Photodecarbonylation of 1,3-dithiophenyl propanone: using nanocrystals to overcome the filtering effect of highly absorbing trace impurities.

Irradiation of crystalline 2,4-dimethyl-2,4-di(thiophen-3-yl)pentan-3-one (1) resulted in photodecarbonylation and radical combination to give 2 with >99% selectivity. However, extended irradiation led to no more than ca. 8% conversion due to highly absorbing unidentified trace impurities that act as filters. We report here a simple procedure to improve the reaction efficiency by taking advantage of nanocrystalline suspensions prepared by the reprecipitation method, which leads to shorter reaction times and quantitative yields.