Selenides, allyl alkenyl

Generation of a selenoaldehyde, a selenoketone, and telluroaldehydes by [3,3] sig-matropic rearrangement of allyl alkenyl selenides and tellurides [139]... 

Selenals, selones, and tellurals generated in situ via [3,3] sigmatropic rearrangements of allyl alkenyl selenides and tellurides 167 can be trapped by 2,3-dimethyl-l,3-butadiene affording the expected cycloadducts (Equation 68) <1995CL135>. Higher yields were noted in less-hindered cases where the selenium and tellurium aldehyde... 

Alkyl and allyl sulfides and selenides can be transformed readily into the corresponding alkyl and alkenyl halides respectively. This reaction takes advantage of the easy formation of the corresponding sul-fonium and selenonium salts on reaction with alkyl halides, alkyl bromoacetates or bromine - (Scheme S3). A related process involves the intermediary formation of a selenoxide and its further reaction with hydrochloric or hydrobromic acids. ... 

Lithiated allylic sulfoxides may be a-alkylated and the resulting products subjected to [2,3]-sigmatropic rearrangement induced by a thiophile to give allylic alcohols (eq 43). In contrast, alkenyl aryl sulfoxides produce a-lithiated species which are alkylated with Mel or PhCHO in good yields (eq 44). LDA has also been used to metalate allylic and propargylic selenides as weU as aryl vinyl selenides. ... 

Reductive cleavage of sulphides, selenides, and tellurides on Raney nickeP and cleavage by lithium in THE, leading to secondary or tertiary alkyl-lithium compounds, are useful synthetic operations novel variations are involved in the cleavage of dialkenyl sulphides with EtjSiH (giving low yields of silyl sulphides) and of alkenyl, aryl, and allyl sulphides and selenides with PPhj and... 

In analogy with the sulphur compounds, alkenyl, aryl, and allylic selenides smoothly couple with Grignard reagents in the presence of catalytic quantities of nickel(ll)-phosphine complexes to give unsaturated hydrocarbons (e.g. Scheme 25). Allylic selenides react by both direct and 1,3-substitution to give regioisomeric mixtures of products. 

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