Nicka Chinkov

Enantio- and diastereoselective tandem zn-promoted brook rearrangement/ene-allene carbocyclization reaction.

The zinc-catalyzed addition of various alkynes to acylsilanes followed by a Zn-Brook rearrangement and either the Zn-ene-allene or Zn-yne-allene cyclization led to the enantio- and diastereoselective formation of carbocycles in a single-pot operation.

New preparation of stereodefined α,α-unsaturated ketones by carbomagnesiation of α-allenyl ketones

Abstract The addition of several alkylmagnesium halides to an α-allenyl ketone leads to the corresponding α,β-unsaturated ketones as single geometrical isomers. A π-chelation between the metal and the unsaturation is proposed to explain the steric outcome of this reaction.

New regio-, stereo-, diastereo- and enantioselective one-pot reactions mediated by organometallic derivatives

In the first part of the lecture, we will discuss the one-pot preparation of chiral homoallylic alcohol and amine derivatives by a copper-catalyzed four-component reaction. In this process, three new carbon-carbon bonds as well as a quaternary and a tertiary chiral center are created with excellent regio- and diastereoselectivities. When the reaction was performed without adding external electrophiles, a β-elimination reaction took place to give polysubstituted allenes in good overall yields. This strategy of zinc-homologation followed by a β-elimination reaction was also synthetically used for the transformation of sp3 sulfoxides into olefins with potential application in asymmetric synthesis. Finally, in the second part of this lecture, the stereoselective preparation of metallated dienes in only two chemical steps from commercially available products will be described. This new strategy is based on a tandem allylic C-H bond activation of a remote ω-double bond followed by an elimination reaction.