Selenoxides acid, reduction with

Oxidation of alkyl iodides, bearing electron-withdrawing groups such as car-bomethoxy and sulfonyl at the a-carbon, with m-chloroperbenzoic acid results in clean elimination to give olefins [Eq. (27)]. This reaction involves reductive / -elimination of the intermediate iodosylalkanes, as observed in thermal peri-cyclic -elimination of sulfoxides and selenoxides. Exclusive syn stereochemistry in the reductive /1-elimination was established by deuterium labeling... 

P-Hydroxy selenides are conveniently prepared from epoxides by treatment with sodium phenylse-lenide (Scheme 32) and by the addition of benzeneselenenic acid and its derivatives to alkenes (Scheme 33), - -" although in some cases these reactions are not regioselective. Useful phenylseleno -etherification and -lactonization reactions have been developed which can be regioselective (equation 42 and Schemes 34 and 35). -" " Selenide- and selenoxide-stabilized carbanions have been used in addition reactions with aldehydes and ketones, - and the reduction of a-seleno ketones also provides a route to P-hydroxy selenides. ... 

The tricyclic lactone, 163, was also transformed to a yohimbine precursor by Polniaszek and Stevens (Scheme 3.26). Treatment of 163 with methoxide induced a double bond migration which was followed by Michael addition of methoxide. Subsequent oxidation and thermolysis effected selenoxide elimination to provide 166. Ozonolysis of the double bond followed by reduction yielded a mixture of bis-hemiacetals which were reduced with triethylsilane in trifluoroacetic acid to provide the tricyclic pyran 167. Reduction of the lactone and tritylation of the primary alcohol function afforded 168 which was subjected to xanthate ester elimination to give the enol ether 169. Oxymercuration-reduction and detritylation afforded the methylpyranoside... 

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