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Tsuji–Trost reaction - Wikipedia
The asymmetric allylation of carbonyl compounds is an important process for the formation of carbon–carbon bonds, generating optically active homoallylic alcohols that are versatile building blocks with widespread applications in organic synthesis. The use of readily available unsaturated hydrocarbons as allylating reagents in the transition-metal-catalyzed asymmetric allylation has received increasing interest as either a step- or an atom-economy alternative. This review summarizes transition-metal-catalyzed enantioselective allylations on the basis of the ‘indirect’ and ‘direct’ use of simple unsaturated hydrocarbons (include dienes, allenes, alkynes, and alkenes) as allylating reagents, with emphasis on highlighting conceptually novel reactions.
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The enantioselective synthesis of Nitrogen-containing heterocycles (N-heterocycles) represents a substantial chemical research effort and resonates across numerous disciplines including the total synthesis of natural products and medicinal chemistry. In this manuscript, we describe the highly enantioselective palladium-catalyzed decarboxylative allylic alkylation of readily available lactams to form 3,3,-disubstituted pyrrolidinones, piperidinones, caprolactams, and structurally related lactams. Given the prevalence of quaternary N-heterocycles in biologically active alkaloids and pharmaceutical agents, we envision that our method will provide a synthetic entry into the de novo asymmetric synthesis of such structures. As an entry for these investigations we demonstrate how the described catalysis affords enantiopure quaternary lactams that intercept synthetic intermediates previously employed in the synthesis of the Aspidosperma alkaloids quebrachamine and rhazinilam, but that were previously only available by chiral auxiliary approaches or as racemic mixtures.
The enantioselective version of the Tsuji–Trost ..
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Transition metal-catalyzed allylic alkylation is a key method for the enantioselective preparation of chiral substances and ranks among the best general techniques for the catalytic alkylation of prochiral enolates.,,, We sought to develop a general method for catalytic asymmetric α-alkylation, given the importance of α-quaternary lactams (vide supra). Over the past seven years, our laboratory has reported an array of methods for the synthesis of α-quaternary ketones,,, and demonstrated the use of these methods in a number of complex molecule syntheses.,,, Concurrent to our efforts, the Trost lab,,,, and others,,, have developed a series or related allylic alkylation methods. In the course of our investigations of the ketone enolate allylic alkylation and other alkylation processes, we have often encountered interesting ligand electronic effects and, in certain cases, pronounced solvent effects. In keeping with our ultimate goal of N-heterocycle alkylation, we set out to further probe these subtle effects by examining enolate reactivity in a lactam series that would be amenable to both steric and electronic fine-tuning.
In summary, we have reported the first method for catalytic enantioselective alkylation of monocyclic 5-, 6-, and 7-membered lactam enolate derivatives to form α-quaternary and α-tetrasubstituted tertiary lactams. The reaction discovery process was enabled by parallel screening of reaction parameters and led to the identification of a sterically and electronically tuned system for highly enantioselective alkylation. We have applied this method to the catalytic asymmetric synthesis of key intermediates previously employed for the construction of Aspidosperma alkaloids. Finally, the asymmetric products formed in this investigation are envisioned to be widely useful as building blocks for the preparation of range of nitrogen containing heterocycles in materials science, medicinal chemistry and natural products synthesis.
asymmetric synthesis of primary ..
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Nitrogen-containing heterocycles are ubiquitous in natural products, pharmaceuticals, and materials science.,, Stereoselective methods for the synthesis of 3,3-disubstituted pyrrolidinones, piperidinones, and caprolactams, in addition to the corresponding amines, are valuable for the preparation of a wide array of important structures in these areas of research (). Despite the prevalence of such architectures and the potential of lactam enolate alkylation as a direct method for their synthesis, a paucity of enantioselective lactam alkylations leading to C(α)-quaternary centers are known. While most methods rely on chiral auxiliary chemistry,,, the few catalytic examples that exist are specific to the oxindole lactam nucleus,,,,, α-carbonyl stabilized enolates, or cyclic imides. Importantly, enolate stabilization is critical for success in both of these catalytic systems, thereby limiting the scope of each transformation. To the best of our knowledge, there are no examples of catalytic asymmetric alkylations of simple piperidinone, pyrrolidinone, and caprolactam scaffolds for the formation of C(α)-quaternary or C(α)-tetrasubstituted tertiary centers. Herein, we describe the stereoselective synthesis of a wide range of structurally-diverse, functionalized lactams by palladium-catalyzed enantioselective enolate alkylation. The importance of this chemistry to the synthesis of bioactive alkaloids is specifically demonstrated, and the potential utility of this transformation for the construction of novel building blocks for medicinal and polymer chemistry can be readily inferred.
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