Enantioselectivity Pd-catalyzed

Scheme 0.7. Enantioselective Pd-catalyzed domino reaction for the synthesis of Vitamin E (0-24).

A few intriguing developments in the area of tetrahydro-P-carboline synthetic methodology include the report of a catalytic asymmetric Pictet-Spengler reaction <06JACS1086> and an enantioselective Pd-catalyzed intramolecular allylic alkylation of indoles <06JACS1424>. A one-step synthesis of 1-substituted-P-carbolines from L-tryptophan has appeared that bypassed the tetrahydro intermediate <06T10900>. 

Scheme 19 Highly enantioselective Pd-catalyzed rearrangement of allylic sulfinates to allylic sulfones...

It seems somewhat puzzling to trace the recent remarkable success in attaining highly enantioselective Pd-catalyzed allylic substitution to the external nucleophilic attack as a key step. In other words, it appears a difficult task to control... 

The use of a chiral bisoxazoUne ligand 132 for the enantioselective Pd-catalyzed annelation of allenes has been reported by Larock and Zenner (an example is given in Scheme The use of a chiral phosphinooxazoUne ligand 135 for the enantio-... 

Enantioselective Pd-Catalyzed Domino Cyclization Strategy to (+)-Lysergic acid, (+)-Lysergol, and (+)-Isolysergol... 

Enantioselective Pd-catalyzed hydrogenolysis is still very rare. Many additional examples may be expected to be developed in the future. 

Phenols have also been used as oxygen nucleophiles in enantioselective Pd-catalyzed allylic substitution reactions. The phenyl ether products 184 and 185 were formed with good enantioselectivity and could be subjected to a subsequent Claisen rearrangement.f " ... 

SCHEME 23.53 Enantioselective Pd-catalyzed C-H alkylation with alkyl boronic acids. 

The Brpnsted acid is not always responsible for the chiral induction step as shown in Scheme 26.25, a Friedel-Crafts product can be the substrate for an enantioselective Pd-catalyzed hydrogenation [113]. 

Liu, W., Chen, D., Zhu, X.-Z., Wan, X.-L., Hou, X.-L. (2009). Highly diastereo- and enantioselective Pd-catalyzed cyclopropanation of acyclic amides with substituted allyl carbonates. Journal of the American Chemical Society, 131, 8734-8735. 

Trost BM, Xu JY. Regio- and enantioselective Pd-catalyzed allylic alkylation of ketones through allyl enol carbonates. J.Am. Chem. Soc. 2005 127 2846-2847. 

Klapars A, Campos KR, Waldman JH, Zewge D, Dormer PG, Chen CY. Enantioselective Pd-Catalyzed a-arylation of N-... 

SCHEME 40.24. Synthesis of chiral (—)-tylophorine via enantioselective Pd-catalyzed carboami-... 

Palladium remains the most widely recognized transition metal to effect stereoselective allylic alkylation reactions. Consequently, diastereoselective and enantioselective Pd-catalyzed processes are extensively discussed in Sections 14.2 and 14.3. More recent advances in the field of metal-catalyzed al-lylation reactions include the use of chiral iridium complexes, dealt with in Section 14.4 [33, 34]. Section 14.5 describes selected stereoselective copper-catalyzed SN2 -allylation reactions [33, 35-37], while a brief presentation of allylation reactions with other transition metals including Mo and Rh is given in Section 14.6 [8, 13, 33, 38, 39]. The closing Section 14.7 deals with selected methods for asymmetric ring-opening reactions of unsaturated heterocycles [38, 40, 41]. 

Since Trost s first report of catalytic, enantioselective Pd-catalyzed allylations in the presence of DIOP ligands in 1977 (29, Scheme 14.6) [52], numerous chiral ligands for these transformations have been designed, synthesized, and studied [4, 8, 13, 16, 17, 27-30, 32, 33]. 

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