Diphenylallyl acetate, asymmetric allylic

Chiral nonracemic bidentate 2-[o-(diphenylphosphino)phenyl]-5,6-dihydro-4//-l,3-oxazine derivatives proved to be effective P,N-ligands in Pd-catalyzed asymmetric transformations. When used in the Pd-catalyzed allylic alkylations of 1,3-diphenylallyl acetate with dimethyl malonate, phosphino-oxazines 147 and 148 and the... 

The chiral nonracemic bis-benzothiazine ligand 75 has been screened for activity in asymmetric Pd-catalyzed allylic alkylation reactions (Scheme 42) <20010L3321>. The test system chosen for this ligand was the reaction of 1,3-diphenylallyl acetate 301 with dimethyl malonate 302. A stochiometric amount of bis(trimethylsilyl)acetamide (BSA) and a catalytic amount of KOAc were added to the reaction mixture. A catalytic amount of chiral ligand 75 along with a variety of Pd-sources afforded up to 90% yield and 82% ee s of diester 303. Since both enantiomers of the chiral ligand are available, both R- and -configurations of the alkylation product 303 can be obtained. The best results in terms of yield and stereoselectivity were obtained in nonpolar solvents, such as benzene. The allylic alkylation of racemic cyclohexenyl acetate with dimethyl malonate was performed but with lower yields (up to 53%) and only modest enantioselectivity (60% ee). 

Scheme 3 Asymmetric allylic alkylation of symmetric 1,3-diphenylallyl acetate by malonic dimethylester...

In the field of C—C bond forming reactions, palladium occupies a privileged position. In this context, the asymmetric allylic alkylation attracted our interest due to its unique outersphere attack of the malonate on the 77 -coordinated 1,3-diphenylallyl moiety. Following the above-described chemogenetic optimization procedure, we screened twenty one biotinylated ligands in conjunction with twenty two (strept)avidin isoforms for the allylic alkylation of 1,3-diphenylallyl acetate. Addition of didodecyldimethylam-... 

Hybrid catalysts for the asymmetric allylic alkylation of 1,3-diphenylallyl acetate with dimethyl malonate were obtained by incorporation of the biotinylated diphosphine Pd(II) complexes 8 or 9 (Figure 10.9) to wild-type SAV and mutants. The best combinations afforded the product with nearly quantitative yield and 90% ee (R) and 82% ee (S) [54], Supramolecular association between SAV and biotinylated Hoveyda-Gnibbs-type catalyst 10 catalyzed the ring-closing metathesis (RCM) of Af-tosyl diallylamine (Scheme 10.13) [55]. 

In order to assess the scope of Ugand-directed asymmetric allylations with chelated enolates, a representative set of substrates was investigated (Scheme 12.29) [50]. High levels of selectivity were achieved with 1,3-diphenylallyl acetate 58 as substrate especially with the PHOX Hgand LI, a diastereoselectivity of up to 95 5 in favor of the anti-isomer 60 and enantiomeric excess values of up to 94% could be achieved. AUyHc alkylations of cychc substrates such as cyclohexenyl acetate 57 led to the cydohexenyl-glydne derivative 59. With the chiral ligand L2, the syn product is formed preferentially. Enantiomeric excess values of up to 93% can be obtained with this Hgand, which is remarkable for such a cydic system. 

Successful asymmetric allylations have been carried out with high ee values using many kinds of chiral ligands. 1,3-Diphenylallyl acetate is used as a standard substrate to compare different chiral ligands based on desymmetrization of its meio-Tr-allylpalladium intermediate. Asymmetric allylation is treated in Sect. V.2.4. 

To perform asymmetric amination reactions the transformation of ( )-l,3-diphenylallyl acetate with pyrrolidine or di-n-propylamine was investigated by Lyubimov et al. [54] This reaction may serve as a model reaction for metal-catalyzed aUylation reactions, which involve the attack of nucleophiles at an allylic metal intermediate (Schane 22.11). C-, H-, N-, 0-, or S-centerded substrates can be employed as nucleophiles, which leads to a high flexibility in the type of bonds that can be created. Thus, this reaction leads to a high degree of asymmetric induction and is tolerant to a wide range of functional groups [55]. 

SCHEME 22.13 Asymmetric allylic alkylation and allylic sulfonylation of (Sl-l.S-diphenylallyl acetate. 

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