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.