Synthesis of Sulfanyl-, Sulfinyl-, and Sulfonyl-Substituted Bicyclic Dioxetanes and Their Base-Induced Chemiluminescence

The singlet oxygenation of 4-tert-butyl-3,3-dimethyl-5-(3-oxyphenyl)-2,3-dihydrothiophenes 5c−e bearing an acetoxy or methoxy group at the 2-position exclusively gave the corresponding sulfanyl-substituted bicyclic dioxetanes 2c−e, while that of 5a without 2-substituent mainly gave sulfoxide 11 along with a small amount of dioxetane 2a. These dioxetanes were sufficiently stable thermally to permit handling at room temperature. Sulfanyl-substituted dioxetanes, 2c and 2e, were further oxidized with m-chloroperbenzoic acid to afford the corresponding sulfinyl-substituted dioxetanes 3c, 3e and sulfonyl-substituted dioxetanes 4c, 4e. X-ray single crystallographic analysis was performed for 2c and 4e. Base-induced decomposition of the dioxetanes in DMSO gave light with a maximum wavelength λ_max^CL at 554 nm for 2a and 565 nm for 2e in moderate light yields, while sulfinyl-derivative 3e gave weak light with λ_max^CL = 795 nm and sulfonyl-derivative 4e gave very weak light with λ_max^CL = 848 nm.