The utility of the thio acid-azide coupling reaction to afford amides is explored in imidazole-containing substrates for application in the total synthesis of examples of oroidin alkaloids. Good yields of the expected amides are obtained in both monomeric and dimeric substrates. Bis azides react preferentially at the 2-azido position but hydrosulfenylation and reduction interfere. 2-Thiophenyl and 2-oxo groups were evaluated as 2-amino surrogates, the thioether delivered the expected amide, whereas 2-imidazolone gave a mixture of the expected amide and the hydrosulfenylation product.
Keywords: Azide synthesis; Cross-coupling; Hydrosulfenylation; Nagelamides; Natural products.