Topic
Alkylation
About: Alkylation is a research topic. Over the lifetime, 29915 publications have been published within this topic receiving 464944 citations. The topic is also known as: alkylation reaction.
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TL;DR: A formal regioselective cross-coupling of various pyridines with alkyl and aryl groups can be achieved by a BF3·OEt2-mediated addition of Grignard or organozinc reagents.
Abstract: A formal regioselective cross-coupling of various pyridines with alkyl and aryl groups can be achieved by a BF3·OEt2-mediated addition of Grignard or organozinc reagents to pyridines bearing various substituents (chloro, bromo, cyano, vinyl, phenyl, carbethoxy, nitro, etc.) followed by an oxidative aromatization mediated by chloranil. Good regioselectivity and wide functional group tolerance make this method very versatile for the preparation of polyfunctional pyridines. No transition-metal catalyst is required in these coupling reactions.
110 citations
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TL;DR: Curtius rearrangement of the resulting carboxylic acid provided the enantiopure benzyloxycarbonyl (Cbz)-protected β-amino esters 6 in good yields (74−79%).
Abstract: A general procedure for the synthesis of enantiopure β-substituted, β-amino acids is presented. Alkylation of the sodium enolates derived from chiral N-acyloxazolidinone imides 2 (R = Me, i-Pr, t-Bu, Ph, Bn) with tert-butyl bromoacetate afforded the 2-substituted succinate derivatives 3 in good yields (82−89%) and with high selectivity (≥93:7). Following hydrolysis, Curtius rearrangement of the resulting carboxylic acid provided the enantiopure benzyloxycarbonyl (Cbz)-protected β-amino esters 6 in good yields (74−79%).
110 citations
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TL;DR: Two different possibilities for the preparation of immobilised ionic liquids are presented in this article, and different methods used, as well as analytical data and some catalytical results achieved by these catalysts.
Abstract: Two different possibilities for the preparation of immobilised ionic liquids are presented. Lewis acidic ionic liquids which have been shown to be highly active catalysts in alkylation reactions of the Friedel–Crafts type were supported on amorphous silica and MCM 41 materials. We describe the different methods used, as well as analytical data and some catalytical results achieved by these catalysts.
110 citations
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TL;DR: Three pyridine- and quinoline-based ligands are developed to match different classes of amine substrates, demonstrating a rare example of ligand-enabled C(sp(3))-H olefination reactions and a significant step toward practical C-H functionalizations of alkyl amines.
Abstract: Pd(II)-catalyzed olefination of γ-C(sp3)–H bonds of triflyl (Tf) and 4-nitrobenzenesulfonyl (Ns) protected amines is achieved. Subsequent aza-Wacker oxidative cyclization or conjugate addition of the olefinated intermediates provides a variety of C-2 alkylated pyrrolidines. Three pyridine- and quinoline-based ligands are developed to match different classes of amine substrates, demonstrating a rare example of ligand-enabled C(sp3)–H olefination reactions. The use of Ns protecting group to direct C(sp3)–H activation of alkyl amines is also a significant step toward practical C–H functionalizations of alkyl amines.
110 citations
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TL;DR: The exploration of novel, concise methodologies that allow the rapid establishment of these polycyclic indole skeletons in a single operation is highly desired.
Abstract: Liang Hong, Wangsheng Sun, Chunxia Liu, Lei Wang, and Rui Wang* b] The pyrrolo ACHTUNGTRENNUNG[1,2-a]indole tricyclic ring structures are widely presented in a number of naturally occurring products and have attracted much attention due to the broad scope of their biological activities. Representative examples are mitomycins, some of the most effective antitumor agents, and yuremamine, a new phytoindole recently isolated from the stem bark of Mimosa hostilis, which shows hallucinogenic and psychoactive effects. In addition to being an important motif in many biologically and pharmaceutically interesting compounds, they are also useful intermediates for the synthesis of polyheterocycles. Although several approaches for the synthesis of this system have been explored, they usually require several steps and expensive reagents. Thus, the exploration of novel, concise methodologies that allow the rapid establishment of these polycyclic indole skeletons in a single operation is highly desired. On the other hand, modifications of the indole structure mainly focus on enantioselective alkylation at the C3-position, probably because of the privileged C3-chemoselectivity of indole compounds. Recently, the enantioselective synthesis of C2-substituted indoles has also been realized through the asymmetric alkylation of 4,7-dihydroindoles and subsequent oxidation. In sharp contrast, the enantioselective N-alkylation of indoles has rarely been explored, probably due to the reduced nucleophilicity of the N H functionality of indoles. As noted above, the use of indoles in direct catalytic asymmetric N-alkylation is challenging because the N H proton of indoles, which must be removed to generate the nucleophile, has a relatively high pKa value of 16.97 (Scheme 1). Direct organocatalytic methods based on amine
110 citations