3-Bromopyrylium salts
Three new methods have been proposed for the synthesis of 3-bromopyrylium salts. An unsaturated 1,5-diketone is converted into a 3-bromopyrylium salt by allyl bromination and the addition of bromine to the double bond. 3-Bromopyrone, obtained by the bromination of dibenzoylacetone is converted by treatment with Grignard reagents into 3-bromopyrylium salts. Similar compounds have also been synthesized by the pyrylation of aromatic and heterocyclic compounds with 3-bromo-4-chloropyrylium salts obtained from 3-bromopyrone.