With the aid of a microreactor, chemists in Japan have combined light-mediated and thermal reactions to improve the synthesis of vitamin D-3. Many foods are fortified with vitamin D-3, but industrial routes to the vitamin have yields of less than 20%. The penultimate step in industrial syntheses, a light-mediated isomerization, is not selective, and it’s tough to clear away by-products of the reaction. Shinichiro Fuse, a member of a group led by Takashi Takahashi of Tokyo Institute of Technology, described a continuous-flow microreactor process that avoids these problems. The team’s microreactor performs the light-mediated isomerization and the next step in the synthesis, a thermal isomerization, at the same time (Chem. Commun., DOI: 10.1039/c0cc02239j). The process reduces purification waste and has an isolated vitamin D-3 yield of 32%, the highest yield so far that doesn’t involve expensive specialized laser equipment. This is the first time researchers have combined thermal and photoreactions in a single microreactor, Fuse notes. Fuse and coworkers are now working to make analogs of vitamin D-3 with their system.