Carbocationoids: a concept for controlling highly reactive cationic species

Carbocations, which are positively charged highly electrophilic intermediates, are efficacious for the direct alkylation of low-reactive nucleophiles. The utilization of carbocations in SN1 reactions relies on the activation of their precursors in the presence of a nucleophile, which limits the scope of acceptable nucleophiles. Here we report a strategy to conduct SN1 reactions involving unstable carbocations in an alternative stepwise procedure, which was demonstrated by the primary benzylation of various neutral nucleophiles. In the first step, carbocations were accumulated in a nucleophile-free solution in the form of carbocationoids utilizing the coordinative stabilization of triazinediones. Subsequently, the addition of these solutions in the second step enabled room temperature alkylation without the need for acidic additives. This methodology overcomes the inherent challenges of carbocations in SN1 reactions.