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Aldol and related condensations

26 real reactions from the literature: intramolecular aldol on methyl ketones, aryl ketones and dialkyl ketones; aldol condensation on aromatic aldehydes, aryl ketones and five-membered cyclic ketones; and more. Each scheme shows starting materials, conditions and products, with the yield and reference where the source reports them.

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  1. Intramolecular aldol: (4R)-4-ethyl-6-oxoheptanal (a methyl ketone) with NaOH; Et2O / H2O gives (4S)-4-ethyl-2-methylcyclopentene-1-carbaldehyde (the cyclic enone). 85% yield.
    Intramolecular aldolEur. J. Org. Chem. 2001, 2435

  2. Aldol condensation: cyclopentanone (a five-membered cyclic ketone) with NaOH; H2O gives cyclopentylidenecyclopentan-2-one (the α,β-unsaturated ketone). 60% yield.
    Aldol condensationGreen Chem. 2013, 15, 1932

  3. Aldol addition: acetone (a methyl ketone) with Ba(OH)2; Δ gives diacetone alcohol (the β-hydroxy ketone).
    Aldol additionOrg. Synth. Coll. Vol. 1, p. 199

  4. Knoevenagel: 2,3-dimethoxybenzaldehyde (an aromatic aldehyde) with piperidine, pyridine, Δ; 2) aq. HCl gives 2',3'-dimethoxycinnamic acid (the condensation product).
    KnoevenagelOrg. Synth. Coll. Vol. 4, p. 327

  5. Mannich: acetophenone (an aryl ketone) with (CH3)2NH2Cl; HCl, CH3CH2OH, Δ gives 3-(dimethylamino)-1-phenyl-1-propanone (the β-amino ketone (Mannich base)).
    MannichOrg. Synth. Coll. Vol. 3, p. 305

  6. Darzens: 2-chlorocyclopentanone (an α-halo ketone) and benzaldehyde (an aromatic aldehyde) with DBU; CH2Cl2 gives the glycidic epoxide. 74% yield.
    DarzensTetrahedron Lett. 2019, 60, 1949

  7. Intramolecular aldol: 2-(2-acetylphenyl)benzaldehyde (an aryl ketone) with 1) cat. TsOH EtOH/H2O; 1 min / RT; 2) then add NaOH; 10 min / 70 ºC gives 5H-dibenzo(a,c)cyclohepten-5-one (the cyclic enone). 99% yield.
    Intramolecular aldolJ. Org. Chem. 2009, 74, 3948

  8. Aldol condensation: benzaldehyde (an aromatic aldehyde) with NaOH, aq. CH3CH2OH gives (1E,4E)-1,5-diphenyl-1,4-pentadien-3-one (the α,β-unsaturated ketone).
    Aldol condensationOrg. Synth. Coll. Vol. 2, p. 167

  9. Aldol addition: (2,4,6-trimethylphenyl) propanoate (an ester) and isobutyraldehyde (an aliphatic aldehyde) with 1) LDA, THF; 2) isobutyraldehyde gives 2,4,6-trimethylphenyl 3-hydroxy-2,4-dimethylpentanoate (the β-hydroxy ester). 60% yield.
    Aldol additionOrg. Synth. 1985, 63, 99

  10. Knoevenagel: diphenic anhydride (a cyclic anhydride) and diethyl malonate (a malonate ester) with Et3N gives the condensation product. 65% yield.
    KnoevenagelChem. Ber. 1971, 104, 1573

  11. Mannich: cyclohexanone (a six-membered cyclic ketone), dimethylamine (a secondary amine) and formaldehyde with Me2NH, CH2O (Mannich) gives 2-((dimethylamino)methyl)cyclohexanone (the β-amino ketone (Mannich base)).
    MannichRealOChem worksheet

  12. Intramolecular aldol: 2-(3-oxobutyl)isoindoline-1,3-dione (a methyl ketone) with TfOH; PhMe gives 3,4-dihydropyrido[1,2-b]isoindole-2,6-dione (the cyclic enone). 94% yield.
    Intramolecular aldolOrg. Lett. 2020, 22, 239

  13. Aldol addition: a dialkyl ketone with 1) TiCl4 / Ti(OiPr)4, -78 C / CH2Cl2, 2 min; 2) iPr2NEt / 30 min; 3) 1.5 equiv 3-methylbutanal gives the β-hydroxy ketone.
    Aldol additionJ. Org. Chem. 2005, 70, 6533

  14. Aldol addition: a β-keto ester with 1) LDA, -78 C; 2) isobutyraldehyde gives the β-hydroxy ketone.
    Aldol additionJ. Am. Chem. Soc. 1988, 110, 3560

  15. Aldol condensation: furfural (an aromatic aldehyde) with 1) acetone, NaOH; H2O; 2) H2SO4 gives furfuralacetone (the α,β-unsaturated ketone).
    Aldol condensationOrg. Synth. Coll. Vol. 1, p. 283

  16. Aldol condensation: benzaldehyde (an aromatic aldehyde) with 1) acetone, aq. NaOH; 2) HCl gives benzylideneacetone (the α,β-unsaturated ketone).
    Aldol condensationOrg. Synth. Coll. Vol. 1, p. 77

  17. Intramolecular aldol: a methyl ketone with NaOH; MeOH / RT gives the cyclic enone. 90% yield.
    Intramolecular aldolAngew. Chem. Int. Ed. 2011, 50, 5878

  18. Intramolecular aldol: a methyl ketone with 1) KOH; MeOH / H2O; 3 h / RT; 2) MsCl / Et3N; CH2Cl2 gives the cyclic enone. 99% yield.
    Intramolecular aldolCan. J. Chem. 1986, 64, 1404

  19. Aldol condensation: benzaldehyde (an aromatic aldehyde) and acetophenone (an aryl ketone) with TsOH gives chalcone (the α,β-unsaturated ketone). 98% yield.
    Aldol condensationInd Pat App 2014DE00146

  20. Aldol condensation: 4'-hydroxyacetophenone (an aryl ketone) and 3-fluorobenzaldehyde (an aromatic aldehyde) with KOH; EtOH gives the α,β-unsaturated ketone. 83% yield.
    Aldol condensationBioorg. Med. Chem. Lett. 2017, 27, 1205

  21. Intramolecular aldol: a methyl ketone with 1) KOH, MeOH / H2O, 3 h / RT; 2) MsCl / Et3N, CH2Cl2 gives the cyclic enone.
    Intramolecular aldolCan. J. Chem. 1986, 64, 1404

  22. Intramolecular aldol: a methyl ketone with KOH, MeOH / H2O, 2 h / RT gives the cyclic enone.
    Intramolecular aldolPCT Int. Appl. WO2014070915

  23. Intramolecular aldol: a methyl ketone with NaOH, MeOH / H2O, 20 min / RT gives the cyclic enone. 90% yield.
    Intramolecular aldolAngew. Chem. Int. Ed. 2011, 50, 5878

  24. Intramolecular aldol: a methyl ketone with NaOH, H2O, 10 min / RT gives the cyclic enone. 52% yield.
    Intramolecular aldolChem. Eur. J. 2012, 18, 12498

  25. Intramolecular aldol: 2-(2-acetylphenyl)benzaldehyde (an aryl ketone) with 1) cat. TsOH, EtOH/H2O, 1 min / RT; 2) then add NaOH, 10 min / 70 C gives 5H-dibenzo(a,c)cyclohepten-5-one (the cyclic enone). 99% yield.
    Intramolecular aldolJ. Org. Chem. 2009, 74, 3948

  26. Intramolecular aldol: a dialkyl ketone with KOH gives the cyclic enone.
    Intramolecular aldolJ. Org. Chem. 1973, 38, 3663