Chiral thioether ligands

Chiral thioether ligands coordination chemistry and asymmetric catalysis16... 

Derivatives of oxazolines, pyridines and phosphabicyclic compounds as chiral thioether ligands for asymmetric catalysis 03CCR(242)159. 

Masdeu-Bulto AM, Dieguez M, Martin E, Gomez M (2003) Chiral thioether ligands coordination chemistry and asymmetric catalysis. Coord Chem Rev 242 159-201... 

In 2004, a series of other chiral thioether-phosphine ligands based on a cyclopropane backbone were evaluated in the rhodium-catalysed hydrogenation of a dehydroamino acid by Molander el al As shown in Scheme 8.2, even if these ligands were generally active, only moderate enantioselectivities of up to 47% ee were obtained. 

In addition, Peruzzini et al. developed, in 2007, iridium complexes of planar-chiral ferrocenyl phosphine-thioether ligands that were tested in the hydrogenation of simple alkyl aryl ketones.These complexes were diastereoselec-tively generated in high yields (85-90%) by addition of the corresponding... 

Another approach in the use of chiral S/P ligands for the hydrosilylation reaction of ketones was proposed more recently by Evans et Thus, in 2003, these workers studied the application of new chiral thioether-phosphinite ligands to enantioselective rhodium-catalysed ketone hydrosilylation processes. For a wide variety of ketones, such as acyclic aryl alkyl and dialkyl ketones as well as cyclic aryl alkyl ketones and also cyclic keto esters, the reaction gave high levels of enantioselectivity of up to 99% ee (Scheme 10.44). 

Chiral thioether-phosphite ligands (125) derived from 1,2-O-isopropylidenexylofuranose have been synthesized. Reaction of these chiral ligands with [Rh(cod)2]BF4 yielded [Rh(cod)(125)]BF4. These ligands were tested in the Rh-catalyzed hydroformylation of styrene. The hydroformylation results (ee values were insignificant) are discussed according to the solution structure of the species formed under hydroformylation conditions. HP NMR studies show that only the phosphite is coordinated during the catalytic reaction.390... 

Inversion at Co —SR R is fast (0.1-10s ) but diastereoisomeric systems have been detected by H and C NMR spectroscopy. Thus (305) shows clearly resolved signals of the tren ligand arising from the chiral thioether. " Also the related t-(N,S)[Co (R)cys (tren)] chelate shows immediate H-NMR spectral changes on deprotonation of the dangling equatorial carboxylate arising from rapid (< 5 s) mutarotation of the (/ )S(J )C, (5)S(Ji)C diastereoisomeric mixture. Thus inversion appears to be 10 -10 times more rapid than for uncoordinated sulfonium salts, a result in keeping with other M—SR R systems. ... 

This group has been fully dominated by the synthesis of dithiolate complexes, most of them prepared with the aim of obtaining efficient catalysts for hydroformylation. A large number of thioether ligands were prepared for the design of chiral rhodium catalysts." ... 

New chelate chiral phosphorus ligands provided a source for a large number of Rh and other metal-based catalysts. The bis(phosphinoalkyl-ether)arene and bis(phosphinoalkyl-thioether)arene ligands were synthesized allowing the preparation of symmetric bimetallic structures with Rh centers 26. ... 

A series of chiral thioether-phosphite ligands derived from 1,2-0-isopropylidenexylofuranose were synthesized. Reaction of these chiral ligands with [M(cod)2]BF4 (M = Ir, Rh) yielded the complexes [M(cod)(P-S)]BF4. The... 

The chiral compounds 6 have also been considered as potential ligands for palladium-catalyzed aUylic substitution. Thiophosphines have been very rarely used in asymmetric catalysis [85-89]. These compounds represent, to the best of our knowledge, only the second example of thiophosphine-thioether ligands used in asymmetric catalysis [64, 85-89]. Good catalytic activities and enantioselectivities were obtained (e.e. up to 93% for R = tBu, Table 5.3). Ligands 6 are amongst the few best S,S ligands for this reaction [90-93]. 

Routaboul L, Vincendeau S, Turrin C-O, Caminade A-M, Majoral J-P, Daran J-C, Manoury E (2007) New phosphorus dendrimers with chiral ferrocenyl phosphine-thioether ligands on the periphery for asymmetric catalysis. J Organomet Chem 692 1064—1073... 

Malacea R, Manoury E, Routaboul L, Daran J-C, Poli R, Dunne JP, Withwood AC, Godard C, Duckett SB (2006) Coordination chemistry and diphenylacetylene hydrogenation catalysis of planar chiral ferrocenylphosphine-thioether ligands with cyclooctadiene iridium(I). Eur J Inorg Chem 1803-1816... 

Malacea R. Daran J-C, Duckett SB, Dunne JP, Manoury E, Poli R, Withwood AC (2006) Parahydrogen studies of H2 addition to hfl) complexes containing chiral phosphine-thioether ligands implications for catalysis. Dalton Trans 3350-3359... 

Le Roux E, Malacca R, Manoury E, Poli R, Gonsalvi L, Peruzzini M (2007) Highly efficient asymmetric hydrogenation of alkyl aryl ketones catalyzed by iridium complexes with chiral planar ferrocenyl phosphino-thioether ligands. Adv Synth Catal 349 309-313... 

Since carbohydrates constitute an inexpensive and highly modular chiral source for preparing chiral ligands," Claver et al. have reported the use of a series of thioether-phosphite" and thioether-phosphinite furanoside ligands" in the test palladium-catalysed allylic substitution reaction. In the first type of ligand, a systematic variation of the donor group attached to the carbon atom C5 indicated that the presence of a bulky phosphite functionality had a positive effect on the enantioselectivity. Indeed, the enantioselectivity was controlled mainly by the phosphite moiety. This was confirmed by the use of a ligand... 

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