Related Experiment Video
Updated: Aug 18, 2026

A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species
Published on: August 16, 2018
Enzyme-catalyzed regio- and enantioselective ketone reductions
Michael Müller1, Michael Wolberg, Thomas Schubert
1Forschungszentrum Jülich GmbH, 52425 Jülich, Germany. mi.mueller@fz-juelich.de
Abstract:
In this chapter, examples are given of the application of highly reactive prochiral ketones as substrates for enzymatic reductions. 3,5-Dioxocarboxylates are polyketide-like compounds that can be used to synthesize all of the possible stereoisomers of the corresponding 1,3-diols by means of regio- and enantioselective enzymatic reduction. The results obtained from an investigation into the usefulness of the resulting hydroxyl ketones and 1,3-diols in organic synthesis led to the development of non-natural functionalized ynones as a starting material for the enzymatic route to enantiopure propargylic alcohols. A broad variety of substituted acetylenic ketones can be reduced enantioselectively by the oxidoreductases Lactobacillus brevis ADH (LBADH), Candida parapsilosis carbonyl reductase (CPCR), horse liver ADH (HLADH) and Thermoanaerobium brockii ADH (TBADH). The resulting propargylic alcohols can be obtained in either enantiomeric form, since (R)- and (S)-specific oxidoreductases can be applied. By varying the size of the substituents, the enantiomeric excess can be tuned, or the enantioselectivity can even be reversed. The obtained highly functionalized enantiopure alcohols are synthetically flexible chiral building blocks that offer new synthetic strategies for target- and diversity-oriented synthesis.
Related Concept Videos
Alcohols from Carbonyl Compounds: Reduction
Catalytic hydrogenation is similar to the reduction of an alkene or alkyne by adding H2 across the pi bond in the presence of transition metal catalysts like Raney Ni, Pd–C, Pt, or Ru. Aldehydes and ketones can be reduced by this method, often under mild to moderate heat (25–100°C) and...
α-Alkylation of Ketones via Enolate Ions
Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
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...
Acid Halides to Ketones: Gilman Reagent
As shown below, the mechanism proceeds in two steps. First, one of the alkyl groups of the reagent acts as a nucleophile and attacks the acyl carbon of the acid chloride to form a tetrahedral intermediate. This is followed by the reformation of the carbon–oxygen double...
Regioselective Formation of Enolates
Acid-Catalyzed α-Halogenation of Aldehydes and Ketones
In the first step of the mechanism, the acid protonates the carbonyl oxygen resulting in a resonance-stabilized cation, which subsequently loses an α-hydrogen to form an enol tautomer. The C=C bond in an enol is highly nucleophilic because of the electron-donating nature of the –OH group. Consequently, the double bond attacks an electrophilic halogen to form a...

