Lithium diisopropylamide → 2-[(E)-2-(2,6-dibromophenyl)ethenyl]-5-methoxy-1H-indole

Participants

Reaction Steps

The 5-methoxy-1H-indole-2-carbaldehyde (1) was reacted with (2,6-dibromobenzyl)(triphenyl)phosphonium bromide (516) prepared as described in example 107 using the procedure described in example 37, except that the ratio of LDA:aldehyde was 1.37:1 and the reaction time was 5 h, to give (after crystallisation from CH2Cl2/hexane) the diene (517) as a yellow solid (the pure E isomer) (80%), mp 140–141° C. 1H NMR (CDCl3) δ 8.20 (br s, 1H), 7.60 (d, J=8.1 Hz, 1H), 7.27 (d, J=8.2 Hz, 1H), 7.05 (br s, 1H), 7.03 (d, J=16.7 Hz, 1H), 6.96 (t, J=8.0 Hz, 1H), 6.88 (dd, J=8.7, 2.5 Hz, 1H), 6.82 (d, J=16.7 Hz, 1H), 6.61 (d, J=1.9 Hz, 1H), 3.86 (s, 3H). Found: C, 50.37; H, 3.24; N, 3.37. C17H13Br2NO requires C, 50.16; H, 3.22; N, 3.44.

Provenance & Evidence