List of used abbreviations - RosDok - Universität Rostock

1. Synthesis of functionalized 2-(arylthio)benzoates by formal [3+3]
cyclizations of 3-arylthio-1-silyloxy-1,3-butadienes with 3-silyloxy-2-
en-1-ones and 1,1-diacylcyclopropanes
1.1 Introduction
Functionalized diaryl sulfides are pharmacologically important molecules which occur
in various natural products. For example, they are present in dibenzothiophenes, 9
varacins (lissoclinotoxins), 10 lissoclibadins, 11 cyclic sulfides, 12 and various other
natural products isolated from Streptomyces griseus. 13 Diaryl sulfides are
synthetically available by reaction of arenes with sulphur 14 and sulphur dichloride, 15
by condensation of organometallic reagents with chlorophenyl-sulfide 16 and by basemediated
reaction of chloroarenes with thiophenols. 17 These reactions often suffer
from their low regioselectivity and from the formation of polysulfides, due to the harsh
reaction conditions.
An alternative approach to diaryl sulfides is based on the use of sulfur-containing
building blocks in cyclization reactions. Hilt and coworkers reported a convenient
approach to diaryl sulfides by cobalt(I)-catalyzed [4+2] cycloaddition of alkynyl
sulfides with 1,3-butadienes. 18 Recently, Langer et al. studied 19 the synthesis of 3-
and 5-(arylthio)salicylates by TiCl4-mediated formal [3+3] cyclizations 20 of 1,3bis(silyloxy)-1,3-butadienes
21 with 3-silyloxy-2-en-1-ones. 22 Chan et al. reported the
synthesis of methyl 4,6-dimethyl-2-(phenylthio)benzoate by TiCl4-mediated [3+3]
cyclization of 4-trimetyhlsilyloxy-3-penten-2-one with 1-methoxy-3-phenylthio-1trimethylsilyloxy-1,3-butadiene.
23 I recently prepared 2-(arylthio)benzoates by
catalytic cyclizations of 3-arylthio-1-trimethylsilyloxy-1,3-butadienes with 1,1,3,3tetramethoxypropane.
24 In addition, the synthesis of 6-alkyl- and 6-aryl-2-
(arylthio)benzoates by cyclization of 3-arylthio-1-trimethylsilyloxy-1,3-butadienes with
13