R. W. Clawson, B. C. G. So¨derberg / Tetrahedron Letters 48 (2007) 6019–6021
6021
rator at water aspirator pressure. The resulting tan residue
was recrystallized from pentane affording a pale yellow
solid (1) (520 mg, 2.41 mmol, 99%). Analytical data: mp
54–55 ꢁC; 1H NMR (270 MHz, CDCl3) d 7.95 (d, J =
8.7 Hz, 1H), 7.29 (d, J = 2.5 Hz, 1H), 7.19 (dd, J = 2.5,
8.9 Hz, 1H), 3.98 (s, 3H); 13C NMR (67.5 MHz, CDCl3) d
164.3 (+), 163.8 (+), 149.4 (+), 133.3 (À), 120.8 (+), 117.1
(À), 110.3 (À), 54.5 (À); IR (neat) 1752, 1605, 1537,
phenylphosphino)propane (14.0 mg, 0.0340 mmol), and
1,10-phenanthroline monohydrate (13.0 mg, 0.0680 mmol)
were dissolved in anhydrous DMF (2 mL) in a threaded
ACE glass pressure tube. The tube was fitted with a
pressure head, and the solution was saturated with carbon
monoxide (four cycles of 6 atm of CO). The reaction vessel
was heated at 120 ꢁC under CO (6 atm) for 20 h. Water
(10 mL) was added and the brown solution was extracted
with ethyl acetate (3 · 40 mL). The combined organic
phases were dried (MgSO4), filtered, and the solvent was
removed on a rotary evaporator at water aspirator
pressure. The resulting crude product was purified by
chromatography (pentane–acetone, 8:2 then pentane–ace-
tone, 1:1) to afford 3 (91.0 mg, 0.423 mmol, 75%) as a light
tan solid. Analytical data: mp 279–280 ꢁC; 1H NMR
(270 MHz, DMSO-d6) d 11.88 (s, 1H), 8.22 (d, J = 5.7 Hz,
1H), 7.77 (d, J = 8.7 Hz, 1H), 6.91 (d, J = 2.2 Hz, 1H),
6.86 (dd, J = 2.0, 8.9 Hz, 1H), 6.39 (d, J = 5.7 Hz, 1H),
3.83 (s, 3H); 13C NMR (67.5 MHz, DMSO-d6) d 169.0
(+), 159.9 (+), 153.4 (À), 144.4 (+), 137.5 (+), 123.9 (+),
120.0 (À), 114.0 (À), 112.1 (À), 109.1 (+), 94.4 (À), 55.4
1243 cmÀ1
.
11. Compound 1 has been reported in the literature but we
were unable to find any analytical data.
12. Koreeda, M.; Akagi, H. Tetrahedron Lett. 1980, 21, 1197–
1200.
13. Morgan, T.; Ganem, B. Tetrahedron Lett. 1980, 21, 2973–
2974.
14. Experimental procedure: Potassium 1,1-dimethylethoxide
(599 mg, 5.34 mmol) was added to dry THF (12 mL)
under a positive flow of nitrogen gas. The flask was cooled
to À78 ꢁC and trans-methoxy-3-buten-2-one (540 lL,
5.34 mmol) was added drop-wise (10 min). After stirring
for 30 min, a solution of freshly prepared acid chloride (1)
(520 mg, 2.41 mmol) in dry THF (8 mL) was added drop-
wise via a cannula over 15 min. The resulting yellow
solution was stirred at À78 ꢁC (1 h) then gradually
warmed to ambient temperature (3 h). Water (5 mL) was
carefully added and the cloudy solution was stirred
overnight before diluting with additional water (15 mL).
The resulting solution was extracted with diethyl ether
(3 · 100 mL), the combined organic phases were dried
(MgSO4), filtered, and the solvents were removed on a
rotary evaporator at water aspirator pressure. The crude
product was purified by chromatography (hexanes–
EtOAc, 1:1 followed by pentane–acetone, 1:1) to afford
the product (2) (460 mg, 1.86 mmol, 77%) as a pale yellow
solid. Analytical data: mp 170–171 ꢁC; 1H NMR
(270 MHz, CDCl3) d 7.72 (d, J = 5.9 Hz, 1H), 7.55 (d,
J = 2.6 Hz, 1H), 7.50 (d, J = 8.5 Hz, 1H), 7.22 (dd,
J = 2.6, 8.5 Hz, 1H), 6.51 (d, J = 2.4 Hz, 1H), 6.39 (dd,
J = 2.4, 5.7 Hz, 1H), 3.95 (s, 3H); 13C NMR (67.5 MHz,
CDCl3) d 178.6 (+), 162.6 (+), 161.8 (+), 155.1 (À), 148.7
(+), 132.2 (À), 119.1 (+), 118.9 (À), 117.1 (À), 115.9 (À),
(À); IR (neat) 3143, 1618 cmÀ1
; HRMS Calcd for
C12H10NO3 (M+H+) 216.0661; found, 216.0660. Anal.
Calcd for C12H9NO3: C, 66.97; H, 4.22; N, 6.51. Found:
C, 66.69; H, 4.51; N, 6.85.
16. Experimental procedure: Sodium hydride (11.0 mg,
0.437 mmol) was washed with hexanes (5 · 1 mL) before
adding dry DMF (0.5 mL) under a positive flow of N2. A
solution of 7-methoxypyrano[3,2-b]indol-4(5H)-one (3)
(47.0 mg, 0.218 mmol) in DMF (1 mL) was added slowly
over 5 min. The resulting orange solution was heated at
60 ꢁC for 30 min followed by slow addition of iodome-
thane (300 lL, 0.437 mmol). The brown solution was
stirred for 1 h at 60 ꢁC before cooling to ambient
temperature. DMF was removed via bulb-to-bulb distil-
lation and the crude brown solid was dissolved in diethyl
ether (10 mL). The ether solution was washed with brine
(3 · 10 mL) and water (3 · 10 mL), the dried (MgSO4),
filtered and the solvent was removed on a rotary evapo-
rator at water aspirator pressure. The resulting solid was
purified by chromatography (hexanes–ethyl acetate, 6:4)
to afford koniamborine (46.0 mg, 0.201 mmol, 92%) as a
white solid. Analytical data: mp 141–142 ꢁC (lit. mp
142 ꢁC), 13C NMR (67.5 MHz, CDCl3, lit. values in
parenthesis) 171.0 (170.7), 160.6 (160.3), 151.4 (151.3),
145.1 (144.8), 139.0 (138.8), 123.4 (123.1), 120.5 (120.1),
115.3 (115.0), 111.9 (111.6), 109.0 (108.6), 91.7 (91.3), 55.6
(55.3), 31.2 (30.9).
110.6 (À), 56.2 (À); IR (neat) 3052, 1654, 1519, 927 cmÀ1
;
HRMS Calcd for C12H10NO5 (M+H+) 248.0559; found,
248.0559. Anal Calcd for C12H9NO5: C, 58.30; H, 3.67; N,
5.67. Found: C, 58.15; H, 3.38; N, 5.31.
15. Experimental procedure: 2-(4-Methoxy-2-nitrophenyl)-4H-
pyran-4-one (2) (140 mg, 0.566 mmol), bis(dibenzyliden-
acetone)palladium (20.0 mg, 0.0340 mmol), 1,3-bis-(di-