Enantioselective Rhodium-Catalyzed Synthesis of α-Chloromethylene-γ-Butyrolactams from <i>N</i>-Allylic Alkynamides

The first enantioselective cycloisomerization with intramolecular halogen migration of various 1,6-enynes promoted by a cationic Rh-Synphos catalyst is reported. This method provides an efficient route to enantiomerically enriched γ-butyrolactam derivatives, which are important core scaffolds found in numerous natural products and biologically active molecules. Good yields and enantiomeric excesses up to 96% are achieved

Stereodivergent Silylzincation of α‑Heteroatom-Substituted Alkynes

Zinc reagents (Me₂PhSi)₂Zn and [(Me₃Si)₃Si]₂Zn undergo highly regio- and stereoselective addition across the carbon–carbon triple bond of nitrogen-, sulfur-, oxygen-, and phosphorus-substituted terminal alkynes in the absence of copper or any other catalyst. Both reagents yield exclusively β-isomers, and the stereoselectivity is determined by the silyl group: Me₂PhSi for <i>cis</i> or (Me₃Si)₃Si for <i>trans</i>. These stereodivergent silylzincation protocols offer an efficient access to heteroatom-substituted vinylsilanes with either double bond geometry, including trisubstituted vinylsilanes by one-pot electrophilic substitution of the intermediate C­(sp²)–Zn bond by copper­(I)-mediated carbon–carbon bond formation