5-Bromopyrimidine
[CAS 4595-59-9]

Identification

• Classification: Pharmaceutical intermediate >> Heterocyclic compound intermediate >> Pyrimidine compound >> Bromopyrimidine
• Name: 5-Bromopyrimidine
• Molecular Formula: C₄H₃BrN₂
• Molecular Weight: 158.98
• CAS Registry Number: 4595-59-9
• EC Number: 224-992-1
• SMILES: C1=C(C=NC=N1)Br

Properties

• Density: 1.7±0.1 g/cm³ Calc.^*
• Melting point: 67 - 73 °C (Expl.)
• Boiling point: 201.4±13.0 °C 760 mmHg (Calc.)^*
• Flash point: 75.6±19.8 °C (Calc.)^*
• Index of refraction: 1.568 (Calc.)^*

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H315-H319-H335
• Safety Statements: P261-P264-P264+P265-P271-P280-P302+P352-P304+P340-P305+P351+P338-P319-P321-P332+P317-P337+P317-P362+P364-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315
Specific target organ toxicity - single exposure	STOT SE	3	H335
Acute toxicity	Acute Tox.	4	H302
Eye irritation	Eye Irrit.	2A	H319
Serious eye damage	Eye Dam.	1	H318

chemBlink Chemical Story

A single bromine atom can mark the position at which a small heterocycle becomes part of a larger molecule. In 5-bromopyrimidine, CAS 4595-59-9, that position is carbon 5 of a six-membered aromatic ring containing two nitrogen atoms. The compound is a building block rather than a finished application: its value lies in providing a defined ring and a site for further bond construction.

Pyrimidine is the 1,3-diazine arrangement, with two ring nitrogens separated by one carbon. This distinguishes it from other diazines that have the same types of atoms arranged differently. The bromine position adds another level of specificity. A coupling at carbon 5 leaves a different substitution pattern from one performed at carbon 2 or carbon 4, so the full name conveys information that the phrase brominated nitrogen heterocycle does not.

In cross-coupling chemistry, a carbon-halogen bond can be used to connect the ring to another carbon-containing group. The purpose is not simply to remove bromine, but to replace a defined connection with a new one while retaining the useful ring framework. The catalyst, coupling partner, and surrounding functionality determine whether a particular transformation is suitable.

An independently checked Organic Syntheses procedure provides a direct example. It uses 5-bromopyrimidine with a furanylboronic acid in a nickel-catalyzed Suzuki-Miyaura coupling to prepare 5-(furan-3-yl)pyrimidine. This is evidence for an actual carbon-carbon bond-forming application involving the product, rather than a general inference that every heteroaryl bromide must behave identically.

A 2012 study explored a complementary strategy, combining Suzuki-Miyaura chemistry with substitution of a ring hydrogen to obtain more extensively substituted pyrimidines bearing pyrrole or indole fragments. The two operations address different positions and different bond changes. Together they show how a relatively simple starting material can support a sequence of controlled modifications rather than a single isolated reaction.

Such examples explain the usefulness of small, well-defined intermediates in molecular discovery. Researchers can vary the group installed at one position while retaining other structural features, making it easier to compare a family of products. That is a design opportunity, not evidence that the starting bromopyrimidine itself has the biological or optical properties of any final derivative.

The two ring nitrogens also distinguish the framework electronically from a brominated benzene. They change the distribution of electron density and provide possible interactions with other components of a reaction mixture. This helps explain why a method developed for an ordinary aryl bromide still needs evaluation when the substrate is a nitrogen heterocycle. The name of a coupling reaction does not remove differences among its substrates.

It is equally useful to distinguish this starting ring from biologically familiar substituted pyrimidines. A pyrimidine skeleton alone does not identify a nucleobase or establish a medicinal effect. Additional groups and their positions define those different compounds. In synthetic research, the ability to introduce such groups deliberately is precisely the advantage: a small ring becomes a controlled point of departure for testing how a larger structure behaves.

The chemical story of 5-bromopyrimidine is therefore about an address on a ring. Its two nitrogens define the heterocycle, and its brominated carbon defines a documented point for construction. Precise connectivity allows synthetic methods to turn a compact starting structure into a much wider set of molecules. That precision also makes experimental comparisons clearer, because the modified position remains explicit throughout a reaction sequence.

References:
1. NIST Chemistry WebBook. Pyrimidine, 5-bromo-, CAS 4595-59-9. https://webbook.nist.gov/cgi/cbook.cgi?ID=C4595599
2. Nickel-Catalyzed Suzuki-Miyaura Coupling in t-Amyl Alcohol for the Preparation of 5-(Furan-3-yl)pyrimidine. Org Synth. 2016;93:306. https://doi.org/10.15227/orgsyn.093.0306
3. Verbitskiy EV et al. Consecutive SNH and Suzuki-Miyaura Cross-Coupling Reactions: an Efficient Synthetic Strategy to Pyrimidines Bearing Pyrrole and Indole Fragments. Eur J Org Chem. 2012. https://doi.org/10.1002/ejoc.201201035

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