Catalytic Asymmetric Couplings of Ketenes with Aldehydes To Generate Enol Esters

With a little help from the ferrocenyl catalyst ((−)-1), a wide array of α-arylalkanoic acid derivatives can be produced from the catalytic asymmetric coupling of ketenes with aldehydes (see scheme). The enol esters are readily transformed into other useful families of compounds such as carboxylic acids and alcohols.