Homo-Michael-type additions

The [3+2] cycloaddition reaction with indoles developed by Kerr and co workers led to the belief that cyclopropanes had a very similar reactivity to a,p-unsaturated carbonyl moieties in their ability to react with nucleophiles in a homo-Michael type addition. Hence, the use of substituted cyclopropanes as precursors for cycloaddition reactions has become very popular due to their ability to undergo ring-opening while in the presence of a Lewis acid. 

Reaction of monosubstituted hydrazines with the readily available spirocyclic cyclo-propanedicarboxylates (163) gives 1-substituted l,4,5,6-tetrahydropyridazin-3(2/i)-ones (164) in a one-pot reaction (Scheme 123). Initial attack is thought to be a homo-Michael type of addition by the substituted hydrazine nitrogen decarboxylation occurs under the reaction conditions. The formation of the alternative pyridazinone (165) by attack of the unsubstituted hydrazino nitrogen was only observed (<5%) with (4-chloro-2-methylphenyl)hydrazine <93H(36)219>. 

Most frequently, cuprates or other C-nucleophiles are employed in homo-Michael additions which often serve as the basic reactions for constructing natural product skeletons The preparation of optically active compounds also profits from this type of... 

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