3-Acetylindole is a substituted indole and a reactant in the first step of multiple biological synthesis applications. Indoles, especially 3-acetylindole derivatives, possess a wide variety of biological activities. Many biological molecules, from Antibacterial agents against Staphylococcus to anti-HIV synthesis agents like N-arylsulfonyl-3-acetylindoles, use 3-acetylindole as a starting reagent. They can react with aromatic aldehydes to produce chalcones, which are intermediates for biologically active heterocyclic compounds. 3-Acetylindole is also the reactant for the synthesis of inhibitors that are used with hepatitis protease and nuclear factor kappa-light-chain enhancer of B cells (NF-κB).

4-(Benzyloxy)aniline is used as a building block for biochemical synthesis.

4-Acetoxyindole is an indole with an acetyl group. It is used as a starting reactant in the preparation of 4-oxoquinoline, which is used as an anti-HIV agent. In chromatography it is used to help optimize peak capacity for the separation of low molecular weight molecules during gradient elution.

4-Azaindole is used a reagent for the creation of complex molecules. When combined with a bisalkoxyalkyl spacer, they can be used to target melatonin MT 1 receptors over MT 2 receptors.

4-Benzyloxyindole-2-carboxylic acid ethyl ester is a reagent for building organic molecules.

4-Chloroindole is a reagent for chemical synthesis. One of the most popular applications involves reacting 4-Chloroindole with acetic acid to produce 4-Chloroindole-3-acetic acid (4-Cl-IAA), an auxin, which is a natural plant hormone and may be a death signaling hormone for maturing seeds.

4-Chlorophenylhydrazine is a reagent used for chemical synthesis. It is a reactant in the synthesis of 5-Aminopyrazole-4-carbonitriles.