5014
E. Franchi et al. / Tetrahedron 59 (2003) 5003–5018
4.3.2. 1,4-Dimethyl-3-(3-hydroxyl-1-carbophenoxy)-7-
isopropylazulene (4b). The crude product was purified by
column chromatography on silica gel using a 9/1 (v/v)
benzene/ethyl acetate mixture as the eluant. Pure 4b (0.36 g,
43%) and the diester 5b (ca. 4%) were obtained as blue-
violet solids.
H, 6.8%. Found: C, 79.4; H, 6.7%. Mp 146–1478C. nmax
(KBr) 1657 and 1729 (CO), 3361 (OH) cm21
.
1H NMR of 4e (R1¼CH3, R2¼R3¼R4¼H) (200 MHz,
CDCl3, Me4Si): d 1.12 (6H, d, J¼7.0 Hz, Ha); 2.19 (3H, s,
R1); 2.42 (3H, s, Hd); 2.69 (1H, m, J¼7.0 Hz, Hb); 3.12 (3H,
s, Hm); 4.82 (1H, s, OH); 6.47 (1H, d, J¼11 Hz, Ho); 6.82–
7.13 (4H, m, Hn, R2–R4); 8.11 (1H, s, Hc); 8.40 (1H, s, He)
ppm. Anal. calcd for C23H24O3 4e (348.44): C, 79.31; H,
6.8%. Found: C, 79.4; H, 6.8%. Mp 136–1378C. nmax (KBr)
1H NMR of 4b (200 MHz, CDCl3, Me4Si): d 1.10 (6H, d,
J¼6.8 Hz, Ha); 2.38 (3H, s, Hd); 2.72 (1H, m, J¼6.8 Hz,
Hb); 3.07 (3H, s, Hm); 4.79 (1H, s, OH); 6.50 (1H, m, Hl);
6.78–7.10 (5H, m, Hf, Hg, Hh, Hn, Ho); 8.11 (1H, d, J¼2 Hz,
Hc); 8.30 (1H, s, He) ppm. Anal. calcd for C22H22O3 4b
(334.41): C, 78.8; H, 6.6%. Found: C, 79.0; H, 6.6%. Mp
126–1278C. nmax (KBr) 1678 and 1712 (CO), 3384 (OH)
1682 (CO), 3385 (OH) cm21
.
4.3.5. 1,4-Dimethyl-3-(4-hydroxyl-3-tert-butyl-1-carbo-
phenoxy)-7-isopropyl-azulene (4f) and 1,4-dimethyl-3-
(4-hydroxyl-2-tert-butyl-1-carbophenoxy)-7-isopropyl-
azulene (4g). Both these compounds were purified by
column chromatography on silica gel using a 9/1 (v/v)
benzene/ethyl acetate mixture as the eluant. The desired
monoesters 4f (0.3 g, 30%) and 4 g (0.1 g, 10%) and the
diester 5f (ca. 5%) were obtained as blue-violet solids.
cm21
.
1H NMR of 5b (200 MHz, CDCl3, Me4Si): d 1.15 (12H, d,
J¼6.7 Hz, Ha); 2.42 (6H, s, Hd); 2.72 (2H, m, J¼6.7 Hz,
Hb); 3.10 (6H, s, Hm); 6.82–7.25 (8H, m, Hf, Hg, Hh, Hn,
Ho); 8.13 (2H, d, J¼2.1 Hz, Hc); 8.32 (2H, s, He) ppm. Anal.
calcd for C38H38O4 5b (558.72): C, 81.7; H, 6.9%. Found:
C, 81.7; H, 6.8%. Mp.2508C (dec.). nmax (KBr) 1716 (CO)
1H NMR of 4f (R1¼R3¼R4¼H, R2¼But) (200 MHz,
CDCl3, Me4Si): d 1.16 (6H, d, J¼7 Hz, Ha); 1.49 (9H, s,
R2); 2.45 (3H, s, Hd); 2.75 (1H, m, J¼7 Hz, Hb); 3.17 (3H, s,
Hm); 4.17 (1H, s, OH); 6.10 (1H, d, J¼8.4 Hz, R3); 6.90
(1H, d, J¼11 Hz, Hn); 7.12 (1H, dd, J¼8.4, 2.6 Hz, R4);
7.40 (1H, d, J¼2.6 Hz, R1); 8.18 (1H, d, J¼2 Hz, Hc); 8.42
(1H, s, He) ppm. Anal. calcd for C26H30O3 4f (390.52): C,
79.9; H, 7.7%. Found: C, 80.0; H, 7.7%. Mp 158–1598C.
cm21
.
4.3.3. 1,4-Dimethyl-3-(2-hydroxyl-1-carbophenoxy)-7-
isopropylazulene (4c). The crude product was purified
by column chromatography on silica gel using a 9/1
(v/v) benzene/ethyl acetate mixture. 4c (0.4 g, 48%) and
the diester 5c (ca. 4%) were obtained as a blue-violet
solids.
nmax (KBr) 1697 (CO), 3439 (OH) cm21
.
1H NMR of 4c (200 MHz, CDCl3, Me4Si): d 1.11 (6H, d,
J¼6.8 Hz, Ha); 2.35 (3H, s, Hd); 2.70 (1H, m, J¼6.8 Hz,
Hb); 3.05 (3H, s, Hm); 6.05 (1H, s, Hl); 6.7–7.3 (6H, m, Hf,
Hg, Hh, Hi, Hn, Ho); 8.10 (1H, d, J¼2.1 Hz, Hc); 8.23 (1H, s,
He) ppm. Anal. calcd for C22H22O3 4c (344.41): C, 79.0; H,
6.6%. Found: C, 78.8; H, 6.6%. Mp 105–1068C. nmax (KBr)
1H NMR of 4g (R1¼But, R2¼R3¼R4¼H) (200 MHz,
CDCl3, Me4Si): d 1.16 (6H, d, J¼7 Hz, Ha); 1.50 (9H, s,
R1); 2.40 (3H, s, Hd); 2.70 (1H, m, J¼7 Hz, Hb); 3.15 (3H, s,
Hm); 4.32 (1H, s, OH); 6.40 (1H, dd, J¼8.7, 3.0 Hz, R2);
6.80 (1H, d, J¼3 Hz, R3); 6.90 (1H, d, J¼11 Hz, Hn); 8.10
(1H, d, J¼2 Hz, Hc); 8.45 (1H, s, He) ppm. Anal. calcd for
C26H30O3 4g (390.52): C, 79.9; H, 7.7%. Found: C, 80.1; H,
7.7%. Mp 172–1738C. nmax (KBr) 1698 (CO), 3447 (OH)
1685 (CO), 3379 (OH) cm21
.
1H NMR of 5c (200 MHz, CDCl3, Me4Si): d 1.24 (12H, d,
J¼6.9 Hz, Ha); 2.54 (6H, s, Hd); 2.71 (6H, s, Hm); 2.95 (2H,
m, J¼6.9 Hz, Hb); 6.68 (4H, m, Hf, Hg); 6.90 (2H, d,
J¼11.0 Hz, Hn); 7.30 (2H, dd, J¼11.0, 2.1 Hz, Ho); 7.5
(2H, s, He); 8.08 (2H, d, J¼2.1 Hz, Hc) ppm. Anal. calcd
for C38H38O4 5c (558.72): C, 81.7; H, 6.9%. Found: C,
81.8; H, 6.9%. Mp.2508C (dec.). nmax (KBr) 1712 (CO)
cm21
.
1H NMR of 5f (R1¼R3¼R4¼H, R2¼But) (200 MHz,
CDCl3, Me4Si): d 1.12 (12H, d, J¼7 Hz, Ha); 1.47 (9H, s,
R2); 2.42 (6H, s, Hd); 2.70 (2H, m, J¼7 Hz, Hb); 3.16 (6H, s,
Hm); 6.93 (2H, d, J¼11 Hz, Hn), 6.95–7.60 (4H, m, R1, R3,
R4, Ho); 8.13 (2H, d, J¼2 Hz, Hc); 8.45 (2H, s, He) ppm.
Anal. calcd for C42H46O4 5f (614.82): C, 82.0; H, 7.5%.
Found: C, 81.8; H, 7.6%. Mp.2508C (dec.). nmax (KBr)
cm21
.
4.3.4. 1,4-Dimethyl-3-(3-methyl-4-hydroxyl-1-carbo-
phenoxy)-7-isopropyl-azulene (4d) and 1,4-dimethyl-3-
(2-methyl-4-hydroxyl-1-carbophenoxy)-7-isopropyl-
azulene (4e). Both these compounds were purified by
column chromatography on silica gel using a 9/1 (v/v)
benzene/ethyl acetate mixture as the eluant. 4d (0.27 g,
31%) and 4e (0.24 g, 28%) were obtained as blue-violet
solids.
1715 (CO) cm21
.
4.3.6. 1,4-Dimethyl-3-(2,3-dimethyl-4-hydroxyl-1-carbo-
phenoxy)-7-iso-propylazulene (4h). The crude product
was dissolved in the minimum amount of n-hexane and
purified by column chromatography on Alumina. The
column was eluted first with n-hexane, which allowed the
separation of the unreacted guaiazulene, then with a 1/1
(v/v) benzene/ethyl acetate mixture, which yielded the
diester 5 h as blue crystals (0.160 g, 22%), then with
benzene, which allowed to separate the unreacted hydro-
quinone and, finally, with ethyl formate, which yielded 4 h
as a crystalline blue solid (0.362 g, 27%).
1H NMR of 4d (R1¼R3¼R4¼H, R2¼CH3) (200 MHz,
CDCl3, Me4Si): d 1.11 (6H, d, J¼7.0 Hz, Ha); 2.03 (3H, s,
R2); 2.42 (3H, s, Hd); 2.70 (1H, m, J¼7.0 Hz, Hb); 3.12 (3H,
s, Hm); 4.39 (1H, s, OH); 6.37 (1H, d, J¼11 Hz, Ho); 6.85–
7.15 (4H, m, Hn, R1, R3, and R4); 8.12 (1H, s, Hc); 8.39 (1H,
s, He) ppm. Anal. calcd for C23H24O3 4d (348.44): C, 79.31;
1H NMR of 4h (R1¼R2¼CH3, R3¼R4¼H) (200 MHz,