Tetrathiaheterohelicene Phosphanes as Helical-Shaped Chiral Ligands for Catalysis

Monteforte, M, Cauteruccio, S, Maiorana, S, Benincori, T, Forni, A, Raimondi, L, Graiff, C, Tiripicchio, A, Stephenson, GR and Licandro, E (2011) Tetrathiaheterohelicene Phosphanes as Helical-Shaped Chiral Ligands for Catalysis. European Journal of Organic Chemistry, 2011 (28). pp. 5649-5658. ISSN 1099-0690

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Abstract

Tetrathia[7]helicene-based phosphanes thiaheliphos (2a), nPr-thiaheliphos (2b) and di-nPr-thiaheliphos (2c) have been prepared from the 2,13-dilithio derivatives of thiahelicenes 1a–c by reaction with an excess of Ph2PCl. Protection of the air-sensitive products as BH3 adducts, from which the phosphanes 2a–c are easily regenerated on heating with ethanol, is described. New rhodium(I) complexes 8 and 9 were obtained by reaction of 2c with [Rh(COD)2]+[BF4]– and [BARF]–, respectively, which were converted by oxidation into the chelating phosphane–phosphane oxide RhI complexes 10 and 11. The monophosphane 5 was similarly prepared, andreaction of the dilithio species with ClP(O)(OEt)2 gave the diphosphonate 17, which was characterized by X-ray crystallography. Comparison of data from DFT calculations (B3LYP/SVP) on 2c, 8 and 10 and X-ray data for 17 reveals a strong tension within the thiaheliphos ligands that is partially relaxed by increasing the Rh–P distances and the bite angle of the chelating ligand. Compound (P)-(+)-1c, obtained by chromatographic resolution, was transformed into optically pure (P)-(+)-2c, which was used in the asymmetric hydrogenation of itaconic acid ester and methyl 2-acetamidoacrylate (product ees up to 40%).

Item Type: Article
Faculty \ School: Faculty of Science > School of Chemistry
Related URLs:
Depositing User: Deborah Clemitshaw
Date Deposited: 10 Jan 2012 14:28
Last Modified: 01 Nov 2018 10:30
URI: https://ueaeprints.uea.ac.uk/id/eprint/36049
DOI: 10.1002/ejoc.201100726

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