Lithium diisopropylamide → 2-[(E)-2-(2-chloro-4-methoxyphenyl)ethenyl]-5-methoxy-1H-indole

Participants

Reaction Steps

The 5-methoxy-1H-indole-2-carbaldehyde (1) was reacted with (2-chloro-4-methoxybenzyl)(triphenyl)phosphonium bromide (574) prepared as described in example 162 using the procedure described in example 37, except that the LDA and aldehyde were sequentially added at 0° C., the ratio of LDA:aldehyde was 1.5:1 and the reaction time was 5 h, to give (after crystallisation from CH2Cl2/pentane) the diene (575) as a pale yellow solid (the pure E isomer) (64%), mp 129–132° C. 1H NMR (CDCl3) δ 8.17 (br s, 1H), 7.60 (d, J=8.8 Hz, 1H), 7.25 (d, J=8.3 Hz, 1H), 7.19 (d, J=16.5 Hz, 1H), 7.03 (d, J=2.4 Hz, 1H), 6.96 (d, J=17.3 Hz, 1H), 6.94 (d, J=2.4 Hz, 1H), 6.86 (dd, J=8.7, 2.6 Hz, 1H), 6.85 (dd, J=8.7, 2.8 Hz, 1H), 6.54 (d, J=1.7 Hz, 1H), 3.85 (s, 3H), 3.83 (s, 3H). Found: C, 69.05; H, 5.41; N, 4.68. C18H16ClNO2 requires C, 68.90; H, 5.14; N, 4.46.

Provenance & Evidence