Cascade [5 + 1] Cycloaddition of 1-Diazonaphthalen-2(1 <i>H</i> )-ones with Sulfoxonium Ylides for the Synthesis of Functionalized 1 <i>H</i> -Naphtho[1,2- <i>e</i> ][1,3,4]oxadiazines

We developed a novel protocol for the synthesis of functionalized 1<i>H</i>-naphtho[1,2-<i>e</i>][1,3,4]oxadiazines (NODZs) <b>3</b> from 1-diazonaphthalen-2(1<i>H</i>)-ones with sulfoxonium ylides via a [5 + 1] cycloaddition. This process involves heating a mixture of substrates with DCM catalyzed by Sc(OTf)₃, resulting in the cleavage of a C═S bond and the formation of C-O and C═N bonds. The reaction consists of a [3 + 2] cycloaddition followed by intramolecular cyclization, coupled with the elimination of DMSO and an H atom through [1,3] σ-migration. Significantly, 1-diazonaphthalen-2(1<i>H</i>)-one acts as a C5 synthon, enabling capture by sulfoxonium ylides. This work demonstrates the utility of 1-diazonaphthalen-2(1<i>H</i>)-one as a C5 synthon and paves the way for synthesizing diverse cyclic structures via different cycloaddition strategies. These methodologies may also facilitate the one-pot synthesis of functionalized <i>N</i>-oxadiazolines and their derivatives for combinatorial applications.