Sulfurated intermediates, functionalized Sulfur compounds

There are many examples of /3-amido and /3-oxido functionalized organolithium compounds, which were prepared mainly using the stoichiometric version of the arene-promoted lithiation ". In this section, the preparation of the same type of intermediates by halogen-or sulfur-lithium exchange will be considered, using the catalytic version of the mentioned lithiation. 

Y = O) or —90°C (Y = NMe, S) gave the corresponding intermediates 427 resulting from a carbon-sulfur cleavage. Further reaction of these functionalized organolithium compounds with different electrophiles at the same temperature, followed by hydrolysis with water, yielded products 428 (Scheme 120) . 

Figure 2. Radioactivity chromatogram of sulfur compounds derivatized with monobromobimane. The reversed-phase HPLC separation is based on the hydrophobic properties of the bimane-sulfur adducts but peak area is based on "S-radioactivity of the compounds. At time 0 sulfite and thiosulfate impurities are present before addition of the hepatopancrease tissue homogenate. This was a 60 min experiment to determine the sulfide detoxifying functions of the hepatopancrease of the hydrothermal vent crab Bythograea thermydron. During this time the proportion of radioactivity in sulfide rapidly decreases and thiosulfate and sulfate accumulate as end products. Two intermediates, pi and p2 accumulate then decrease during the experiment. The two intermediates are believed to be polysulfides based on similar elution times of polysulfide standards. (Figure is the unpublished chromatograms from the data in Vetter et al. (24)-) continued on next page.

The potassio intermediates give excellent results in a number of derivatizations. For other functionalizations, particularly those with carbonyl compounds, potassium has to be replaced by lithium, this can be done most simply by addition of an equivalent amount of anhydrous lithium bromide, dissolved in THF. Although both vinyl ethers and the corresponding sulfides can be metallated in a short time, it is quite clear from the preparative experiments that the sulfides react faster [9]. A similar difference between oxygen and sulfur compounds has been observed in retaliations of other types of substrates. Some authors have invoked d-orbital effects to explain the easier retaliations of sulfur compounds [83], but an explanation on the basis of polarizability seems more satisfactory [84]. Using the kinetically very active bases mentioned, clean a-metallations of simple vinylic ethers and -thioethers can be realized at low temperatures. Under modified conditions two other processes have been observed [9,85] ... 

We have previously reported on the excellent properties of the mustard-type sulfur compound 12 (Fig. 11.3) as a scaffold for the synthesis of functional molecules. The nucleophilic displacement of the chlorides in 12 occurs in high efficiency with a variety of nucleophiles using on water conditions. These reactions occur via episulfonium ion intermediates, and are therefore uniquely assisted by the aqueous medium. ... 

Stabilized organolithium compounds, such as lithium enolate intermediates [5], a-organolithium compounds bearing electron-withdrawing groups (RSO, RSOj, CN, NOj, etc.) and heteroatoms such as sulfur [6], selenium and phosphorus as well as functionalized aryllithium compounds will not be consider in depth in this chapter due to the limited length of this review. 

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