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