Allenes selenium electrophiles

Selenium electrophiles add to conjugated dienes, only forming 1,2-adducts. Although Maricovnikov addition is seen, only a few examples have been reported. With allenes the additions are re ospeciric, with the i enylseleno group usually adding to the rp-carbon. Unfortunately, all four stereoisomers of halide attadc are seen with unsymmetrically substituted allenes. ... 

A number of useful enantioselective syntheses can be performed by attaching a chiral auxihary group to the selenium atom of an appropriate reagent. Examples of such chiral auxiliaries include (49-53). Most of the asymmetric selenium reactions reported to date have involved inter- or intramolecular electrophilic additions to alkenes (i.e. enantioselective variations of processes such as shown in equations (23) and (15), respectively) but others include the desymmefrization of epoxides by ringopening with chiral selenolates, asymmetric selenoxide eliminations to afford chiral allenes or cyclohexenes, and the enantioselective formation of allylic alcohols by [2,3]sigmafropic rearrangement of allylic selenoxides or related species. 

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