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通过脱碳化交叉合的Ni-催化Enantioselective Dialkyl Carbinol合成:发展,范围和应用

  • 0Department of Chemistry, Scripps Research, 10550 North Torrey Pines Road, La Jolla, California 92037, United States.

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Malonic ester synthesis is a method to obtain α substituted carboxylic acids from ꞵ-diesters such as diethyl malonate and alkyl halides.

The reaction proceeds via abstraction of the acidic α hydrogen from a ꞵ-diester to produce a doubly stabilized enolate ion. The nucleophilic enolate attacks the alkyl halide in an SN2 manner to form an alkylated malonic ester intermediate with a new C–C bond. Further treating the intermediate with aqueous acid or base results in...

β-Dicarbonyl Compounds via Crossed Claisen Condensations 01:18

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Crossed Claisen condensations are base-promoted reactions between two different ester molecules producing β-dicarbonyl compounds.  The reaction involving esters, with both containing α hydrogen, results in a mixture of four different products that are difficult to isolate. This reduces the synthetic utility of the reaction.

This problem is resolved by using one of the esters without any α hydrogen, such as aryl esters.

Additionally, highly reactive molecules like formate esters serve as...

Cyclohexenones via Michael Addition and Aldol Condensation: The Robinson Annulation 01:27

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Robinson annulation is a base-catalyzed reaction for the synthesis of 2-cyclohexenone derivatives from 1,3-dicarbonyl donors (such as cyclic diketones, β-ketoesters, or β-diketones) and α,β-unsaturated carbonyl acceptors. Named after Sir Robert Robinson, who discovered it, this reaction yields a six-membered ring with three new C–C bonds (two σ bonds and one π bond).

The ring-forming reaction occurs in two stages: Michael addition and the subsequent...

Vicinal Diols via Reductive Coupling of Aldehydes or Ketones: Pinacol Coupling Overview 01:27

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Wilhelm Rudolph Fittig discovered the pinacol coupling reaction in 1859. It is a radical dimerization reaction and involves the reductive coupling of aldehydes or ketones in the presence of hydrocarbon solvent to yield vicinal diols.

The radical reaction is initiated by a single electron transfer from metals like sodium and magnesium to a spin-paired molecule like aldehydes or ketones to generate a ketyl—a radical anion. The ketyl has a radical character on the carbon atom and a charge...

Cycloaddition Reactions: Overview 01:16

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Cycloadditions are one of the most valuable and effective synthesis routes to form cyclic compounds. These are concerted pericyclic reactions between two unsaturated compounds resulting in a cyclic product with two new σ bonds formed at the expense of π bonds. The [4 + 2] cycloaddition, known as the Diels–Alder reaction, is the most common. The other example is a [2 + 2] cycloaddition.

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Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...