Selenium oxide conjugate

Dehydration of cortisone (198) affords the diene 199. This is then converted to ketal 200. The selectivity is due to hindrance about both the 11- and 20-carbonyl groups. The shift of the double bond to the 5,6-position is characteristic of that particular enone. Treatment of protected diene 200 with osmium tetroxide results in selective oxidation of the conjugated double bond at C-16,17 to afford the cis-diol (201). Reduction of the ketone at C-ll (202) followed by hydrolysis of the ketal function gives the intermediate 203. Selenium dioxide has been... 

Yur ev and Khmel nitskii39 developed a synthesis of selenophene and its homologs from the reaction of paraffins, olefins, or conjugated dienes with selenium dioxide in the presence of chromic oxide on alumina at 450°-500°C. 

Evidence for the preferential formation of the rraRS-substituted product of selenium dioxide allylic oxidation is seen in the synthesis of part of (13Z)-retinoic acid (equation 48). Reaction took place exclusively at the exocyclic double bond without rearrangement. Allylic oxidation of this nature has also been used in the synthesis of 6-conjugated 2-pyrones (equation 49). This intermediate was employed in the total synthesis of natural pyrones such as yangonin. 

Amax 263 mfjL. In accord with the assigned structure there was no resonance for a vinyl proton in the NMR spectrum. Selenium dioxide oxidation of 69 gave the conjugated ketone 74, v ax I , nd 1628 cm . The single vinyl proton in the NMR spectrum of this compound appeared at S 6.02. Catalytic reduction of 74 to 70 proved that rearrangement had not occurred in this series of reactions. 

Hanten Synthesis. A hapten suitable for conjugation to a carrier protein was synthesized as outlined in Figure 1. Basically, The Diels-Alder addition of hexachlorocyclopentadiene and cyclopentadiene gave 4,5,6,7,8,8-hexachloro-3a,4,7,7a-tetrahydro-4,7-methanoindene that was oxidized with selenium dioxide to l-exo-hydroxy-4,5,6,7,8,8-hexachloro-3a,4,7,7a-tetrahydro-4,7-methanoindene as described (UJ. 

The cheletropic reaction between conjugated dienes and sulfur dioxide yields cyclic sulfones. However, the isolated adducts of selenium dioxide and dienes possess the selenalactone structures (174). The only apparent explanation for the different stabilities of the cheletropic products (175) is that selenium is softer and tends to avoid a higher oxidation state. 

Many reports of selenium relate to its use as a source of double bonds. Continuing this theme, phenols are formed from cyclohexenones by phenyl-selenation (PhSeCl) and oxidative removal of the selenyl group (MCPBA). In their turn cyclohexenones have been prepared by a similar sequence. The interesting point here is that the double bond can be inserted at the less substituted conjugated position by base isomerization of the phenylselenocyclo-hexanone. For example, the phenylseleno-group in the cyclohexanone (283)... 

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