Global Chemical Database

Molecular Building Blocks

This topic covers important starting materials, intermediates, and molecular building blocks used in organic synthesis, medicinal chemistry, and materials chemistry.

2-Chloro-3',4'-dihydroxyacetophenone

A catechol ring and an alpha-chloroketone make CAS 99-40-1 a compact but versatile gateway to more elaborate organic structures.

2-(1H-Benzotriazole-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate

HBTU became a peptide-chemistry workhorse by making one of biology's most important bonds faster and more reliable to construct.

2-(Benzo[D][1,3]dioxol-5-YL)-N-(2,3-dimethoxybenzyl)ethan-1-amine hydrochloride

A familiar scaffold can suggest a question, but only evidence can turn that suggestion into a chemical fact.

2,5-Diphenylquinone

A quinone core supplies redox chemistry; two phenyl groups prebuild a larger aromatic skeleton. That combination makes this compound more useful as an intermediate than as a bulk product.

Phenyl dichlorophosphate

Two chlorides on one phosphorus atom mean two stages of substitution - and an opportunity to build unsymmetrical phosphorus chemistry deliberately.

9-Anthracenecarboxylic acid

One molecule, two laboratories: fluorescence/materials chemistry sees an anthracene building block; physiology sees a chloride-channel probe.

Methyl 4-aminobenzoate

A useful intermediate often succeeds by giving chemists choices. In methyl 4-aminobenzoate, NH2 and ester chemistry can be manipulated separately.

p-Toluenesulfonic acid monohydrate

Sometimes reagent form matters almost as much as reagent identity. One crystal water helps define the familiar solid form of p-TsOH.

Aluminium isopropoxide

One reagent, two traditions: carbonyl transfer hydrogenation in organic chemistry and oxide formation in materials chemistry.

2-Amino-5-fluorobenzoic acid

Keep the useful scaffold, replace one H with F: a tiny structural edit can open a new electronic and synthetic space.

2-Bromo-3-fluoro-6-methylpyridine

A small building block can contain a synthetic plan. In this pyridine, different substituents are installed because they are meant to do different jobs.

m-(Trifluoromethyl)phenylacetic acid

A useful building block often divides labor: the COOH group provides the reaction point, while CF3 tunes the molecular environment.

2-Fluorobenzyl chloride

Two halogens, two jobs: Cl is designed to leave; F is designed to stay. That contrast makes 2-fluorobenzyl chloride a useful fluorinated intermediate.

Pyrazole-4-boronic acid pinacol ester

The boron is not usually meant to stay. In this pyrazole building block, Bpin is a temporary handle for constructing a permanent carbon-carbon bond.

Diphenylphosphoryl azide

Some reagents outgrow the reaction that made them famous. DPPA now appears across rearrangement, coupling, azidation and complex synthesis.

Diphenyl chlorophosphate

In this phosphorus reagent, chlorine is temporary. The useful design feature is a programmable P-Cl bond that opens the route to new phosphate derivatives.

1-Bromopyrene

Why brominate pyrene? Often the bromine is not the destination - it is the doorway to a whole family of new conjugated molecules.

8-Aminoquinoline-7-carbaldehyde

A useful intermediate does not need a famous end use. Sometimes its value is simply putting the right two reactive groups in the right positions.

4,6-Dibromo-2-fluoro-1,3-benzenediacetonitrile

Some building blocks are valuable because they contain several different kinds of future chemistry at once. CAS 2789616-13-1 is a particularly dense example.

2,4,6-Trioxo-1,3,5-triazine-1,3,5(2H,4H,6H)-triacetic acid

Three carboxylic acids, one rigid center: CAS 1968-52-1 shows how molecular symmetry can turn a small heterocycle into a three-way chemical connector.

1,5-Dibromo-3-fluoro-2,4-dimethylbenzene

Some molecules are valuable because they already contain the “handles” needed for the next reactions. CAS 1781113-11-8 is a compact example.

2-(2-tert-Butylaminoethoxy)ethanol

2-(2-tert-Butylaminoethoxy)ethanol is a reminder that small structural details can have large practical consequences.

3-Methyl-3-pentanol

A closer look at 3-Methyl-3-pentanol: the structure tells the story.

Chloromethyltrimethylsilane

Today's Chemical Story: Chloromethyltrimethylsilane — one molecular feature, one real-world consequence.

cis-1,4-Dichloro-2-butene

A four-carbon intermediate can already encode two reaction sites, an alkene, and a fixed three-dimensional geometry.

tert-Octylamine

A molecular formula cannot show everything: branching can change the behavior of an amine without changing its functional group.

Hexamethylditin

An Sn-Sn bond that can relay carbon-bond construction - with an important toxicity trade-off.

4-Acetyl-2-methylbenzoic acid

Sometimes an intermediate's most valuable property is simply having every substituent in exactly the right place.

2-Bromo-6-fluorotoluene

Two halogens, two jobs: why 2-bromo-6-fluorotoluene is more useful than its simple structure suggests.

1,3-Dimethylurea

What does a 3-carbon molecule have to do with caffeine—and a modern electrochemical reaction inspired by batteries?

4-Methoxybenzylchloride

How do chemists tell one protected alcohol: —Your turn.— while telling another:

3,5-Difluoropyridine-2-carboxylic acid

Fluorine forms one of the strongest bonds to carbon. So once F is attached to an aromatic ring, it must be difficult to replace... right?

3,5-Dimethoxybenzaldehyde

Why would chemists hide two hydroxyl groups before building a natural product?

Ethyl N-(diphenylmethylene)glycinate

Why would chemists turn tiny glycine into a molecule carrying two large phenyl rings?

Methylurea

ow much difference can one methyl group make? Start with urea:

5-Bromo-3-nitropyridine-2-carbonitrile

Which group would you expect fluoride to replace? Look at 5-bromo-3-nitropyridine-2-carbonitrile.

4-Benzyloxyaniline hydrochloride

Why would a chemist deliberately add an entire benzyl group to a molecule...

4-Pyridazinecarboxylic acid

How can a molecule with only five carbons become useful in drug discovery?

4-Methyl-1,3-benzenediol

How much difference can one carbon make? Resorcinol has two hydroxyl groups on a benzene ring.

6-Chlorouracil

What happens if you take one of RNA's familiar molecular building blocks...

N-(Trifluoroacetyl)glycine

Sometimes the most useful thing a chemist can tell part of a molecule is:

Cyclobutanecarboxylic acid

What's the difference between a triangle and a folded square?

3-Amino-2-ethoxycarbonylpyrrole hydrochloride

Can a tiny molecule already contain the blueprint for a ring that doesn't exist yet?

Cyclopropyl carbinol

How much chemistry can hide inside four carbon atoms? Quite a lot.

4-Bromo-1H-imidazole

What do the proteins in your body and a bottle of laboratory reagent have in common?

Methyl (Z)-3-aminocrotonate

How does a straight-chain molecule turn into a nitrogen ring?

7-Bromo-1,2,3,4-tetrahydroisoquinoline

How do medicinal chemists explore thousands of possible molecules without starting from scratch every time?

(Bromomethyl)cyclobutane

Can changing one tiny side group change how an entire drug molecule behaves?

Cyclopropanecarboxaldehyde

What's the smallest carbon ring you can build? Three carbon atoms.

2,5-Dibromofluorobenzene

Two bromine atoms. Same molecule. Same element. So surely a chemist can't tell them apart?

2-Bromo-5-chlorophenol

Bromine and chlorine sit next to the same benzene ring. Surely they're basically doing the same job?

trans-1,2-Cyclobutanedicarboxylic acid

Can two molecules contain exactly the same atoms, connected in exactly the same order—and still be different chemicals?

5-Bromo-2-fluorophenol

What can a chemist do with one tiny benzene ring? Quite a lot—if the right pieces are attached to it.

Methyl 4-bromocrotonate

How much chemistry can you pack into five carbon atoms? Quite a lot.

2-Amino-5-bromo-4-chloropyridine

Can a molecule have more than one "door" for chemists to open?

3-Methoxy-5-methyl-2-pyrazinamine

How do scientists discover a better drug molecule? Often, they don't make one giant leap.

2,6-Dichloro-3,5-dimethoxyphenyl isocyanate

A chemical with a name this long probably doesn't sound like it has a story.

cis-3,5-Diacetoxy-1-cyclopentene

Can an enzyme tell the difference between two parts of a molecule that look identical?

Piperazine-2,6-dione hydrochloride

Can a molecule be important even if it never becomes a medicine?

(2-Cyano-4-(methoxycarbonyl)phenyl)boronic acid pinacol ester

Most chemicals never become famous. Some are born to become parts of something else.

5'-O-(4,4'-Dimethoxytrityl)-N4-benzoyl-2'-deoxycytidine-3'-(2-cyanoethyl-N,N-diisopropyl)phosphoramidite

How do scientists make DNA? Not by growing it. By building it—one letter at a time.

1,2,4-Triazol-5-one

Some of the most important molecules in medicine are astonishingly small.

3,4,5-Trimethoxybenzaldehyde

Why do so many drug molecules begin with the same aromatic ring?

(S)-(+)-2,2-Dimethyl-1,3-dioxolane-4-methanol

Imagine trying to repaint a house without getting any paint on the windows.

Cyclopropylboronic acid

Why are medicinal chemists so fascinated by triangles? Not geometric triangles—but molecular ones.

2-Fluoro-5-nitrotoluene

Why do chemists put fluorine into so many modern medicines? The answer isn't simply "because fluorine is reactive." In fact, the opposite is often true. Why do chemists put fluorine into so many modern medicines? The answer isn't simply "because fluorine is reactive." In fact, the opposite is often true.

2-Butyl-2-ethyloxirane

Three atoms. That's all it takes to change the way chemists build molecules.