The Markó–Lam deoxygenation is an organic chemistry reaction where the hydroxy

functional group In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the rest ...

in an

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...

is replaced by a

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...

atom to give an

alkyl group In organic chemistry, an alkyl group is an alkane missing one hydrogen. The term ''alkyl'' is intentionally unspecific to include many possible substitutions. An acyclic alkyl has the general formula of . A cycloalkyl is derived from a cycloalk ...

. The Markó-Lam reaction is a variant of the

Bouveault–Blanc reduction The Bouveault–Blanc reduction is a chemical reaction in which an ester is reduced to primary alcohols using absolute ethanol and sodium metal. It was first reported by Louis Bouveault and Gustave Louis Blanc in 1903. Bouveault and Blanc demons ...

and an alternative to the classical

Barton–McCombie deoxygenation The Barton–McCombie deoxygenation is an organic reaction in which a hydroxy functional group in an organic compound is replaced by a hydrogen to give an alkyl group. It is named after British chemists Sir Derek Harold Richard Barton and Stuart W ...

. It is named for the Belgian chemists István Markó and Kevin Lam. The main features of the reaction are: *short reaction time (5 seconds to 5 minutes). *the use of a stable toluate derivative. *the use of SmI₂/

HMPA Hexamethylphosphoramide, often abbreviated HMPA, is a phosphoramide (an amide of phosphoric acid) with the formula This colorless liquid is a useful reagent in organic synthesis. Structure and reactivity HMPA is the oxide of the highly basic ter ...

system or electrolysis instead of the classical and difficult to remove

tributyltin hydride Tributyltin hydride is an organotin compound with the formula (C4H9)3SnH. It is a colorless liquid that is soluble in organic solvents. The compound is used as a source of hydrogen atoms in organic synthesis. Synthesis and characterization The ...

Mechanism

A hydroxyl group is first derivitised into a stable and very often crystalline toluate derivative. The aromatic ester is submitted to a monoelectronical reduction, by the use of SmI₂/

or by electrolysis, to yield the a radical-anion which decomposes into the corresponding carboxylate and into the radical of the alkyl fragment. Mechanism_MarkoLam

This radical could be used for further chemical reactions or can abstract a hydrogen atom to form the deoxygenated product.

Variations

In presence of methanol or isopropanol, the reduction lead to the selective deprotection of the aromatic esters. MarkoLam_Hydrolysis_colored

In presence of ketones, allylic derivatives lead to the coupling product when treated in Barbier's conditions with samarium diiodide. MarkoLam_Allylation

Scope

The Markó-Lam reaction was used as a final step in the total synthesis of Trifarienol B: Trifarienol_B_via_MarkoLam

References

{{DEFAULTSORT:Marko-Lam Deoxygenation Free radical reactions Organic redox reactions Name reactions