The azirinyl ester 2 (R = Bu t ) has been generated by thermolysis of t-butyl 2-azidoacrylate. It is too unstable to allow its full characterisation but it has been intercepted by Diels-Alder cycloaddition to several dienes. Addition to a chiral diene 8 is highly diastereoselective. ... The title azirine, generated from t-butyl 2-azidoacrylate in boiling heptane, adds to electron rich dienes with high diastereoselectivity. ... The product from step ii in Scheme 1 was a 3:1 mixture ...