Sulfur-, Stannane- and Selenium-Based Linkers

Linkers based on sulfur, stannane and selenium chemistry are certainly some of the most flexible systems, because these elements can favorably be tailored for the use as fragile points of attachment. 

The development of sulfone linkers, the exploration of sulfone based chemical transformations and cleavage strategies are an important objective in soHd-phase organic synthesis. This kind of Hnker (Tab. 3.7) has been used with thioethers [108], sulfoxides [109], sulfones [110], sulfonic acids and their corresponding derivatives [111]. Because carbon-sulfur bonds can be cleaved under very mild conditions, some Hnkers have been based on this effect. They can be cleaved under reductive conditions ]112, 113], photolytic conditions [114, 115] or with strong bases [116]. Various safety catch Hnkers have been developed based on the fact that thiols can be oxidized to sulfoxides and sulfones [112, 113]. 

Stannane based Hnkers (Tab. 3.8) are used for the StiUe reaction (see below, section 3.3.2.1) onsoHd supports [119]. Nicolaouetal. developed polymer-bound aUcenylstan-nanes to obtain the natural product (S)-zearalenone by an intramolecular StiUe reaction and a cyclative cleavage [120]. 

The preparation of solid-supported selenium resins and their application as linkers and reagents for sohd-phase synthesis have heen described [121, 122]. These reagents have proven to be useful for applications in sohd-phase and combinatorial synthesis because of their versatility and ease of handling. 

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