Thietanes are pharmaceutically important cores of some biological compounds and intermediates of organic synthesis. Various thietanes were prepared from thiiranes via ring expansion through a reaction with trimethyloxosulfonium iodide in the presence of sodium hydride. The reaction process is a nucleophilic ring-opening reaction of thiiranes with dimethyloxosulfonium methylide, generated from trimethyloxosulfonium iodide and sodium hydride, and subsequent intramolecular displacement (cyclization) of thiolates to the dimethyloxosulfonium moiety. The current method provides a new strategy for efficient preparation of thietanes from readily available thiiranes.
Direct 1,2-oxosulfenylation of acetylenic sulfones with dimethyl sulfoxide (DMSO) is realized under microwave irradiation. The current method provides a direct and efficient route to synthesize β-keto thiosulfones from acetylenic sulfones and DMSO, featuring metal-free, low cost, and convenient advantages. The mechanistic investigations in-dicate that acetylenic sulfones first react with DMSO to generate sulfonium ylides through the nucleophilic addition, cyclization, and 4e ring opening. The sulfonium ylides and the DMSO-generated dimethyl sulfide at the aid of the ylides undergo a radical process to form β-keto thiosulfones under heating.
Various functionalized thietanes
were prepared from thiiranes via
an electrophilic ring expansion with rhodium carbenoids as electrophiles
generated from safe and readily accessible dimethylsulfonium acylmethylides.
The reaction appears to proceed through electrophilic metallocarbenoid-induced
activation of thiiranes, nucleophilic ring-opening of the activated
thiiranes with dimethyl sulfide as a transient nucleophile, and nucleophilically
intramolecular cyclization. The Umpolung from the nucleophilic ylides
to the electrophilic carbenoids plays an important role in both the
activation and ring opening of thiiranes and subsequent cyclization.
The current method provides a new strategy for the efficient preparation
of functionalized thietanes from readily available thiiranes.
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