Silicon-Containing Macrocyclic Peroxides

An unusual thing happened to an international research team when its members set out to prepare new silicon-containing peroxides: Rather than obtaining oligomeric or polymeric products as expected, they produced unprecedented macrocyclic rings instead (Organometallics 2014, DOI: 10.1021/om500095x). Organic peroxides have been in high demand in industry and scientific research for more than 50 years as oxidants, polymerization initiators, cross-linking agents, and chemical building blocks. More recently, cyclic peroxides have attracted attention for their antimalarial, antiparasitic, and antitumor activity. Peroxides with –Si–O–O– fragments have similar applications but are much less developed. Aiming to prepare new types of these silicon-containing peroxides, Alexander O. Terent’ev of the Russian Academy of Sciences’ N. D. Zelinsky Institute of Organic Chemistry and his colleagues carried out a series of base-promoted reactions of difunctional chlorosilylethanes, -ethenes, and -ethynes with difunctional hydroperoxides (one shown). Rather than forming linear polymeric peroxides, they came up with cyclic peroxides containing two, four, or six silicon atoms arranged in nine- to 36-membered rings, depending on the reagents used. The team needed an assortment of mass spectrometry, X-ray, and NMR methods to elucidate the structures.