A continuous flow microwave-assisted fischer indole synthesis of 7-Ethyltryptophol

A new procedure of microwave-assisted organic synthesis in flow was designed and introduced for Fischer indole synthesis of 7-ethyltryptophol (7-ET). By using back-pressure regulator (BPR), a reaction temperature of 180   °C could be easily and readily achieved even in a low-boiling solvent [water/ethylene glycol(EG)]. At this temperature, the synthesis of 7-ET from 2-ethylphenylhydrazine and 4-hydroxybutanal in flow was successful (78% net yield) and practical (short residence time: 30   s) with a simple purification process of extraction.