The application of novel boron complexes in asymmetric transfer hydrogenation of aromatic ketones


Temel H. , Pasa S., Aydemir M.

TETRAHEDRON-ASYMMETRY, vol.26, no.18-19, pp.1058-1064, 2015 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 26 Issue: 18-19
  • Publication Date: 2015
  • Doi Number: 10.1016/j.tetasy.2015.08.007
  • Title of Journal : TETRAHEDRON-ASYMMETRY
  • Page Numbers: pp.1058-1064

Abstract

Asymmetric transfer hydrogenation using iso-PrOH as a hydrogen source offers an attractive route for reducing simple unsymmetrical functionalized ketones to chiral alcohols. The combined use of organometallic and coordination chemistry has produced a number of new and powerful synthetic methods for important classes of compounds in general and for optically active substances in particular. For this aim, the (S,Z)-1-((1-hydroxy butane-2-yl imino)methyl)naphthalene-2-ol chiral ligand was chosen to obtain boron complexes. Boronic derivative compounds such as phenylboronic acid, 6-methoxynaphthalen-2-ylboronic acid, 4-methyl-3-nitrophenylboronic acid and 1,4-phenylenediboronic acid were applied to obtain complexation with chiral based ligands. The structures of these ligands and their complexes have been elucidated by a combination of multinuclear NMR spectroscopy, LC MS/MS, TGA/DTA, UV Vis., elemental analysis, XRD, SEM, and FTIR. These boron complexes have also been tested as catalysts in the enantioselective transfer hydrogenation of acetophenone derivatives to afford the corresponding product, (S)-1-phenylethanol with high conversions (up to 99%) and modest enantioselectivities (up to 70% ee). The substituents on the backbone of the ligands had a significant effect on both the activity and % ee. (C) 2015 Elsevier Ltd. All rights reserved.