Viirre et al.
5,6-Methylenedioxy-2-undecylbenzoxazole (4r). The product
was isolated as a white solid in 86% yield (68 mg). Mp ) 69–70
°C; 1H NMR (CDCl3, 300 MHz) δ 7.07 (s, 1H), 6.96 (s, 1H), 5.99
(s, 2H), 2.85 (t, 2H, J ) 7.5 Hz), 1.84 (tt, 2H, J ) 7.5 Hz, J ) 7.5
Hz), 1.42–1.23 (m, 16H), 0.88 (t, 3H, J ) 6.5 Hz); 13C NMR
(CDCl3, 75 MHz) δ 166.7, 145.6, 145.6, 145.1, 135.1, 101.5, 99.2,
92.3, 31.9, 29.6, 29.4, 29.3, 29.2, 29.1, 28.6, 26.8, 22.6, 14.1 (1
carbon signal missing: aliphatic); HRMS (ESI-QStar) calculated
for C19H28NO3 (M + H)+ 318.2063; observed 318.2055.
Hz, J ) 3.5 Hz), 7.12 (s, 1H), 7.01 (s, 1H), 6.02 (s, 2H); 13C NMR
(CDCl3, 75 MHz) δ 158.6, 146.2, 145.7, 145.4, 135.9, 129.8, 129.3,
128.7, 128.1, 101.7, 99.3, 92.4; HRMS (ESI-QStar) calculated for
C12H8NO3S (M + H)+ 246.0219; observed 246.0215.
2-(2-Furyl)-6-methylbenzoxazole (4aa). The product was iso-
lated as a brown solid in 90% yield (45 mg). Mp ) 52–53 °C; 1H
NMR (CDCl3, 300 MHz) δ 7.64 (dd, 1H, J ) 2.0 Hz, J ) 0.5 Hz),
7.61 (d, 1H, J ) 8.0 Hz), 7.34–7.33 (m, 1H), 7.22 (dd, 1H, J )
3.5 Hz, J ) 0.5 Hz), 7.17–7.13 (m, 1H), 6.59 (dd, 1H, J ) 3.5 Hz,
J ) 2.0 Hz), 2.48 (s, 3H); 13C NMR (CDCl3, 75 MHz) δ 154.8,
150.4, 145.4, 142.7, 139.4, 135.7, 126.0, 119.4, 113.7, 112.1, 110.6,
21.7; HRMS (ESI-QStar) calculated for C12H10NO2 (M + H)+
200.0706; observed 200.0716.
6-Fluoro-2-styrylbenzoxazole (4t). The product was isolated as
1
an off-white solid in 62% yield (37 mg). Mp ) 97–100 °C; H
NMR (CDCl3, 300 MHz) δ 7.75 (d, 1H J ) 16.5 Hz), 7.65–7.56
(m, 3H), 7.44–7.37 (m, 3H), 7.24 (dd, 1H, J ) 8.0 Hz, J ) 2.5
Hz), 7.10–7.04 (m, 1H), 7.03 (d, 1H, J ) 16.5 Hz); 13C NMR
(CDCl3, 75 MHz) δ 163.4, 160.7 (d, J ) 243.0 Hz), 150.4 (d, J )
14.5 Hz), 139.5, 138.5 (d, J ) 1.5 Hz), 135.0, 129.8, 129.0, 127.5,
120.1 (d, J ) 10.0 Hz), 113.6, 112.4 (d, J ) 25.0 Hz), 98.4 (d, J
) 28.0 Hz); HRMS (ESI-QStar) calculated for C15H11FNO (M +
H)+ 240.0819; observed 240.0822.
2-(2-Furyl)-6-fluorobenzoxazole (4ab). The product was iso-
lated as a pale brown solid in 61% yield (31 mg). Mp ) 69–73
1
°C; H NMR (CDCl3, 300 MHz) δ 7.70–7.65 (m, 2H), 7.30–7.24
(m, 2H), 7.14–7.07 (m, 1H), 6.61 (dd, 1H, J ) 3.5 Hz, J ) 2.0
Hz); 13C NMR (CDCl3, 75 MHz) δ 160.7 (d, J ) 243.0 Hz), 155.9
(d, J ) 3.5 Hz), 150.1 (d, J ) 15.0 Hz), 145.8, 142.2, 137.9 (d, J
) 1.5 Hz) 120.3 (d, J ) 10.0 Hz), 114.3, 112.8 (d, J ) 25.0 Hz),
112.2, 98.7 (d, J ) 28.5 Hz); HRMS (ESI-QStar) calculated for
C11H7FNO2 (M + H)+ 204.0455; observed 204.0456.
2-Styryl-5-trifluoromethylbenzoxazole (4u). The product was
isolated as a yellow solid in 21% yield (15 mg). Mp ) 97–100 °C;
1H NMR (CDCl3, 300 MHz) δ 7.98 (s, 1H), 7.84 (d, 1H, J ) 16.5
Hz), 7.63–7.59 (m, 4H), 7.48–7.38 (m, 3H), 7.08 (d, 1H, J ) 16.5
Hz); 13C NMR (CDCl3, 75 MHz) δ 164.5, 152.2, 142.3, 140.9,
134.8, 130.2, 129.1, 127.7, 127.3 (q, J ) 32.5 Hz), 124.2 (q, J )
272.0 Hz), 122.4 (q, J ) 3.5 Hz), 117.5 (q, J ) 4.0 Hz), 113.3,
110.7; HRMS (EI) calculated for C16H9F3NO (M - H)+ 288.0636;
observed 288.0639.
2-(2-Furyl)-5-trifluoromethylbenzoxazole (4ac). The product
was isolated as an off-white solid in 63% yield (40 mg). Mp )
1
102–105 °C; H NMR (CDCl3, 300 MHz) δ 8.02 (s, 1H), 7.71
(dd, 1H, J ) 2.0 Hz, J ) 0.5 Hz), 7.65–7.64 (m, 2H), 7.34 (dd,
1H, J ) 3.5 Hz, J ) 0.5 Hz), 6.66 (dd, 1H, J ) 3.5 Hz, J ) 2.0
Hz) 13C NMR (CDCl3, 75 and 125 MHz) δ 156.8, 151.9, 146.4,
142.0, 141.9, 127.8 (q, J ) 32.5 Hz), 124.1 (q, J ) 272.0 Hz),
122.5 (q, J ) 3.5 Hz), 117.8 (q, J ) 4.0 Hz), 115.5, 112.5, 111.0;
HRMS (ESI-QStar) calculated for C12H7F3NO2 (M + H)+ 254.0423;
observed 254.0420.
5,6-Methylenedioxy-2-styrylbenzoxazole (4v). The product was
isolated as a yellow solid in 66% yield (44 mg). Mp ) 161–162
1
°C; H NMR (CDCl3, 300 MHz) δ 7.63 (d, 1H, J ) 16.5 Hz),
7.57–7.54 (m, 2H), 7.42–7.34 (m, 3H), 7.10 (s, 1H), 6.99 (s, 1H),
6.98 (d, 1H, J ) 16.5 Hz), 6.01 (s, 2H); 13C NMR (CDCl3, 75
MHz) δ 162.4, 146.4, 145.6, 145.5, 137.6, 136.2, 135.3, 129.4,
128.9, 127.3, 113.9, 101.7, 99.3, 92.3; HRMS (ESI-QStar) calcu-
lated for C16H12NO3 (M + H)+ 266.0811; observed 266.0817.
6-Methyl-2-(2-thienyl)benzoxazole (4w). The product was
isolated as an off-white solid in 91% yield (49 mg). Mp ) 74–76
°C; 1H NMR (CDCl3, 300 MHz) δ 7.86 (dd, 1H, J ) 4.0 Hz, J )
1.0 Hz), 7.58 (d, 1H, J ) 8.0 Hz), 7.51 (dd, 1H, J ) 5.0 Hz, J )
1.0 Hz), 7.33–7.31 (m, 1H), 7.17–7.12 (m, 2H), 2.47 (s, 3H); 13C
NMR (CDCl3, 75 MHz) δ 158.5, 150.7, 139.7, 135.5, 129.8, 129.5,
128.1, 125.9, 119.1, 110.5, 21.7 (1 carbon signal missing: C-2);
HRMS (EI) calculated for C12H9NOS (M+) 215.0405; observed
215.0408.
2-(2-Furyl)-5,6-methylenedioxybenzoxazole (4ad). The product
was isolated as an off-white solid in 70% yield (40 mg). Mp )
1
179–181 °C; H NMR (CDCl3, 300 MHz) δ 7.62 (d, 1H, J ) 1.5
Hz), 7.15 (d, 1H, J ) 0.5 Hz), 7.14 (s, 1H), 7.03 (s, 1H), 6.58 (dd,
1H, J ) 3.5 Hz, J ) 2.0 Hz), 6.03 (s, 2H); 13C NMR (CDCl3, 75
MHz) δ 154.9, 146.4, 145.8, 145.2, 145.1, 142.7, 135.6, 112.8,
112.1, 101.8, 99.5, 92.5; HRMS (ESI-QStar) calculated for
C12H8NO4 (M + H)+ 230.0447; observed 230.0436.
2-(2-Chlorophenyl)-6-fluorobenzoxazole (4af). The product was
isolated as a white solid in 65% yield (40 mg). Mp ) 97–99 °C;
1H NMR (CDCl3, 300 MHz) δ 8.11 (dd, 1H, J ) 7.0 Hz, J ) 2.5
Hz), 7.77 (dd, 1H, J ) 9.0 Hz, J ) 5.0 Hz), 7.56 (dd, 1H, J ) 7.5
Hz, J ) 2.0 Hz), 7.47–7.38 (m, 2H), 7.33 (dd, 1H, J ) 8.0 Hz, J
) 2.5 Hz), 7.17–7.10 (m, 1H); 13C NMR (CDCl3, 75 MHz) δ 161.5
(d, J ) 3.5 Hz), 160.9 (d, J ) 243.0 Hz), 150.5 (d, J ) 15.0 Hz),
138.0 (d, J ) 2.0 Hz), 133.4, 132.0, 131.6, 131.4, 126.9, 125.9,
120.8 (d, J ) 10.0 Hz), 112.7 (d, J ) 25.0 Hz), 98.7 (d, J ) 28.0
Hz); HRMS (ESI-QStar) calculated for C13H8ClFNO (M + H)+
248.0272; observed 248.0274.
2-(2-Chlorophenyl)-5-trifluoromethylbenzoxazole (4ag). The
product was isolated as a white solid in 71% yield (53 mg). Mp )
74–75 °C; 1H NMR (CDCl3, 300 MHz) δ 8.18–8.13 (m, 2H),
7.73–7.64 (m, 2H), 7.60–7.56 (m, 1H), 7.52–7.41 (m, 2H); 13C
NMR (CDCl3, 75 MHz) δ 162.7, 152.3, 141.8, 133.7, 132.5, 131.9,
131.5, 127.5 (q, J ) 32.5 Hz), 127.0, 125.5, 124.1 (q, J ) 270.5
Hz), 122.8 (q, J ) 3.5 Hz), 118.2 (q, J ) 4.0 Hz), 111.2; HRMS
(EI) calculated for C14H7ClF3NO (M+) 297.0168; observed 297.0175.
2-(2-Chlorophenyl)-5,6-methylenedioxybenzoxazole (4ah). The
product was isolated as an off-white solid in 59% yield (40 mg).
Mp ) 142–144 °C; 1H NMR (CDCl3, 300 MHz) δ 8.10–8.06 (m,
1H), 7.55–7.52 (m, 1H), 7.43–7.35 (m, 2H), 7.23 (s, 1H), 7.08 (s,
1H), 6.04 (s, 2H); 13C NMR (CDCl3, 75 MHz) δ 160.5, 146.9,
145.9, 135.9, 133.0, 131.5, 131.5, 131.4, 129.0, 127.0, 126.4, 101.9,
99.9, 92.6; HRMS (ESI-QStar) calculated for C14H9ClNO3 (M +
H)+ 274.0265; observed 274.0272.
6-Fluoro-2-(2-thienyl)benzoxazole (4x). The product was iso-
lated as a white solid in 80% yield (44 mg). Mp ) 113–114 °C;
1H NMR (CDCl3, 300 MHz) δ 7.87 (dd, 1H, J ) 4.0 Hz, J ) 1.5
Hz), 7.64 (dd, 1H, J ) 9.0 Hz, J ) 5.0 Hz), 7.55 (dd, 1H, J ) 5.0
Hz, J ) 1.0 Hz), 7.26 (dd, 1H, J ) 8.0 Hz, J ) 2.5 Hz), 7.17 (dd,
1H, J ) 5.0 Hz, J ) 4.0 Hz), 7.12–7.05 (m, 1H); 13C NMR (CDCl3,
75 MHz) δ 160.6 (d, J ) 243.0 Hz), 159.6 (d, J ) 3.5 Hz), 150.3
(d, J ) 15.0 Hz), 138.3 (d, J ) 2.0 Hz), 130.3, 129.9, 129.2, 128.2,
120.0 (d, J ) 10.0 Hz), 112.6 (d, J ) 24.5 Hz), 98.6 (d, J ) 28.0
Hz) (1 carbon signal missing: C-2); HRMS (ESI-QStar) calculated
for C11H7FNOS (M + H)+ 220.0226; observed 220.0217.
2-(2-Thienyl)-5-trifluoromethylbenzoxazole (4y). The product
was isolated as a white solid in 31% yield (21 mg). Mp ) 98–101
°C; 1H NMR (CDCl3, 300 MHz) δ 7.99 (s, 1H), 7.95 (dd, 1H, J )
4.0 Hz, J ) 1.0 Hz), 7.65–7.61 (m, 3H), 7.21 (dd, 1H, J ) 5.0 Hz,
J ) 3.5 Hz); 13C NMR (CDCl3, 75 MHz) δ 160.7, 152.2, 142.2,
131.2, 130.8, 128.8, 128.4, 127.5 (q, J ) 32.5 Hz), 124.1 (q, J )
270.0 Hz), 122.3 (q, J ) 4.0 Hz), 117.4 (q, J ) 4.0 Hz), 110.8;
HRMS (ESI-QStar) calculated for C12H7F3NOS (M + H)+ 270.0194;
observed 270.0208.
5,6-Methylenedioxy-2-(2-thienyl)benzoxazole (4z). The product
was isolated as a white solid in 65% yield (40 mg). Mp ) 184 °C;
1H NMR (CDCl3, 300 MHz) δ 7.78 (dd, 1H, J ) 3.5 Hz, J ) 1.0
Hz), 7.48 (dd, 1H, J ) 5.0 Hz, J ) 1.0 Hz), 7.14 (dd, 1H, J ) 5.0
3458 J. Org. Chem. Vol. 73, No. 9, 2008