Design of Exceptional Strong Organosuperbases Based on Iminophosphorane and Azaphosphiridine Derivatives: Harnessing Ring Strain and Aromaticity to Engineer Neutral Superbases

Abstract

A new class of non-ionic organosuperbases was designed using iminophosphorane and azaphosphiridine frameworks, and their gas phase proton affinity (PA) and gas phase basicity (GB) were assessed by using density functional theory computations. The utilized strategy for tailoring the organosuperbases is based on stimulating of ring opening upon protonation bearing substituents which have the ability of positive charge delocalization. After protonation, most of the superbases formed positive aromatic rings (C 3 H 3 + and C 7 H 7 + ). This strategy led to the design of organobases with exceptional basicity in the range of 1013-1317 kJ mol À 1 . Five designed organosuperbases show the PA values > 1254 kJ mol À 1 , above the range of a hyperbase. To better comprehend the basicity of the compounds, the aromaticity indices (NICS and HOMA data) associated with the organosuperbases and their corresponding conjugate acids have been calculated and compared with each other.[a] Dr.

Strong Bases Design: Predicted Limits of Basicity

“…Both GB and p K a are widely used to rank different families of superbases, − and both are computable by means of quantum chemistry, although p K a requires more effort. That encourages the theoretical design of new organic superbases in silico , usually yielding high values of GB for large carbon-protonated structures with lots of electron-donating groups. − However, none of these superbasic structures claimed to be record-breaking have been implemented in vitro . It appears that very high basicity implies new deprotonation sites on the hydrocarbon skeleton making the neutral base unstable against self-deprotonation.…”

Substituted ketenes offer exceptional carbon bases in gas phase: Computational study by density functional theory method

“…In most cases, the basicity of the designed compounds exceeds the superbasicity limit. [ 32–36 ] In this work, we decided to systematically investigate cyclopropene and methylenecyclopropene‐substituted ketene derivatives 1–15 by the density functional theory (DFT) method to check whether these frameworks can be considered as new organic superbases (Scheme 1).…”