3594
J.-B. Daskiewicz et al. / Tetrahedron 58 (2002) 3589±3595
N,N-diisopropylethylamine (11.7 mmol, 3 equiv.) dropwise
at 08C. After 15min, 0.6 ml of benzoyl chloride (5.2 mmol,
1.3 equiv.) were added dropwise, still at 08C. Reaction was
allowed to take place at room temperature for 1 h. Dilution
of the medium with water resulted in the formation of a
bulky precipitate which was isolated by ®ltration and
washed with cold ethanol. Yield: 1.4 g (3.9 mmol, 100%).
White solid, mp 191.5±1928C. UV/Vis (MeOH): lmax
(0.48 mmol) of compound 3d plus 50 mg (0.048 mmol) of
Eu(fod)3 were suspended in 10 ml of cycloheptane and the
mixture heated at 1008C for 4 h. Puri®cation of the medium
by MPLC on diol-bonded silica using a gradient of CHCl3 in
hexane as solvent led to the isolation of 31 mg (0.07 mmol,
15%) of 8-(3,3-dimethylallyl)-7-benzoyl chrysin 4d, and of
145mg (0.34 mmol, 71%) of 6-(1,1-dimethylallyl)-7-
benzoyl chrysin 5d.
1
(nm)300sh, 269, 228. H NMR (CDCl3, 300 MHz): d
12.78 (s, 5-OH), 8.22 (m, H-2000/6000), 7.91 (m, H-20/60),
3.5.5. 7-Benzoyl-8-(3,3-dimethylallyl) chrysin 4d. Pale
yellow crystals, mp 184.8±1858C. UV/Vis (MeOH): lmax
000
7.69 (brt, J7.5Hz, H-4 ), 7.56 (m, H-30/40/50 and H-3000/
1
5000), 7.01 (d, J1.9 Hz, H-8), 6.77 (s, H-3), 6.72 (d,
J1.9 Hz, H-6). 13C NMR (CDCl3, 75.5 MHz): d 182.89
(C-4), 164.71 (C-2), 164.18 (C-7000), 161.97 (C-5), 156.80
(nm)335, 272. H NMR (CDCl3, 300 MHz): d 12.67 (s,
5-OH), 8.22 (m, H-2000/6000), 7.90 (m, H-20/60), 7.68 (brt,
J7.5Hz, H-4 000), 7.54 (m, H-30/40/50 and H-3000/5000), 6.77
(s, H-3), 6.69 (s, H-6), 5.20 (brt, J6.0 Hz, H-200), 3.54 (d,
0
(C-9), 156.29 (C-7), 134.07 (C-4000), 132.15(C-4 ), 130.96
13
J6.0 Hz, H-100), 1.61 (brs, H-400), 1.59 (brs, H-500).
C
(C-10), 130.32 (C-2000/6000), 129.17 (C-30/50), 128.80 (C-1000),
128.72 (C-3000/5000), 126.40 (C-20/60), 108.98 (C-10), 106.14
(C-3), 105.68 (C-6), 101.19 (C-8). MS (CI) m/z: 35 9
(M1H1). HRMS (CI): m/z calcd for C22H15O5, 359.0919,
found 359.0911. Anal. calcd for C22H14O5: C, 73.74; H,
3.94. Found C, 73.66; H, 3.95.
NMR (CDCl3, 75.5 MHz): d 183.33 (C-4), 164.53 (C-7000),
164.27 (C-2), 159.51 (C-5), 154.81 (C-9), 154.61 (C-7),
133.97 (C-4000), 132.68 (C-300), 132.06 (C-40), 131.36
(C-1000)0, 130.33 (C-2000/6000), 129.18 (C-30/50), 128.80
(C-1 ), 128.68 (C-3000/5000), 126.42 (C-20/60), 121.40
(C-200), 113.26 (C-8), 109.43 (C-10), 106.49 (C-6), 106.10
(C-3), 25.58 (C-400), 22.94 (C-100), 17.98 (C-500). MS (CI)
m/z: 426 (M1). HRMS (CI): m/z calcd for C27H22O5,
426.1467, found 426.1464. Anal. calcd for C27H22O510.1
hexane: C, 76.19; H, 5.42. Found C, 76.33; H, 5.66.
3.5.2. 7-Benzoyl-5-O-prenyl chrysin 3d. 1 g (2.8 mmol) of
7-benzoyl-chrysin 2d was dissolved in a mixture of 45ml of
CH2Cl2 and 30 ml of toluene. The solution was cooled to
08C (ice bath) and 4.5g (5.6 mmol, 2 equiv.) of tetra-
butylammonium hydroxide 30 hydrate, followed by 0.7 ml
(6 mmol, 2 equiv.) of prenyl bromide were added under
stirring. After addition of all the reagents, the reaction was
allowed to take place at room temperature for 2 h under
stirring. The organic layer was washed with water and
evaporated. The residue was taken in a minimum amount
of acetone and diluted with hexane until the solution turned
slightly cloudy. Overnight crystallization at 48C led to the
isolation of 0.88 g (2.1 mmol, 75%) of 3d. Cream crystals,
mp 133±1408C. UV/Vis (MeOH): lmax (nm)319, 295sh,
3.5.6. 7-Benzoyl-6-(1,1-dimethylallyl) chrysin 5d. Pale
yellow crystals, mp 138±1398C. UV/Vis (MeOH): lmax
1
(nm)340, 307sh, 274, 231. H NMR (CDCl3, 300 MHz):
d 13.85(s, 5-OH), 8.15(m, H-2 000/6000), 7.88 (m, H-20/60),
000
7.66 (brt, J7.5Hz, H-4 ), 7.53 (m, H-30/40/50 and H-3000/
5000), 6.75(H-8), 6.74 (H-3), 6.23 (dd, J17.3 and 10.6 Hz,
H-200), 4.81 (dd, J17.3 and 1.1 Hz, H-300), 4.59 (dd,
J10.6 and 1.1 Hz, H-300), 1.62 (s, H-400/500). 13C NMR
(CDCl3, 75.5 MHz): d 183.50 (C-4), 164.90 (C-7000),
164.24 (C-2), 161.96 (C-5), 154.89 (C-9), 154.56 (C-7),
148.51 (C-200), 133.75(C-4 000), 132.07 (C-40), 130.96
(C-10), 130.39 (C-2000/6000), 129.34 (C-1000), 129.13 (C-30/
50), 128.60 (C-3000/5000), 126.35(C-2 0/60, 123.28 (C-6),
108.97 (C-10), 108.02 (C-300), 105.85 (C-3), 102.69 (C-8),
41.30 (C-100), 27.76 (C-400/500). MS (CI) m/z: 426 (M1).
HRMS (CI): m/z calcd for C27H22O5, 426.1467, found
426.1467. Anal. calcd for C27H22O5: C, 76.04; H, 5.20.
Found C, 76.08; H, 5.57.
1
264. H NMR (CDCl3, 300 MHz): d 8.23 (m, H-2000/6000),
000
7.88 (m, H-20/60), 7.69 (brt, J7.5Hz, H-4 ), 7.54 (m,
H-30/40/50 and H-3000/5000), 7.11 (d, J2.3 Hz, H-8), 6.73 (d,
J2.3 Hz, H-6), 6.72 (s, H-3), 5.61 (brt, J6.4 Hz, H-200),
4.73 (d, J6.4 Hz, H-100), 1.80 (brs, H-400), 1.76 (brs, H-500).
13C NMR (CDCl3, 75.5 MHz): d 177.37 (C-4), 164.26
(C-7000), 161.04 (C-2), 160.10 (C-5), 158.69 (C-9), 154.73
(C-7), 138.12 (C-300), 134.07 (C-4000), 131.32 (C-10 and
C-40), 130.28 (C-2000/6000), 128.94 (C-30/50), 128.85(C-1 000),
128.73 (C-3000/5000), 126.02 (C-20/60), 118.98 (C-200),
113.00 (C-10), 109.18 (C-3), 103.24 (C-8), 102.69 (C-6),
66.86 (C-100), 25.80 (C-400), 18.41 (C-500). MS (CI) m/z:
427 (M1H1), 359 (M1H±C5H81). HRMS (CI): m/z
calcd for C27H23O5, 427.1545, found 427.1548. Anal.
calcd for C27H22O5: C, 76.04; H, 5.20. Found C, 75.84; H,
5.28.
3.6. Unprotected ®nal products
3.6.1. 6-(1,1-Dimethylallyl) chrysin 7. 102 mg
(0.24 mmol) of compound 3d plus 25mg (0.024 mmol) of
Eu(fod)3 were suspended in 10 ml of cycloheptane and the
mixture heated at 1008C for 4 h. The solution was evapo-
rated to dryness, the residue redissolved in methanolic KOH
(5%) and submitted to sonication for 5 min. After dilution of
the medium with water, acidi®cation (1N HCl) and extrac-
tion with ethyl acetate, 45mg (0.14 mmol, 58%) of 7 were
isolated by VLC on diol-bonded silica using a gradient of
CHCl3 in hexane as solvent. Yellow crystals, mp 193.6±
3.5.3. Rearrangement of 3d in N,N-diethylbutylamine.
200 mg of 3d (0.47 mmol) were re¯uxed in 5ml of
N,N-diethylbutylamine (oil bath at 1608C) for 3 days. The
medium was diluted with water, acidi®ed (1N HCl) and
extracted with ethyl acetate. Puri®cation of the extract
by VLC on diol-bonded silica, using 5% CHCl3 in hexane
as solvent, afforded 74 mg of compound 8 (0.23 mmol,
49%).
1
2088C. UV/Vis (MeOH): lmax (nm)320, 274, 250sh. H
NMR (acetone-d6, 300 MHz): d 13.97 (s, 5-OH), 8.04 (m,
H-20/60), 7.59 (m, H-30/40/50), 6.77 (s, H-3), 6.58 (s, H-8),
6.37 (dd, J17.7 and 10.6 Hz, H-200), 4.96 (dd, J17.7 and
1.1 Hz, H-300), 4.87 (dd, J10.6 and 1.1 Hz, H-300), 1.63 (s,
3.5.4. Eu(fod)3 catalyzed rearrangement of 3d. 204 mg