Preparation of substituted furan- and thiophen-2-carbaldehydes and -2-[2H]carbaldehydes, and of 2-furyl ketones

A series of heterocyclic 2-carbaldehydes and 2-[2H]carbaldehydes have been prepared, most of them by Vilsmeier formylation of mono- and di-substituted furans and thiophens. Isopropylation of methyl furan-2-carboxylate was used to obtain the 4- and 5-monoisopropyl- and 4,5-di-isopropyl-furan-2-carboxylic acids. With different aryl 2-furyl ketones bromine may attack either the benzenoid ring or the heterocyclic ring preferentially.