Methylenecyclopropanes in Elimination and Addition Reactions: Quantification of the Effects of Strain

Abstract

The effect of strain in 1,2-elimination reactions that form methylenecyclopropanes has been evaluated for a series of leaving groups. The worse the leaving group, the greater is the inhibitory effect of strain build-up, which reaches 50% of the excess enthalpy differential for the poorest leaving group studied.In nucleophilic addition to an electrophilic methylenecyclopropane, comparison of strained and unstrained systems shows that about 60% of the excess enthalpy differential promotes the reactivity of the strained system.

Synthesis of aryl cyclopropyl sulfides through copper-promoted S-cyclopropylation of thiophenols using cyclopropylboronic acid

“…In addition, an electron-withdrawing group (EWG) must be present on the aryl fluoride 16 for the S N Ar reaction to proceed. Aryl cyclopropyl sulfides can also be accessed by the addition of thiophenols 14 to cyclopropenes 18 (Scheme 2) [19–20] or to exo -methylenecyclopropanes 20 (Scheme 2) [21–22]. While these methods give access to highly substituted products, the requirement for a strong base could jeopardize their application in the context of synthesis of complex molecules.…”

Recent developments in the reactivity of methylene- and alkylidenecyclopropane derivatives

“…187 Another nucleophilic addition to alkylidenecyclopropane, described by Karoyan et al, dealt with the aminoezinceenolate carbometallation cyclisation of a hindered alkylidenecyclopropane, which provided after subsequent hydrolysis the corresponding proline derivative in good yield as a single diastereoisomer (Scheme 112). 188 In 2005, de Meijere et al reported the synthesis of spirocyclopropanated analogues of biologically active demethoxyfumitremorgine C and tadalafil.…”