Difluorocarbeneꢀderived NHꢀazomethine ylides
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 5, May, 2008
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analysis of all the transition states showed that in their vibrational
spectra, only one normal vibration with imaginary frequency is
present. The location of transition states in the same with reagents
and products energy profile was traced through by the internal
reaction coordinate (IRC).39
4ꢀ[2ꢀ(4ꢀChlorophenyl)ꢀ4ꢀfluoroꢀ5ꢀphenylꢀ5ꢀ(triꢀ
fluoromethyl)ꢀ2,5ꢀdihydroꢀ1,3ꢀoxazolꢀ2ꢀyl]benzonitrile (7c).
Compound 7c (0.089 g, 10%) was obtained from imine 2c
(0.481 g, 2 mmol) and trifluoroacetophenone 6a according to the
general procedure as a colorless oily mixture of stereoisomers in
ratio 2 : 1. 1H NMR (CDCl3), δ: 7.23—7.79 (m, Ar). 13C NMR
(CDCl3), δ of major isomer: 85.3 (m, C(5)), 106.21 (d, C(2),
3JC,F = 21.6 Hz), 118.2 (CN), 122.4 (m, CF3,), 126.1—146.1
(Ar), 160.7 (d, C(4), 1JC,F = 299.9 Hz). 13C NMR (CDCl3), δ of
minor isomer: 85.3 (m, C(5)), 106.18 (d, C(2), 3JC,F = 21.3 Hz),
118.1 (CN), 122.4 (m, CF3,), 126.1—146.4 (Ar), 160.7 (d, C(4),
1JC,F = 299.9 Hz). According to the 1H NMR data, the product
contains ~5% of the corresponding benzophenone.
4ꢀFluoroꢀ5ꢀphenylꢀ5ꢀ(trifluoromethyl)ꢀ2,2ꢀbis(4ꢀtriꢀ
fluoromethylphenyl)ꢀ2,5ꢀdihydroꢀ1,3ꢀoxazole (7d). Compound 7d
(0.120 g, 12%) was obtained from imine 2d (0.634 g, 2 mmol)
and trifluoroacetophenone 6a according to the general procedure,
m.p. 88—89 °C (from hexane). Found (%): C, 55.12; H, 2.83;
N, 2.46. C24H13F10NO. Calculated (%): C, 55.29; H, 2.51;
N, 2.69. IR (KBr), ν/cm–1: 1725 (C=N). 1H NMR (CDCl3), δ:
7.39—7.85 (m, 13 H, Ar). 13C NMR (CDCl3), δ: 85.4 (quint,
Starting imines 2a—e were synthesized according to the
procedure described earlier.40
Reaction of diarylmethanimines with difluorocarbene (general
procedure). Lead filings (1.243 g, 6 mmol), diphenylmethanimine
(0.362 g, 2 mmol), tetrabutylammonium bromide (1.932 g,
6 mmol), dibromodifluoromethane (0.55 mL, 6 mmol), and
anhydrous dichloromethane (10 mL) were placed in a roundꢀ
bottom flask. If the reaction was carried out in the presence of
dipolarophiles, either methyl methacrylate (5 equiv.) or aryl
trifluoromethyl ketone or fluorenone (3 equiv.) were added to
the mixture. The flask was corked in such a way that the system
could have held some excess pressure, and it was placed into an
ultrasonic bath (160 W). The processing was carried out at 30—40 °C
and continued until all the lead metal was consumed. Dichloroꢀ
methane was removed, the residue was separated by column
chromatography on silica gel (eluent hexane—diethyl ether).
Crystalline products were recrystallized from hexane or from
hexane—diethyl ether.
2
3
C(5), JC,F = 33.0 Hz), 106.4 (d, C(2), JC,F = 21.4 Hz), 121.9
1
3
(q.d, CF3, JC,F = 286.5 Hz, JC,F = 4.9 Hz), 123.7 (q,
1
1
Nꢀ(Diphenylmethylene)difluoromethanamine (3a). Compound
3a (0.042 g, 9%) was obtained from imine 2a (0.362 g, 2 mmol)
according to the general procedure with addition of methyl
methacrylate (1.0 g, 10 mmol) as a colorless liquid. 1H NMR
(CDCl3), δ: 6.35 (t, 1 H, CHF2, JH,F = 70.5 Hz); 7.28—7.85 (m,
8 H, Ph). 13C NMR (CDCl3), δ: 115.2 (t, CHF2, 1JC,F = 231.8 Hz),
127.9, 128.1, 128.4, 129.7, 129.9, 134.0, 137.3 (Ar), 176.7 (t,
CF3, JC,F = 273.1 Hz), 123.8 (q, CF3, JC,F = 272.6 Hz),
125.3—125.7 (m), 126.0, 126.1 (m), 127.7 (m), 128.9, 130.5,
130.8 (q, Ar, 4JC,F = 32.6 Hz), 144.9, 145.2 (Ar), 160.8 (d, C(4),
1JC,F = 300.6 Hz). 19F NMR (CDCl3), external standard C6F6,
δ: 82.2 (q, F—C(4), JF,F = 3.2 Hz), 86.6 (d, CF3, JF,F = 3.2 Hz),
99.3 (CF3), 99.4 (CF3).
4ꢀFluoroꢀ5ꢀphenylꢀ5ꢀ(trifluoromethyl)ꢀ2,2ꢀbis(3ꢀtriꢀ
fluoromethylphenyl)ꢀ2,5ꢀdihydroꢀ1,3ꢀoxazole (7e). Compound 7e
(0.395 g, 38%) was obtained from imine 2e (0.634 g, 2 mmol)
and trifluoroacetophenone 6a according to the general procedure,
m.p. 79—80 °C (from hexane). Found (%): C, 55.09; H, 2.72;
N, 2.94. C24H13F10NO. Calculated (%): C, 55.29; H, 2.51;
N, 2.69. IR (KBr), ν/cm–1: 1725 (C=N). 1H NMR (CDCl3), δ:
7.39—8.13 (m, 13 H, Ar). 13C NMR (CDCl3), δ: 85.5 (quint,
3
CPh2, JC,F = 15.7 Hz). According to the 1H NMR data, the
product contains ~10% of benzophenone.
4ꢀFluoroꢀ2,2ꢀdiphenylꢀ2,5ꢀdihydroꢀ9´Hꢀspiro[1,3ꢀoxazoleꢀ
5,9´ꢀfluorene] (5). Compound 5 (0.161 g, 21%) was obtained
from imine 2a (0.362 g, 2 mmol) and fluorenone according to
the general procedure, m.p. 82—84 °C (from hexane). Found (%):
C, 82.74; H, 4.81; N, 3.46. C27H18FNO. Calculated (%):
C, 82.85; H, 4.63; N, 3.58. IR (CHCl3), ν/cm–1: 1725 (C=N).
1H NMR (CDCl3), δ: 7.01—7.91 (m, 18 H, Ar). 13C NMR
2
3
C(5), JC,F = 32.7 Hz), 106.3 (d, C(2), JC,F = 21.4 Hz), 121.9
1
4
(q.d, CF3, JC,F = 286.4 Hz, JC,F = 4.9 Hz), 123.5 (q,
2
1
1
(CDCl3), δ: 89.7 (d, C(5), JC,F = 38.4 Hz), 105.8 (d, C(2),
CF3, JC,F = 274.2 Hz), 123.6 (q, CF3, JC,F = 272.6 Hz),
3JC,F = 21.6 Hz), 120.3, 125.2, 125.8, 128.0, 128.3, 128.4, 130.5,
122.3—142.9 (Ar), 160.9 (d, C(4), JC,F = 300.9 Hz).
1
1
140.7, 141.4, 144.7 (Ar), 166.7 (d, C(4), JC,F = 294.3 Hz).
4ꢀFluoroꢀ5ꢀ(4ꢀmethylphenyl)ꢀ2,2ꢀdiphenylꢀ5ꢀ(triꢀ
fluoromethyl)ꢀ2,5ꢀdihydroꢀ1,3ꢀoxazole (7f). Compound 7f (0.503 g,
63%) was obtained from imine 2a (0.362 g, 2 mmol) and ketone
6b according to the general procedure, m.p. 86—87 °C (from
hexane). Found (%): C, 69.20; H, 4.26; N, 3.48. C23H17F4NO.
4ꢀFluoroꢀ2,2,5ꢀtriphenylꢀ5ꢀ(trifluoromethyl)ꢀ2,5ꢀdihydroꢀ
1,3ꢀoxazole (7a). Compound 7a (0.515 g, 66%) was obtained
from imine 2a (0.362 g, 2 mmol) and trifluoroacetophenone 6a
according to the general procedure. Physical and spectroscopic
characteristics and Xꢀray data for compound 7a are given in Ref. 1.
Compound 7a (0.288 g, 37%) was also obtained by similar
procedure from imine 2a (0.362 g, 2 mmol) with the use of zinc
dust (0.39 g, 6 mmol) instead of lead (the reaction time was 150 h).
2,2ꢀBis(4ꢀchlorophenyl)ꢀ4ꢀfluoroꢀ5ꢀphenylꢀ5ꢀ(triꢀ
fluoromethyl)ꢀ2,5ꢀdihydroꢀ1,3ꢀoxazole (7b). Compound 7b
(0.551 g, 61%) was obtained from imine 2b (0.5 g, 2 mmol) and
trifluoroacetophenone 6a according to the general procedure as
colorless glassꢀlike substance. IR (CCl4), ν/cm–1: 1730 (C=N).
1H NMR (CDCl3), δ: 7.22—7.72 (m, 13 H, Ar). 13C NMR
(CDCl3), δ: 82.2 (quint, C(5), 2JC,F = 32.8 Hz), 106.6 (d, C(2),
3JC,F = 21.4 Hz), 120.1 (d.q, CF3, 1JC,F = 286.6 Hz, 3JC,F = 5.0 Hz),
126.2, 127.1, 128.5, 128.6, 128.8, 130.1, 131.3, 134.5, 134.6,
Calculated (%): C, 69.17; H, 4.29; N, 3.51. IR (KBr), ν/cm–1
:
1720 (C=N). 1H NMR (CDCl3), δ: 2.37 (s, 3 H, Me); 7.19—7.71
(m, 14 H, Ar). 13C NMR (CDCl3), δ: 21.0 (CH3), 85.0 (q.d, C(5),
2JC,F = 34.0 Hz, 2JC,F = 32.5 Hz), 107.5 (d, C(2), 3JC,F = 21.3 Hz),
122.3 (d.q, CF3, 1JC,F = 286.9 Hz, 4JC,F = 4.7 Hz), 125.8, 125.9,
4
126.3 m, 128.1 (q, JC,F = 4.1 Hz), 128.2, 129.3, 139.9, 141.9,
142.4 (Ar), 160.4 (d, C(4), 1JC,F = 298.6 Hz).
5ꢀ(4ꢀChlorophenyl)ꢀ4ꢀfluoroꢀ2,2ꢀdiphenylꢀ5ꢀ(trifluoroꢀ
methyl)ꢀ2,5ꢀdihydroꢀ1,3ꢀoxazole (7g). Compound 7g (0.279 g, 54%)
was obtained from imine 2a (0.22 g, 1.23 mmol) and ketone 6c
according to the general procedure, m.p. 81—82 °C (from
hexane—diethyl ether). Found (%): C, 62.89; H, 3.52; N, 3.22.
C22H14ClF4NO. Calculated (%): C, 62.94; H, 3.36; N, 3.34.
1
1
139.1, 140.4, 140.8 (Ar), 160.4 (d, C(4), JC,F = 299.8 Hz).
IR (KBr), ν/cm–1: 1725 (C=N). H NMR (CDCl3), δ: 7.28—7.71
According to the 1H NMR data, the product contains ~5% of
the corresponding benzophenone.
(m, 14 H, Ar). 13C NMR (CDCl3), : 84.5 (q.d, C(5), 2JC,F = 34.5 Hz,
δ
2JC,F = 32.9 Hz), 107.8 (d, C(2), 3JC,F = 21.0 Hz), 120.1 (q.d, CF3,