References
-
For related phenyl-carbonyl coupling
reactions, see:
-
1a
Shiue J.-S.
Lin M.-H.
Fang J.-M.
J.
Org. Chem.
1997,
62:
4643
-
1b
Kuo Ch.-W.
Fang J.-M.
Synth. Commun.
2001,
31:
877
-
1c
Schmalz H.-G.
Kiehl O.
Gotov B.
Synlett
2002,
1253
-
1d
ref.(14).
-
Selected reviews on samarium diiodide
promoted chemistry:
-
2a
Kagan HB.
Namy JL.
Tetrahedron
1986,
42:
6573
-
2b
Molander GA.
Harris CR.
Chem.
Rev.
1996,
96:
307
-
2c
Molander GA.
Harris CR.
Tetrahedron
1998,
54:
3321
-
2d
Krief A.
Laval A.-M.
Chem. Rev.
1999,
99:
745
-
2e
Steel PG.
J. Chem. Soc., Perkin Trans. 1
2001,
2727
-
2f
Hölemann A.
Synlett
2001,
1497
- 3
Berndt M.
Reissig H.-U.
Synlett
2001,
1290
-
4a
Dinesh CU.
Reissig H.-U.
Angew.
Chem. Int. Ed.
1999,
38:
789 ; Angew. Chem. 1999, 111, 874
-
4b
Nandanan E.
Dinesh CU.
Reissig H.-U.
Tetrahedron
2000,
56:
4267
- 5
Gaunt MJ.
Spencer JB.
Org. Lett.
2001,
3:
25
-
7a
Inanaga J.
Ishikawa M.
Yamaguchi M.
Chem. Lett.
1987,
1485
-
7b
Shabangi M.
Flowers RA.
Tetrahedron Lett.
1997,
38:
1137
-
7c
Miller RS.
Sealy JM.
Shabangi M.
Kuhlman ML.
Fuchs JR.
Flowers RA.
J.
Am. Chem. Soc.
2000,
122:
7718
-
7d
Knettle BW.
Flowers RA.
Org.
Lett.
2001,
3:
2321
-
7e
Prasad E.
Flowers RA.
J. Am.
Chem. Soc.
2002,
124:
6895
-
10a
List B.
J. Am. Chem. Soc.
2000,
122:
9336
-
10b
Notz W.
Sakthivel K.
Bui T.
Zhong G.
Barbas CF.
Tetrahedron Lett.
2001,
42:
199
-
10c
List B.
Pojarliev P.
Biller WT.
Martin HJ.
J. Am. Chem. Soc.
2002,
124:
827 ; Basically, this Mannich reaction leads to
optically active compounds with considerable enantioselectivity,
but since our interest was focused on the chemo- and diastereoselectivity
of the cyclization reaction the enantiomeric excess of these starting
materials and the resulting products was so far not determined.
- 14 For a recent report on related samarium
diiodide induced spirocyclizations to electron-deficient aromatic
compounds, see: Ohno H.
Maeda S.
Okumura M.
Wakayama R.
Tanaka T.
Chem. Commun.
2002,
316
6
Typical procedure,
cyclization of 16 to 17:
Samarium (0.329 g, 2.19 mmoL) and 1,2-diiodoethane (0.571 g, 2.02 mmol)
were suspended in freshly distilled THF (30 mL) under an argon atmosphere
and stirred for 2 h at room temperature. To the resulting dark blue
solution HMPA (1.45 g, 8.1 mmol) was added. Ketone 16 (200
mg, 0.81 mmol) and tert-butanol (0.15
mL, 1.62 mmol), dissolved in THF (20 mL), were then added in one
portion to the deep violet solution. After 16 h the reaction was
quenched with saturated aqueous solution of sodium bicarbonate,
the organic layer was separated and the aqueous layer was extracted
with diethyl ether (3 ¥ 25 mL). The combined ether extracts
were washed with brine (25 mL), dried over anhydrous magnesium sulfate,
filtered and evaporated. The resulting crude product was purified
by flash chromatography on silica gel using hexane-ethyl
acetate (5:1 to 1:3) to give 17 (0.128
g, 63%) as a colourless solid. Data for (2R*,4S*,4aS*)-1-acetyl-2-(iso-propyl)-4-hydroxy-4-methyl-1,2,3,4,4a,7-hexahydroquinoline
(17): colourless crystals; mp 164 °C; 1H
NMR (C6D6, 270 MHz): δ = 0.82,
0.91 (2d, J = 6.6
Hz, 3 H each, CH3), 1.18 (s, 3 H, 4-CH3),
1.74 (mc, 2 H, 3-H, 2-CH), 2.05 (s, 3 H, COCH3), 2.05
(mc, 1 H, 3-H), 2.25 (s, 1 H, br, OH), 2.67 (mc,
1 H, 4a-H), 2.28 (mc, 2 H, 7-H), 4.33 (dd, J = 6.6,
11.8 Hz, 1 H, 2-H), 5.58 (s, 1 H, br, 8-H), 5.81 (mc,
2 H, 5-H, 6-H); 13C NMR (CDCl3,
68 MHz): δ = 19.8,
20.3 (2q, CH3), 21.8 (q, COCH3),
24.4 (q, 4-CH3), 27.1 (t, C-7), 28.7 (d, 2-CH), 40.4 (t,
C-3), 48.9 (d, C-4a), 55.7 (d, C-2), 73.0 (s, C-4), 123.3 (d, C-8),
123.9 (d, C-6), 124.4 (d, C-5), 134.6 (s, C-8a), 169.2 (s, CO);
IR (KBr): ν = 3390 (OH), 3030
(=CH), 2975-2820 (CH), 1610 (CO) cm-1;
Calcd. for C15H23NO2 (249.4): C 72.23,
H 9.30, N 5.62; Found: C 72.49, H 9.10, N 5.50.
8 Since samarium(II/III) species
are Lewis acids one might assume a simple electrophilic substitution
reaction for the formation of 2 and 4. This possibility was excluded by performing
a test reaction with preformed samarium(III) iodide under the same
reaction conditions but no cyclization product was observed (in
the presence of HMPA as strong donor ligand the Lewis acidity of
the samarium salts is effectively reduced).
9 The relative configuration was determined
by NOESY-NMR spectroscopy. For 17 a crystal
structure was obtained to prove the relative configuration.
11 Brüdgam, I.; Hartl, H. Institut
für Chemie, FU Berlin, 2002 unpublished results.
12 When phenol was applied in related
SmI2-induced cyclizations yields were at least equivalent
to those with tert-butanol as proton
source, however, so far no rule is recognizable for which substrates
phenol improves the outcome. Other proton sources were also examined (including
2,6-di-tert-butylphenol or 2,2,2-trifluoroethanol) but
no effect similar to that of phenol was discovered.
13 The related ortho-
and meta-substituted aromatic compounds
generally cyclize with considerably lower efficiency. For cyano-substituted
derivatives the yields are particularly low.