HETEROCYCLES, Vol. 91, No. 3, 2015
599
2
.58 (t, 2H, J = 8.3 Hz), 3.06 (t, 2H, J = 8.3 Hz), 3.65 (s, 3H), 4.58 (d, 2H, J = 5.5 Hz), 5.22 (d, 1H, J =
0.6 Hz), 5.25 (d, 1H, J = 17.3 Hz), 5.63 (d, 1H, J = 12.8 Hz), 5.92 (ddt, 1H, J = 17.3, 10.6, 5.5 Hz), 6.72
1
(
d, 1H, J = 12.8 Hz), 6.76 (d, 1H, J = 2.8 Hz), 8.81 (br, 1H); (Z) δ = 1.56 (s, 9H), 2.55 (t, 2H, J = 8.3 Hz),
.08 (t, 2H, J = 8.3 Hz), 3.75 (s, 3H), 4.58 (d, 2H, J = 5.5 Hz), 5.219 (d, 1H, J = 6.9 Hz), 5.224 (dd, 1H, J
10.6 Hz), 5.30 (dd, 1H, J = 17.3 Hz), 5.92 (ddt, 1H, J = 17.3, 10.6, 5.5 Hz), 6.07 (d, 1H, J = 6.9 Hz),
3
=
1
3
7
8
6
1
.32 (d, 1H, J = 3.2 Hz), 8.87 (br, 1H); C NMR (CDCl , 100 MHz): (E) δ = 20.6, 28.4, 35.5, 56.3, 64.9,
3
1.0, 95.9, 116.9, 118.0, 120.5, 120.8, 126.6, 132.3, 147.5, 161.0, 172.8; (Z) δ = 20.3, 28.4, 35.5, 60.1,
4.9, 80.9, 96.6, 118.0, 119.1, 119.8, 121.9, 126.2, 132.3, 145.5, 161.1, 172.9; IR (neat) 3312, 2977, 2933,
–
1
736, 1685, 1663, 1560, 1455, 1401, 1368, 1288, 1259, 1130, 1050, 987, 941, 781 cm ; HRMS (DART):
+
m/z calcd for C H NO : 336.1811: [M+H] ; found: 336.1803.
1
8
26
5
General Procedure for Hydrolysis of Vinyl Ether 9 (Table 1): To a solution of vinyl ether 9 (0.5
9
9
mmol) in CHCl (4.5 mL), oxalyl chloride (63 mg, 0.5 mmol) in CHCl (0.5 mL) was added at rt. To
3
3
this reaction mixture, ethanol (29 µL, 0.5 mmol) and H O (9 µL, 0.5 mmol) were subsequently added and
2
the whole was stirred at rt. After reaction was completed (monitored by TLC), the reaction was quenched
by the addition of sat. aqueous solution of NaHCO and the mixture was subsequently extracted with
3
CHCl . The combined extracts were washed with brine, dried over Na SO and condensed under reduced
3
2
4,
pressure. The residue was purified by column chromatography.
1
3
tert-Butyl 3-(3-(allyloxy)-3-oxopropyl)-4-(2-oxoethyl)-1H-pyrrole-2-carboxylate (3): To a solution of
9
vinyl ether 8 (63 mg, 0.2 mmol) in CHCl (5.5 mL), oxalyl chloride (25 mg, 0.2 mmol) in CHCl (0.5
3
3
9
mL) was added at room temperature. To this reaction mixture, ethanol (11 µL, 0.2 mmol) and H O (4 µL,
2
0
.2 mmol) were subsequently added and the whole was stirred at rt for 0.5 h. The reaction was quenched
by the addition of sat. aqueous solution of NaHCO and the mixture was subsequently extracted with
3
CHCl . The combined extracts were washed with brine, dried over Na SO and condensed under reduced
3
2
4,
pressure. The residue was purified by column chromatography (SiO , hexane/Et O = 4/1 to 2/1, v/v) to
2
2
1
give aldehyde 3 (53 mg, 83% yield) as an oil. H NMR (CDCl , 400 MHz): δ = 1.58 (s, 9H), 2.59 (t, 2H, J
3
=
7.8 Hz), 2.97 (t, 2H, J = 7.8 Hz), 3.59 (d, 2H, J = 1.8 Hz), 4.56 (d, 2H, J = 5.6 Hz), 5.22 (dd, 1H, J =
1
1.9, 1.5 Hz), 5.28 (dd, 1H, J = 15.9, 1.5 Hz), 5.89 (ddt, 1H, J = 15.9, 11.9, 5.6 Hz), 6.78 (d, 1H, J = 3.2
1
3
Hz), 9.41 (br, 1H), 9.68, (t, 1H, J = 1.8 Hz); C NMR (CDCl , 100 MHz): δ = 20.3, 28.4, 35.2, 40.1, 65.0,
3
8
1
3
1.3, 114.6, 118.1, 120.9, 121.2, 128.2, 132.2, 160.7, 172.7, 199.4; IR (neat) 3312, 2977, 2935, 1727,
–
1
685, 1508, 1456, 1409, 1368, 1289, 1172, 1132 cm ; HRMS (DART): m/z calcd for C H NO :
1
7
24
5
+
22.1655: [M+H] ; found: 322.1651.
tert-Butyl
4-(3-(4-ethyl-5-oxo-2,5-dihydro-1H-pyrrol-3-yl)propyl)-3-(3-methoxy-3-oxopropyl)-1H-
n
pyrrole-2-carboxylate (4): To a mixture of 11 (49 mg, 0.27 mmol) and Bu P (0.64 ml, 2.67 mmol) in
3
THF (3 mL), [Pd(PPh ) ] (15.5 mg, 0.013 mmol)and NaBr (55 mg, 0.52 mmol) in MeOH (3 mL) was
3
4