Chemical Reactivity Controlled by Negative Hyperconjugation: A Theoretical Study

Abstract Negative hyperconjugation is a general phenomenon that can be observed in many areas of chemistry. The knowledge of its impact on structural parameters and conformational issues is well established, but little is known about its importance for chemical reactivity. Here we present a systematic study of different aspects of negative hyperconjugation on the reactivity of complex heterocyclic systems using density functional theory. Intermediates from the reaction of nitrogen‐based nucleophiles with bis(1,3,4‐thiadiazolo)‐1,3,5‐triazinium halides serve as benchmark systems to demonstrate the effects of negative hyperconjugation on bond lengths, on the relative stability of conformational isomers and transition structures and, most importantly, on the different reaction pathways of these species. The computational results provided here are in part supported by experiments reported elsewhere.