Palladium-Catalyzed Synthesis of 2,3-Disubstituted Benzofurans: An Approach Towards the Synthesis of Deuterium Labeled Compounds.

Palladium-catalyzed oxidative annulations between phenols and alkenylcarboxylic acids produced a library of benzofuran compounds. Depending on the nature of the substitution of the phenol precursor, either 2,3-dialkylbenzofurans or 2-alkyl-3-methylene-2,3-dihydrobenzofurans can be synthesized with excellent regioselectivity. Reactions between conjugated 5-phenylpenta-2,4-dienoic acids and phenol gave 3-alkylidenedihydrobenzofuran alkaloid motifs while biologically active 7-arylbenzofuran derivatives were prepared by starting from 2-phenylphenols. More interestingly, selective incorporation of deuterium from D2O has been discovered, which offers an attractive one-step method to access deuterated compounds.