Cyclopropane Synthesis via Cycloaddition

Aliphatic diazo compounds bearing electron withdrawing groups are moderately stable and can be easily prepared from readily available precursors. Photolysis of these diazo compounds or thermolysis in the presence of a metal salt (Cu, Rh reaction are among the most widely applicable protocols of cyclopropanations. 

Finally, a fairly convenient protocol for carbene transfer reactions utilizes species like ICH(R)ZnI (a carbenoid), generated in situ by the interaction of 1,1 -di-iodides, RCHI2, with a zinc-copper pair (Simmons-Smith procedure, reaction 

Cyclopropanation of enol ethers, for example the conversion of 399 - 400, proceeds especially easy under Simmons-Smith conditions. This reaction offers additional options for the synthetic utilization of carbonyl compounds capable of forming enol ethers. Some of them will be considered later in this chapter (see Section 2.23.2). 

Here again it is not an exaggeration to claim that, in planning a synthesis, if it becomes expedient to resort to a cyclopropanation of the double bond, there should be no doubt about the possibility of selecting suitable conditions to achieve this conversion. 

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