References
1 For a review see: Bellus D.
Ernst B.
Angew. Chem. Int. Ed. Engl.
1988,
27:
797
2a
Nemoto H.
Ishibashi H.
Nagamochi M.
Fukumoto K.
J. Org. Chem.
1992,
57:
1707
2b
Nemoto H.
Shiraki M.
Fukumoto K.
Tetrahedron
1994,
50:
10391
2c
Nemoto H.
Miyata J.
Fukumoto K.
Heterocycles
1996,
42:
165
2d
Nemoto H.
Miyata J.
Yoshida M.
Raku N.
Fukumoto K.
J. Org. Chem.
1997,
62:
7850
2e
Chevtchouk T.
Ollivier J.
Salaun J.
Tetrahedron: Asymmetry
1997,
8:
1011
2f
Cho SY.
Cha JK.
Org. Lett.
2000,
9:
1337
3a
Trost BM.
Top. Curr. Chem.
1986,
133:
3
3b
Salaun J.
Top. Curr. Chem.
1988,
144:
1
4 For a review see: Conia JM.
Salaun J.
Acc. Chem. Res.
1972,
5:
33
5a
Salaun JR.
Conia JM.
J. Chem. Soc., Chem. Commun.
1971,
1580
5b
Salaun J.
Garnier B.
Conia JM.
Tetrahedron
1974,
30:
1413
5c
Salaun J.
Champion J.
Conia JM.
Org. Synth.
1977,
57:
46
5d
Salaun J.
Champion J.
Conia JM.
Org. Synth. Coll. Vol. VI
1988,
320
6 It has not been possible to isolate the oxaspiropentane 2e, as it is transformed to the corresponding cyclobutanone 3e during the epoxidation reaction.
Some derivatives have been previously reported. For 1a-e, g see:
7a
Bernard AM.
Piras PP.
Synth. Commun.
1997,
27:
709
7b
Bernard AM.
Piras PP.
Synlett
1997,
5:
585
7c
Brandi A.
Carli S.
Goti A.
Heterocycles
1988,
27:
17
7d For 2a,b, 3a see: Bernard AM.
Floris C.
Frongia A.
Piras PP.
Synlett
1998,
668
7e For 3b see: Bernard AM.
Floris C.
Frongia A.
Piras PP.
Tetrahedron
2000,
56:
4555
8 Typical procedure for the preparation of chromenes 4a-f: A stirred solution of cyclobutanone 3 (2.7 mmol) and p-toluenesulfonic acid (0.27 mmol, 0.046 g) in benzene (10 mL) was refluxed for 6 h. The reaction mixture was diluted with CH2Cl2 and washed with 10% NaHCO3 and brine, dried (Na2SO4) and evaporated to remove the solvent. The residue was purified by chromatography on silica gel with Et2O-light petroleum (1:1) as eluent.
All new compounds have been fully characterized by 1H NMR (300 MHz), 13C NMR (75.4 MHz) and mass spectra (70 eV). Analytical data for some representative derivatives are reported. 1f: colorless oil; yield: 70%. 1H NMR (CDCl3) δ: 1.00-1.22 (m. 4 H), 1.52 (d, 3 H, J = 6.6 Hz), 1.84 (s, 3 H), 5.05 (q, 1 H, J = 6.6 Hz), 6.90-7.28 (m, 5 H). 13C NMR (CDCl3) δ: 1.14, 2.76, 15.10, 19.71, 78.56, 115.65, 118.76, 120.65, 124.74, 129.12, 158.16. 3e: yellow oil; yield: 85%. 1H NMR (CDCl3) δ: 2.48-2.58 (m, 1 H), 2.73-2.82 (m, 1 H), 2.98-3.10 (m, 1 H), 3.18-3.30 (m, 1 H), 3.97, 4.23 (AB q, 2 H, J = 9 Hz), 7.22-7.44 (m, 10 H). 13C NMR (CDCl3) δ: 21.09, 44.09, 72.06, 72.54, 114.58, 121.25, 126.58, 127.50, 128.69, 129.43, 137.83, 158.43, 210.17. IR (neat, cm-1) : 1782. MS m/z: 252 [M+ (0.4)], 209(5), 195(9), 159(100), 131(23), 117(60). 4e: yellow oil; yield 60%. 1H NMR (CDCl3) δ: 2.13-2.27 (m, 1 H), 2.19 (br s, 1 H), 2.26-2.33 (m, 2 H), 2.54-2.61 (m, 1 H), 4.05,4.14 (AB q, 2 H, J = 11.4 Hz), 6.85-7.65 (m, 9 H). 13C NMR (CDCl3) δ: 19.94, 36.76, 52.91, 71.74, 72.68, 117.29, 122.08, 127.22, 127.32, 127.58, 128.57, 128.79, 129.73, 138.37, 154.17. IR (neat, cm-1) : 3450. MS m/z: 252 [M+(6)], 234(5), 224(8), 121(100). 5e: red oil; yield 56%. 1H NMR (CDCl3) δ: 2.41 (s, 3 H), 2.81 (t, 2 H, J = 7.5 Hz), 3.99 (t, 2 H, J = 7.5 Hz), 4.78 (s, 2 H), 6.81-7.64 (m, 10 H). 13C NMR (CDCl3) δ: 21.55, 26.98, 68.19, 69.39, 116.19, 121.51, 122.60, 123.25, 124.00, 127.69, 127.78, 128.02, 128.77, 128.91, 129.69, 132.69, 134.34, 13.44, 144.54, 153.89. IR (neat, cm-1): 1160,1350.
9a
Gauthier S.
Caron B.
Cloutier J.
Dory YL.
Favre A.
Larouche D.
Mailhot J.
Ouellet C.
Schwerdtfeger A.
Leblanc G.
Martel C.
Simard J.
Merand Y.
Belanger A.
Labrie C.
Labrie F.
J. Med. Chem.
1997,
40:
2117
9b
Varma RS.
Dahiya R.
J. Org. Chem.
1998,
63:
8038
