Photochemical Synthesis of Phosphonium-Substituted Oxazoles
tions of the ylide 6 with the three nitriles afforded the ox- 118.20 (d, 1JC,P = 94.4 Hz, Cipso arom.), 130.20 (d, 3JC,P = 13.2 Hz,
C
=
m
arom.), 134.17 (d, 2JC,P = 11.0 Hz, C arom.), 135.22 (d, 4JC,P
o
azoles 11a, 11b, and 11c in yields of 60%, 60%, and 35%,
respectively. Moreover the ylide 6 also reacted with
2.2 Hz, C
p
3
arom.), 159.44 (d, 3JC,P = 19.0 Hz, C=N), 169.12 (s,
1
C–O) ppm. P NMR (CDCl
3
): δ = 8.56 ppm. IR: ν˜ = 980–1120
) 1230–1630 (cycle) cm . MS: m/z = 402 [M – BF ] .
4 4
4-cyanopyridine (15) and diethylcyanamide (16) to yield the
–
1
+
(BF
oxazoles 17 and 18, respectively (Scheme 5).
9
c: Yields of isolated products: 9c (25 mg, 15%), 12 (80 mg, 60%),
1
triphenylphosphane oxide (20 mg, 25%). 9c: H NMR (CDCl
3
): δ
=
1.11 (t, 3 H, CH
3
), 4.51 (q, 2 H, CH
2
), 7.48–7.98 (m, 20 H,
Conclusions
1
3
arom.) ppm. C NMR (CDCl
3
3
): δ = 14.28 (s, CH ), 71.17 (s,
1
We have found a novel class of photochemical reactions OCH ), 117.90 (d, JC,P = 95.2 Hz, C
between mixed phosphonium-iodonium ylides and nitriles arom.), 129.04 (s, C
ipso
arom.), 126.34 (s, Co
arom.), 130.32 (d, JC,P = 13.1 Hz, C
2
3
m
m
arom.),
2
to yield polyfunctional 2,4,5-trisubstituted oxazoles.
131.41 (s, C
1.0 Hz, C arom.), 135.44 (s, C
C=N), 166.83 (d, JC,P = 27.1 Hz, C–O) ppm. 31P NMR (CDCl
p C,P
arom.), 132.96 (s, Cipso arom.), 134.24 (d, J =
3
1
o
p
arom.), 155.13 (d, JC,P = 19.8 Hz,
):
2
3
–
1
δ = 8.81 ppm. IR: ν˜ = 1260–1630 (cycle), 1000–1200 (BF
NO P (537.30): calcd. C 64.80, H 4.66, N 2.61; found
C 64.78, H 4.81, N 2.68.
4
) cm .
Experimental Section
C
29
H25BF
4
2
General: The H, 31P, and 13C NMR spectra were recorded on a
1
Bruker Avance 400 instrument operating at 400 MHz in CDCl
CD CN with Me Si as the internal standard. The IR spectra were
measured on a UR-20 instrument in CCl . The elemental analysis
was carried out on a Vario-II CHN analyzer. The mass spectra
were obtained on a Finnigan Mat Incos50 quadrupole mass spec-
trometer (EI, 70 eV, direct inlet) and an Agilent LC/MSD 1100 SL
instrument with electrospray ionization at atmospheric pressure
3
or
1
0a: Yields of isolated products: 10a (35 mg, 25%), 13 (55 mg,
3
4
1
49%), triphenylphosphane oxide (25 mg, 30%). 10a: H NMR
4
(
CDCl
m, 15 H, arom.) ppm. C NMR (CDCl
0.61 (s, OCH
), 118.16 (d, 1JC,P = 95.1 Hz, Cipso arom.), 130.18
C,P = 13.9 Hz, C C,P = 11.0 Hz, C
arom.), 134.18 (d, 2
C,P = 2.2 Hz, C arom.), 156.01 (s, C=N),
C,P = 26.3 Hz, C–O) ppm. P NMR (CDCl
.88 ppm. IR: ν˜ = 1280–1680 (cycle), 1000–1200 (BF
NO P (461.20): calcd. C 59.87, H 4.56, N 3.04; found
C 60.24, H 4.75, N 2.91.
3
): δ = 2.50 (s, 3 H, CH
3
), 3.98 (s, 3 H, OCH
3
), 7.67–7.83
1
3
(
6
3
): δ = 14.14 (s, CH
3
),
3
3
(
d,
J
m
J
o
4
arom.), 135.20 (d,
J
p
(AP-ESI) in the positive ion detection mode (an ion trap as a mass
2
31
1
8
C
67.58 (d,
J
3
): δ =
analyzer). Recording conditions: temperature of the drying gas (ni-
–
1
4
) cm .
–1
trogen) 300 °C, flow rate 12 Lmin , power supply voltage 5000 V,
capillary outlet voltage 150 V, acetonitrile as solvent. The reaction
progress and the purity after chromatographic separation were
monitored by TLC on Silufol plates. Chromatographic separation
was carried out on columns with Merck 60 (0.063–0.200 mm) silica
gel.
23
H21BF
4
2
10b: Yields of isolated products: 10b (20 mg, 15%), 13 (60 mg,
45%), triphenylphosphane oxide (35 mg, 40%). 10b: H NMR
(CDCl ): δ = 1.34 (t, J = 7.6 Hz, 3 H, CH ), 2.83 (q, J = 7.5 Hz,
1
3
3
2
H, OCH
C NMR (CDCl
2
), 3.06 (s, 3 H, OCH
3
), 7.65–7.84 (m, 15 H, arom.) ppm.
General Procedure for the Reactions between Ylides 4–6 and Nitriles:
An ylide 4–6 (0.2 g) was added to a nitrile (2–4 mL). In the case of
1
3
3
): δ = 10.43 (s, CH
3
), 21.76 (s, CH
2
), 60.55 (s,
1
3
OCH
3.1 Hz, C
s, C arom.), 159.40 (s, JC,P = 18.3 Hz, C–O), 167.41 (d, JC,P
7.0 Hz, C–O) ppm. 31P NMR (CDCl
): δ = 8.92 ppm. IR: ν˜ =
280, 1680 (cycle), 1000–1200 (BF
3
), 118.12 (d, JC,P = 94.4 Hz, Cipso arom.), 130.20 (d, JC,P =
4-cyanopyridine we used dichloromethane as solvent. The reaction
2
1
(
2
1
m o
arom.), 134.17 (d, JC,P = 11.0 Hz, C arom.), 135.25
mixtures were irradiated under argon in a quartz flask with a mer-
cury light (254 nm) source. The course of the reaction was moni-
tored by TLC. After the end of the reaction the mixtures with ace-
tonitrile or dichloromethane as solvents were concentrated in vacuo
3
2
p
=
3
–
1
4
) cm . MS: m/z: 388
+
4
[M – BF ] .
2 2
and the residue was dissolved in a minimum of CH Cl and chro-
matographed on silica gel. The reaction mixtures with other nitriles
were chromatographed on silica gel without concentration. To elute
1
0c: Yields of isolated products: 10c (20 mg, 13%), 13 (60 mg,
1
45%), triphenylphosphane oxide (35 mg, 40%). 10c: H NMR
the nitriles and admixtures, benzene and CH
phenylphosphane oxide, the corresponding oxazole, and the phos-
phonium salt (12–14) were eluted with CH Cl /MeOH mixtures in
2 2
Cl were used; tri-
(
CDCl
3
): δ = 4.04 (s, 3 H, OCH
C NMR (CD CN): δ = 60.43 (s, OCH
4.4 Hz, Cipso arom.), 125.94 (s, C arom.), 129.25 (s, C
arom.), 131.39 (s, C arom.), 134.41
arom.), 135.38 (s, J = 3.0 Hz, C arom.),
3
), 7.58–8.03 (m, 20 H, arom.) ppm.
13
1
3
3 C,P
), 118.06 (d, J =
2
2
9
1
(
m
arom.),
o
a ratio from 100:1 to 20:1 (all oxazoles were eluted with a CH
MeOH mixture in a 100:1 ratio).
2
Cl
2
/
3
30.12 (d, JC,P = 13.2 Hz, C
d, JC,P = 11.0 Hz, C
m
p
2
o
p
3
2
9
a: Yields of isolated products: 9a (50 mg, 35%), 12 (50 mg, 35%),
154.58 (d, JC,P = 19.0 Hz, C=N), 167.38 (d, JC,P = 26.3 Hz, C–
1
O) ppm. 31P NMR (CDCl ): δ = 9.21 ppm. IR: ν = 1000–1140
and triphenylphosphane oxide (25 mg, 30%). 9a: H NMR
3
–
˜
1
(
CDCl
3
): δ = 0.99 (t, 3 H, CH
3
), 2.49 (s, 3 H, CH
3
), 4.32 (q, 2 H,
(BF
4
), 1290–1620 (cycle) cm . C28
H23BF
4
NO
2
P (523.27): calcd. C
), 7.65–7.80 (m, 15 H, arom.) ppm. 13C NMR (CDCl
64.24, H 4.40, N 2.68; found C 63.96, H 4.52, N 2.60.
CH
1
9
2
3
1
): δ =
4.15 (s, CH
3
), 14.22 (s, CH
3
), 70.63 (s, OCH
2
), 118.21 (d, JC,P
arom.), 134.19
arom.), 155.47 (s, C–
) ppm. 31P NMR (CDCl
): δ = 8.64 ppm. IR:
=
11a: Yields of isolated products: 11a (90 mg, 60%), 14 (60 mg,
3
5.3 Hz, Cipso arom.), 130.19 (d, JC,P = 13.9 Hz, C
m
1
30%), triphenylphosphane oxide (8 mg, 10%). 11a: H NMR
2
o p
(d, JC,P = 11.0 Hz, C arom.), 135.21 (s, C
(
CDCl
3
): δ = 2.62 (s, 3 H, CH
C NMR (CDCl ): δ = 14.06 (s, CH
ipso arom.), 128.50 (s, C arom.), 128.66 (s, C
arom.), 130.87 (s, C arom.), 134.46 (d, JC,P
arom.), 135.66 (s, C arom.), 163.88 (d, J = 30.0 Hz,
C–O), 164.25 (d, 3J = 19.0 Hz, C=N) ppm. 31P NMR (CDCl
):
3
), 7.59–7.87 (m, 20 H, arom.) ppm.
O), 167.01 (c, C–CH
ν˜ = 1590, 1630 (cycle), 1730 (C=O) cm . MS: m/z = 388
3
3
1
13
1
3
3
), 116.89 (d, JC,P = 93.7 Hz,
arom.), 130.42 (d,
–
C
m
o
+
[M – BF
4
] .
3
2
J
C,P = 13.2 Hz, C
m
p
2
9
b: Yields of isolated products: 9b (30 mg, 20%), 12 (55 mg, 40%),
= 10.2 Hz, C
o
p
1
triphenylphosphane oxide (25 mg, 30%). 9b: H NMR (CDCl
=
2
3
): δ
), 4.34 (q,
), 7.68–7.82 (m, 15 H, arom.) ppm. 13C NMR (CDCl
): δ
10.44 (s, CH ), 14.22 (s, CH ), 21.75 (s, CH ), 70.56 (s, OCH ),
3
–
1
1.01 (t, 3 H, CH
H, CH
3
), 1.34 (t, 3 H, CH
3
), 2.82 (q, 2 H, CH
2
δ = 11.84 ppm. IR: ν˜ = 980–1120 (BF
NOP (507.28): calcd. C 66.27, H 4.54, N 2.76; found C
66.24, H 4.25, N 2.58.
4
), 1180, 1630 (cycle) cm .
2
3
28 4
C H23BF
=
3
3
2
2
Eur. J. Org. Chem. 2009, 2323–2327
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
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