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: Overall, it is demonstrated that Meldrum's acid and its derivatives provide access to a broad range of reactivities that, combined with their ease of handling and preparation, make them ideal electrophiles.
Abstract: Meldrum's acid (2,2-dimethyl-1,3-dioxane-4,6-dione) is a molecule with a unique history, owing to its originally misassigned structure, as well as a unique place among acylating agents, owing to its high acidity and remarkable electrophilicity. In this Account, we outline the work of our group and others toward harnessing the reactivity of Meldrum's acid derivatives in catalytic C-C bond-forming reactions. Taking advantage of the ability of Meldrum's acid to decompose to CO(2) and acetone following acyl substitution, we have shown that intramolecular Friedel-Crafts acylations can be performed under mild Lewis acidic conditions to yield a variety of benzocyclic ketones. In a further expansion of this method, a domino Friedel-Crafts acylation/alpha-tert alkylation reaction was used to complete the first total synthesis of (+/-)-taiwaniaquinol B. The unique characteristics of Meldrum's acid extend to its alkylidene derivatives, which have also proven exceptionally useful for the development of new reactions not readily accessible from other unsaturated carbonyl electrophiles. By combining the electrophilicity and dienophilicity of alkylidene Meldrum's acid with our Friedel-Crafts chemistry, we have demonstrated new domino syntheses of coumarin derivatives and tetrahydrofluorenones by conjugate additions, Diels-Alder cycloadditions, and C-H functionalizations. Additionally, we have used these powerful acceptors to allow conjugate alkenylation with functionalized organostannanes, and conjugate allylation under very mild conditions. We have also shown that these molecules permit the asymmetric formation of all-carbon quaternary stereocenters via enantioselective conjugate additions. These reactions employ dialkylzinc nucleophiles, maximizing functional group compatibility, while the presence of a Meldrum's acid moiety in the product allows a variety of postaddition modifications. A full investigation of this reaction has determined the structural factors of the alkylidene that contribute to optimal enantioselectivity. We have also used these acceptors to form tertiary propargylic stereocenters in very high enantiomeric excess by an extremely mild, Rh(I)-catalyzed addition of TMS-acetylene. Overall, we demonstrate that Meldrum's acid and its derivatives provide access to a broad range of reactivities that, combined with their ease of handling and preparation, make them ideal electrophiles.
131 citations
TL;DR: In this paper, an efficient catalyst for α-alkylation of arylacetonitriles and methyl ketones with alcohols was proposed, which works with turnover frequencies between 675 and 176 h-1 for nitriles, and between 194 and 28 h -1 for ketones.
Abstract: Complex [Os(η6-p-cymene)(OH)(IPr)]OTf is an efficient catalyst precursor for the α-alkylation of arylacetonitriles and methyl ketones with alcohols, which works with turnover frequencies between 675 and 176 h–1 for nitriles and between 194 and 28 h–1 for ketones.
131 citations
TL;DR: The newly developed method led to the total synthesis of (+)-perophoramidine in a highly efficient manner and with outstanding diastereo- and enantiocontrol.
Abstract: Highly congested vicinal all-carbon quaternary stereocenters were generated via catalytic asymmetric alkylation reaction of 3-bromooxindoles with 3-substituted indoles. These catalytic reactions proceeded in excellent yields with a broad scope on either reaction partner, and with outstanding diastereo- and enantiocontrol. The newly developed method led to the total synthesis of (+)-perophoramidine in a highly efficient manner.
131 citations
TL;DR: From dual-catalyst combination studies varying the transition metal and main group metal partner, the efficiency of the present catalysts is attributed to the electrophilic "IrIII-SnIV" core.
Abstract: The highly active Friedel−Crafts alkylation (FCA) catalyst, [Ir(COD)Cl(SnCl3)(SnCl4)(arene)]+Cl- (1-SnCl4), is easily generated in one-pot from [Ir(COD)Cl]2 or [Ir(COD)(μ-Cl)Cl(SnCl3)]2 (1) and SnC...
130 citations
TL;DR: Reactions of 4-alkyl Hantzsch nitriles as tertiary radical donors joined two contiguous all-carbon quaternary centers intermolecularly, and this chemistry was used to synthesize a common precursor of a class of hydroxysteroid dehydrogenase inhibitors.
Abstract: For the first time, 4-alkyl Hantzsch esters were used to construct molecules with all-carbon quaternary centers by visible light-induced photoredox catalysis via transfer alkylation. Up to a 1500 h–1 turnover frequency was achieved in this reaction. Reactions of 4-alkyl Hantzsch nitriles as tertiary radical donors joined two contiguous all-carbon quaternary centers intermolecularly, and this chemistry was used to synthesize a common precursor of a class of hydroxysteroid dehydrogenase inhibitors.
130 citations