Multiple mechanisms in Pd(II)-catalyzed S(N)2' reactions of allylic alcohols.

Abstract

Density functional calculations and experiments were used to examine mechanisms of Pd(II) catalyzed intramolecular cyclization and dehydration in acyclic and bicyclic monoallylic diols, a formal S(N)2' reaction. In contrast to the previously proposed syn-oxypalladation mechanism for acyclic monoallylic diols, calculations and experiments strongly suggest that hydrogen bonding templates a hydroxyl group and Pd addition across the alkene and provides a low energy pathway via anti-addition (anti-oxypalladation) followed by intramolecular proton transfer and anti-elimination of water. This anti-addition, anti-elimination pathway also provides a simple rationale for the observed stereospecificity. For bicyclic monoallylic diol compounds, Pd(II) is capable of promoting either anti- or syn-addition. In addition, palladium chloride ligands can mediate proton transfer to promote dehydration when direct intramolecular proton transfer between diol groups is impossible.

• Authors: Thomas Ghebreghiorgis, Brian H Kirk, Aaron Aponick, Daniel H Ess
• Journal: The Journal of organic chemistry (J Org Chem) Vol. 78 Issue 15 Pg. 7664-73 (Aug 02 2013) ISSN: 1520-6904 [Electronic] United States
• PMID: 23862564 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Ethers, Cyclic
• Ligands
• Organometallic Compounds
• Propanols
• Protons
• allyl alcohol
• Palladium

Topics

• Catalysis
• Cyclization
• Ethers, Cyclic (chemical synthesis, chemistry)
• Hydrogen Bonding
• Ligands
• Molecular Structure
• Organometallic Compounds (chemistry)
• Palladium (chemistry)
• Propanols (chemistry)
• Protons
• Quantum Theory