Kinetics and mechanism of nucleophilic halogen exchange in furan derivatives

Studies are made of the reaction of 5-bromofurfurylidenaniline with aromatic amines (reaction 1), of the disproportionation of 5-bromofurfurylidenaniline (reaction 2), and of the reaction of 5-bromofurfurylidenaniline and 5-bromofurfural with saturated secondary amines (reaction 3). It is shown that these reactions are of the autocatalytic type (the catalyst being a reaction product, the hydrobromide of the amine), that addition of acid accelerates them, while they are retarded by addition of alkali. The hypothesis is advanced that in these reactions the active form of the substrate is the salt containing the fragment. The latter arises by protonation of the Schiff's base (reactions 1 and 2), or by quaternization of aminoacetals (which are products formed by addition of a secondary amine across the (double) bonds in through the action of the hydrohalide salt of the amine (reaction 3).