Odorless Diphenyl Diselenide and Disulfide: Syntheses and Applications

Abstract

phenyl]diselenide (3) and bis [4-(trimethylsilyl)phenyl]disulfide (31) are found to be odorless equivalents of the commonly used diphenyl diselenide and diphenyl disulfide, respectively. The diselenide 3 is shown to be useful in the preparation of odorless selenium(II) chloride 26 and selenium(IV) trichloride 28 that follow similar reactivity patterns to their phenyl derivatives and can be stored refrigerated under dry conditions. The corresponding selenium(II) bromide had to be prepared fresh from 3 before use. It is also shown that the trimethylsilyl group in the sulfide products can be protodesilylated quantitatively using TFA.The versatility and the overall synthetic utility of various reagents containing selenium and sulfur have been exemplified in their increasing use in synthesis. 1 Especially in the synthesis of complex natural products, these reagents have been indispensable. 2 During the last three decades we have seen the literature flooded with papers containing selenium-based reagents. Why has this exotic element, a member of the well known family of chalcogens, enjoyed such interest, even though the known toxicity of organoselenium compounds called for caution and their malodorous reputation made them doubly unattractive to any chemist who wanted a social life outside the laboratory? This is due to the mixed metallic and non-metallic nature of the element, its unique reactivity towards oxidation and reduction and the capacity of the selenium-based reagents to perform highly chemoselective transformations. 1,3 Among the selenium reagents, diphenyl diselenide is commonly employed for organoselenylation reactions because of its versatile reactivity (nucleophilic as well as electrophilic) depending on the reaction conditions and thus allows a myriad of transformations through a-seleno carbanions, 4 a-seleno carbeniums 5 and a-seleno carboncentered radicals. 6 Similarly, diphenyl disulfide is an important and powerful reagent for phenyl sulfanylation and related reactions that has closely followed the former in various applications. 7 The malodorous nature of these reagents has remained a potential drawback and it was only in 1998 that Nicolaou, Ruhland et al. expedited the polymer-supported selenium reagents that were odorless. 8During the last few years, we have systematically studied and developed odorless thiol and sulfide reagents and attempted to replace the commonly used malodorous sulfur reagents with odorless equivalents. 9 By elongating the carbon chain or substituting the aromatic ring with n-heptyl or, more effectively, a trimethylsilyl group (in the case of benzene and benzyl thiols), we found a surprising reduction of odor or no odor at all. 9f,10 In this paper, we present our successful approach to replace the foul smelling diphenyl diselenide and disulfide with bis[4-(trimethylsilyl)phenyl]diselenide and bis[4-(trimethylsilyl)phenyl]disulfide, respectively. Their syntheses and applications in various reactions are presented. Bis[4-(trimethylsilyl)phenyl]diselenideThe starting 1-bromo-4-(...