326
S. Quideau et al. / Tetrahedron 57 (2001) 319±329
EIMS m/z (relative intensity) 353 (M2Me1, 1), 311 (12),
173 (100).
(bs, 1H), 6.65±6.69 (m, 2H), 6.84 (d, J7.9 Hz, 1H); 13C
NMR (CDCl3, 62.5 MHz) d 154.9, 146.5, 144.1, 130.7,
121.4, 114.3, 111.2, 55.8, 42.5, 35.8, 17.7, 12.0; EIMS
m/z (relative intensity) 367 (M1, 3), 324 (100); Anal.
Calcd for C19H33NO4Si: C, 62.09; H, 9.06; N, 3.81.
Found: C, 62.01; H, 9.03; N, 3.87.
3.1.6. Orthoquinol acetate 13f. This orthoquinol acetate
was prepared as a yellow oil in 98% yield according to
the oxidative acetoxylation method we previously
1
described:36 IR (NaCl) 1737, 1684 cm1; H NMR (CDCl3)
d 1.03 (s, 9H), 1.37±1.59 (m, 6H), 2.06 (s, 3H), 2.19 (bt,
J6.8 Hz, 2H), 3.43 (s, 3H), 3.65 (t, J6.3 Hz, 2H), 5.86
(bs, 1H), 6.09 (d, J10.0 Hz, 1H), 6.74 (dd, J2.1, 10.0 Hz,
1H), 7.33±7.72 (m, 10H); 13C NMR (CDCl3) d 191.8,
169.3, 142.7, 138.7, 135.4, 134.0, 129.5, 128.7, 127.6,
125.7, 93.1, 63.7, 51.2, 34.9, 32.2, 27.5, 26.8, 25.2, 20.5,
19.2; EIMS m/z (relative intensity) 507 (MH1, 8), 429 (12),
257 (79), 211 (100); HRMS (CI) calcd for C30H39O5Si
507.2566, found 507.2566.
3.1.10. Orthoquinol acetate (20). A solution of phenol 19
(400 mg, 1.09 mmol) in dry CH2Cl2 (2 mL) was added drop-
wise to a stirring solution of oxidizing agent (LTA,
1.1 equiv, or PIDA, 1.0 equiv.) in 5 mL of dry CH2Cl2 at
2788C. The reaction mixture immediately became bright
yellow. After 1 h, TLC monitoring [hexanes±Et2O (1:1)]
indicated complete consumption of the starting material.
The mixture was poured into ice-cold saturated aqueous
NaHCO3 (10 mL), extracted with CH2Cl2 (2£20 mL),
washed with brine (10 mL), dried over Na2SO4, ®ltered
and evaporated at room temperature. The residue was
further dried under high vacuum for a couple of hours to
give the orthoquinol acetate 20 as a bright yellow oil
(454 mg, 98%). This oil was used without further puri®-
3.1.7. Alcohol 15. Orthoquinol acetate 13f (361 mg,
0.80 mmol) was treated with tetrabutylammonium ¯uoride
(TBAF) according to the method we previously described.36
Puri®cation of the resulting dark oil by column chromato-
graphy, eluting with hexanes±EtOAc (9:1) followed by
EtOAc, afforded 15 as a dark oil (24 mg, 14%): IR (NaCl)
1
cation: IR (NaCl) 3394, 1750, 1672, 1682 cm21; H NMR
(CDCl3, 200 MHz) d 1.03 (d, J6.7 Hz, 18H), 1.25 (h,
J6.7 Hz, 3H), 2.05 (s, 3H), 2.37±2.43 (m, 2H), 3.03±
3.19 (m, 1H), 3.33±3.50 (m, 1H), 3.41 (s, 3H), 4.94±5.00
(m, 1H), 5.93 (bs, 1H), 6.10 (d, J9.9 Hz, 1H), 6.76 (dd,
J2.2, 9.9 Hz, 1H); 13C NMR (CDCl3, 50 MHz) d 191.5,
169.6, 154.8, 141.9, 135.5, 131.0, 126.3, 92.8, 51.2, 38.9,
35.2, 20.5, 17.7, 11.9; EIMS m/z (relative intensity) 425
(M1, 1), 382 (16), 324 (100), 137 (56); HRMS (EI) calcd
for C21H35NO6Si 425.2234, found 425.2230.
1
3401 cm21; H NMR (CDCl3, 250 MHz) d 1.25±1.67 (m,
6H), 2.54 (bt, J7.4 Hz, 2H), 3.64 (bt, J6.4 Hz, 2H), 3.87
(s, 3H), 6.64±6.67 (m, 2H), 6.82 (dd, J1.5, 8.5 Hz, 1H);
13C NMR (CDCl3, 62.5 MHz) d 146.2, 143.5, 134.5, 120.8,
114.1, 110.9, 62.9, 55.8, 35.5, 32.6, 31.5, 25.3; EIMS m/z
(relative intensity) 211 (MH1, 7), 210 (M1, 52), 137 (100).
3.1.8. O-Spirocyclohexadienone tetrahydrofuran 17.
Alcohol 16 (185 mg, 1.02 mmol) was submitted to the
oxidative acetoxylation conditions we previously
described36 to furnish 17 (182 mg, 74%) as a yellow oil:
3.1.11. 2,3-Dihydroindole (21). To a stirring ice-cold solu-
tion of 20 (380 mg, 0.89 mmol) in dry THF (8 mL) was
added dropwise a commercial solution of TBAF (1 M in
THF, 1.1 equiv.). The reaction mixture immediately became
darker. After 15 min, the ice bath was removed, and the
reaction was stirred at room temperature for 2.5 h. Pro-
gression of the reaction was monitored by the disappearance
of the orthoquinol acetate, as indicated by TLC [hexanes±
Et2O (1:1), and then CH2Cl2±MeOH (20:1)]. The mixture
was diluted with EtOAc (50 mL), poured into ice-cold water
(15 mL), extracted with EtOAc (2£20 mL), washed with
brine (2£20 mL), dried over Na2SO4, ®ltered and evapo-
rated at room temperature. The resulting dark oily residue
was puri®ed by column chromatography, eluting with
CH2Cl2±MeOH (40:1), to afford 21 as an orange oil
1
IR (NaCl) 1675, 1644 cm21; H NMR (CDCl3) d 2.00±
2.19 (m, 4H), 3.63 (s, 3H), 3.98±4.09 (m, 2H), 5.67 (d,
J2.7 Hz, 1H), 6.09 (d, J9.9 Hz, 1H), 6.77 (dd, J2.7,
9.9 Hz, 1H); 13C NMR (CDCl3) d 180.9, 150.1, 149.7,
126.1, 116.6, 79.3, 68.8, 54.8, 37.6, 26.8; EIMS m/z (rela-
tive intensity) 181 (MH1, 10), 180 (M1, 79), 137 (100);
Anal. Calcd for C10H12O3: C, 66.64; H, 6.72. Found: C,
66.26; H, 6.69.
3.1.9. N-Tsoc-4-hydroxy-3-methoxyphenylethylamine
(19). A stirring solution of 3-O-methyl dopamine hydro-
chloride 18 (500 mg, 2.45 mmol) and triethylamine
(1.02 mL, 7.36 mmol) in dry CH2Cl2 (20 mL) was cooled
at 2788C. Dry ice (5.4 g, ca. 50 equiv.) was added in one
portion. After stirring at 2788C for 1 h, TIPS-OTf (659 mL,
2.45 mmol) was added dropwise via syringe. After 5 min,
the mixture was allowed to warm up to room temperature,
and was stirred for 30 min. The mixture was then poured in
a separatory funnel containing H2O (20 mL). After separa-
tion, the aqueous phase was extracted with CH2Cl2
(2£20 mL); the combined organic layers were washed
with saturated NaHCO3 (20 mL), brine (2£20 mL), and
dried over MgSO4. Evaporation of the solvent afforded
907 mg of an orange oil which was puri®ed by column
chromatography, eluting with hexanes±Et2O (1:1), to give
19 as white crystals (703 mg, 78%): mp 60±618C; IR (KBr)
3378, 3264, 1671 cm21; 1H NMR (CDCl3, 250 MHz) d 1.07
(d, J7.1 Hz, 18H), 1.27 (h, J7.1 Hz, 3H), 2.69±2.77 (m,
2H), 3.30±3.41 (m, 2H), 3.86 (s, 3H), 4.80 (bs, 1H), 5.62
1
(70.8 mg, 48%): IR (NaCl) 3432 cm21; H NMR (CDCl3,
200 MHz) d 2.96 (t, J8.2 Hz, 2H), 3.53 (t, J8.2 Hz, 2H),
3.81 (s, 3H), 6.39 (s, 1H), 6.72 (s, 1H); 13C NMR (CDCl3,
50 MHz) d 145.3, 144.7, 140.5, 120.2, 109.0, 98.4, 57.1,
47.8, 29.9; EIMS m/z (relative intensity) 167 (3), 166
(MH1, 6), 165 (M1, 61), 150 (100); HRMS (EI) calcd for
C9H11NO2 165.0790, found 165.0785.
3.1.12. 2-Benzyloxy-1-naphthaldehyde (23a). To a stirring
solution of commercially available 2-hydroxy-1-naphthal-
dehyde 22 (2 g, 11.6 mmol) in acetone (50 mL) was added
potassium carbonate (1.77 g, 12.8 mmol) and benzyl bro-
mide (1.38 mL, 11.6 mmol), and the mixture was re¯uxed
for 3 h. The solution was ®ltered through celite and the
solvent removed in vacuo. The residue was dissolved with
Et2O (75 mL), washed with 1 M NaOH (50 mL), brine