Unprecedented Halogenation of Biginelli Compounds of Salicyldehyde

Unprecedented results are obtained from bromination of the normal/non-bridged and abnormal/bridged Biginelli compound of salicyldehyde. Bromination with 2,4,4,6-tetrabromocyclohexa-2,5-dienone yields a bridged monobromo-derivative and a bridged dibromo-derivative, respectively, whereas bromination with bromine and acetic acid gives a mixture of those two products in each case. Bromination with N-bromosuccinimide gives a third product, namely a tribromo-derivative, in addition to those two products. Iodination of both the substrates using iodine monochloride (Wijs solution) furnishes a bridged monoiodo-derivative only.