Palladium catalysed allylation

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... 

Figure 6.18. Palladium catalysed allylic alkylation using fluorinated ligands.[60, 61]...

Kaiser, G. Sanders, J. K. M. Synthesis under reversible conditions of cyclic porphyrin dimers nsing palladium-catalysed allyl trausesterification. Chem. 

Tietze, L. F. Hippe, T. Steinmetz, A. Palladium-Catalysed Allylic Substitution on Solid Support, J. Chem. Soc. Chem. Commun. 1998, 793-794. 

H. H. Baer and Z. S. Hanna, The preparation of amino sugars and branched-chain sugars by palladium-catalysed allylic substitution of alkyl hex-2-enopyranosides, Can. J. Chem. 59 889 (1981). 

Evans, RA. and Brandt, T.A., Enantioselective palladium-catalysed allylic alkylation using E- and Z-vinylogous sulfonates, Org. Lett., 1999, 1, 1563-1565. 

Bremberg, U., Lutsenko, S., Kaiser, N.F., Larhed, M., Hallberg, A. et at, Rapid and stereoselective C—C, C—O, C—N andC—S couplings via microwave accelerated palladium-catalysed allylic substitutions, Synthesis, 2000, 1004-1008. 

A regio- and enantio-selective palladium-catalysed allylic alkylation of ketones has been reported, using allyl enol carbonate chemistry in which a CO2 unit tethers the allylating agent to the nucleophile.198... 

Palladium catalysed allylation of ordinary ketone and aldehyde enolates... 

The palladium-catalysed allylic alkylation of dimethylallyl acetate 35 with dimethyl malonate 36 in THF at 25°C was carried out using a combination of Pd2(dba)3 [fris(dibenzylideneacetone)dipalladium] and triphenylphosphine with 0,N-Ws(trimethylsilyl)acetamide (BSA) as a base.87... 

The 3-acetoxymethylazepine 18 formed by RCM of the corresponding allyl acetate 17 underwent palladium-catalysed allylic reduction to give almost exclusively the 3-exo-methylene isomer 19 <07JOC2674>. 

Figure 7.11 Generalized scheme for palladium-catalysed allylic functionalization...

The concept of surfactant-type catalysts described above was also found to be applicable to catalytic systems other than Lewis acid-catalysed reactions. For example, we have developed palladium-catalysed allylic substitution reactions using a combination of Pd(PPh3)4 and a non-ionic surfactant, Triton X-100 [32]. 

Although the hemilabile behaviour of the imino functional group together with an apparent isomerisation process on palladium may make it difficult to achieve high chiral resolution (ee) in asymmetric catalysis. Bonnet and Douthwaite developed an imino functionalised carbene ligand system based on the diamino cyclohexane framework that has achieved ees of up to 92% in palladium catalysed allylic alkylatiou reactions using ( )-l,3-diphenylprop-... 

The same ligand was used by Visentin and Togni [145] in the palladium catalysed allylic amination using racemic 1,3-diphenylallylethyl carbonate and either benzylamine or piperidine. The yields were rather low (32% and 58%, respectively) with very poor chiral resolution (5% ee of the S enantiomer). 

Helping you to understand the details of the palladium-catalysed allylation. 

Groups 10-12. Proton NMR was used to characterise an intermediate r -allyl coordinated pincer complex in the palladium-catalysed allylation of aldehydes and imines.1155 Low-temperature 111 and 13C NMR spectra, and H NOESY data established the mechanism for palladium-catalysed cyclisation/ hydrosilylation of dimethyl diallyl malonate, via (234, E = C02Me).1156 High-pressure 31P 1H NMR studies on coploymerisation of styrene with CO, catalysed by a Pd( 11)-(/L.V-BINAPHOS) complex, gave evidence for a number of active complex intermediates.1157... 

Ins(l,4,5)P3. A number of phosphates, e.g. (37), which act as inositol monophosphatase inhibitors have been synthesised from the l,6-epoxy-4-benzyloxycyc-lohexan-2-ol (36)7" Conduritol derivatives (39) are useful synthetic building blocks. However, the enantioselective palladium-catalysed allyl alkylation and similar reactions of (38) are complex due to C2 symmetry. It has now been reported that dynamic kinetic asymmetric transformation (DYKAT) of racemic... 

In summary, a new simple method for the preparation of axially chiral diphosphine complexes has been developed. The presence of the planar chiral ferrocenyl unit avoids the need of resolution since only one diastereomer is formed in a metal complexation. The new ligand is useful for asymmetric palladium-catalysed allylic substitutions with malonates and amino derivatives (Schemes 1 and 2). 

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