Selenides, allenyl phenyl

Furthermore, allenyl phenyl selenides have been prepared by alkylation of 1-lithioallenyl phenyl selenide, itself produc on metallation of phenyl 1-propynyl selenide or of allenyl phenyl selenide - (Scheme 42). 1-Lithioallenyl phenyl selenide has poorer nucleophilic properties than that of a-seleno-allyllithiums, since the reaction of the former with 2-phenyl-1-bromoethane gives predominantly styrene, whereas the latter leads to products of substitution in good yield. ... 

Metalloamides are suitable for the synthesis of 1-metallovinyl aryl selenides (Scheme 44) and 1-metalloallenyl phenyl selenides (Scheme 45) from the corresponding vinyl or allenyl selenides. The synthesis of the latter organometallics is even more conveniently achieved by metallation of l-phe-nylseleno-l-propyne or by a two-step, one-pot sequence of reactions fiom 2-chloroallyl phenyl selenide (Scheme 45). 

Many total syntheses take advantage of the temporary introduction of a sulfide or a sulfone group. As illustrated in Scheme 5, an allenyl sulfone is a key intermediate in the synthesis of brassinolide reported by Back [31a]. It is obtained through sequential addition of TsSePh, base-promoted migration of the double bond, and oxidative elimination of the phenyl selenide. The addition of EtSH to the... 

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