References and Notes
<A NAME="RW20010ST-1">1</A>
Manahan-Vaughan D.
Reiser M.
Pin J.-P.
Wilsch V.
Bockaert J.
Reymann KG.
Riedel G.
Neuroscience
1996,
72:
999
<A NAME="RW20010ST-2">2</A>
Ishida M.
Saitoh T.
Nakamura Y.
Kataoka K.
Shinozaki H.
Neuropharmacology
1995,
34:
821
<A NAME="RW20010ST-3">3</A>
Chiou W.-H.
Lin G.-H.
Hsu C.-C.
Chaterpaul SJ.
Ojima I.
Org.
Lett.
2009,
11:
2659
<A NAME="RW20010ST-4">4</A>
Tellitu I.
Serna S.
Herrero MT.
Moreno I.
Domínguez E.
SanMartin R.
J. Org. Chem.
2007,
72:
1526
<A NAME="RW20010ST-5">5</A>
Billig E,
Abatjoglou AG, and
Bryant D. inventors; US 4769498.
; the
complete chemical name of BIPHEPHOS is 6,6′-[(3,3′-di-tert-butyl-5,5′-dimethoxy-1,1′-biphenyl-2,2′-diyl)bis(oxy)]bis(dibenzo[d,f][1,3,2]dioxaphosphepin).
<A NAME="RW20010ST-6">6</A>
Cuny GD.
Buchwald SL.
J. Am. Chem. Soc.
1993,
115:
2066
<A NAME="RW20010ST-7">7</A>
(E
)-8-(α-acetyloxy-4′-methoxybenzylidenyl)-5-oxoindolizidine
(2)
Rh(acac)(CO)2 (3.9 mg, 15.0 µmol,
0.5 mol%) and BIPHEPHOS (23.4 mg, 30 µmol, 1.0
mol%) were dissolved in AcOH (1 mL) under nitrogen. The
resulting catalyst solution was degassed by a freeze-thaw
procedure at least three times. Amide 1
4 (730
mg, 3.0 mmol, 1.00 equiv) and PTSA (57 mg, 0.3 mmol, 10 mol%)
were placed in a 100 mL flask. The catalyst solution was transferred
to the reaction flask containing the substrate by a pipette, and
the total volume was adjusted to 60 mL with AcOH. The reaction flask
was placed in a 300 mL stainless steel autoclave and then was pressurized
with CO (2 atm) followed by H2 (2 atm). The reaction
mixture was stirred at 60 ˚C for 16-20
h. Upon completion of the reaction, the gas was carefully released
in a good ventilated hood, and the reaction mixture was concentrated
under reduced pressure to give a crude residue. The residue was
partitioned with CH2Cl2 (20 mL) and aq NaHCO3 (10
mL). After separation of the organic layer, the aqueous layer was
extracted with CH2Cl2 (3 × 10 mL).
The combined organic layers were washed with brine (10 mL), dried
over anhyd Na2SO4, and then concentrated under
reduced pressure to give the crude product. The crude product was
purified by flash chromatography on silica gel using MeOH-CH2Cl2 as
the eluant to give the product in 83% yield
as a light yellow oil. R
f
= 0.45 (MeOH-CH2Cl2 = 1:9). ¹H
NMR (600 MHz, 25 ˚C, CDCl3): δ = 1.35 (dq, J = 5.4, 10.8
Hz, 1 H, H-1), 1.57-1.63 (m, 1 H, H-2), 1.63-1.69
(m, 1 H, H-1), 1.76-1.84 (m, 1 H, H-2), 2.13 (s, 3 H, OCCH3),
2.24 (ddd, J = 3.6,
15.0, 15.0 Hz, 1 H, H-7), 2.36 (ddd, J = 4.2,
15.6, 15.6 Hz, 1 H, H-6), 2.52 (ddd, J = 3.6,
3.6, 15.6 Hz, 1 H, H-6), 2.65 (ddd, J = 3.0,
4.2, 14.4 Hz, 1 H, H-7), 3.30 (dd, J = 3.6,
11.4 Hz, 1 H, H-3), 3.64 (ddd, J = 8.4,
8.4, 12.0 Hz, 1 H, H-3), 3.82 (s, 3 H, OCH3), 4.18 (dd, J = 5.4, 10.8
Hz, 1 H, H-8a), 6.88 (d, J = 8.4
Hz, 2 H, H-3′), 7.28 (d, J = 8.4
Hz, 2 H, H-2′). ¹³C NMR (150 MHz,
25 ˚C, CDCl3): δ = 20.7
(q, CH3CO), 22.1 (t, C-2), 22.6 (t, C-7), 32.2 (t, C-6),
32.4 (t, C-1), 43.6 (t, C-3), 55.1 (q, CH3O), 58.0 (d,
C-8a), 113.7 (d, C-3′), 124.8 (s, C-8), 127.3 (s, C-1′),
130.4 (d, C-2′), 142.2 (s, C-9), 159.8 (s, C-4′),
168.7 (s, CH3CO), 170.0 (s, C-5), HRMS-FAB: m/z
[M + H]+ calcd
for C18H22NO4
+:
316.1549; found: 316.1541 (Δ = 2.5
ppm).
<A NAME="RW20010ST-8">8</A>
The results of DFT calculations for
ketone trans-3 and cis-3 at the
level of B3LYP/6-31G* showed trans-3 is more stable than cis-3 by 2.1 kcal/mol.
<A NAME="RW20010ST-9">9</A>
ten Brink G.-J.
Arends IWCE.
Sheldon RA.
Chem. Rev.
2004,
104:
4105
<A NAME="RW20010ST-10">10</A>
Kobayashi S.
Tanaka H.
Amii H.
Uneyama K.
Tetrahedron
2003,
59:
1547
