Shapiro reaction further functionalization

Removal of the carbonate ring from 7 (Scheme 1) and further functional group manipulations lead to allylic alcohol 8 which can be dissected, as shown, via a retro-Shapiro reaction to give vinyl-lithium 9 and aldehyde 10 as precursors. Vinyllithium 9 can be derived from sulfonyl hydrazone 11, which in turn can be traced back to unsaturated compounds 13 and 14 via a retro-Diels-Alder reaction. In keeping with the Diels-Alder theme, the cyclohexene aldehyde 10 can be traced to compounds 16 and 17 via sequential retrosynthetic manipulations which defined compounds 12 and 15 as possible key intermediates. In both Diels-Alder reactions, the regiochemical outcome is important, and special considerations had to be taken into account for the desired outcome to. prevail. These and other regio- and stereochemical issues will be discussed in more detail in the following section. 

The ability of the trisylhydrazone dianion to undergo alkylation further enhances the synthetic potential of the Shapiro reaction. The initial carbonyl alkylation of acetone trisylhydrazone dianion, followed by fragmentation to the functionalized alkenyllithium reagent and subsequent trapping with carbon diox-... 

The Shapiro reaction of tosylhydrazones with base has now been extended as a route to a wider variety of functionalized olefins. Thus, treatment of tosylhydrazones, which contain only a tertiary a-hydrogen, with lithium iso-propylamide, can now yield trisubstituted olefins. The yields are only moderate, but the procedure is convenient. Regiospecifically generated tosyl-hydrazone dianions may be trapped with aldehydes and ketones to give, on neutralization, /3-hydroxytosylhydrazones further treatment with alkyl-lithium reagents yields allylic and homoallylic alcohols. These procedures are exemplified in Scheme 21. 

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See also in sourсe #XX -- [ ]

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