1
˚C); H-NMR (270 MHz, CDCl3) δ 0.34 (1H, m), 0.69 (3H, s), 0.88 (3H, s), 0.94 (3H, s), 1.00
(1H, m), 1.38-1.48 (2H, m), 2.12 (1H, d, J = 3.0 Hz), 3.19 (1H, dd, J = 3.3, 12.5 Hz), 3.27 (1H,
ddd, J = 3.3, 3.3, 5.9 Hz), 3.42 (1H, dd, J = 3.3, 12.5 Hz), 3.87 (1H, d, J = 5.9 Hz), 7.03 (1H, d, J =
13
7.9 Hz), 7.15 (1H, ddd. J = 1.0, 7.2, 7.9 Hz), 7.26-7.32 (2H, m); C-NMR (67.8 MHz, CDCl3)
δ 11.4 (CH3), 19.2 (CH3), 19.4 (CH3), 25.2 (CH2), 25.5 (CH2), 32.4 (CH2), 36.5 (CH), 37.1 (CH),
53.9 (CH), 55.5 (C), 56.7 (C), 116.7 (CH), 123.8 (CH), 124.4 (CH), 128.4 (CH), 128.7 (C), 129.2
+
+
(CH), 137.1 (C), 150.7 (C), 167.4 (C); MS (m/z) 326 (M , 25%), 298 (M -C2H4, 100%); HRMS
1
Found: 326.1345, Calcd for C20H22O2S: 326.1341. 3e-cis (endo minor): H-NMR (500 MHz,
CDCl3) δ 0.55 (3H, s), 0.69 (3H, s), 0.94 (3H, s), 1.14 (1H, m), 1.24 (1H, m), 1.58 (1H, m), 1.87
(1H, m), 2.09 (1H, d, J = 3.7 Hz), 3.05 (1H, dd, J = 2.7, 12.8 Hz), 3.25 (1H, ddd, J = 2.7, 5.2, 5.9
Hz), 3.33 (1H, dd, J = 5.2, 12.8 Hz), 3.75 (1H, d, J = 5.9 Hz), 7.07-7.31 (4H, m). 3e-trans (exo
1
major): mp 134.8-136.3 ˚C (a mixture of the major and minor); H-NMR (500 MHz, CDCl3)
δ 0.88 (3H, s), 0.90 (3H, s), 1.01 (3H, s), 1.32 (1H, m), 1.58-1.71 (2H, m), 2.20 (1H, m), 2.78 (1H,
d, J = 3.7 Hz), 2.94 (1H, ddd, J = 2.4, 11.3, 13.4 Hz), 3.05 (1H, dd, J = 11.3, 13.1 Hz), 3.44 (1H,
dd, J = 2.4, 13.1 Hz), 3.98, (1H, d, J = 13.4 Hz), 7.09-7.17 (2H, m), 7.29 (1H, m), 7.63 (1H, d, J =
13
7.9 Hz); C-NMR (CDCl3) δ 11.9 (CH3), 19.1 (CH3), 19.8 (CH3), 26.5 (CH2), 27.2 (CH2), 32.8
(CH2), 34.8 (CH), 43.9 (CH), 55.6 (CH), 57.6 (C), 59.9 (C), 117.1 (CH), 124.4 (CH), 126.2 (CH),
1
128.0 (C), 128.2 (CH), 133.5 (C), 139.5 (C), 151.0 (C), 169.7 (C). 3e-trans (exo minor): H-
NMR (CDCl3) δ 0.93 (3H, s), 1.02 (3H, s), 1.03 (1H, m), 1.08 (3H, s), 1.18 (1H, m), 1.62 (1H,
m), 1.95 (1H, m), 2.92 (1H, d, J = 3.7 Hz), 2.94 (1H, ddd, J = 2.4, 11.3, 13.4 Hz), 3.00 (1H, dd, J
= 11.3, 12.5 Hz), 3.27 (1H, dd, J = 2.4, 12.5 Hz), 3.64, (1H, d, J = 13.4 Hz), 7.09-7.17 (2H, m),
13
7.29 (1H, m), 7.47 (1H, dd, J = 1.2, 7.7 Hz); C-NMR (CDCl3) δ 10.7 (CH3), 19.6 (CH3), 20.0
(CH3), 25.3 (CH2), 27.0 (CH2), 31.2 (CH2), 37.4 (CH), 42.4 (CH), 55.1 (CH), 53.1 (C), 55.3 (C),
117.2 (CH), 124.5 (CH), 125.1 (CH), 128.2 (CH), 128.8 (C), 132.4 (C), 137.1 (C), 150.7 (C),
170.0 (C).
1
2
15.
Indeed, thioketone (2b) (R = R = Me) was isolated when the ketone (1b) was treated with LR at
lower temperatures in a refluxing solvent such as dichloromethane, tetrahydrofuran or benzene.
Unpublished results. See also literature in reference 13.
16.
17.
The terms "endo" and "exo" used in the intramolecular Diels-Alder cycloaddition denote the
orientation of the dienophile relative to the diene, as defined by its attachment to the tethering
chain, regardless of the presence or absence of the secondary orbital interaction between the diene
and the dienophile. E. Ciganek, ‘Organic Reactions,’ Vol. 32, Wiley, New York, 1984, p. 1.
Crystal data of cis-3e (endo major): C20H22O2S, M = 326.44. Orthorhombic, a = 8.623(2), b =
12.309(3), c = 16.229(5) Å, U = 1722.5(8) Å3, space group P212121, Z = 4, Dcalcd = 1.259 Mgm-3.
Crystal dimensions 0.25 x 0.36 x 0.43 mm, µ(Mo-Kα) = 0.186 mm-1, F(000) = 696. Enraf-Nonius
CAD-4 diffractometer, ω/2θ scan mode, ω scan speed ca. 4 deg min-1 (h, 0 to 11; k, 0 to 15; l, 0 to
21; 4˚ < 2θ < 55˚), graphite-monochromated Mo-Kα radiation (λ = 0.71073 Å), 2271 reflections
18.
measured, 1701 unique reflections with ⁄ F
0.048, respectively.
o
⁄ ≥ 3σ (⁄ Fo ⁄). Final R and Rw values are 0.047 and