Toggle Main Menu Toggle Search

Open Access padlockePrints

Can a Butadiene-Based Architecture Compete with its Biaryl Counterpart in Asymmetric Catalysis? Enantiopure Me-CATPHOS, a Remarkably Efficient Ligand for Asymmetric Hydrogenation

Lookup NU author(s): Dr Simon Doherty, Catherine Smyth, Emeritus Professor Anthony Harriman, Dr Ross Harrington, Emeritus Professor Bill Clegg

Downloads

Full text for this publication is not currently held within this repository. Alternative links are provided below where available.


Abstract

The double Diels-Alder cycloaddition between 9-methylanthracene and 1,4-bis(diphenylphosphinoyl)buta-1,3-diyne affords the oxide of the atropos diphosphine, Me-CATPHOS, which has an unusual bicyclic buta-1,3-diene-based architecture. Quantum chemical methods using DTF reveal that the barrier to atropinterconversion in Me-CATPHOS is 130 kJ mol(-1), while the corresponding barrier for its unsubstituted counterpart is only 23 kJ mol-1, entirely consistent with the former being an atropos diphosphine while the latter belongs to the tropos class of ligand. rac-Me-CATPHOS can be resolved by fractional crystallization of the diasteresomeric complexes formed with (2R,3R)-(-)-2,3-O-dibenzoyltartaric acid and reduction of the resulting enantiopure oxide, accomplished by silane reduction in xylene at 130 degrees C, to afford an operationally straightforward, three-step synthesis of an entirely new class of atropos buta-1,3-diene-based diphosphine. Rhodium complexes of enantiopure Me-CATPHOS catalyze the asymmetric hydrogenation of a range of dehydroamino acid derivatives, in some cases giving ee's in excess of 99% and in all cases showing a significant enhancement compared with its BINAP counterpart. Gratifyingly, Rh/(S)-Me-CATPHOS outperforms all existing catalysts for the asymmetric hydrogenation of (E)-beta-dehydroamino phosphonates, many of which are based on markedly more expensive biaryl- and ferrocenyl-based diphosphines. Surprisingly, in the case of the dehydroamino acid substrates, (S)-Me-CATPHOS provides product of opposite absolute stereochemistry to that obtained with (S)-BINAP, despite both ligands having an S-ax configuration, whereas (S)-Me-CATPHOS exerts (S)-BINAP-like stereoinduction for the hydrogenation of beta-enamidophosphonates; both ligands afford product with the same absolute configuration.


Publication metadata

Author(s): Doherty S, Smyth CH, Harriman A, Harrington RW, Clegg W

Publication type: Article

Publication status: Published

Journal: Organometallics

Year: 2009

Volume: 28

Issue: 3

Pages: 888-895

Date deposited: 07/06/2010

ISSN (print): 0276-7333

ISSN (electronic): 1520-6041

Publisher: American Chemical Society

URL: http://dx.doi.org/10.1021/om801145v

DOI: 10.1021/om801145v


Altmetrics

Altmetrics provided by Altmetric


Actions

Find at Newcastle University icon    Link to this publication


Share