For the past several years, our group has studied the carbonylation of heterocycles using cobalt catalysts. 11,12 Recently, inspired by work of Jia and co-workers, 13 we have developed an efficient method for the carbonylation of 4- and 5-substituted oxazolines to oxazinones using the catalyst HCo(CO) 4 . 14 Given that HCo(CO) 4 is an effective olefinhydroformylationcatalyst, 15 we hypothesized that the reaction conditions used for ...