F. L. van Delft et al.
FULL PAPER
124.05, 119.40, 110.17, 14.50 ppm. Data in correspondence to com-
mercially available compound (CAS: 95–21–6).
1607, 695 cm–1. 1H NMR (500 MHz, CDCl3): δ = 9.55 (s, 1 H),
7.62 7.50 (m, 3 H), 7.50 7.44 (m, 1 H), 7.43 7.37 (m, 2 H), 7.34
(dd, J = 7.9, 1.4 Hz, 1 H), 7.22 (dd, J = 8.1, 0.8 Hz, 1 H), 7.17 (td,
J = 8.0, 1.1 Hz, 1 H), 4.36 (s, 2 H) ppm. 13C NMR (126 MHz,
CDCl3): δ = 172.25, 171.10, 139.46, 138.80, 131.70, 131.37, 130.29,
129.69, 128.17, 127.27, 123.33, 121.16, 56.69 ppm. HRMS (ESI+)
calcd. for C15H13N2O [M + H]+: 237.1028, found 237.1028.
2-(tert-Butyl)benzoxazole (8f): According to the general procedure
for the aza-Wittig reaction, 7f (20 mg, 91 μmol) was converted into
2-(tert-butyl)benzoxazole (20 mg, 80%) as isolated by column
chromatography (0Ǟ10% Et O in pentane). IR (neat): ν = 2972,
˜
2
1610, 1564, 1455, 1293, 1251, 1243, 1125, 1121, 1098 cm–1. 1H
NMR (300 MHz, CDCl3): δ = 7.72–7.66 (m, 1 H), 7.52–7.44 (m, 1
H), 7.32–7.25 (m, 2 H), 1.49 (s, 9 H) ppm. 13C NMR (75 MHz,
CDCl3): δ = 172.99, 150.31, 140.76, 123.87, 123.45, 119.20, 109.80,
33.66, 27.98 ppm. HRMS (EI+) calcd. for C11H13NO [M]+
175.0997, found 175.0999.
5-Methoxy-1-methyl-1H-benzo-1,4-diazepin-2(3H)-one (10c): Ac-
cording to the general procedure for the aza-Wittig reaction, 9c
(27 mg, 0.13 mmol) was converted into 5-methoxy-1-methyl-1H-
benzo-1,4-diazepin-2(3H)-one (27 mg, 66%) as isolated by column
chromatography (0Ǟ10% EtOAc in heptane) as a colorless oil. IR
(neat): ν = 1675, 1322, 1276, 772 cm–1. 1H NMR (500 MHz,
˜
6-Methoxy-2-phenylbenzoxazole (8 g): According to the general
procedure for the aza-Wittig reaction, 7g (75 mg, 0.28 mmol) was
converted into 6-methoxy-2-phenylbenzoxazole (34 mg, 54%) as
isolated by column chromatography (0Ǟ5% EtOAc in heptane).
CDCl3): δ = 7.69 (ddd, J = 7.6, 1.6, 0.6 Hz, 1 H), 7.55 (ddd, J =
8.3, 7.4, 1.7 Hz, 1 H), 7.28–7.24 (m, 2 H), 4.32 (br. s, 1 H), 3.90 (s,
3 H), 3.66 (br. s, 1 H), 3.39 (s, 3 H) ppm. 13C NMR (126 MHz,
CDCl3): δ = 171.10, 163.97, 142.76, 131.71, 128.45, 124.61, 124.48,
120.90, 54.10, 52.38, 34.99 ppm. HRMS (ESI+) calcd. for
C11H13N2O2 [M + H]+ 205.0977, found 205.0972.
IR (neat): ν = 1618, 1485, 1448, 1143, 1022 cm–1. 1H NMR
˜
(400 MHz, CDCl3): δ = 8.24–8.17 (m, 2 H), 7.64 (dd, J = 8.8,
0.4 Hz, 1 H), 7.52–7.49 (m, 3 H), 7.12 (d, J = 2.3 Hz, 1 H), 6.96
(dd, J = 8.7, 2.4 Hz, 1 H), 3.89 (s, 3 H) ppm. 13C NMR (75 MHz,
CDCl3): δ = 162.40, 158.45, 151.81, 136.05, 134.30, 131.22, 129.02,
127.35, 120.15, 112.97, 95.61, 56.12 ppm. HRMS (EI+) calcd. for
C14H11NO2 [M]+ 225.0790, found 225.0766.
N-(2-Aminobenzoyl)-α-methylalanine Methyl Ester (13b): Accord-
ing to the general procedure for the aza-Wittig reaction, from the
reaction of N-(2-azidobenzoyl)-α-methylalanine methyl ester (11d,
100 mg,
0.381 mmol),
N-(2-amino-benzoyl)-α-methylalanine
methyl ester (52 mg, 58%) was obtained as a yellow oil. IR (neat):
5-Methoxy-2-phenylbenzoxazole (8h): According to the general pro-
cedure for the aza-Wittig reaction, 7h (50 mg, 0.19 mmol) was con-
verted into 5-methoxy-2-benzoxazole (23 mg, 55%) as isolated by
ν = 3464, 3343, 2984, 2946, 1718, 1636, 1515, 1148, 746 cm–1. Mix-
˜
1
ture of rotamers: H NMR (300 MHz, CDCl3): δ = 7.34 (dd, J =
4.9, 3.6 Hz, 1 H), 7.19 (ddd, J = 8.2, 7.3, 1.5 Hz, 1 H), 6.70–6.52
(m, 3 H), 5.52 (br. s, 2 H), 3.75 (d, J = 1.9 Hz, 3 H), 1.64 (s, 6
H) ppm. 13C NMR (75 MHz, CDCl3): δ = 174.74, 168.28, 148.30,
131.90, 126.87, 116.79, 116.03, 115.34, 76.95, 76.72, 76.52, 76.10,
56.01, 52.15, 24.50 ppm. HRMS (ESI+) calcd. for C12H17N2O3 [M
+ H]+ 237.1239, found 237.1251.
column chromatography (0Ǟ5% EtOAc in heptane). IR (neat): ν
˜
= 1602, 1481, 1437, 1196, 1152, 705 cm–1. 1H NMR (500 MHz,
CDCl3): δ = 8.25–8.22 (m, 2 H), 7.53–7.51 (m, 3 H), 7.46 (d, J =
8.8 Hz, 1 H), 7.27 (d, J = 2.5 Hz, 1 H), 6.95 (dd, J = 8.9, 2.6 Hz,
1 H), 3.88 (s, 3 H) ppm. 13C NMR (126 MHz, CDCl3): δ = 163.79,
157.38, 145.41, 142.93, 131.39, 130.31, 128.88, 127.47, 113.70,
110.70, 102.88, 55.93 ppm. HRMS (EI+) calcd. for C14H11NO2
[M]+ 225.0790, found 225.0781.
2-Methoxy-4-methyl-3H-benzo-1,4-diazepin-5(4H)-one (12c): Ac-
cording to the general procedure for the aza-Wittig reaction, N-(2-
azidobenzoyl)sarcosine methyl ester (11b, 150 mg, 604 μmol) was
converted into 12b (28 mg, 23%) which was obtained as a colorless
5-Nitro-2-phenylbenzoxazole (8i): According to the general pro-
cedure for the aza-Wittig reaction, 7i (40 mg, 0.14 mmol) was con-
verted into 5-nitro-2-phenylbenzoxazole (18 mg, 53%) as isolated
by column chromatography (0Ǟ5% EtOAc in heptane). IR (neat):
solid. IR (neat): ν = 2924, 2358, 1653, 1260, 763 cm–1. 1H NMR
˜
(300 MHz, CDCl3): δ = 7.92 (ddd, J = 7.9, 1.7, 0.5 Hz, 1 H), 7.43
(ddd, J = 8.0, 7.3, 1.7 Hz, 1 H), 7.23–7.12 (m, 2 H), 3.90 (s, 3 H),
3.74 (s, 2 H), 3.22 (s, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ =
168.04, 162.98, 144.88, 131.72, 130.88, 127.58, 126.19, 124.52,
54.62, 48.55, 36.50 ppm. HRMS (ESI+) calcd. for C11H13N2O2 [M
+ H]+ 205.0977, found 205.0978.
ν = 1610, 1526, 1348, 819, 735, 702, 686 cm–1. 1H NMR (300 MHz,
˜
CDCl3): δ = 8.63 (dd, J = 2.4, 0.5 Hz, 1 H), 8.31 (dd, J = 8.9,
2.3 Hz, 1 H), 8.28–8.23 (m, 2 H), 7.67 (dd, J = 8.9, 0.4 Hz, 1 H),
7.61–7.52 (m, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 166.10,
154.40, 145.56, 142.69, 132.74, 129.27, 128.16, 126.08, 121.25,
116.39, 110.84 ppm. HRMS (EI+) calcd. for C13H8N2O3 [M]+
256.0535, found 240.0543.
4-Benzyl-2-methoxy-3H-benzo-1,4-diazepin-5(4H)-one (12d): Ac-
cording to the general procedure for the aza-Wittig reaction, N-(2-
azidobenzoyl)-N-benzylglycine methyl ester (11c, 150 mg,
0.462 mmol) was converted to 12c (14 mg, 11%) which was isolated
as a colorless oil; 13d (66 mg, 48%) was obtained as a white solid.
6-Chloro-2-phenylbenzoxazole (8j): According to the general pro-
cedure for the aza-Wittig reaction, 7j (100 mg, 0.365 mmol) was
converted into 6-chloro-2-phenylbenzoxazole (46 mg, 55%) as iso-
lated by column chromatography (0Ǟ5% EtOAc in heptane). IR
IR (neat): ν = 1632, 1597, 1446, 1260, 776, 690 cm–1. 1H NMR
˜
(500 MHz, CDCl3): δ = 8.08–8.02 (m, 1 H), 7.49 (ddd, J = 8.0, 7.3,
1.7 Hz, 1 H), 7.40–7.31 (m, 5 H), 7.26 (ddd, J = 7.9, 7.3, 1.3 Hz, 1
H), 7.18 (dd, J = 8.0, 0.9 Hz, 1 H), 4.87 (s, 2 H), 3.78 (s, 3 H), 3.71
(s, 2 H) ppm. 13C NMR (126 MHz, CDCl3): δ = 167.94, 163.24,
144.94, 136.66, 131.78, 131.02, 128.69, 128.18, 127.73, 127.37,
126.17, 124.46, 54.29, 51.76, 46.03 ppm. HRMS (ESI+) calcd. for
C17H17N2O2 [M + H]+ 281.1290, found 281.1289.
(neat): ν = 1449, 1331, 1051, 807, 699, 682 cm–1. 1H NMR
˜
(300 MHz, CDCl3): δ = 8.25–8.20 (m, 2 H), 7.67 (dd, J = 8.5,
0.4 Hz, 1 H), 7.59 (dd, J = 1.9, 0.4 Hz, 1 H), 7.57–7.49 (m, 3 H),
7.34 (dd, J = 2.0, 8.5 Hz, 1 H) ppm. 13C NMR (75 MHz, CDCl3):
δ = 163.21, 150.44, 140.41, 131.31, 130.18, 128.48, 127.17, 126.23,
124.79, 119.98, 110.75 ppm. HRMS (EI+) calcd. for C13H8NClO
[M]+ 229.0294, found 229.0305.
N-(2-Aminobenzoyl)-N-benzylglycine Methyl Ester (13d): IR (neat):
5-Phenyl-1H-benzo-1,4-diazepin-2(3H)-one (10a): According to the
general procedure for the aza-Wittig reaction, 9a (37 mg,
0.16 mmol) was converted into 5-phenyl-1H-benzo-1,4-diazepin-
2(3H)-one (37 mg, 88%) and isolated by column chromatography
ν = 3218, 1688, 1627, 1476, 1143, 754, 724, 694 cm–1. Mixture of
˜
rotamers: 1H NMR (500 MHz, CDCl3): δ = 8.05 (dd, J = 7.9,
1.5 Hz, 1 H), 7.70 (s, 1 H), 7.54–7.44 (m, 1 H), 7.41–7.28 (m, 6 H),
6.94 (dd, J = 8.0, 0.8 Hz, 1 H), 4.88 (s, 2 H), 3.82 (s, 2 H), 3.49 (d,
J = 5.3 Hz, 3 H) ppm. 13C NMR (126 MHz, CDCl3): δ = 169.85,
(5Ǟ20% EtOAc in heptane) as a yellow solid. IR (neat): ν = 1679,
˜
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Eur. J. Org. Chem. 2013, 7059–7066