Synthesis of cyclopropanes

• irreversible cyclisation • Too much ring strain

• Specific starting material is required • Must have an EWG (scope of molecules which can be synthesised is limited)

• a singluar pair of electrons in an sp² orbital • empty p-orbitals • can act as either a nucleophile or an electrophile • favoursed if R = halogen

• 1e- in the sp² orbital • 1e- in the p-orbital • Unpaired electron hence as similar to radicals • Favoured if R = alkyl

akenes (benefit because really common functional group)

• Generated via α-elimination

• React in a concerted fashion with alkenes (both new C-C bonds formed simultaneously), so alkene geometry is retained in the cyclopropanes product • Are electrophilic, and thus react preferentially with electron-rich alkenes

• Sterochemistry is conserved within the product

• Can be generated via decomposition of diazo compounds • Using light or heat

• Because this reaction isn’t concerted (stepwise), it is non spectrospecific - form two different isomers • This is slower due to having to wait for one of the electrons to revert it’s spin

• Are metal-bound species that exhibits carbene-like reactivity • Has a nucleophilic side (metal) and an electrophilic side • Are typically more stable, and often more selective, than free carbenes

• Zn is nucleophilic side, I is electrophilic side • Concerted syn addition (bonds broken and formed at same time), so alkene geometry is conserved in the product