Selenothioic acids

Keywords Selenocarbonyl group, Selenoaldehydes, Selenoketones, Selenoamides, Selenoesters, Selenothioic acid S-esters, Diselenoesters, Selenourea, Selones... 

The reduction of selenoketones [75] and selenoesters [76] has been known to give selenides. The reduction of selenothioic acid S-esters having allyl groups also proceeds smoothly accompanied with cyclization to afford tetrahydroseleno-phenes with high stereoselectivity (Eq. 23) [77]. 

Neutral nitrogen nucleophiles can react with selenothioic acid S-esters [8 a] and diselenoesters [20 c] to afford selenoamides, whereas lithium salts of aromatic amines are reacted with selenoesters [78]. 

The reaction of l,3-dichalcogeno-2-selones with trialkyl phosphites has been used to synthesize perchalcogenofulvalenes, although the yields of the products are moderate (Eq. 24) [16,87]. On the other hand, the treatment of selenothioic acid S-esters and diselenoesters with trialkylphosphites gives phosphoryl sulfides and selenides in good yields (Eq. 25) [88]. 

The selenium counterparts of enolate ions, i.e., eneselenolate ions, can be generated by the deprotonation of enolizable selenoamides [101],selenoesters [102], and selenothioic acid S-esters [103]. The generated eneselenolate ions are reacted with trimethylsilyl chloride, aldehydes, selenoesters, propargyl bromides, and oxiranes to give the products 47-52. 

Sulfur- and Selenium-containing Compounds. A new route to a-thioalkyl-phosphonates (292) and -phosphinates (294) has been reported from the reaction of selenothioic acid S-esters (291) with phosphites and phosphinites, respectively. By-products (293), derived from the P(III) ester alkylating the Se atom, are formed in many cases. a-Phosphono-p-substituted a,P-unsaturated dithioesters (296), prepared from diethyl phosphonodithioacetate (295), undergo Diels-Alder reactions with enol and thioenol ethers to give excellent yields of novel 5-... 

Keywords Selenothioic acid Diselenoic acid Se-substituted selenothioate Se-substituted selenothioate Diselenoate... 

Selenothioic acid Sc-esters serve as thioacylating agents toward amines and alcohols. Similarly, selenothioic acid S-esters and diselenoic acid esters can be used as selenoacylation agents. In addition, their thiocarbonyl and selenocar-bonyl groups act as dienophiles. The reactions of S-substituted selenothioates with electrophiles under basic conditions were investigated in detail. 

Salts of the selenothio acids exist as resonance structures. This is indicated by the fact that the same compound can be obtained by two different routes. 

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