338
S. Yamaguchi, E. Hamade, H. Yokoyama, Y. Hirai, and S. Shiotani
Vol. 39
2H, CH , J = 7.5 Hz), 6.24 (t, 1H, 5-H, J = 6.6 Hz), 7.29 (d, 2H,
therefore, the anion radicals from 1b,c might not be as sta-
ble as the anion radicals from 1a,d. These are reflected in
the total yields; the yields in 1b,c are not so high (1b: 63%,
1c: 50%) as those in 1a,d (1a: 100%, 1d: 88%). The 7-
anion 4-radical Ib,c would follow the routes A-1 and A-2 to
form ethynylpyridinolates VIb,c and vinylpyridinolates
VIIb,c. The 6-anion 3a-radical IIIb and the 4-anion 7-rad-
icals IVb,c would follow route B to form the corresponding
vinylpyridinolates VIIb,c (for 3b,c). And, a part of the 4-
vinyl-3-pyridinolate VIIb causes a further reduction to give
the 4-ethyl-3-pyridinol 4b, and all of the 3-vinyl-4-pyridi-
nolate VIIc, having a 4-pyridinone structure VIIc', cause a
further reduction to give 3-ethyl-4-pyridinol 4c.
2
4-H and 6-H, J = 6.6 Hz), 12.4-13.4 ppm (br, 1H, NH); ms: m/z
+
123 (M ).
Birch Reduction of 1b.
4-Ethynyl-3-pyridinol (2b).
This compound could not be isolated, but identified with the
pmr data of the sample obtained by metalation of 3-bromo-
furo[2,3-c]pyridine [7]; pmr (CDCl ): δ 3.52 ppm (s, 1H, CH in
3
ethynyl).
4-Vinyl-3-pyridinol (3b).
This compound could not be isolated; pmr: δ 5.52 (d, 1H,
C=CH , J = 11.1 Hz), 6.04 (d, 1H, =CH
, J = 15.9 Hz), 7.05
cis
trans
(dd, 1H, =CH , J = 15.9 and 11.1 Hz).
gem
The 5-anion 7a-radical IIc and the 7-anion 4-radical Id
would follow route C to give the corresponding dihydro-
furopyridines 5c,d.
4-Ethyl-3-pyridinol (4b) [11].
This compound has mp 92-94 °C (lit. 93.5-95 °C); ir: ν
OH
-1
3446, ν
1663 and 1647 cm ; pmr (CDCl ): δ 1.19 (t, 3H,
pyridine
3
CH in ethyl, J = 7.4 Hz), 2.64 (q, 2H, CH in ethyl, J = 7.4 Hz),
3
2
EXPERIMENTAL
7.08 (d, 1H, 5-H, J = 4.8 Hz), 7.93 (d, 1H, 6-H, J = 4.8 Hz), 8.16
+
(s, 1H, 2-H), 8.0-8.6 ppm (br, 1H, OH); ms: m/z 123 (M ).
Melting points were measured on a Yanagimoto micro melting
point apparatus and are unccorected. The ir spectra were
recorded on a JASCO FT/IR spectrometer in liquid films or
potassium bromide disks, the uv spectra were recorded on a
Hitachi 220A spectrophotometer, the pmr spectra were recorded
on a JEOL MAC-FX (90MHz) or A440 (400MHz) spectrometer
in deuteriochloroform solution, and the mass spectra were
recorded on a JEOL JMS-OISG-2 spectrometer.
Birch Reduction of 1c.
3-Ethynyl-4(1H)-pyridinone (2c') (corresponded to 3-ethynyl-4-
pyridinol 2c).
This compound could not be isolated, and was identified with
the pmr data of the sample obtained by metalation of 3-bromo-
furo[3,2-c]pyridine [7].
3-Ethyl-4(1H)-pyridinone (4c') (corresponded to 3-ethyl-4-
pyridinol 4c).
General Procedure for Birch Reduction of 1a-d.
A solution of furopyridine 1a-d [2-5] (1.0 mmol) in dry ether
(ca. 3 ml) was added to liquid ammonia (10 ml), and sodium
metal (3.0 or 1.8 mmol) was then added to the solution, and the
mixture was stirred for 30 minutes. The resulting mixture was
treated with ammonium chloride and the ammonia was allowed
to evaporate. The residue was treated with a small amount of
water and extracted with ethyl acetate. The organic layer was
dried over anhydrous magnesium sulfate. After removal of the
solvent, the residual oil was chromatogramed on a silica-gel col-
umn to give corresponding ethynylpyridinols 2a-d, vinylpyridi-
nols 3b,d, ethylpyridinols 4a-d, and dihydrofuropyridine 5c.
Each product was isolated by silica-ge column chromatography
with hexane-ethyl acetate as eluents). The product ratios were
determined by the pmr spectra of the crude mixture.
-
This compound has ir: ν 3446, ν
1663 and 1647 cm
pyridine
OH
1
; pmr (CDCl ): δ 1.19 (t, 3H, CH , J = 7.3 Hz), 2.55 (q, 2H,
3
3
CH , J = 7.3 Hz), 6.42 (d, 1H, 5-H, J = 7.3 Hz), 7.50-7.62 ppm
2
+
(m, 2H, 2-H and 6-H); ms: m/z 123 (M ).
Anal. Calcd. for C H NO•1/2H O: C, 63.61, H, 7.64, N,
7
9
2
10.60. Found: C, 63.83, H, 7.27, N, 10.38.
2,3-Dihydrofuro[3,2-c]pyridine (5c).
This compound was identical with the sample obtained by
hydrogenation [8]; ir: ν
938, 867, 824 cm ; pmr: δ 3.24 (t, 2H, 3-CH , J = 8.8 Hz), 4.65 (t,
1605, 1587, 1493, 1277, 1237, 976,
pyridine
-1
2
2H, 2-CH , J = 8.8 Hz), 6.73 (d, 1H, 7-H, J = 5.3 Hz), 8.28 (d, 1H,
2
+
6-H, J = 5.3 Hz), 8.34 ppm (s, 1H, 4-H); ms: m/z 121 (M ).
Birch Reduction of 1d.
Birch Reduction of 1a.
2-Ethynyl-3-pyridinol (2d) [7].
3-Ethynyl-2(1H)-pyridinone 2a' (corresponded to 3-ethynyl-
2-pyridinol 2a); mp 148-150 °C (lit. 148-151 °C). This com-
pound was identical with the sample obtained by metalation of 3-
This compound has mp 148-150 °C (lit. 149.5-150.5 °C), this
compound was identified by comparison of the ir and pmr spectra
with those of the sample obtained by metalation of 3-bromo-
bromofuro[2,3-b]pyridine [7]; ir: ν
3444, ν
3217, ν
OH
NH ethynyl
-1
2101, ν
1634, ν
1609, ν
1555, 1464, 1429, 1244,
furo[3,2-b]pyridine [7]; ir: ν
3446, ν
2100 cm ; pmr
C=O
C=C
pyridine
OH
ethynyl
-1
893, 772 cm ; pmr (CDCl ): δ 3.40 (s, 1H, CH in ethynyl), 6.31
(CDCl ): δ 3.58 (s, 1H, CH in ethynyl), 7.11-7.27 (m, 2H, 4-H
3
3
(t, 1H, 5-H, J = 7.0 Hz), 7.52 (dd, 1H, 6-H, J = 7.0 and 2.1 Hz),
7.74 (dd, 1H, 7.0 and 2.1 Hz), 13.0-14.0 ppm (br, 1H, NH); ms:
m/z 119 (M ).
and 5-H), 8.07 ppm (dd, 1H, 6-H, J = 4 .0 and 2.0 Hz); ms: m/z
119 (M ).
+
+
2-Vinyl-3-pyridinol (3d).
3-Ethyl-2(1H)-pyridinone 4a' (corresponded to 3-ethyl-2-
pyridinol 4a)[10]; mp 124-125 °C (lit. 121-121.5 °C); ir: ν
This compound has mp 148-149 °C; ir: ν
3446, ν
ethynyl
OH
OH
-1
3446, ν
1664, 1647, ν
1616, ν
1568, 1481, 1069,
2100 cm ; pmr (CDCl ): δ 5.49 (dd, 1H, 2'-H
, J = 11.1 and
C=O
-1
C=C
pyriudine
3
trans
776 cm ; pmr (CDCl ): δ 1.22 (t, 3H, CH , J = 7.5 Hz), 2.58 (q,
2.1 Hz), 6.25 (dd, 1H, 2'-H , J = 17.6 and 2.1 Hz), 7.42-6.97 (m,
3
3
cis