Study of Radical Decarboxylation Toward Functionalization of Naphthoquinones

Abstract In order to obtain functionalized naphthoquinones, a systematic study of the Kochi–Anderson procedure for the alkylation of quinones is presented. While linear amino acids of different lengths were good substrates for this decarboxylation procedure, chiral α‐amino acids were unsuccessful substrates. The best reaction conditions were evaluated with β‐alanine and then applied to a series of carboxylic acids to obtain chemical diversity on the naphthoquinones. We observed that the substitution of the acids is critical for the alkylation, and that it was possible to realize a double alkylation with 1,4‐naphthoquinone, even with different reactants. The Barton procedure was attempted on some substrates to compare with our results, but no reaction was observed, no matter which radical trap was used. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)