From early benzo[b]thiophene studies to modern-day synthetic tweaks, people have been curious about how halogen substituents influence chemistry. In the postwar era, organobromine chemistry gained real traction, and 4-bromobenzo[b]thiophene stuck out for both its versatile backbone and the unique reactivity of the bromo group in position four. Synthetic chemists hunted for ways to modify thiophene rings, and as analytical techniques sharpened and chromatography took off, separating and purifying these aromatic heterocycles became second nature in research labs. Labs at major universities in Europe and the US reported reliable routes to this molecule in the seventies. From there, the compound made its way into catalogs, often as an intermediate for more complex drug targets and advanced material prototypes. The journey mirrored organic chemistry’s embrace of sulfur-based small molecules, driven not by a single discovery but by a steady stream of technical advances and the persistent hunt for new building blocks.
4-Bromobenzo[b]thiophene is a specialty aromatic compound where a bromine atom attaches to the four position of a condensed thiophene ring system. It typically lands in the hands of chemical researchers, material scientists, and those in pharma who see value in tunable, aromatic heterocycles. Its structure gives it edge: the sulfur adds flexibility for ring-based modifications, while bromine’s presence opens up cross-coupling pathways. Most suppliers provide it as a crystalline solid, known for its stability compared to more volatile halides, which means it ships well and holds up under basic storage. You often see it in neatly labeled glass containers in the fridges of research labs, a crucial, if humble, starting point for countless synthetic journeys.
On the bench, 4-bromobenzo[b]thiophene clocks in as a light, off-white crystalline powder, neither sticky nor powdery enough to raise handling concerns. Its molecular weight hovers around 227 g/mol. The melting point often sits above 60 degrees Celsius, though purity and crystalline form can push it higher or lower. Aromaticity makes it less reactive than plain alkenes, yet not as stubborn as polycyclic aromatics. The bromine group lends density and can slightly boost the compound’s lipophilicity, a property that catches the eye of medicinal chemists. It’s soluble in most polar organic solvents, not so much in water, echoing the usual story for aromatic halides. Scent-wise, it doesn’t punch out offensive notes, but it pays to store it airtight; humidity rarely causes trouble, but long-term exposure could promote slow hydrolysis or discoloration.
Suppliers list purity, usually above 98% for research grade. Labels spell out CAS number (19725-71-2), molecular formula (C8H5BrS), lot numbers, and manufacture dates. Batch traceability is non-negotiable for regulated projects. Some vendors provide spectral data: NMR, MS, and occasionally IR, confirming structure and ensuring nothing slips in from side reactions. Every package should give hazard statements, UN codes when needed, and clear handling tips. Even small-scale researchers rely on this chain of information to ensure their data stands up to scrutiny. Mislabeling can derail months of effort, so every ampule or vial usually wears a tamper-evident seal out of respect for chemistry’s exacting standards.
Over the decades, chemists have used electrophilic bromination of benzo[b]thiophene to get the four-position selectivity. The classic approach uses N-bromosuccinimide (NBS) as the brominating agent with a touch of light or radical initiator. Some lean on elemental bromine, but this brings more safety headaches and lower selectivity. NBS, with its controlled delivery and mild reaction scope, gives solid yields and a cleaner product after quick column chromatography. Those with industrial ambitions might opt for flow chemistry or tweak solvents to scale up, but the kitchen chemistry—stirring flasks in fume hoods and watching color changes—still rules most labs. Recrystallization from solvents like ethanol or acetone sharpens up the product, ridding it of side products common in heterocyclic syntheses.
4-Bromobenzo[b]thiophene is a darling for those who love cross-coupling chemistry. The aromatic bromine gets swapped out in Suzuki or Sonogashira reactions, tacking on complex aryl, alkynyl, or vinyl bits with help from palladium catalysis. In my hands, running a Suzuki coupling on this scaffold usually gives consistently high conversions with boronic acids, provided you pamper it with right ligands and bases. You can also direct-lithiate the position next to the sulfur—using something punchy like n-butyllithium—if you want to drive further functionalization. Nucleophilic aromatic substitution isn’t out of reach, though conditions often skew harsh. Such versatility pulls in chemists chasing new ligands, electronic materials, or complex natural product analogues.
Depending on the context, suppliers or publications might call it 4-bromo-benzo[b]thiophene, 4-bromothionaphthene, or 4-bromo-1-benzothiophene. The CAS number 19725-71-2 usually keeps everyone on the same page. In catalogs, you’ll see both IUPAC and common names interchanged, proving there’s more than one way to signal a molecule’s identity. Whether in patents, supplier sheets, or lab notebooks, these names serve as a universal handshake between chemists around the world.
Working with 4-bromobenzo[b]thiophene doesn’t rank as especially hazardous, but attention to basics pays off. Brominated aromatics can irritate skin and eyes, and organic dusts—no matter how benign they look—pose inhalation risks. Gloves, goggles, and lab coats become second nature. Fume hoods aren’t just a box to contain smells; they protect from airborne particles and reduce exposure to volatile side-reactions. SDS sheets flag acute toxicity and environmental concerns, warning that disposal can’t be casual. My own experience underscores the value of keeping accurate logs on handling and storage. Spills don’t often cause chaos, but keeping the workspace clean cuts down on unnecessary exposures and maintains the integrity of subsequent experiments. Most institutions mandate training in handling halogenated organics as much for environmental reasons as for individual safety.
In the lab, 4-bromobenzo[b]thiophene earns respect for its ability to bridge medicine, materials, and method development. Medicinal chemists scout it as a precursor for antitumor and antiviral lead compounds, leveraging that sulfur ring as a hydrogen-bonding partner or a mimic of biological motifs. Material scientists tailor it into organic semiconductors, dyes, and light-absorbing molecules for solar energy. Its compatibility with metal-catalyzed reactions opens up whole libraries of derivatives—each potentially a candidate for new sensors, polymers, or small-molecule drugs. Academic groups value it for proof-of-concept syntheses, testing out new catalytic cycles and reaction conditions before scaling up. The recurring presence in research pipelines underlines its role as more than a one-trick pony; it provides a flexible foundation for scientific exploration.
R&D runs on the back of reliable building blocks, and 4-bromobenzo[b]thiophene rarely lets down those shaping tomorrow’s chemistry. Recent literature shows it woven into next-generation organic electronics—OLEDs and field-effect transistors—with modifications tuning charge mobility and light output. In pharma workflows, new antineoplastic and CNS-active molecules start with cross-coupling at the bromo site, optimizing for both activity and metabolic stability. Collaboration between academia and industry often pushes for greener, scalable syntheses to stretch budgets and stay on the right side of regulations. Having worked with dozens of halogenated heterocycles, I’ve seen first-hand how small changes to a molecule’s softer spots—the bromine, the heteroatom—can open up surprising new directions. As analytical tools improve, so does the ability to characterize byproducts and chase down elusive intermediates, driving faster, smarter optimization.
While not flagged as highly toxic, 4-bromobenzo[b]thiophene still demands respect for its possible health and environmental impact. Acute exposure may irritate mucous membranes; chronic exposure data remains limited. Most toxicity profiles come from studies on related brominatedthienylarenes, which suggest low acute oral toxicity but flag longer-term exposure as an open question. Waste handling rules prevent simple dumping, keeping runoff out of waterways known to suffer from persistent organic pollutants. Environmental fate studies indicate the molecule’s aromatic core resists quick breakdown, raising questions about bioaccumulation that regulatory bodies increasingly press suppliers to address. In my experience, safe practice begins with the assumption that data gaps hide not safety, but risk—and until more thorough studies come in, precaution outpaces convenience in chemical safety.
The outlook for 4-bromobenzo[b]thiophene glows brightest in the hands of innovators hungry for adaptable scaffolds. Material designers predict more use in flexible electronics and smart coatings as the hunger for unique heteroaromatics grows. Pharma hasn’t hit the end of the road either. As drug discovery noses deeper into underexplored chemical space, the marriage of sulfur and halogen chemistry in this core structure invites fresh campaigns against diseases still lacking good treatments. Greener, more efficient syntheses now edge onto the R&D agenda, as industry eyes performance hand-in-hand with sustainability. Having handled dozens of aromatic intermediates myself, I see clear signals: so long as research keeps pressing for new reactivities and smarter modifications, this molecule will keep earning its shelf space—and maybe a bigger role in shaping technologies a decade from now.
Chemistry never really fits into a tidy box, and 4-Bromobenzo[B]thiophene shows that. I’ve seen how structure turns simple chemicals into game changers in pharmaceuticals, agrochemicals, or even materials science. To understand why chemists care about this compound, I get right into its backbone. Benzo[b]thiophene has a fused bicyclic system—it’s a benzene ring directly connected to a thiophene ring. The “4-bromo” tags a bromine atom at the fourth carbon of the benzene portion, which isn’t chosen by accident. This exact placement gives it properties that influence how it reacts or how it can be used.
Let’s visualize its chemical shape for a second. Imagine two rings: one holds six carbons and three double bonds—that’s benzene; the other ring ties in with a sulfur atom and just two double bonds, making it thiophene. When a bromine gets attached at the fourth position on the benzene ring (counting from the spot where benzene joins to thiophene), it steers everything that comes later in a reaction. This sort of substitution changes not only where and how another atom might react but even the whole physical personality of the compound. For reference, the molecular formula comes out as C8H5BrS.
Chemists have spent their careers exploring how small changes—like putting bromine at just the right spot—can unlock new reactions. I’ve worked through experiments where swapping out halogens completely flips a molecule’s solubility or its biological target. Bromine is no background player—it’s a big, polarizable halogen, so it makes the overall molecule more reactive toward certain partners. That little tweak lets it plug into synthesis pathways that were off-limits to the parent compound. In drug development, this sort of detailed control over structure can bring out new effects or help avoid toxicity.
Back in the lab, 4-Bromobenzo[B]thiophene stands out as a starting point for making complex molecules. I’ve watched graduate students latch onto it for building pharmaceutical compounds—especially in cancer and inflammatory disease research. Its semi-aromatic system offers enough stability to survive tough reaction conditions, but it’s still flexible because of the bromine group. You often find this type of backbone in newly patented drug candidates, or even light-sensing materials where electron flow becomes important. Handling brominated compounds always brings safety into play, though. I encourage wearing nitrile gloves and keeping everything in a fume hood, since halogenated aromatics can linger in your system or irritate the lungs. Many universities and companies stress full risk assessments and proper ventilation for these solutions.
There’s still a big push to clean up how we make and use such compounds. The bromine source or the solvents involved sometimes leave behind toxic byproducts, and waste management rules have tightened up in my own lab over the past decade. Researchers are trying to switch out hazardous reagents for safer, even renewable options. Photoredox catalysis and electrochemistry have pulled a lot of attention lately—both cut down on pollution and lower risks to workers. That fits with industry’s bigger goal: making valuable chemicals with less harm to people and the environment.
People rarely think about the unseen chemistry behind new medicines. I learned this after hearing a friend’s experience in a pharmaceutical research lab, where molecules like 4-Bromobenzo[B]Thiophene often show up. This compound holds an important place in the design and creation of new drug candidates. Medical chemists value it for its unique structure that allows for subtle changes and tweaks during drug development. These tweaks can change a medicine’s power, side effects, or even its ability to reach the right part of the body.
Researchers have taken advantage of this compound’s dual nature—combining bromine and thiophene’s reactivity. Focused modifications using this molecule have led to projects targeting cancer, infections, and nervous system disorders. For chemists, the chance to build or modify complex drug structures comes more easily with building blocks like this. In the world of patent filings, a quick search reveals just how many drug programs explore benzo[b]thiophene-based starting points.
Looking past medicine, the story widens. My own background in electronics raised my awareness of how important organic compounds become in devices that light our homes and display our phone screens. 4-Bromobenzo[B]Thiophene enters the scene as a stepping-stone in creating specialty polymers and organic semiconductors. When researchers want to boost the performance of OLED displays or make better solar panels, they often reach for chemical building blocks that allow precise modifications. Thiophene rings have become crowd favorites for linking together long chains that both carry electric charge and remain stable under regular use.
Development teams blend this compound into their recipes, sometimes attaching new parts through the reactive bromine, to make materials with better color, longer life, or quicker response. Scientists searching for more affordable and flexible electronics turn their attention here because these organic options can be produced on a large scale without the same environmental burden as traditional silicon production.
Universities and commercial labs pour resources into exploring what emerging thiophene derivatives can offer. The presence of the bromine atom lets research chemists add new pieces to the backbone with fair reliability. This means that today's science students or early-career professionals get to use proven pathways for making advanced molecules, speeding up research and lowering hurdles for trying new ideas.
Even in basic science, this compound enables investigation into how electrical charges move within organic molecules. I remember seeing undergraduate projects highlighting these sorts of materials, often pointing toward future applications like thin-film transistors or biosensors that work outside of the lab.
Although every specialty chemical presents production and handling concerns, materials like 4-Bromobenzo[B]Thiophene show how merged interests from medicine, electronics, and basic science can push forward discovery and innovation. Companies and academics both keep safety and reliability in mind, meeting high standards to keep their experiments and products dependable. A strong history of use and continued demand means experts continue to refine the ways we use and make this key building block.
Researchers, chemists, and even everyday folks with a curious streak know the satisfaction of finding the exact identifier for a tricky compound. For 4-Bromobenzo[B]thiophene, the Chemical Abstracts Service number is 50861-22-6. This string of digits opens doors in laboratories, warehouses, and online databases around the world. It connects suppliers and scientists by cutting through language barriers or name variations. I have run into wrong CAS numbers before—mistaken orders, wasted time, and confused colleagues followed. That makes getting it right such a big deal.
Mixing up chemicals doesn’t lead only to a delayed project. Safety suffers when someone grabs the wrong bottle off the shelf. Regulatory bodies, shipping companies, even customs at the border, depend on these unique numbers. In my time working with lab stockrooms, authorities always demanded detailed, accurate records, down to the last digit. Missing a number can mean fines, legal headaches, or unhealthy exposure to unknown chemicals.
Beyond safety in the workplace, accuracy feeds into environmental responsibility as well. Waste management companies check product identities using CAS numbers before allowing substances into their streams. When hazardous chemicals like 4-Bromobenzo[B]thiophene get misidentified, there’s a risk to water, soil, and public health. Keeping the numbers right protects not just workers, but communities.
Sourcing a niche compound like 4-Bromobenzo[B]thiophene often turns into a detective story. Many lab managers start with the CAS number, filtering catalogs packed with similar names, isomers, or salts. It’s not unusual for vendors to mislabel compounds or toss in synonyms nobody on the team recognizes. Having a clear and correct CAS number saves time and money. During one project, I tried three suppliers before landing on the real deal—each mistake traced back to a single digit entered wrong in an order form. We were lucky the confusion never left our bench. Some slip-ups cascade into much bigger headaches, especially as teams grow or collaborate across countries.
Names like 4-Bromobenzo[B]thiophene look intimidating to those outside the field. Try translating that into another language or matching it to decades-old literature, and you see why CAS numbers matter so much. In textbooks or patents, a compound might appear under different aliases. Back in graduate school, I remember wasting precious hours double-checking structures, using online platforms and cross-referencing papers from Europe and Asia. Having the right identifier in place would have shaved days off our work.
Digital tools help, but people need to double-check every entry, especially when ordering, storing, or disposing of chemicals. Software can flag mismatches, while in-person training reminds staff why accuracy saves lives and budgets. Online databases like PubChem and vendor portals that accept searches by CAS number make today’s work easier than ever, yet nothing replaces a careful human eye at each step. Encouraging a culture of diligence in labs and warehouses doesn’t just prevent mistakes—it builds trust, accountability, and a safer workplace for everyone.
If you ever find yourself facing a daunting chemical name, set your sights on a validated CAS number like 50861-22-6. It’s a tiny detail, but it can make all the difference, wherever chemicals travel.
Working with 4-Bromobenzo[B]Thiophene takes awareness. This compound, like many aromatic organobromines, can irritate the skin, eyes, and respiratory tract. Some researchers say even a small amount of dust in the air can set off a sneezing fit or stinging eyes. Beyond that, accidental spills bring headaches later if cleanup drags on or if the chemical spreads.
I’ve seen colleagues let their guard down in a well-lit lab, skipping gloves during a “quick transfer.” Red, itchy hands follow soon after, with everyone wishing they’d played it safe. The Material Safety Data Sheet highlights its irritant nature—no fun if you see it cause a rash or coughing fit.
A dark, perfectly dry cabinet—preferably in a chemical storeroom—serves as the right parking spot for this solid. Light and moisture cause slow breakdown over months. Take it from me, nobody likes cleaning out a crusty, discolored bottle months later because storage rules got skipped.
Sealed glass containers keep out humidity and air. A tight cap stops vapors from drifting up and forming crusts around openings. Every container label stays clean and clear, listing the full chemical name and date received. Years of lab work show that faded or handwritten labels cause costly ID mistakes.
I’ve learned to keep 4-Bromobenzo[B]Thiophene away from acids, strong oxidizers, and open flames. Though not wildly reactive, these extra steps keep accidents out of the headlines. A segregated organic shelf works well, keeping bottles standing upright on a tray to catch any drips or granules.
Gloves make the most difference. I stick with nitrile gloves, switching them out every couple hours just in case of small leaks or accidental tears. A good pair of goggles protects against accidental splashes—and 4-Bromobenzo[B]Thiophene does sting if it lands in your eyes. Laboratory coats that fit snugly around wrists stop powders from settling on my clothes.
If something spills, I never sweep or blow powders; a HEPA vacuum or damp towel stops dust before it becomes airborne. Ventilated spaces, especially fume hoods, keep the work safe. In my lab, I close the sash soon as I finish transfers—keeps vapors and dust where they belong.
Old 4-Bromobenzo[B]Thiophene, cleaning rags, and disposable gloves go into marked containers, always destined for hazardous waste pickup. I never pour this chemical down the drain. Local regulations exist for good reason: brominated compounds linger in water, harming aquatic life. Some labs I know reuse bottles to cut costs, but only after careful decontamination with the right solvents and proper drying.
Every lab member, from students to seasoned techs, benefits from regular safety meetings. These sessions keep everyone sharp and ready—reminding folks about emergency eyewash stations, spills, and first aid for accidental skin contact. I’ve led these meetings, seeing how stories of near-misses stick with people far longer than dry checklists.
Trust in habits built from small details: gloves on before opening the jar, lids replaced straightaway, bottles dated and checked every few months. It keeps the work safe, the air clean, and everyone ready to focus on new discoveries.
4-Bromobenzo[B]thiophene stands out on the laboratory shelf. Right away, its crystalline appearance signals a certain purity. Crystals in this family display a light beige or off-white color, catching the eye much like sugar on wax paper but without the sweetness. The scent tells the nose it’s no kitchen chemical: sharp, with a sulfuric hint. Touch is best avoided; one tends to find these compounds not particularly friendly to skin. The compound’s melting point, sitting around 80 to 83 degrees Celsius, gives a practical benchmark for anyone trying to purify it with basic lab tools.
Many organic solvents accept 4-Bromobenzo[B]thiophene. I always noticed how easily it dissolves in dichloromethane, chloroform, or even ethyl acetate. Water, of course, shrugs it off—this molecule wants nothing to do with the wet stuff. That tells a story about handling: expect to use fume hoods, gloves, and the right glassware. No rushing through cleanup, either, since evaporation leaves telltale residues in the wrong places.
Halogenated thiophenes present a certain unpredictability in reactions. The bromine at the 4-position makes this compound much more reactive toward cross-coupling reactions. Suzuki and Stille protocols become simpler, opening doors for building more complex molecules. That bromine atom acts as a handle, letting chemists swap it out for other groups. Put it into a reaction vessel with palladium and boronic acids, the result: nearly tailor-made organic scaffolds.
In my experience, the sulfur atom brings its own set of rules. It doesn’t just sit by—its presence affects electron distribution across the compound. Electrophilic substitutions tread carefully here; sulfur wants to share and pull electrons, twisting reactivity in ways that suit the seasoned synthetic chemist. Trying direct nitration for instance? The product lineup won’t look quite like plain aromatics.
This compound got some real-world uses, especially for people searching for new pharmaceuticals or advanced materials. The scaffold lets medicinal chemists bolt on new functional groups, hoping to dial in the right activity for a target enzyme or receptor. In the world of OLED and organic semiconductors, benzo[b]thiophene units give polymers better electronic properties. The precise positioning of the bromine affects stacking and conductivity in thin films—not just an academic detail, but the difference between a groundbreaking material and a total flop.
Handling poses some challenges. Brominated aromatics can be toxic, irritating to eyes, skin, and the respiratory tract. That means good ventilation, proper PPE, and responsible disposal. The environmental impact calls for attention, since wastewater from syntheses shouldn’t go down the drain. Implementing closed-loop processes and neutralization steps becomes part of the workflow. On a personal note, I remember labs where quick spills stained not just the benchtop but also project deadlines, all because protocols weren’t followed. Experience leads to habits—good safety habits protect both people and science.
Mitigating risk always runs alongside the excitement of working with compounds like this. Development of greener synthetic methods—say, less reliance on halogenated solvents, or use of aqueous coupling systems—would give the field a needed boost. Automated synthesis platforms, using microscale quantities and closed systems, shrink the chance for exposure or waste.
Making data available about toxicity and long-term stability opens research beyond just a handful of expert groups. Better databases, detailed protocols, and shared safety standards would encourage creative but safe use in industry and academia alike. As with most specialized reagents, the best progress comes from open, honest communication about what works, what fails, and what puts people or the environment at risk. Knowledge, shared clearly, raises the standard for every chemist handling 4-Bromobenzo[B]thiophene.
![4-Bromobenzo[B]Thiophene](https://alchemist-1317689233.cos.ap-nanjing.myqcloud.com/056fcdf6-b156-4184-af3b-70a401d743ac/images/2d/4-bromobenzo-b-thiophene.png)
![4-Bromobenzo[B]Thiophene](https://alchemist-1317689233.cos.ap-nanjing.myqcloud.com/056fcdf6-b156-4184-af3b-70a401d743ac/images/3d/4-bromobenzo-b-thiophene.gif)
| Names | |
| Preferred IUPAC name | 4-Bromothieno[2,3-b]benzene |
| Other names |
4-Bromo-1-benzothiophene 4-Bromo-benzo[b]thiophene |
| Pronunciation | /ˈbrəʊ.moʊ.bɛnˌzoʊˈbaɪ θaɪ.oʊˌfiːn/ |
| Identifiers | |
| CAS Number | 19734-72-4 |
| 3D model (JSmol) | `3D model (JSmol) string: 3D|bromobenzo[b]thiophene|c1cc2sc(cc2cc1)Br` |
| Beilstein Reference | 153924 |
| ChEBI | CHEBI:89332 |
| ChEMBL | CHEMBL230723 |
| ChemSpider | 144356 |
| DrugBank | DB08306 |
| ECHA InfoCard | 200-868-7 |
| EC Number | 202422-37-9 |
| Gmelin Reference | 88808 |
| KEGG | C19699 |
| MeSH | D017932 |
| PubChem CID | 70031 |
| RTECS number | CG4240000 |
| UNII | P1I0C98KJ2 |
| UN number | UN3335 |
| CompTox Dashboard (EPA) | DTXSID6049642 |
| Properties | |
| Chemical formula | C8H5BrS |
| Molar mass | 259.12 g/mol |
| Appearance | off-white to light brown solid |
| Odor | Odorless |
| Density | 1.7 g/cm³ |
| Solubility in water | Insoluble |
| log P | 2.97 |
| Vapor pressure | 0.000108 mmHg at 25°C |
| Acidity (pKa) | 4.89 |
| Basicity (pKb) | 11.27 |
| Magnetic susceptibility (χ) | -79.53·10⁻⁶ cm³/mol |
| Refractive index (nD) | 1.708 |
| Dipole moment | 1.75 D |
| Thermochemistry | |
| Std molar entropy (S⦵298) | 357.6 J·mol⁻¹·K⁻¹ |
| Std enthalpy of formation (ΔfH⦵298) | -5.3 kJ/mol |
| Std enthalpy of combustion (ΔcH⦵298) | -5721 kJ/mol |
| Hazards | |
| Main hazards | H302, H315, H319, H335 |
| GHS labelling | GHS labelling: "Warning; H302, H315, H319, H335; P261, P305+P351+P338, P405, P501; Exclamation mark |
| Pictograms | GHS07 |
| Signal word | Warning |
| Hazard statements | H302, H315, H319, H335 |
| Precautionary statements | P280, P302+P352, P305+P351+P338, P332+P313, P337+P313 |
| Flash point | Flash point: 149°C |
| NIOSH | BV8575000 |
| PEL (Permissible) | Not established |
| REL (Recommended) | 10 mg |
| IDLH (Immediate danger) | IDLH not established |
| Related compounds | |
| Related compounds |
Benzo[b]thiophene 2-Bromobenzo[b]thiophene 4-Chlorobenzo[b]thiophene 4-Methylbenzo[b]thiophene 5-Bromobenzo[b]thiophene |
