Intramolecular iron(II)-catalyzed addition reactions of propargyloxycarbonyl azides

The Fe(II)-catalyzed dediazotation of the propargyl-oxycarbonyl azides 2-4 was studied. In the case of phenyl- (2) and n-butyl-substituted (3) alkynes the products 5 and 6 of an intramolecular syn-aminochlorination were isolated in excellent yields (81-99%). The t-butyl-substituted substrates 4 yielded the 4-alkylidene-5-alkoxyoxazolidinones 7-9 (91-99%) which did not contain a chlorine atom. Their formation is explained by a consecutive ionic reaction which occurs after the cyclization.