Organocatalysis Linked to Charge-Enhanced Acidity with Superelectrophilic Traits

Hydrogen bonding is ubiquitous throughout nature and serves as a versatile platform for accessing chemical reactivity. In leveraging this force, chemists have utilized organocatalysts to expand the spectrum of chemical reactivity enabled by hydrogen bonding and at the extreme proton transfer. Despite this broad utility, exploiting charge as a hydrogen-bond activation strategy is unknown for squaramide catalysts. Considering this deficiency, herein, we disclose a cationic squaramide-cyclopropenium organocatalyst displaying charge-enhanced acidity. Key to this advancement was cationic charge, linked to superelectrophilic traits and strong Bronsted acidity, allowing for the construction of unprecedented oxime ether functionality among other important chemical transformations. The origin of this remarkable reactivity was delineated by computational analysis and in-depth experimental mechanistic studies.

Automated summary

This study presents a cationic squaramide-cyclopropenium organocatalyst with charge-enhanced acidity, enabling novel chemical transformations. The origin of this reactivity was determined through computational analysis and in-depth experimental mechanistic studies.