Verga et al.
JOCArticle
4,7-Dibromo-3-hydroxynaphthalene-2-carboxamide (6d). Com-
pound 6c (100 mg, 0.279 mmol) was dissolved in NH3 32%/
CH3CN (8:2, 10 mL). This solution was stirred at rt. After 24 h
the reaction mixture was cooled at 0 °C, and HCl 10% was
added until pH 1-2 was reached. A solid precipitated. The solid
was filtered and dried under vacuum. Pale yellow crystals were
obtained (91 mg, yield 95%). Mp > 235 °C dec. 1H NMR
(DMSO): δ 7.82 (dd, J =9.1, 2.0 Hz, 1H), 7.98 (d, J =9.1 Hz,
1H), 8.05 (d, J =2.0 Hz, 1H), 8.44 (bs, 1H), 8.59 (s, 1H), 9.21
(bs, IH), 13.88 (s, 1H). 13C NMR (DMSO): δ 105.8, 117.1, 117.4,
127.1, 127.8, 128.4, 130.9, 132.9, 133.1, 154.7, 171.5. Anal. Calcd
for C11H7Br2NO2: C, 38.30; H, 2.05; Br, 46.32; N, 4.06; O, 9.28.
Found: C, 38.37; H, 1.98; Br, 46.30; N, 4.15.
(cyclohexane/ethyl acetate = 98:2) following solvent removal
by vacuum concentration gave 20 mg of 8a (20%, yield) and 9
mg of 5a (11%, yield). The other preparative irradiations were
performed under similar conditions (Supporting Information)
(Z)-6-Bromo-1-(3-(trimethylsilyl)prop-1-enyl)naphthalen-2-ol
1
(8a). Colorless oil. H NMR (CDCl3): δ -0.09 (s, 9H), 1.51
(d, J=8.4 Hz, 2H), 5.61 (s, 1H), 6.31 (dt, J=11.0, 8.4 Hz, 1H),
6.41 (d, J=11.0 Hz, 1H), 7.24 (d, J=8.9 Hz,1H), 7.51 (dd, J =
9.0, 1.8 Hz, 1H), 7.63-7.67 (m, 2H), 7.93 (s, J =1.8 Hz, 1H). 13
C
NMR (CDCl3): δ -1.9, 20.8, 115.8, 116.8, 118.0, 118.5, 126.0,
127.9, 129.3, 129.8, 129.9, 131.3, 136.2, 149.6. Anal. Calcd for
C16H19BrOSi: C, 57.31; H, 5.71; Br, 23.83; O, 4.77; Si, 8.38.
Found: C, 57.40; H, 5.75; Br, 23.62; Si, 8.49.
4,7-Dibromo-3-hydroxy-N,N-dimethylnaphthalene-2-carboxa-
mide (6e). Compound 6c (500 mg, 1.40 mmol) was dissolved in
NHMe2 40%, water solution (20 mL) and stirred at rt for 24 h.
The reactionmixturewas cooled at 0 °C, and HCl 10% was added
until pH 1-2 was reached. After a few minutes a solid precipi-
tated. The solid was filtered and dried under vacuum. The
reaction mixture was purified by chromatography on silica gel
60 HR, eluting with cyclohexane/ethyl acetate=7:3. The product
was obtained as white crystals (233 mg, yield 45%). Mp 193.5-
194.9 °C. 1H NMR (CDCl3): δ 3.22 (s, 6H), 7.68 (dd, J=9.1, 1.9
Hz, 1H), 7.72 (s, 1H), 7.94 (d, J=1.9 Hz, 1H), 8.03 (d, J=9.1 Hz,
1H), 9.17 (bs, 1H). 13C NMR (CDCl3): δ 37.6, 107.7, 118.4, 121.8,
127.2, 127.6, 128.5, 130.3, 132.2, 132.3, 150.9, 169.6. Anal. Calcd
for C13H11Br2NO2: C, 41.86; H, 2.97; Br, 42.84; N, 3.75; O, 8.58.
Found: C, 41.76; H, 3.05; Br, 42.82; N, 3.78.
tert-Butyl(1,6-dibromonaphthalen-2-yloxy)dimethylsilane (7a).
To a solution of 6a (100 mg, 0.331 mmol) and imidazole
(42 mg, 0.622 mmol) in CH2Cl2 (10 mL) was added TBDMSCl
(90 mg, 0.596 mmol). After the mixture stirred overnight at rt,
H2O (5 mL) was added. The phases were separated, and the
aqueous phase was extracted twice with CH2Cl2 (2 Â 5 mL). The
combined organic layers were dried over Na2SO4 and evapo-
rated to dryness under reduced pressure. The residue was
purified by column chromatography (cyclohexane/CH2Cl2=
98:2), yielding 7a as a colorless oil (138 mg, yield 98%). 1H NMR
(CDCl3): δ 0.34 (s, 6H), 1.12 (s, 9H), 7.15 (d, J =8.9 Hz, 1H),
7.60-7.63 (m, 2H), 7.94 (d, J=1.8 Hz, 1H), 8.10 (d, J=9.1 Hz,
1H). 13C NMR (CDCl3): δ -4.0, 18.4, 25.7, 112.1, 118.2, 121.9,
127.4, 128.3, 129.7, 130.5, 130.8, 132.0, 150.9. Anal. Calcd for
C16H20Br2OSi: C, 46.17; H, 4.84; Br, 38.39; O, 3.84; Si, 6.75.
Found: C, 46.24; H, 4.73; Br, 38.46; Si, 6.74.
(Z)-7-Bromo-3-hydroxy-N,N-dimethyl-4-(3-(trimethylsilyl)prop-
1-enyl)naphthalene-2-carboxamide (8e). Colorless oil. 1H NMR
(CDCl3): δ 0.10 (s, 9H), 1.46 (dd, J =8.5, 1.2 Hz 1H), 3.16 (s,
6H), 6.23 (dt, J =11.1, 8.5 Hz, 1H), 6.41 (dd, J =11.1, 1.2 Hz,
1H), 7.54 (dd, J = 9.0, 1.9 Hz, 1H), 7.66 (s, 1H), 7.72 (d, J = 9.0
Hz, 1H), 7.93 (d, J =1.9 Hz, 1H). 13C NMR (CDCl3): δ -1.8,
20.9, 30.8, 117.4, 118.6, 123.4, 126.4, 128.4, 130.3, 130.4, 130.8,
131.8, 135.0, 148.6, 169.9. Anal. Calcd for C19H24BrNO2Si C,
56.15; H, 5.95; Br, 19.66; N, 3.45; O, 7.87; Si, 6.91. Found: C,
56.13; H, 5.98; Br, 19.74; N, 3.38; Si, 7.04.
6-Bromonaphthalene-1,2-dione (9). Compound 9 was synthe-
sized according to a published procedure.15 Mp 166.5-167.8 °C.
1H NMR (DMSO): δ 6.46 (d, J=10.2 Hz, 1H), 7.62 (d, J=10.2
Hz, 1H), 7.76 (d, J=8.1 Hz, 1H), 7.84 (d, J = 8.2 Hz 1H), 7.89
(s, 1H). 13C NMR (DMSO): δ 129.1, 129.3, 130.3, 130.9, 132.3,
133.0, 136.5, 142.7, 177.5, 179.8. Anal. Calcd for C10H5BrO2:
C, 50,67; H, 2,13; Br, 33,71; O, 13,50. Found: C, 50.60; H, 2.15;
Br, 33.78.
6-Bromonaphthalene-1,2-diol (10).16 To a solution of 9 (100
mg, 0.422 mmol) in acetonitrile (10 mL) was added a water
solution of Na2S2O4. The color of the solution instantaneously
changed from orange to pale yellow. After 10 min, oxygen was
bubbled into the resulting solution in order to removed the
unreacted Na2S2O4 in excess. The solvent was evaporated under
reduced pressure. A pale yellow solid was obtained that was
dried under vacuum (99 mg, yield 98%). Mp>198 °C dec. 1H
NMR (DMSO): δ 7.18 (d, J=8.7 Hz, 1H), 7.27 (d, J=8.7 Hz,
1H), 7.44 (dd, J=9.0, 2.0 Hz, 1H), 7.93 (d, J=9.0 Hz 1H), 7.98
(d, J =2.0 Hz 1H), 9.50 (bs, 2H). 13C NMR (DMSO): δ 115.7,
118.1, 119.7, 123.3, 127.3, 129.0, 129.4, 129.5, 137.8, 140.7.
Anal. Calcd for C10H7BrO2: C, 50,24; H, 2,95; Br, 33,42; O,
13,38. Found: C, 50.37; H, 2.90; Br, 33.39.
Methyl 4,7-Dibromo-3-methoxynaphthalene-2-carboxylate (7c).
Compound 6c (100 mg, 0.279 mmol) was dissolved in anhydrous
THF (10 mL) containing K2CO3 (46 mg, 0.335 mmol) and 2.5% 18-
crown-6 (2 mg, 0.838 Â 10-2 mmol). The suspension was stirred for
10 min, and CH3I (48 mg, 0.335 mmol, 0.021 mL) was added. The
mixture was stirred at rt for 4 h, and a second portion of CH3I
(48 mg, 0.335 mmol, 0.021 mL) was added. After 5 h, the solvent
was evaporated, and water was added to the residue. The K2CO3
and 18-crown-6 were dissolved, and the product remained in
suspension. The white solid was filtered and dried under vacuum
(Z)-Methyl-7-bromo-3-hydroxy-4-(3-(trimethylsilyl)allyl)naphtha-
lene-2-carboxylate (11c). The compound was purified by column
chromatography and eluted with cyclohexane. White crystals.
Mp 104.2-105.9 °C. 1H NMR (CDCl3): δ 0.31 (s, 9H), 3.96 (dd,
J = 6.4, 2.4 Hz 2H), 4.05 (s, 3H), 5.64 (dd, J=14.0, 2.4 Hz, 1H),
6.25 (dt, J=14.0, 6.4 Hz, 1H), 7.61 (dd, J=9.2, 2.0 Hz, 1H), 7.81
(d, J =9.2 Hz, 1H), 7.98 (d, J =2.0 Hz, 1H), 8.34 (s, 1H). 13
C
NMR (CDCl3): δ 0.0, 28.5, 52.6, 114.5, 117.0, 120.9, 125.0,
128.0, 129.8, 130.1, 131.6, 132.0, 134.7, 146.0, 153.8, 170.2. m/z:
379 (100.0%), 394 (55.1%), 347 (48.6%), 281 (21.7%), 361
(10.9%), 334 (10.9%). Anal. Calcd for C18H21BrO3Si: C,
54.96; H, 5.38; Br, 20.31; O, 12.20; Si, 7.14. Found: C, 54.90;
5.46; Br, 20.25; Si, 7.34.
(Z)-7-Bromo-3-hydroxy-N,N-dimethyl-4-(3-(trimethylsilyl)allyl)
naphthalene-2-carboxamide (11e). Colorless oil. 1HNMR(CDCl3):
δ 0.30 (s, 9H), 3.24 (s, 6H), 3.96 (dd, J =6.4, 1.8 Hz, 2H), 5.63
(d, J =14.0, 1.8 Hz, 1H), 6.27 (dt, J =14.0, 6.4 Hz, 1H), 7.59
(dd, J=9.1, 2.0 Hz, 1H), 7.64 (s, 1H), 7.82 (d, J=9.1, 1H), 7.92
(d, J=2.0 Hz, 1H), 9.61 (s, 1H). 13C NMR (CDCl3): δ 0.0, 28.5,
38.3, 117.0, 120.2, 121.3, 125.0, 126.6, 127.8, 130.0, 130.8, 130.9,
132.8, 146.1, 152.1, 171.2. Anal. Calcd for C19H24BrNO2Si: C,
56.15; H, 5.95; Br, 19.66; N, 3.45; O, 7.87; Si, 6.91. Found: C,
56.02; H, 5.98; Br, 19.61; N, 3.53; Si, 6.97.
1
(101 mg, yield 97%). Mp 132.2-133.9 °C. H NMR (CDCl3): δ
4.01 (s, 3H), 4.03 (s, 3H), 7.74 (dd, J=9.1, 1.9 Hz, 1H), 8.05 (d, J=
1.9 Hz, 1H), 8.15 (d, J = 9.1 Hz, 1H), 8.26 (s, 1H). 13C NMR
(CDCl3): δ 52.2, 61.8, 117.3, 120.1, 125.9, 128.2, 130.4, 130.6, 130.7,
132.2, 132.8, 153.2, 164.9. Anal. Calcd for C13H10Br2O3: C, 41.75;
H, 2.69; Br, 42.73; O, 12.83. Found: C, 41.83; H, 2.60; Br, 42.70.
General Procedure for the Irradiation of 6a in the Presence of
Allyltrimethylsilane. An argon-purged solution of 6a (91 mg,
0.3 mmol), freshly distilled allyltrimethylsilane (3.43 g, 30
mmol), and Et3N (607 mg, 6 mmol) in 300 mL of CH3CN was
irradiated for 3 h by using argon-purged solutions in Pyrex tubes
(20 mL) and a multilamp reactors fitted with four 15 WT8
PREHEAT COOL WHITE 4500 K lamps, with maximum
emission centered at 450 nm. Chromatographic separation
5318 J. Org. Chem. Vol. 74, No. 15, 2009