4-Pyridinecarboxaldehyde → (Z)-4-[2-(3-Cyclopentyloxy-4-methoxyphenyl)ethenyl]pyridine

Beteiligte Stoffe

Reaktionsschritte

A solution of sodium ethoxide [prepared from sodium (0.10 g, 4.50 mmol)] in ethanol (50 ml) was added over 5 min to a stirred mixture of 4-pyridine carboxaldehyde (0.44 g, 4.10 mmol) and (3-cyclopentyloxy-4-methoxyphenyl)-methyltriphenylphosphonium chloride (2.00 g, 4.08 g) in ethanol (30 ml). After 2h, the reaction mixture was concentrated in vacuo and the residue partitioned between EtOAc (75 ml) and brine (50 ml). The organic layer was separated, then dried (MgSO4) and concentrated in vacuo. A 1H n.m.r. spectrum indicated that the mixture consisted of a 3:2 mixture of (Z): (E)title compound (and triphenylphosphine oxide). A portion (0.6 g) of the mixture was subjected to chromatography (SiO2 ; hexane to EtOAc) to afford pure/Z-title compound (0.14 g) as a pale yellow solid m.p. (Found: C, 77.18; H, 7.16; N, 4.63. C19H21NO2 requires C, 77.26; H, 7.17; N, 4.74%); δH (300 MHz; CDCl3) 1.5-1.55 (2H, br m, cyclopentyl H's), 1.65-1.9 (6H, br m, cyclopentyl H's), 3.83 (3H, s, OMe), 4.44 (1H, br m, OCHCH2), 6.40 (1H, d, J 12.2 Hz, CH=CH), 6.65-6.80 (4H, m, ArH ortho to OMe+2×ArH meta to OMe+CH=CH), 7.15 (2H, ca. d, J 6.0 Hz, pyridine H2, H6); m/z 295 (M+, 22%), 228 (15), 227 (100), 226 (94), 198 (35), 184 (15), 166 (12), 43 (19), and 41 (29).

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