反应详情

A stirred mixture of 5-chloro-1H-indole-2,3-dione, starting material VIII, (90.8 g, 0.5 mol) and methyl cyanoacetate (44.1 ml, 0.5 mol) in methanol (1000 ml) was treated with piperidine (2 ml) and heated under reflux for 5 hours before standing overnight at ambient temperature. The crude (5-chloro-2-oxo-1,2-dihydro-indol-3-ylidene)-cyanoacetic acid methyl ester was removed by filtration, washed with cold methanol (2×150 ml) and dried in vacuo to give 117.6 g (90%) of a dark purple solid. This was a 6.5:1 mixture of geometric isomers which was sufficiently pure by 1H NMR for subsequent reaction.

1. temperatureheated
2. temperatureunder reflux for 5 hours
3. customThe crude (5-chloro-2-oxo-1,2-dihydro-indol-3-ylidene)-cyanoacetic acid methyl ester was removed by filtration
4. washwashed with cold methanol (2×150 ml)
5. customdried in vacuo