Asymmetric Reduction of Ketones with Catecholborane Using 2,6-BODOL Complexes of Titanium(iv) as Catalysts
2001 (English)In: Chemistry - A European Journal, Vol. 7, no 10, 2158-66 p.Article in journal (Refereed) Published
Reductions performed with TiIV complexes of ligands based on bicyclo[2.2.2]octane diols 5 and 6 are effective catalysts in the reduction of prochiral ketones to optically active alcohols, with catecholborane as the reducing agent. Methyl ketones are favored and enantiomeric excesses (ee) of 98 % have been achieved with acetophenone as the substrate. Several other substrates were tested, among them 2-octanone, which gave 2-octanol in 87 % ee. Further details of the method were examined, for example, temperature, solvent composition, amount of molecular sieves (4 Å), and catecholborane quality, as well as the sensitivity of the ligands towards acids. NMR spectroscopic methods were used to gain some insight into the complexes formed between the ligands and [Ti(OiPr)4]. A dimeric structure is proposed for the pre-catalyst.
Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2111/2001/f2647_s.pdf from the author.
Place, publisher, year, edition, pages
2001. Vol. 7, no 10, 2158-66 p.
IdentifiersURN: urn:nbn:se:umu:diva-9595DOI: doi:10.1002/1521-3765(20010518)7:10<2158::AID-CHEM2158>3.0.CO;2-IOAI: oai:DiVA.org:umu-9595DiVA: diva2:149266