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. However, undesirable interactions between the nucleophile and the leaving group activator limit 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 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.

Development of a triazinedione-based dehydrative condensing reagent containing 4-(dimethylamino)pyridine as an acyl transfer catalyst.

A new triazinedione-based reagent, (N,N'-dialkyl)triazinedione-4-(dimethylamino)pyridine (ATD-DMAP) was developed for the operationally simple dehydrative condensation of carboxylic acids. This reagent comprises an ATD core and DMAP as the leaving group, which is liberated into the reaction system to accelerate acyl transfer reactions. Upon adding ATD-DMAP to a mixture of carboxylic acids and alcohols in the presence of an amine base, the corresponding esters were formed rapidly at room temperature. Moreover, dehydrative condensation between carboxylic acids and amines using ATD-DMAP proceeded in high yield.