To gain mechanistic insights of the chemical reactions, we conducted DFT calculations using a polarized continuum model for DCM solvation at -10 °C to identify transition states and intermediates for acyclic and cyclic N-sulfonylimines (Figures ). The nucleophilic attack by negatively charged carbon atom of PINC on the electrophilic center of N-sulfonylimine yields Intermediate-1. The subsequent Intermediate-2 is formed by a nucleophilic attack of benzoic acid. Next, intramolecular cyclization at the carbonyl carbon and subsequent removal of triphenylphosphine oxide yields the desired 1,3,4-oxadiazole containing the product. Both imines have the same rate-limiting step where the PINC reagent attacks the carbonyl carbon and both steps have small activation energies (12.6 kcal/mol and 16.3 kcal/mol for the cyclic and acyclic imines respectively), suggesting both reactions will occur quickly (see Supporting text for reaction mechanism section for a detailed description). Scheme 3. Substrate scope for representative cyclic N-sulfonyl-imine with various carboxylic acids used as training data.