Selectivity in Metal‐Catalyzed CarbonCarbon Bond Cleavage of Alkylidenecyclopropanes

Abstract

When more complex system leads to simpler reactivity profile; the ring-opening of strained three-membered rings such as methylene- and alkylidenecyclopropanes generally lead to several products. If one starts with more functionalized carbon skeletons, selective reactions are now observed and rationalization as well as synthetic applications are described in this concept article. This methodology could be used to the preparation of challenging structural motifs possessing quaternary carbon stereocenters in acyclic systems.

Cyclopropene Derivatives as Precursors to Enantioenriched Cyclopropanols and n‐Butenals Possessing Quaternary Carbon Stereocenters

“…[18] As we have ad irect approach to the polysubstituted copper cyclopropanolate 3 as asingle diastereoisomer and in as ingle-pot operation from the cyclopropenyl ether 1,w e were then interested in using the inherent ring strain of these three-membered rings to perform the subsequent selective carbon-carbon bond fragmentation as an ew entry to the acyclicenal 5,which possesses the desired quaternary carbon stereocenter (Scheme 2). [19] However,w hen 3e (R 1 = Bu, R 2 = Ph, R 3 = Me) was warmed to room temperature or even refluxed for few hours in THF,the ring fragmentation was not observed and the cyclopropanol 4e was quantitatively recovered after hydrolysis.S imilarly,a ddition of aL ewis acid such as BF 3 ·OEt 2 to 3e did not promote the fragmentation.…”

Cyclopropene Derivatives as Precursors to Enantioenriched Cyclopropanols and n‐Butenals Possessing Quaternary Carbon Stereocenters

“…Having in hand the cyclopropylcopper species,aselective oxidation reaction needs to be performed with complete retention of configuration. [19] However,w hen 3e (R 1 = Bu, R 2 = Ph, R 3 = Me) was warmed to room temperature or even refluxed for few hours in THF,the ring fragmentation was not observed and the cyclopropanol 4e was quantitatively recovered after hydrolysis.S imilarly,a ddition of aL ewis acid such as BF 3 ·OEt 2 to 3e did not promote the fragmentation. After acidic hydrolysis,t he corresponding 2,2,3,3-tetrasubstituted cyclopropanols 4ai were obtained as single diastereoisomers (entries 1-9).…”

Diastereodivergent Carbometalation/Oxidation/Selective Ring Opening: Formation of All‐Carbon Quaternary Stereogenic Centers in Acyclic Systems

“…In contrast, strained substrates do not require such precoordination but the selectivity of the carbon–carbon bond cleavage may be difficult to control 3. Controlling such selectivity would be crucial for further synthetic applications,4 particularly if the selectivity leads to the formation of enantiomerically enriched products such as ones possessing challenging all‐carbon quaternary stereocenters in acyclic systems 5. In this context, we have developed in the past few years various approaches to selectively cleave the primary carbon–carbon bond of enantiomerically enriched alkylidenecyclopropanes 6.…”