Triethyloxonium tetrafluoroborate/l,2-dimethoxyethane -a versatile substitute for trimethyloxonium tetrafluoroborate in 0-methylation reactions

Abstract

The triethyloxonium tetrafluoroborate/l,2-dimethoxyethane (TEO/DME) mixture is a versatile and cheap substitute for trimethyloxonium tetrafluoroborate in O-methylations of pyrrolin-2-ones, quinolones, acridones, and 1-oxo-β-carbolines. Undesired O-ethylation can be avoided by preincubation of triethyloxonium tetrafluoroborate and 1,2-dimethoxyethane for 1 h, prior to addition of the substrate. In the course of these investigations it was found that the structures assigned to the alkaloids taraxacine A and B are erroneous. © Verlag der Zeitschrift für Naturforschung.