Access to 5-bromopentanal and 6-bromohexanal derivatives via the bromination/hydrolysis of C,O-bis-zirconocenes generated from unsaturated Weinreb amides

Access to 5-bromopentanal and 6-bromohexanal derivatives from Weinreb amides is described. The method relies on the sequential C-bromination/zircona-aminal hydrolysis of bis-C,O-zirconocenes, which are generated in situ from unsaturated Weinreb amides using Schwartz's reagent. Synthetic illustrations of such bromo-aldehydes, which can act as carbocycle and heterocycle precursors, are also presented.