Propargylation of indole under a new dual-site phase-transfer catalyst: A kinetic study

A new multi-site phase-transfer catalyst viz., N,N’-dihexyl-4,4’-bipyridinium dibromide (DSPTC) was synthesized from the low cost starting materials. The structures of the synthesized DSPTC and 1-(prop-2-ynyl)-1H-indole were evidenced by 1H NMR and 13C NMR. The potentiality of the new multi-site phase transfer catalyst was demonstrated by following the kinetics propargylation of the indole under pseudo-first order conditions by using the aqueous sodium hydroxide and indole in excess, and the reaction was monitored by gas chromatography. Moreover, the catalytic efficiency of the DSPTC was compared with the single-site phase-transfers catalysts.