Photocarboxylation of Arylated 2H-Azirines Exploiting Continuous Flow Technology

Abstract

A robust and efficient continuous flow set-up is presented for the orchestrated use of CO₂ gas and photochemistry in flow mode. This study explores the catalyst-free cycloaddition between azomethine ylides generated in situ from simple 2H-azirines and CO₂. Using UV−A light (365 nm) as energy source and CO₂ as inexpensive and abundant building block provides an attractive strategy affording isomeric oxazolones which were subsequently aromatised to yield novel oxazole products in a convergent manner. Continuous flow processing substantially improves the reaction performance allowing for the safe exploitation of this intriguing transformation. This enables the effective fixation of CO₂ to generate valuable building blocks that can be scaled to gram scale with ease.