Regioselective Arene and Heteroarene Functionalization: N-Alkenoxypyridinium Salts as Electrophilic Alkylating Agents for the Synthesis of α-Aryl/α-Heteroaryl Ketones

A direct regioselective functionalization of arenes and heteroarenes using N-alkenoxypyridinium salts as electrophilic alkylating agents for the synthesis of α-aryl/heteroaryl ketones has been developed. The method generates alkylating agents from alkynes and N-pyridine oxide followed by site-selective electrophilic substitution with a broad range of arenes and heteroarenes including benzene derivates, phenols, ethers, indoles, pyrroles, furans, and thiophenes in one pot. Kinetic isotope effect measurements and DFT studies reveal that this reaction likely proceeds through a carbon-cation intermediate.