o-lithiothiophenol equivalents: Generation, reactions, and applications in synthesis of hindered thiolate ligands

Eric Block, Venkatachalam Eswarakrishnan, Michael Gernon, Gabriel Ofori-Okai, Chantu Saha, Kaluo Tang, Jon A Zubieta

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Abstract

Treatment of 2-(phenylthio)tetrahydropyran (11) with tert-butyllithium in THF-HMPA at -90°C followed by chlorotrimethylsilane or chlorotriethylsilane and then mercuric chloride-hydrogen sulfide affords 2-(trimethylsilyl)benzenethiol (13) or 2-(triethylsilyl)benzenethiol (14), respectively. Compounds 13 and 14 can also be obtained directly from thiophenol by conversion of the latter to lithium 2-lithiobenzenethiolate (16) followed by quenching of a THF solution of 16 at -78°C with an equivalent of the appropriate chlorosilane; by this same procedure, 4-tert-butylbenzenethiol can be converted into 4-tert-butyl-2-(trimethylsilyl)benzenethiol (18) via lithium 4-tert-butyl-2-lithiobenzenethiolate (17) and 2-naphthalenethiol can be transformed into 3-(trimethylsilyl)-2-naphthalenethiol (31) via lithium 3-lithio-2-naphthalenethiolate (30). Reaction of 13 with n-butyllithium in hexane followed by chlorotrimethylsilane gives 2,6-bis(trimethylsilyl)benzenethiol (15) together with products derived from lithiation of the silyl methyl groups. Treatment of a solution of 16 in THF with dichlorodimethylsilane, dichlorodiethylsilane, 1,2-dichlorotetramethyldisilane, or 1,2-bis(chlorodimethylsilyl)ethane affords bis(2-mercaptophenyl)-dimethylsilane (23), bis(2-mercaptophenyl)diethylsilane (24), 1,2-bis(2-mercaptophenyl)tetramethyldisilane (25a), or 1,2-bis[(2′-mercaptophenyl)dimethylsilyl]ethane (25b), respectively. Oxidation of 23 yields 11,11-dimethyl-11H-dibenzo[c,f]-[1,2,5]dithiasilepin (26). Treatment of 17 with diethyldichlorosilane and dichlorodiphenylsilane affords bis(5-tert-butyl-2-mercaptophenyl)diethylsilane (27) and bis(5-tert-butyl-2-mercaptophenyl)diphenylsilane (28), respectively. The latter compound upon exposure to air gives 29, the diphenyl analogue of 26. Thiophenol can be transformed into 1,2-benzenedithiol (32a) by way of 12; similarly 4-tert-butylbenzenethiol can be converted into 4-tert-butyl-1,2-benzenedithiol (32b). Compound 32a can be further transformed into 1,2,3-benzenetrithiol (34) via a trilithio species 33. The 1H and 13C NMR spectra of dilithio salts 16 and 17 were determined.

Original languageEnglish (US)
Pages (from-to)658-665
Number of pages8
JournalJournal of the American Chemical Society
Volume111
Issue number2
StatePublished - 1989
Externally publishedYes

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ASJC Scopus subject areas

  • Chemistry(all)

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