Diastereoselective Synthesis of Methylenecyclopropanes from Chiral Cyclopropene Derivatives

Directed Regioselective Carbometallation of 1,2-Dialkyl-Substituted Cyclopropenes

A regio- and diastereoselective copper-catalyzed carbomagnesiation of 1,2-dialkylated cyclopropenes is reported. The regioselectivity is controlled by a subtle tethered Lewis basic moiety. The chelating moieties allow the differentiation between two electronically tantamount organometallic intermediates. Further functionalization grants access to polysubstituted stereodefined cyclopropanes bearing up to five alkyl groups.

Recent advances in transition-metal-catalyzed intermolecular carbomagnesiation and carbozincation

Carbomagnesiation and carbozincation reactions are efficient and direct routes to prepare complex and stereodefined organomagnesium and organozinc reagents. However, carbon-carbon unsaturated bonds are generally unreactive toward organomagnesium and organozinc reagents. Thus, transition metals were employed to accomplish the carbometalation involving wide varieties of substrates and reagents. Recent advances of transition-metal-catalyzed carbomagnesiation and carbozincation reactions are reviewed in this article. The contents are separated into five sections: carbomagnesiation and carbozincation of (1) alkynes bearing an electron-withdrawing group; (2) alkynes bearing a directing group; (3) strained cyclopropenes; (4) unactivated alkynes or alkenes; and (5) substrates that have two carbon-carbon unsaturated bonds (allenes, dienes, enynes, or diynes).

Enantiomerically enriched cyclopropene derivatives: versatile building blocks in asymmetric synthesis

Enantiomerically enriched cyclopropene derivatives, the smallest possible unsaturated carbocycles, are of great synthetic interest since they serve as versatile reactive building blocks. Their reactivity results from the relief of the ring strain in the small molecule. They can be transformed into a wide variety of complex chiral structures and a special emphasis will be directed towards the preparation of enantiomerically enriched methylene- and alkylidenecyclopropane derivatives. The ready availability of a wide range of these chiral entities now provides an excellent opportunity to discover new and unique transformations that can further enrich mainstream synthetic methodology.