Preparation of deuteriated furan- and thiophen-2-carbaldehydes and -2-carboxylic esters

Methods have been developed for introducing deuterium at some or all of the furan and thiophen ring positions. The compounds prepared include all the mono-, di-, and tri-deuteriofuran-2-carbaldehydes and -2-carboxylic acids, 5-deuteriofuran-2-[2H]carbaldehyde, and the monodeuteriothiophen-2-carbaldehydes. Furyl- and thienyl-lithium compounds are the key intermediates for replacing hydrogen or halogen atoms by deuterium, and for carrying out selective reactions at the α- or β-positions of the heterocyclic rings.