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Ligands for enantioselective catalysis

Contact : Duncan Carmichael

[1] [1b] [2]

Enantioselection is still dominated by experimental testing. It is well established that ligands for enantioselection should form part of a series whose stereoelectronic properties can be varied in modular fashion wherever possible. The Josiphos series provides a benchmark in this area. 

                                                                                               

We have been able to prepare a series of 'push-pull' enantiopure ligands which contain a soft p acceptor phosphametallocene and a classical sp3 hybridised phosphine. The phosphametallocene enatiomers are conveniently resolved on a multigram scale through fractional crystallisation of quite easily available diastereomeric menthyl ester precursors[1a3] and the products can be elaborated straightforwardly.[4] [1b] The phospharuthenocene series is especially simple to develop because enantiopure phospharuthenocenemethylium cations can be crystallised and stored on the bench for months. Addition of nucleophiles to these cations gives rise to a very wide range of ligands. 

 

[1]        a): D. Carmichael, G. Goldet, J. Klankermayer, L. Ricard, N. Seeboth, M. Stankevic, Chemistry-a European Journal 2007, 13, 5492-5502 Link; b): D. Carmichael, J. Klankermayer, E. Muller, K. M. Pietrusiewicz, L. Ricard, N. Seeboth, S. Sowa, M. Stankevic, Organometallics 2011, 30, 1804-1811. Link

[2]        D. Carmichael, X. F. le Goff, E. Muller, L. Ricard, M. Stankevic, Dalton Transactions 2012, 41, 5155-5162. Link

[3]        D. Carmichael, J. Klankermayer, L. Ricard, N. Seeboth, Chemical Communications 2004, 1144-1145. Link

[4]        D. Carmichael, F. Mathey, L. Ricard, N. Seeboth, Chemical Communications 2002, 2976-2977. Link