Enantioselective Synthesis and Application to the Allylic Imidate Rearrangement of Amine‐Coordinated Palladacycle Catalysts of Cobalt Sandwich Complexes. Issue 52 (21st November 2013)

• Record Type: Journal Article
• Authors: Cassar, Doyle J.; Ilyashenko, Gennadiy; Ismail, Muhammad; Woods, James; Hughes, David L.; Richards, Christopher J.
• Is Part Of: Chemistry. Volume 19:Issue 52(2013)
• Page Start: 17951
• Page End: 17962
• Publication Date: 2013-11-21
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201302922
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>The reaction of (η<sup>5</sup>‐(<italic>N</italic>, <italic>N</italic>‐dimethylaminomethyl)cyclopentadien‐yl)(η<sup>4</sup>‐tetraphenylcyclobutadiene)cobalt with sodium tetrachloropalladate and (<italic>R</italic>)‐<italic>N</italic>‐acetylphenylalanine gave planar chiral palladacycle di‐μ‐chloridebis[(η<sup>5</sup>‐(<italic>S</italic><sub>p</sub>)‐2‐(<italic>N</italic>, <italic>N</italic>‐dimethylaminomethyl)cyclopentadienyl, 1‐<italic>C</italic>, 3′‐<italic>N</italic>)(η<sup>4</sup>‐tetraphenylcyclobutadiene)cobalt]dipalladium [(<italic>S</italic><sub>p</sub>)‐Me<sub>2</sub>‐CAP‐Cl] in 92 % <italic>ee</italic> and 64 % yield. Enantiopurity (>98 % <italic>ee</italic>) was achieved by purification of the monomeric (<italic>R</italic>)‐proline adducts and conversion back to the chloride dimer. Treatment with AgOAc gave (<italic>S</italic><sub>p</sub>)‐Me<sub>2</sub>‐CAP‐OAc which was applied to asymmetric transcyclopalladation (up to 78 % <italic>ee</italic>). The (<italic>R</italic>)‐<italic>N</italic>‐acetylphenylalanine mediated palladation methodology was applicable also to the corresponding <italic>N</italic>, <italic>N</italic>‐diethyl (82 % <italic>ee</italic>, 39 % yield) and pyrrolidinyl (>98 % <italic>ee</italic>, 43 % yield) cobalt sandwich complexes. A combination of 5 mol % of the latter [(<italic>S</italic><sub>p</sub>)‐Pyrr‐CAP‐Cl] and AgNO<sub>3</sub> (3.8 equiv) is a catalyst for the allylic imidate rearrangement of an (<italic>E</italic>)‐<italic>N</italic>‐aryltrifluoroacetimidate (up to 83 % <italic>ee</italic>), and this catalyst system is also applicable to the rearrangement of a range of (<italic>E</italic>)‐trichloroacetimidates (up to 99 % <italic>ee</italic>). This asymmetric efficiency combined with the simplicity of catalyst synthesis provides accessible solutions to the generation of non‐racemic allylic amine derivatives.</p> </abstract>