Helvetica Chimica Acta Vol. 87 (2004)
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C(6)); 33.3 (t, C(9)); 26.7 (q, Me-C(3a)); 26.0 (q, Me-C(9a)); 21.4 (q, MebÀC(6)); 19.4 (t, C(8 )); 17.7 (t, C(5)).
MS: 234 (12, M ), 219 (100), 149 (17), 123 (17), 110 (31), 97 (69), 81 (49), 69 (32).
Data of 14b: 1H-NMR: 0.93 (s, 3 H); 0.94 (s, 3 H); 1.15 (s, 3 H); 1.42 (s, 3 H); 1.00 2.00 (11 H); 4.47 (dd,
J 13, 3, 1 H); 4.56 (dd, J 13, 1.5, 1 H); 5.42 (br. s, 1 H). 13C-NMR: 150.8( s, C(9b)); 116.6 (d, C(1)); 86.6 (s,
C(3a)); 71.5 (t, C(2)); 50.5 (d, C(5a)); 44.2 (t, C(7)); 39.9 (t, C(9)); 37.2 (s, C(9a)); 37.0 (t, C(4)); 34.8( s, C(6)),
33.1 (q, MeaÀC(6)); 32.1 (q, MeÀC(9a)); 28.0 (q, MeÀC(3a); 26.1 (q, MebÀC(6)); 20.3 (t, C(5)); 19.0 (t, C(8)).
MS: 234 (7, M ), 219 (65), 110 (70), 97 (100), 81 (58), 69 (30).
1
Data of 14c: M.p. 37 408. IR (CHCl3): 2950, 1460, 1380, 1140, 1100, 1060, 1020. H-NMR: 0.86 (s, 3 H);
0.87 (s, 3 H); 0.94 (dd, J 13, 3.5, 1 H); 1.08( s, 3 H); 1.16 (m, 1 H); 1.38( s, 3 H); 1.35 1.80 (8 H); 2.00 (dt, J
13, 3.5, 1 H); 4.47 (dd, J 13, 3.5, 1 H); 4.58( dd, J 13, 1.5, 1 H); 5.23 (br. s, 1 H). 13C-NMR: 156.5 (s, C(9b));
113.1 (d, C(1)); 87.2 (s, C(3a)); 72.1 (t, C(2)); 55.3 (d, C(5a)); 42.2 (t, C(4)); 42.1 (t, C(7)); 38.1 (t, C(9)); 37.7 (s,
C(9a)); 33.6 (s, C(6)); 33.4 (q, MeaÀC(6)); 26.4 (q, MeÀC(3a)); 21.5 (q, MebÀC(6)); 20.3 (t, C(5)); 19.9 (q,
MeÀC(9a)); 18.6 (t, C(8)). MS: 234 (19, M ), 219 (100), 191 (32), 110 (36), 97 (66), 81 (51), 69 (37).
Data of 14d: 1H-NMR: 0.91 (s, 3 H); 1.17 (s, 3 H); 1.39 (s, 3 H); 1.41 (s, 3 H); 1.00 2.00 (11 H); 4.47 (dd,
J 13, 3, 1 H); 4.59 (dd, J 13, 1.5, 1 H); 5.47 (br. s, 1 H). 13C-NMR: 154.8( s, C(9b)); 118.5 (d, C(1)); 86.6 (s,
C(3a)); 71.6 (t, C(2)); 52.5 (d, C(5a)); 40.5 (t, C(4)); 39.6 (s, C(9a)); 34.9 (t, C(7)); 33.7 (s, C(6)); 33.7 (q,
MebÀC(6)); 32.2 (t, C(9)); 31.4 (q, MeaÀC(6)); 27.6 (q, MeÀC(9a)); 25.7 (q, MeÀC(3a)); 23.9 (t, C(5)); 19.3 (t,
C(8)). MS: 234 (8, M ), 219 (40), 149 (11), 110 (58), 97 (100), 81 (32).
Catalytic Hydrogenation of 14a d: (3aRS,5aRS,9aRS,9bSR)-, (3aRS,5aRS,9aSR,9bSR)-, (3aRS,5aSR,-
9aSR,9bSR)-, and (3aRS,5aSR,9aRS,9bSR)-Dodecahydro-3a,6,6,9a-tetramethylnaphtho[2,1-b]furan (4a d).
A stirred soln. of 14a (8%), 14b (24%), 14c (64%), and 14d (4%) (0.1 g, 0.43 mmol) in toluene (2 ml)
containing 10% Pd/C (0.1 g) was hydrogenated (1 bar H2) at r.t. during 3 h. After filtration (Celite), the product
was analyzed by GC and, by comparison with authentic samples of 4a d [5], shown to consist of a mixture of 4a
(8%), 4b (4%), 4c (63%), and 4d (4%), besides unreacted 14b (20%) and 14c (1%). GC (column temp.
100 2208, 158/min): tR 5.91 (4a), 6.06 (4b), 6.27 (4c), and 6.37 (4d).
Acid-Mediated Cyclization (95% aq. H2SO4 soln./CH2Cl2) of 10. A soln. of 10 (11 g, 0.044 mol) in CH2Cl2
(30 ml) was added dropwise during 1 h to a mechanically stirred slurry of 95% aq. H2SO4 soln. (11 g, 0.11 mol)
in CH2Cl2 (110 ml) at À408 under N2. The dark-red mixture was stirred for a further 3 h at À408 and then poured
slowly into a cold soln. of NaHCO3 (20 g) in H2O (250 ml), which was stirred during 30 min, allowing the
mixture to attain r.t. The resulting white emulsion was partially concentrated i.v. (308/15 mbar), and the residue
was extracted with Et2O. Workup gave a viscous orange oil (11.2 g), which was distilled i.v. (Vigreux column):
colorless oil (6.5 g, 64%) composed of 14a (5%), 14b (23%), 14c (69%), and 14d (3%). Trace amounts of
(6aRS,10aSR)-3,5,6,6a,7,8,9,10-octahydro-4,6a,10,10-tetramethyl-2H-naphtho[8a,1-b]furan (15; ca. 0.5% of
crude product mixture) and 2,5-dihydro-2-methyl-2-[2-(2,6,6-trimethylcyclohex-1-en-1-yl)ethyl]furan (16; ca.
2.5% of crude product mixture) were isolated from head fractions and purified by CC (toluene) and bulb-to-
bulb distillation i.v. (b.p. 130 1508/0.05 mbar).
Data of 15: Rf (toluene) 0.36. IR (CHCl3): 2930, 1458, 1380, 1362, 1040, 1020, 970. 1H-NMR: 0.71 (s, 3 H);
0.85 (s, 3 H); 0.92 (s, 3 H); 1.10 (m, 2 H); 1.27 (br. d, J 11, 1 H); 1.39 (m, 1 H); 1.55 1.70 (3 H); 1.70 (s, 3 H);
1.90 2.20 (3 H); 2.52 (2 H); 3.60 (dd, J 18, 9, 1 H); 4.02 (ddd, J 18, 7.5, 3.5, 1 H). 13C-NMR: 131.8( s, C(3a));
126.3 (s, C(4)); 87.6 (s, C(10a)); 67.0 (t, C(2)); 40.4 (s, C(10)); 38.1 (s, C(6a)); 37.1 (t, C(9)); 36.7 (t, C(7)); 31.5 (t,
C(3)); 30.5 (q, MeaÀC(10)); 29.8( t, C(6)); 28.3 (t, C(5)); 26.6 (q, MeÀC(6a)); 24.5 (q, MebÀC(10)); 20.3 (q,
MeÀC(4)); 18.3 (t, C(8)). MS: 234 (4, M ), 219 (2), 150 (100), 135 (28), 91 (11), 79 (9).
Data of 16: Rf (toluene) 0.30. IR (CHCl3): 2950, 1460, 1082, 1048, 916. 1H-NMR: 0.97 (s, 3 H); 0.98( s, 3 H);
1.29 (s, 3 H); 1.40 (2 H); 1.58( s, 3 H); 1.50 1.75 (4 H); 1.89 (t, J 7, 2 H); 2.00 (m, 2 H); 4.65 (m, 2 H); 5.71 (dt,
J 7, 3, 1 H); 5.83 (br. d, J 7, 1 H ) . 13C-NMR: 137.2 (s); 133.6 (d); 126.8( s); 125.6 (d); 90.4 (s); 74.8( t); 41.2 (t);
40.0 (t); 35.1 (s); 32.8( t); 28.7 (2q); 26.3 (q); 23.2 (t); 19.7 (q); 19.6 (t). MS: 234 (1, M ), 121 (5), 95 (19), 83
(100), 55 (10).
4-Methyl-6-(2,5,6,6-tetramethylcyclohex-1-en-1-yl)hex-2-yne-1,4-diol (18a; 1:1 diastereoisomer mixture). A
mixture of 4-(2,5,6,6-tetramethylcyclohex-1-en-1-yl)butan-2-one [2] (17; 13 g, 0.061 mol; Rf (cyclohexane/
AcOEt 7 :3) 0.55) and prop-2-yn-1-ol (4 g, 0.071 mol) was added dropwise during 1.5 h to a mechanically stirred
slurry of powdered KOH (26 g, 0.46 mol) in THF (100 ml) at 208 under N2. After 3 h at 208, the brown mixture
was poured into a cold soln. of NH4Cl (28g) in H 2O (100 ml). Extraction (Et2O), workup, CC (cyclohexane/
AcOEt 7:3), and bulb-to-bulb distillation i.v. afforded 18a (12.3 g, 77%). Viscous, pale-yellow oil. B.p. 180
2008/0.5 mbar. Rf (cyclohexane/AcOEt 7:3) 0.14. IR (CHCl3): 3620, 3388 (br.), 3019, 2970, 1374, 1215, 1056,
932. 1H-NMR (after exchange with D2O): 0.85 (s, 3 H); 0.8 7 (d, J 7, 3 H); 1.02 (2s, 3 H); 1.25 2.05 (7 H); 1.50
(s, 3 H); 1.62 (s, 3 H); 2.20 (m, 2 H); 4.30 (s, 2 H). 13C-NMR: 136.4 (s); 127.2 (s); 89.5 (s); 81.7 (s); 68.3 (s); 50.7