Smirnov P, Mathew J, Nijs A, Katan E, Karni M, Bolm C, Apeloig Y, Marek I * Technion-Israel Institute of Technology, Haifa, Israel and RWTH Aachen University, Germany
One-Pot Zinc-Promoted Asymmetric Alkynylation/Brook-Type Rearrangement/Ene–Allene Cyclization: Highly Selective Formation of Three New Bonds and Two Stereocenters in Acyclic Systems.
Angew. Chem. Int. Ed. 2013;
52: 13717-13721
Key words
zinc - Brook rearrangement - alkynylation
Significance
In a one-pot operation, two stereocenters and three new bonds were created with high selectivity. The reaction proceeds through a sequence of asymmetric alkynylation of an acyl silane, tandem Brook-type rearrangement, ene–allene cyclization, addition of an electrophile, and finally oxidation. It will be extremely useful in organic synthesis, and it is a new approach to synthetic transformations.
Comment
Quantum mechanical calculations show that this method passes through an allenyl Zn-Brook rearrangement and that this transformation bypasses the intermediate derived from the classic [1,2]-Brook rearrangement. This important finding nicely rationalizes the observation that the rearrangement proceeds without racemization.
