Allylic displacement reactions palladium catalyzed

Allylic displacements. Palladium-catalyzed allylic displacement reactions have been carried out in ionic liquids at room temperature. 

Acetate ion is also a competent nucleophile for displacement of hydroxyl groups under Mitsunobu-type (Appel) reaction conditions (eq 13), and has been used in palladium-catalyzed allylic displacement reactions (eq 14)T ... 

Azide salts are a class of versatile nitrogen nucleophiles that can be readily employed as reaction partners in palladium-catalyzed allylic displacement reactions. A telling example was documented by Trost in the desymmetrization of bis-carbonate 51 to give azide 52 in an excellent 95% ee (Scheme 14.10) [66]. The fact that the reaction proceeds under mild conditions ensures that any undesired rearrangement of the allylic azide 52 is suppressed. 

Phenols have been documented to serve as a versatile class of 0-nucleophiles in asymmetric allylic alkylation events. Even a sterically hindered ortho-disubstituted phenol such as 59 participated in a palladium-catalyzed allylic displacement reaction with carbonate 60 (Scheme 14.12) [69]. Product 62 was obtained in 88% ee and subsequently converted into (-)-galantha-mine (63), a selective inhibitor of acetylcholinesterase with potential in the treatment of Alzheimer s disease [69, 70). 

For our definition of the term a position , see [6]. There is an older usage of the terms a and y in the discussion of palladium-catalyzed allylic displacement reactions, where... 

Allylic diacetates were converted into N,N, 0,0, and N, O-heterocycles in a palladium catalyzed two step nucleophilic displacement sequence. The reaction of o-aminophenol and cyclopentenyl-diacetate, for example, gave the cyclopentene condensed phenoxazine derivative in acceptable yield (4.21.), while o-phenylenediamine and catechol gave the corresponding phenazine and dioxine derivative in good yield.24... 

The various allylic substitution reactions are illustrated in a synthesis of Tipranavir (11), an HIV protease inhibitor. A palladium-catalyzed opening of a vinyl epoxide set the quaternary stereogenic center (Scheme 22.23). A molybdenum-catalyzed allylic nuclophilic displacement was used to access the benzylioc stereogenic center (Scheme 22.24).153... 

Palladium-catalyzed heteroannulation is illustrated by synthesis of substituted l//-benzo[rf]azonine 227, which was prepared from allene and tosylamide-containing aryl halide (Equation 26). The reaction was suggested to proceed by addition of an arylpalladium compound to the allene to generate a 7i-allylpalladium intermediate, which subsequently undergoes nucleophilic displacement of palladium at the less-hindered end of the 7i-allyl system <1998JOC6859>. 

The research group of Trost has shown that stabilized enolates derived from -diesters and a-phe-nylsulfonyl esters are excellent nucleophiles for palladium(0)-catalyzed reactions with allylic acetates. Since these reactions involve ir-allylpdladium intermediates, they proceed with net retention of configuration and, therefore, differ from traditional displacement reactions where inversion is the rule. Moreover, the transition metal imposes a template effect on intramolecular versions of these reactions and... 

Nucleophilic Displacement. PhTMS-BF3 0Et2 system has been shown to be useful in the transformation of allylic alcohols to allylic sulfides (eq IS). Preparation of unsymmetrical diaryl sulfides can be achieved by reaction of arenediazonium tetraflu-oroborates with PhSTMS (eq 19). In some cases, addition of cupric sulfide increases the yield of the diaryl sulfides. The use of (phenylthio)trimethylsilane as a coupling partner in palladium catalyzed reactions with aUyl carbonates (eq 20) and aryl iodide (eq 21) has been explored. ... 

It is clear from Figure 8.3 that the B3LYP-D3 functional in combination with the cc-PVTZ basis set yields results comparable to the CCSD(T)/CBS level for the parallel displaced benzene dimer. As exemplified above in the palladium-catalyzed enantioselective allylic alkylation using BlNAP-type ligands [21], this accurate description of dispersion effects can be decisive for discriminating between different reaction pathways. 

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