Exceptional design of super/hyperbases based on spiro‐alleneic structures in gas phase: A density functional theory study

Abstract

AbstractIn this investigation, some of the designed spiro‐alleneic derivatives with variety electron‐donating substituents have been studied by B3LYP/6‐311 + G(d,p) level of theory to assess their potential as strong hyperbases and superbases. The results showed that the protonation at alleneic C (sp) site gives 14 novel neutral organic bases with significant proton affinities (PAs) = 252.83–318.44 kcal·mol−1, in which six of them are hyperbases and the rest of them are superbases. The PAs of designed spiro‐alleneic derivatives were improved by substitution of electron‐releasing groups on the molecular structure. Two indices of aromaticity, nucleus‐independent chemical shift (NICS) and harmonic oscillator model of aromaticity (HOMA), were also applied for the explanation of basicity of three spiro‐alleneic derivatives, which indicates that cyclopropene and cycloheptatriene rings on some of the designed structures turn aromatic upon protonation of alleneic central carbon atom.