A Short Effective Preparation of Chiral N,3-Dimethyl-5,7-Dioxo-2-Phenylhexahydro-1,4-Oxazepines

Abstract
An improved two-stage procedure has been devised for the synthesis in 50% yield of the title compounds from ephedrine or pseudoephedrine enantiomers and dimethyl malonate using cyanuric chloride/pyridine to lactonise the intermediate ∊-hydroxyacids.