Selenocarbonyl groups

Cations [(RR C=Se)2I]+ In the case of A-methylbenzothiazole-2(3//)-selone (mbts), one equivalent of iodine provides a molecular adduct in dichloromethane solution 50 crystallisation, however, leads to a ionic compound of the type [(RR C Se)2I]+I3, 43 This compound was the first one reported in the literature featuring a two coordinated iodine(I) complex with two donor molecules containing selenocarbonyl groups. In the solid state two molecules of mbts are linearly coordinating a central I+ ion to give a slightly... 

The relatively poor 2p-4p r-overlap of carbon-selenium double bonds makes selenocarbonyl groups less stable than the corresponding thiocarbonyl and carbonyl analogs. Until the mid-1970s, only those selenocarbonyl compounds where the bond order of the C=Se bond was lowered by coordination or resonance were known. However, the isolation of two deep blue, thermally stable selones (46) and (47) proved that such... 

Studies on the chemistry of selenocarbonyl compounds have been increasingly reported din ing the past decade. Initially, the focus had been mainly on the development of new synthetic methods for the preparation of selenocarbonyl compoimds. The various achievements have allowed the evaluation of a wide range of applications. X-ray molecular structures of some derivatives have been disclosed. Selenocarbonyl compoimds that are relatively stable but still retain high reactivity have exhibited unique reactions. The present review outlines the characteristic features of selenocarbonyl compounds. Their syntheses and reactions are classified on the basis of reaction patterns rather than the substituents adjacent to selenocarbonyl group. Several types of metal complexes having selenocarbonyl groups are described as well. 

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

The selenocarbonyl compounds can be classified into three categories on the basis of the substituents adjacent to the carbon atom of the selenocarbonyl group (Scheme 1). 

The reactivity and reaction patterns of selenocarbonyl compounds vary considerably from the compounds in categories A-C in Scheme 1. The substituents adjacent to the selenocarbonyl group attenuate the polarity of the compounds. As a result, less polar selenoaldehydes and selenoketones behave as olefins, and the carbon selenium double bond of heteroatom-substituted selenocarbonyl compounds becomes more polar. In this section, a variety of transformations of selenocarbonyl compounds have been classified based on the reagents reacted with selenocarbonyl compounds. 

One of the synthetic procedures of metal complexes of type 53 is the reaction of metal-carbene complexes with selenium sources such as alkyneselenolates [109]. The stability of selenobenzaldehyde is enhanced by coordinating to metal carbonyls, and the reactivity of the complexes has been studied [110]. For example, the selenobenzaldehyde complexes reacts with methylthiohexyne even at - 30 °C to afford another type of complex where the selenium atom of the selenocarbonyl group is still coordinated to the metal (Eq. 29) [llOd]. 

Like the reaction in Eq. 29, the selenoamide dianion 117 is generated by reacting iST-benzyl selenobenzamide with 2 equiv of BuLi (Eq. 45) [78]. Alkylation of 117 takes place selectively at the carbon atom adjacent to the nitrogen atom to the selenocarbonyl group. Alkyl halides, acid chlorides, and oxiranes are used as carbon electrophiles. Trimethylsilyl chloride performs silylation of 117, giving the selenoamide 118. 

Certain benzyl sulfides are converted to the benzyl methyl ethers by reaction with thallium(III) nitrate in methanol (21). The soft donor characteristic of thiocarbonyl and selenocarbonyl groups has been exploited in the replacement of hydroxy functions with halogen atoms (22). Thus, xanthates and thiobenzoates are activated by alkyl halides. 

Sulfuric acid dimethyl sulfoxide Carbonyl from selenocarbonyl groups s. 27, 231... 

Wu R, Barr ME, Hernandez G, Oiji CC, Silks LA. Recent progress in the synthesis and application of chiral selones exploitation of the selenocarbonyl group. Recent Res. Devel Org. Bioorg. Chem. 1998 2 29-42. 

---