CHIRAPHOS palladium complexes

Legros and Fiaud also developed enantioselective benzyiic alkylation of 1-naphthylethyl esters with dimethyl sodiomalonate and dimethyl sodiomethylmalonate in the presence of a catalytic amount of a palladium complex and a chiral diphosphine such as BINAP 113, Chiraphos 114, or DIOP 115 (Equation (45)). Use of BDPP 116 as a chiral... 

Alkene Hydroarylation. The enantioselective addition of aryl iodides to norbomene has been reported using a palladium(II) complex of (5, iS )-CHIRAPHOS. The reaction of norbomadiene with 4-methoxyiodobenzene proceeded with 30% ee (eq 5). Enantioselectivities were dependent upon phosphine structure (see (+)-trans-(2S,3S)-Bis(diphenylphosphino)bicyclo[2.2.1 ]hept-5-ene). 

Thus, the combination of 2-sulfonylmethyl-2-propenyl carbonate with an unsaturated ester or ketone, catalyzed by chiral ferrocenylphosphane palladium(O) complexes, forms a mixture of cis- and /ra/w-products. The ratio of the products as well as their corresponding ee is dependent on the precise nature of the ferroceny]-based phosphane. The use of the ligand incorporating an additional 1,2-diol functionality leads to the best results with ee values of 75 % and 78 % from the unsaturated ketone, as determined by chiral shift reagent NMR [Eu(hfc),]. For comparison, the use of (S.S)-Chiraphos or (+)-BINAP as phosphane leads to ee values in the range 4 46%. 

The group of Miyaura [78, 89] applied arylbismuth compounds [88] in these metal-catalyzed reactions. The application of this compound type in such met2il-catalyzed reactions is stiU rare. In fact, as has already been mentioned, Miyaura s group reported the use of chiral phosphane/dicationic palladium(II) complexes (based on (S,S)-Chiraphos and (S,S)-Dipamp) in the 1,4-addition of triaryl-bismuth reagents to cyclic and acyclic enones in aqueous methanol at low temperature (Scheme 5.32). Enantioselectivities of up to 95% ee were achieved for cyclic enones. The use of Cu(BF4)2 to help the reoxidation of Pd(0) to the catalyticaUy active Pd(II) species was an advantage, as well as the efficiency of the aryl transfer, allowing utilization of 2-2.8 of the three phenyl groups on the bismuth atom. Several years ago, Yamamoto, Nishikata, and Miyaura [68c] published a personal account of... 

Nishikata, T. Yamamoto, Y. Gridnev, I. D. Miyaura, N. Enantioselective 1,4-Addition of Ar3Bi, [ArBF3]K, and ArSiF3 to Enones Catalyzed by a Dicationic Palladium(II)-Chiraphos or -Dipamp Complex. Organometallics 2005,24,5025-5032. 

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