Nature Chooses Rings: Synthesis of Silicon-Containing Macrocyclic Peroxides

The reactions of 1,2-bis­(dimethylchlorosilyl)­ethane (1), 1,2-bis­(dimethylchlorosilyl)­ethene (6), and 1,2-bis­(dimethylchlorosilyl)­ethyne (7) with gem-bis­(hydroperoxides) 2a–h and 1,1′-bis­(hydroperoxy)­bis­(cycloalkyl)­peroxides 4a–c were found to proceed in an unusual way. Thus, the reactions do not give the expected polymeric peroxides; instead, they produce cyclic silicon-containing peroxides containing 2, 4, or 6 silicon atoms in the ring: 9- (3a–h), 12- (5a–c), 18- (8, 12), 24- (9, 10), 27- (13), and 36-membered (11) compounds. The size of the rings produced in the reactions increases in the series 1,2-bis­(dimethylchlorosilyl)­ethane < 1,2-bis­(dimethylchlorosilyl)­ethene < 1,2-bis­(dimethylchlorosilyl)­ethyne. The resulting 9- and 12-membered cyclic peroxides are stable under ambient conditions. These compounds were isolated by chromatography and characterized by 1H, 13C, and 29Si NMR spectroscopy, X-ray diffraction, elemental analysis, and high-resolution mass spectrometry. The yields vary from 77 to 95%. Structures of the larger-size rings (18-, 24-, 27-, and 36-membered peroxides) were confirmed by 1H, 13C, and 29Si NMR spectroscopy using 2D (COSY, HSQC, and HMBC), 2D DOSY 1H, 3D 1H–29Si HMBC-DOSY NMR experiments, and elemental analysis.