organic chemistry Organic chemistry is a subdiscipline within chemistry involving the science, scientific study of the structure, properties, and reactions of organic compounds and organic matter, organic materials, i.e., matter in its various forms that contain ...

, the Fráter–Seebach alkylation (also known as Seebach–Fráter alkylation or Fráter–Seebach reaction) is a

diastereoselective In stereochemistry, diastereomers (sometimes called diastereoisomers) are a type of stereoisomer. Diastereomers are defined as non-mirror image, non-identical stereoisomers. Hence, they occur when two or more stereoisomers of a compound have dif ...

alkylation of

chiral Chirality () is a property of asymmetry important in several branches of science. The word ''chirality'' is derived from the Greek language, Greek (''kheir''), "hand", a familiar chiral object. An object or a system is ''chiral'' if it is dist ...

beta-hydroxy esters using strong bases. The reaction was first published by Georg Fráter in 1979; in 1980,

Dieter Seebach Dieter Seebach is a German chemist known for his synthesis of biopolymers and dendrimers, and for his contributions to stereochemistry. He was born on 31 October 1937 in Karlsruhe. He studied chemistry at the University of Karlsruhe (TH) under t ...

reported about a similar reaction with

malic acid Malic acid is an organic compound with the molecular formula . It is a dicarboxylic acid that is made by all living organisms, contributes to the sour taste of fruits, and is used as a food additive. Malic acid has two stereoisomeric forms ( ...

ester.

Outline and mechanism

Chiral beta-hydroxy esters can be treated with two equivalents of a strong base ( lithium diisopropylamide (LDA) or lithium bis(trimethylsilyl)amide (LHMDS) are popular choices) to both remove the proton on the alcohol and enolize the ester. An alkylating agent (

methyl iodide Iodomethane, also called methyl iodide, and commonly abbreviated "MeI", is the chemical compound with the formula CH3I. It is a dense, colorless, volatile liquid. In terms of chemical structure, it is related to methane by replacement of one h ...

in the case of Fráter's publication) is then added. This attacks from the opposite face of the chiral

hydroxyl In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy ...

group to avoid

steric hindrance Steric effects arise from the spatial arrangement of atoms. When atoms come close together there is generally a rise in the energy of the molecule. Steric effects are nonbonding interactions that influence the shape ( conformation) and reactivi ...

as shown below in the 6-membered

transition state In chemistry, the transition state of a chemical reaction is a particular configuration along the reaction coordinate. It is defined as the state corresponding to the highest potential energy along this reaction coordinate. It is often marked w ...

with

chelating Chelation () is a type of bonding of ions and their molecules to metal ions. It involves the formation or presence of two or more separate coordinate bonds between a polydentate (multiple bonded) ligand and a single central metal atom. These l ...

metal ions. This reaction has since been used in the synthesis of many natural products due to its high yield and diastereoselectivity.

References

{{DEFAULTSORT:Frater-Seebach alkylation Name reactions