8712
Y. Hari et al. / Tetrahedron 65 (2009) 8708–8713
and concentrated in vacuo. The residue was purified by silica gel
column chromatography (hexane–AcOEt or hexane–CHCl3 system)
to give the following products.
18.35, 25.78, 28.17, 81.58, 82.96, 85.66, 112.63, 119.74, 121.14, 131.54,
134.47, 153.11, 158.03; IR (neat) 2214, 1708, 1151 cmꢀ1; FABMS m/z:
333 (MHþ). HRMS calcd for C19H29O3Si: 333.1886. Found 333.1877.
4.3.1. Ethyl benzofuran-3-carboxylate (3). See Ref. 3
4.3.10. tert-Butyl 2-(tert-butyldimethylsilyl)benzofuran-3-carboxyl-
ate (18). Colorless oil; yield 28%; 1H NMR (CDCl3)
d
0.43 (6H, s), 1.02
(9H, s), 1.65 (9H, s), 7.24–7.33 (2H, m), 7.48–7.51 (1H, m), 7.94–7.97
(1H, m); 13C NMR (CDCl3)
4.3.2. tert-Butyl benzofuran-3-carboxylate (4). Yellow oil; yield
55%; 1H NMR (CDCl3)
d
1.63 (9H, s), 7.32–7.37 (2H, m), 7.49–7.53
d
ꢀ5.44, 18.09, 26.89, 28.50, 81.03, 111.24,
(1H, m), 8.01–8.04 (1H, m), 8.18 (1H, s); 13C NMR (CDCl3)
d
28.4,
122.11, 123.21, 124.72, 125.51, 125.84, 157.50, 163.58, 169.39; IR
(neat) 1712, 1242 cmꢀ1; FABMS m/z: 333 (MHþ). HRMS calcd for
C19H29O3Si: 333.1886. Found 333.1871.
81.2, 111.5, 116.0, 121.9, 123.8, 124.7, 124.9, 150.5, 155.4, 162.6; IR
(neat) 1716 cmꢀ1; EIMS m/z: 218 (Mþ, 22.4), 162 (100). HRMS calcd
for C13H14O3: 218.0943. Found 218.0964.
4.3.11. 1-Methoxy-2-(prop-1-ynyl)benzene (20). See Ref. 18
4.3.3. tert-Butyl 3-(2-methoxyphenyl)propiolate (5). Red oil; yield
16%; 1H NMR (CDCl3)
d
1.54 (9H, s), 3.89 (3H, s), 6.87–6.95 (2H, m),
4.3.12. tert-Butyl 5-methoxybenzofuran-3-carboxylate (28). Colorless
7.38 (1H, t, J¼7.9 Hz), 7.51 (1H, t, J¼7.9 Hz); 13C NMR (CDCl3)
d
28.1,
oil; yield 47%; 1H NMR (CDCl3)
d
1.63 (9H, s), 3.86 (3H, s), 6.92 (1H,
dd, J¼2.7, 9.2 Hz), 7.37 (1H, d, J¼9.2 Hz), 7.50 (1H, d, J¼2.7 Hz), 8.13
(1H, s); 13C NMR (CDCl3)
28.36, 55.70, 81.09, 103.53, 111.98, 114.23,
55.8, 80.7, 83.2, 85.9, 109.1, 110.7, 120.4, 131.8, 134.7, 153.1, 161.2; IR
(neat) 2210, 1701 cmꢀ1; EIMS m/z: 232 (Mþ, 34.0), 176 (100). HRMS
calcd for C14H16O3: 232.1099. Found 232.1105.
d
115.82, 125.35, 150.31, 151.05, 156.63, 162.62; IR (neat) 1713 cmꢀ1
;
EIMS m/z: 248 (Mþ, 22.8), 192 (100). HRMS calcd for C14H16O4:
4.3.4. tert-Butyl 3-(2-ethoxyphenyl)propiolate (12). Brown solid
248.1049. Found 248.1045.
(mp 73–75 ꢁC); yield 6%; 1H NMR (CDCl3)
d
1.48 (3H, t, J¼7.0 Hz),
1.54 (9H, s), 4.11 (2H, q, J¼7.0 Hz), 6.87 (1H, d, J¼8.4 Hz), 6.90 (1H, t,
4.3.13. tert-Butyl 3-(2,5-dimethoxyphenyl)propiolate (35). Yellow
J¼7.6 Hz), 7.35 (1H, dd, J¼7.6, 8.4 Hz), 7.50 (1H, d, J¼7.6 Hz); 13C
oil; yield 12%; 1H NMR (CDCl3)
d 1.54 (9H, s), 3.75 (3H, s), 3.85 (3H,
NMR (CDCl3)
d
14.70, 28.13, 64.39, 80.91, 83.10, 85.86,109.39,111.85,
s), 6.81 (1H, d, J¼9.2 Hz), 6.94 (1H, dd, J¼3.0, 9.2 Hz), 7.04 (1H, d,
120.23, 131.74, 134.65, 153.18, 160.76; IR (Nujol) 2208, 1697 cmꢀ1
;
J¼3.0 Hz); 13C NMR (CDCl3)
d 28.11, 55.83, 56.35, 80.58, 83.29, 85.72,
EIMS m/z: 246 (Mþ, 23.0), 144 (100). HRMS calcd for C15H18O3:
109.34, 112.05, 118.38, 118.63, 152.89, 153.01, 155.80; IR (neat) 2212,
1697 cmꢀ1; EIMS m/z: 262 (Mþ, 24.7), 206 (100). HRMS calcd for
C15H18O4: 262.1205. Found 262.1207.
246.1256. Found 246.1241.
4.3.5. tert-Butyl 3-[2-(allyloxy)phenyl]propiolate (13). Red oil; yield
9%; 1H NMR (CDCl3)
d
1.54 (9H, s), 4.63 (2H, d, J¼4.9 Hz), 5.31 (1H,
4.3.14. tert-Butyl 5-methylbenzofuran-3-carboxylate (29). Yellow
dd, J¼1.6, 10 Hz), 5.54 (1H, dd, J¼1.6, 17 Hz), 5.99–6.13 (1H, m),
6.86–6.95 (2H, m), 7.35 (1H, dt, J¼1.6, 7.6 Hz), 7.52 (1H, dd, J¼1.6,
solid (mp 46–47 ꢁC); yield 42%; 1H NMR (CDCl3)
d
1.65 (9H, s), 2.48
(3H, s), 7.14 (1H, d, J¼8.4 Hz), 7.38 (1H, d, J¼8.4 Hz), 7.85 (1H, s), 8.14
(1H, s); 13C NMR (CDCl3)
21.42, 28.37, 81.09, 110.91, 115.56, 121.59,
7.6 Hz); 13C NMR (CDCl3)
d
28.14, 69.08, 80.65, 83.13, 86.08, 109.64,
d
112.19, 117.23, 120.56, 131.68, 132.36, 134.60, 153.14, 160.38; IR
(neat) 2212, 1630 cmꢀ1; EIMS m/z: 258 (Mþ, 22.9), 144 (100). HRMS
calcd for C16H18O3: 258.1256. Found 258.1249.
124.73, 126.12, 133.38, 150.55, 153.89, 162.68; IR (Nujol) 1717 cmꢀ1
;
EIMS m/z: 232 (Mþ, 40.3), 176 (100). HRMS calcd for C14H16O3:
232.1099. Found 232.1096.
4.3.6. tert-Butyl 3-[2-(2-methoxyethoxy)phenyl]propiolate (14). Red
4.3.15. tert-Butyl 3-(2-methoxy-5-methylphenyl)propiolate (36). Yel-
oil; yield 16%; 1H NMR (CDCl3)
d
1.53 (9H, s), 3.53 (3H, s), 3.83 (2H, t,
low oil; yield 15%; 1H NMR (CDCl3)
d 1.53 (9H, s), 2.25 (3H, s), 3.85
J¼4.9 Hz), 4.19 (2H, t, J¼4.9 Hz), 6.90 (1H, d, J¼8.1 Hz), 6.93 (1H, t,
(3H, s), 6.77 (1H, d, J¼8.6 Hz), 7.17 (1H, dd, J¼1.9, 8.6 Hz), 7.32 (1H,
J¼8.1 Hz), 7.36 (1H, td, J¼1.9, 8.1 Hz), 7.51 (1H, dd, J¼1.9, 8.1 Hz); 13C
d, J¼1.9 Hz); 13C NMR (CDCl3)
d 20.17, 28.12, 55.88, 80.97, 83.11,
NMR (CDCl3)
d
28.12, 59.78, 68.89, 70.77, 80.71, 83.06, 85.99, 109.70,
85.65, 108.68, 110.61, 129.66, 132.43, 134.96, 153.12, 159.25; IR
(neat) 2210, 1697 cmꢀ1; EIMS m/z: 246 (Mþ, 34.8), 190 (100). HRMS
calcd for C15H18O3: 246.1256. Found 246.1257.
112.17, 120.72, 131.76, 134.61, 153.13, 160.74; IR (neat) 2212,
1701 cmꢀ1; EIMS m/z: 276 (Mþ, 46.7), 59 (100). HRMS calcd for
C16H20O4: 276.1362. Found 276.1348.
4.3.16. tert-Butyl 5-chlorobenzofuran-3-carboxylate (30). Red oil;
4.3.7. tert-Butyl 3-[2-(methoxymethoxy)phenyl]propiolate (15). Yellow
yield 40%; 1H NMR (CDCl3)
d
1.63 (9H, s), 7.30 (1H, dd, J¼2.2, 8.6 Hz),
oil; yield 14%; 1H NMR (CDCl3)
d
1.54 (9H, s), 3.53 (3H, s), 5.26 (2H,
7.43 (1H, d, J¼8.6 Hz), 8.00 (1H, d, J¼2.2 Hz), 8.18 (1H, s); 13C NMR
s), 6.99 (1H, t, J¼8.4 Hz), 7.14 (1H, d, J¼8.4 Hz), 7.36 (1H, t, J¼8.4 Hz),
(CDCl3) d 28.42, 81.76, 112.56, 115.79, 121.73, 125.33, 126.11, 129.74,
7.52 (1H, d, J¼8.4 Hz); 13C NMR (CDCl3)
d
28.11, 56.39, 80.58, 83.22,
151.60, 153.79, 162.05; IR (Nujol) 1714 cmꢀ1; EIMS m/z: 254 (Mþ,
6.8), 252 (Mþ, 20.9), 196 (100). HRMS calcd for C13H1335ClO3:
252.0553. Found 252.0546. Calcd for C13H1337ClO3: 254.0524.
Found 254.0497.
85.71, 94.91, 110.46, 114.97, 121.67, 131.67, 134.50, 153.07, 159.04; IR
(neat) 2212, 1701 cmꢀ1; EIMS m/z: 262 (Mþ, 1.4), 144 (100). HRMS
calcd for C15H18O4: 262.1205. Found 262.1227.
4.3.8. tert-Butyl 2-(methoxymethyl)benzofuran-3-carboxylate (17). Yel-
4.3.17. tert-Butyl 3-(5-chloro-2-methoxyphenyl)propiolate (37). Brown
low oil; yield 30%; 1H NMR (CDCl3)
d
1.66 (9H, s), 3.49 (3H, s), 4.96
oil; yield 13%; 1H NMR (CDCl3)
d 1.54 (9H, s), 3.87 (3H, s), 6.82 (1H,
(2H, s), 7.31–7.37 (2H, m), 7.49–7.53 (1H, m), 7.98–8.01 (1H, m); 13C
d, J¼9.2 Hz), 7.32 (1H, dd, J¼2.7, 9.2 Hz), 7.47 (1H, d, J¼2.7 Hz); 13C
NMR (CDCl3)
d
28.4, 58.7, 65.5, 81.6, 111.3, 112.6, 122.2, 123.7, 125.1,
NMR (CDCl3) d 28.10, 56.18, 78.91, 83.54, 86.53, 110.70, 111.93,
125.5, 153.9, 159.8, 162.7; IR (neat) 1708 cmꢀ1; EIMS m/z: 262 (Mþ,
125.13, 131.56, 133.85, 152.72, 159.84; IR (neat) 2217, 1705 cmꢀ1
;
4.7),173 (100). HRMS calcd for C15H18O4: 262.1205. Found 262.1205.
EIMS m/z: 268 (Mþ, 10.8), 266 (Mþ, 32.8), 210 (100). HRMS calcd for
C14H1535ClO3: 266.0710. Found 266.0722. Calcd for C14H1537ClO3:
268.0680. Found 268.0679.
4.3.9. tert-Butyl 3-[2-(tert-butyldimethylsilyloxy)phenyl]propiolate
(16). Yellow oil; yield 10%; 1H NMR (CDCl3)
d 0.25 (6H, s), 1.05 (9H,
s), 1.53 (9H, s), 6.83 (1H, d, J¼8.4 Hz), 6.93 (1H, t, J¼7.2 Hz), 7.29 (1H,
4.3.18. tert-Butyl 6-methoxybenzofuran-3-carboxylate (31). Yellow
dd, J¼7.2, 8.4 Hz), 7.48 (1H, d, J¼7.2 Hz); 13C NMR (CDCl3)
d
ꢀ4.26,
oil; yield 62%; 1H NMR (CDCl3)
d 1.62 (9H, s), 3.85 (3H, s), 6.97 (1H,