Polyaza 𝛼-oxoketene 𝑆,𝑁-acetals can exist as either enamino or imino tautomeric forms. Based on the spectroscopic data and structural analysis of one of the 𝑆,𝑁-acetals, the stereochemistry was unambiguously assigned as an all-𝐸-configuration. The crystal structure confirms the enamino structure and shows extensive use of C-H…X (X = N, O, and S) weak hydrogen bonding interactions, thereby generating a 3-dimensional network in solid state.
