purification. Di-
azonium tetrafluoroborates were prepared according to a standard
Complete crystallographic data (excluding structural factors) have
been deposited with the Cambridge Crystallographic Data Centre
as supplementary publications number CCDC-933274. Copies of
the data can be obtained, free of charge, via www.ccdc.cam.ac.uk./
conts/retrieving.html or on application to CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK [Fax: +44(0)-1223-336033, E-mail:
deposit@ccdc.cam.ac.uk].
2
procedure involving diazotization using cold NaNO /HCl with
subsequent precipitation of the filtered solution of diazonium
chloride by aqueous sodium tetrafluoroborate. The precipitated di-
azonium tetrafluoroborates were dried in vacuo in a desiccator and
stored in a refrigerator.
Elemental analyses were performed with a Flash 2000 CHNS Ele-
mental Analyzer. Melting points were measured with a Kofler hot-
stage microscope Boetius PHMK 80/2644 and are not corrected.
Mass spectra were measured with a high-resolution MALDI mass
spectrometer LTQ Orbitrap XL (Thermo Fisher Scientific, Bremen,
Germany) equipped with a nitrogen UV laser (337 nm, 60 Hz). The
LTQ Orbitrap instrument was operated in the positive-ion mode
over a normal mass range (m/z 50–2000). The used matrix were 2,5-
dihydroxybenzoic acid (DHB) or trans-2-[3-(4-tert-butylphenyl)-2-
methylprop-2-en-1-ylidene]malonnitrile (DCTB). Mass spectra
were averaged over the whole MS record for all measured samples.
NMR spectra were measured with a Bruker AVANCE III spec-
1
13
19
trometer operating at 400.13 ( H), 100.62 ( C), 376.46 ( F) and
15
4
0.56 MHz ( N). All the pulse sequences were taken from the
Bruker software library.
1H NMR spectra measured in CDCl
were calibrated with internal
3
8
TMS (δ = 0.00 ppm) and in [D ]toluene on the middle signal of the
solvent multiplet (δ = 2.09 ppm). H,H-COSY spectra were mea-
sured by using gradient pulses, 8 scans per t1 increment. Time do-
main 2kϫ160, zero filled to 2kϫ1k.
13C NMR spectra were measured in a standard way by using
power-gated decoupling and were calibrated on the middle signal
of the solvent multiplet (δ = 77.23 ppm). The carbon signals were
General Procedure for the Preparation of Azo Coupling Products
7
: An equimolar amount of enaminone 6a and the corresponding
diazonium tetrafluoroborate together with anhydrous sodium acet-
ate (3 equiv.) was stirred in anhydrous CH Cl at ambient tempera-
ture for the given time (2.75 h in the case of 7a, 17 h in the case of
b, 80 min for 7c). The insoluble fraction was removed by suction
1
13
assigned by using 2D H– C HSQC measured in phase-sensitive
mode with multiplicity editing and decoupling during acquisition,
optimized to 1J( C, H) = 145 Hz. Time domain 1kϫ256, zero
filled to 2kϫ1k, sine-bell squared in both dimensions, 16 scans per
t1 increment, gradient ratio 80:20.1. Quaternary carbon atoms were
13
1
2
2
7
and the filtrate was evaporated to dryness in vacuo. The residue
was purified by recrystallization from ethanol.
1
13
assigned by using 2D H– C HMBC with no decoupling during
acquisition. Gradient ratios 50:30:40.1, time domain 4kϫ128, zero
filling to 4kϫ1k, sine-bell windowing applied in both dimensions,
The following compounds were prepared, according to the above
protocol: 2-(4-fluorophenyldiazenyl)-4,4-dimethyl-1-methylamino-
1-phenylpent-1-en-3-one (7a), 2-(4-methoxyphenyldiazenyl)-4,4-di-
methyl-1-methylamino-1-phenylpent-1-en-3-one (7b), and 2-(3-tri-
fluoromethylphenyldiazenyl)-4,4-dimethyl-1-methylamino-1-phen-
ylpent-1-en-3-one (7c). Their yields, melting points, elemental
analyses, MALDI and NMR spectroscopic data are presented in
the Supporting Information.
16 scans per t1 increment. One-bond coupling was set to 145 Hz,
optimization was done to long-range coupling 10 Hz.
1
5
N NMR chemical shifts were obtained in an indirect way by using
1
15
2
D gs H– N HMBC pulse sequence. The gradient ratios were
70:30:50.1. NH one-bond coupling was set to 90 Hz, long-range
couplings were optimized on 5 Hz. Time domain 4kϫ128, zero
filling to 4kϫ1k, sine-bell windowing in both dimensions, 160
scans per t1 increment. Calibration of the nitrogen spectra was
done on an external neat 15N nitromethane placed in coaxial capil-
lary (δ = 0.00 ppm).
19F NMR spectra were measured by using waltz-16 proton decou-
pling and were standardized against fluorobenzene as the second-
General Procedure for the Synthesis of Acylated Formazans 9a–g:
A mixture of 7 (1 equiv.), the corresponding diazonium tetra-
fluoroborate (1 equiv.), and anhydrous sodium acetate (3 equiv.) in
dichloromethane (7 mL/mmol) was stirred at ambient temperature
for 3 d. The insoluble fraction was then removed by suction and
5690
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Eur. J. Org. Chem. 2013, 5683–5691