In situ photo-on-demand phosgenation reactions with chloroform for syntheses of polycarbonates and polyurethanes

Abstract

Phosgene is an important carbonyl source for industrial production of polycarbonates (PCs) and polyurethanes (PUs). However, since it is highly toxic, alternative compounds and/or new phosgenation reactions have been explored for safety reasons. Given this background, we found a novel photochemical reaction enabling the synthesis of phosgene from chloroform. Subsequently, we developed new phosgenation reactions and reaction systems, and the key objective was “safe application” to organic synthesis. This focus review reports our recent use of in situ photo-on-demand phosgenations of alcohols and amines in synthesizing PC, PU, and their precursors, such as chloroformates, carbonate esters, and diisocyanates, in batch reaction systems, which are preferable for laboratory or small-scale industrial syntheses. We believe that the present reactions have advantages over conventional phosgenation reactions, especially in terms of safety and environmental impacts, and are expected to make positive contributions to practical organic syntheses in both academia and industry.