Using sunlight to incorporate CO2 into alpha-amino ketones

The research group of Masahiro Murakami at Kyoto University (Kyoto, Japan; www.sbchem.kyoto-u.ac.jp/murakami-lab) have synthesized a promising pharmaceutical precursor using only sunlight (as energy source) and CO2 (as co-reagent). The solar-driven process involves two consecutive reactions (diagram): first, light transforms an alpha-methylamino ketone into an energized, cyclic intermediate through intramolecular rearrangement; then, CO2 is incorporated into highly-strained (thus highly reactive) ring to form a cyclic amino-substituted carbonic acid diester, which could be useful precursor for chemical syntheses. The second step, which occurs in the dark, can be carried out in the same glass reaction vessel by simple addition of a base (cesium carbonate), and heating to 60°C. An 83% yield is achieved after 7 h sunlight irradiation and 10 h for CO2 capture. Murakami says the technique is very simple to perform and that even diffuse sunlight on cloudy days is enough to drive the process. Also, the process is very adaptable because a wide variety of alpha-methylamino ketones could be used as starting materials, he says. Although the Murakami consecutive process does not involve CO2 reduction into carbohydrates, its mechanistic energy…