A one-pot synthesis of tetrazolones from acid chlorides: understanding functional group compatibility, and application to the late-stage functionalization of marketed drugs.

A one-pot and scalable synthesis of tetrazolones (tetrazol-5-ones) from acid chlorides using azidotrimethylsilane is presented. The reaction tolerates many functional groups and can furnish aryl-, heteroaryl-, alkenyl-, or alkyl-substituted tetrazolone products in moderate to excellent yield (14-94%). No reduction in yield was observed when the reaction was undertaken on a larger-scale (20-36 g). The method could be used for the late-stage functionalization of pharmaceuticals, to provide tetrazolone congeners of the marketed drugs aspirin, indomethacin, probenecid, telmisartan, bexarotene, niacin (vitamin B3), and the active metabolite of the recently-launched immuno-modulatory agent, BG-12 (Tecfidera). The ability of a tetrazolone group to serve as a bioisostere of a carboxylic acid, and to improve drug pharmacokinetic profiles is also highlighted.