Reading a scheme

Start with the conditions. A strong base, an acid, a metal, a peroxide: the reagent line narrows the reaction type before you look at a single bond.

Find what changed. Compare starting material and product atom by atom: which bond formed, which left, and whether the carbon count grew.

Substitution vs. elimination vs. addition is a bookkeeping question: same number of σ bonds, fewer, or more.

Mechanism follows structure. A tertiary or benzylic center with a weak nucleophile points to a cation; a primary center with a strong nucleophile does not.

Every example here is a real reaction with a real citation. The yields are the authors’ own.

Aldol and related condensations: All · Intramolecular aldol · Aldol condensation · Aldol addition · Knoevenagel condensation · Mannich reaction · Darzens condensation

Darzens glycidic ester condensation

1 real reaction from the literature, on α-halo ketones. Each scheme shows starting materials, conditions and products, with the yield and reference where the source reports them.

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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