Viability of 4,5‐Dihydro‐1,2,3,4‐oxatriazoles Reinvestigated

Abstract

The first procedures to prepare 4-bromo-4-methylpentanal and 4-azido-4-methylpentanal are reported. The latter compound and also the parent 4-azidobutanal do not lead to 4,5-dihydro-1,2,3,4-oxatriazoles by intramolecular 1,3-dipolar cycloaddition, although it was claimed to be so in the literature. The NMR spectroscopic data of such heterocycles reported previously do not agree with those of similar substances and are incompatible with (13)C NMR spectroscopic chemical shifts calculated by quantum chemical methods in the presented work. These calculations show furthermore that the intramolecular cycloaddition of 4-azidobutanals to give the title compounds is strongly endothermic and thus most probably not possible.