2991-28-8

Basic information

• Product Name: 2,5-Difluorobenzoic acid
• Synonyms: 2,5-DIFLUOROBENZOIC ACID;RARECHEM AL BO 0019;Benzoic acid, 2,5-difluoro-;2,5-Difluorobenzic acid;2-chloro-6-flurobenzyl cyanide;2,5-Difluorobenzoic;2,5-Difluorobenzoic acid 98%;2,5-Difluorobenzoicacid98%
• CAS NO: 2991-28-8
• Molecular Formula: C₇H₄F₂O₂
• Molecular Weight: 158.1
• EINECS: 221-060-6
• Product Categories: Fluorin-contained Benzoic acid series;blocks;Carboxes;FluoroCompounds;Aromatic Carboxylic Acids, Amides, Anilides, Anhydrides & Salts;Fluorobenzene;Miscellaneous;Fluorobenzoic acids;C7;Carbonyl Compounds;Carboxylic Acids;Benzoic acid series;Aryl Fluorinated Building Blocks;Building Blocks;Carbonyl Compounds;Carboxylic Acids;Chemical Synthesis;Fluorinated Building Blocks;Organic Building Blocks;Organic Fluorinated Building Blocks;Other Fluorinated Organic Building Blocks;Fluorine series;Indazoles
• Mol File: 2991-28-8.mol
• Article Data: 5

Chemical Properties

• Melting Point: 132-134 °C(lit.)
• Boiling Point: 244.7 °C at 760 mmHg
• Flash Point: 101.8 °C
• Appearance: white crystalline powder
• Density: 1.3486 (estimate)
• Vapor Pressure: 0.016mmHg at 25°C
• Storage Temp.: Sealed in dry,Room Temperature
• Solubility: acetone: soluble25mg/mL, clear, faintly yellow
• PKA: 2.93±0.10(Predicted)
• Water Solubility: Insoluble in water.
• BRN: 973351
• CAS DataBase Reference: 2,5-Difluorobenzoic acid(CAS DataBase Reference)
• NIST Chemistry Reference: 2,5-Difluorobenzoic acid(2991-28-8)
• EPA Substance Registry System: 2,5-Difluorobenzoic acid(2991-28-8)

Safety Data

• Hazard Codes: Xi
• Statements: 36/37/38
• Safety Statements: 26-37/39
• WGK Germany: 3
• HazardClass: IRRITANT
• Hazardous Substances Data: 2991-28-8(Hazardous Substances Data)

Usage

Chemical Properties

white crystalline powder

Uses

2,5-Difluorobenzoic acid is used in the preparation of hydrazone derivatives, which acts as a potential antibacterial agent.

Synthesis Reference(s)

Journal of Medicinal Chemistry, 28, p. 1864, 1985 DOI: 10.1021/jm00150a018

General Description

2,5-Difluorobenzoic acid has been quantitated in ground water samples by liquid chromatography-tandem mass spectrometry.

InChI:InChI=1/C7H4F2O2/c8-4-1-2-6(9)5(3-4)7(10)11/h1-3H,(H,10,11)/p-1

Synthetic route

2-bromo-1,4-difluorobenzene (399-94-0) + carbon dioxide (124-38-9) → 2,5-difluorobenzoic acid (2991-28-8)

Conditions	Yield
With n-butyllithium 1) hexane, Et2O, 2 min, -78 deg C. 2) ether; Yield given. Multistep reaction;

carbon dioxide (124-38-9) + para-difluorobenzene (540-36-3) → 2,5-difluorobenzoic acid (2991-28-8)

Conditions	Yield
With sec.-butyllithium 1.) THF, -78 deg C, 0.5 h, 2.) THF, a) -78 deg C, 15 min, b) from -78 deg C to RT; Yield given. Multistep reaction;

2,3,6-trifluorobenzoic acid (2358-29-4) → 3-fluorobenzoic acid (455-38-9) + benzoic acid (65-85-0) + 2,5-difluorobenzoic acid (2991-28-8)

Conditions	Yield
With ammonia; sodium at -45℃; for 0.25h; Reduction; Hydrodefluorination; Title compound not separated from byproducts;	A 9 % Spectr. B 9 % Spectr. C 16 % Spectr.

2',5'-difluoroacetophenone (1979-36-8) → 2,5-difluorobenzoic acid (2991-28-8)

Conditions	Yield
With potassium permanganate Oxidation;

para-difluorobenzene (540-36-3) → 2,5-difluorobenzoic acid (2991-28-8)

Conditions	Yield
Multi-step reaction with 2 steps 2: KMnO4 View Scheme

1,2,3,5-tetrafluorobenzene (2367-82-0) → 2,5-difluorobenzoic acid (2991-28-8)

Conditions	Yield
Multi-step reaction with 3 steps 1.1: BuLi / tetrahydrofuran / -70 °C 1.2: tetrahydrofuran 2.1: 9 percent Spectr. / Zn; NH3 / -45 °C 3.1: 16 percent Spectr. / Na; NH3 / 0.25 h / -45 °C View Scheme
Multi-step reaction with 3 steps 1.1: BuLi / tetrahydrofuran / -70 °C 1.2: tetrahydrofuran 2.1: 12 percent Spectr. / Na; NH3 / 0.25 h / -45 °C 3.1: 16 percent Spectr. / Na; NH3 / 0.25 h / -45 °C View Scheme

1,2,4-trifluorobenzene (367-23-7) → 2,5-difluorobenzoic acid (2991-28-8)

Conditions	Yield
Multi-step reaction with 2 steps 1.1: BuLi / tetrahydrofuran / -70 °C 1.2: tetrahydrofuran 2.1: 16 percent Spectr. / Na; NH3 / 0.25 h / -45 °C View Scheme

2,3,4,6-tetrafluorobenzoic acid (32890-92-9) → 2,5-difluorobenzoic acid (2991-28-8)

Conditions	Yield
Multi-step reaction with 2 steps 1: 9 percent Spectr. / Zn; NH3 / -45 °C 2: 16 percent Spectr. / Na; NH3 / 0.25 h / -45 °C View Scheme
Multi-step reaction with 2 steps 1: 12 percent Spectr. / Na; NH3 / 0.25 h / -45 °C 2: 16 percent Spectr. / Na; NH3 / 0.25 h / -45 °C View Scheme

2,5-difluoro-α,α-dichloroacetophenone + sodium disulfite → 2,5-difluorobenzoic acid (2991-28-8)

Conditions	Yield
With hydrogenchloride In sodium hypobromide; water

C7H3F2O2(1-)*C25H30N3(1+) → crystal violet carbinol base (467-63-0) + 2,5-difluorobenzoic acid (2991-28-8)

Conditions	Yield
With water In chlorobenzene at 28℃; Equilibrium constant; Further Variations:; Temperatures;

2,5-difluorobenzoic acid (2991-28-8) → 2,5-difluorobenzoyl chloride (35730-09-7)

Conditions	Yield
Stage #1: 2,5-difluorobenzoic acid With N,N-dimethyl-formamide In dichloromethane at 0℃; for 0.0833333h; Stage #2: With oxalyl dichloride In dichloromethane at 20℃; for 12h;	100%
With thionyl chloride Heating;	97%
With sulfuryl dichloride for 4h; Heating;	73%

ethanol (64-17-5) + 2,5-difluorobenzoic acid (2991-28-8) → ethyl 2,5-difluorobenzoate (708-25-8)

Conditions	Yield
With sulfuric acid at 100℃; for 12h; Sealed tube;	95%
With sulfuric acid Reflux;
With sulfuric acid for 10h; Reflux;

2,5-difluorobenzoic acid (2991-28-8) → 4,7-difluoro-3-hydroxy-1(3H)-isobenzofuranone (111608-81-2)

Conditions	Yield
With sec-BuLi In tetrahydrofuran; hydrogenchloride; N,N-dimethyl-formamide	93%
With sec-BuLi In tetrahydrofuran; hydrogenchloride; N,N-dimethyl-formamide	93%
Multi-step reaction with 5 steps 1: 73 percent / SO2Cl / 4 h / Heating 2: CH2Cl2 / 6 h / Ambient temperature 3: SOCl2 / 12 h 4: 1.) sec-BuLi / 1.) THF, -78 deg C, 30 min, 2.) THF, -78 deg C, 2 h 5: 5 N HCl / Heating View Scheme

tributyltin acetate (56-36-0) + 2,5-difluorobenzoic acid (2991-28-8) → tri-n-butyltin 2,5-difluorobenzoate

Conditions	Yield
In ethanol; toluene byproducts: acetic acid; equimolar amts. of Sn-compd. and the benzoic acid are mixed with toluene/EtOH (3:1), mixt. refluxed (4 h); the azeotrope acetic acid/EtOH/toluene followed by the azeotrop toluene/EtOH is distilled off to 50% of the initial vol., evapn. (reduced pressure);	92%

t-butoxycarbonylhydrazine (870-46-2) + 2,5-difluorobenzoic acid (2991-28-8) → C12H14F2N2O3 (1079843-62-1)

Conditions	Yield
With dmap; 1-ethyl-(3-(3-dimethylamino)propyl)-carbodiimide hydrochloride In tetrahydrofuran; N,N-dimethyl-formamide	91%
With 1-ethyl-(3-(3-dimethylamino)propyl)-carbodiimide hydrochloride; dmap In tetrahydrofuran; N,N-dimethyl-formamide at 20℃; for 3h;
With 1-ethyl-(3-(3-dimethylamino)propyl)-carbodiimide hydrochloride; dmap In tetrahydrofuran; N,N-dimethyl-formamide for 16h;

2,5-difluorobenzoic acid (2991-28-8) → N-t-Butyl-2,5-difluorobenzamide (223444-58-4)

Conditions	Yield
	91%

europium(III) hydroxide + 2,5-difluorobenzoic acid (2991-28-8) → C21H13EuF6O8

Conditions	Yield
In methanol; acetone at 60℃; for 1h;	91%

methanol (67-56-1) + 2,5-difluorobenzoic acid (2991-28-8) → methyl 2,5-difluorobenzoate

Conditions	Yield
With thionyl chloride Reflux;	90.7%
With sulfuric acid for 12h; Reflux;	66%
With thionyl chloride at 60℃; for 3h; Cooling with ice;

2-(3,4-bis(benzyloxy)phenyl)-7-(benzyloxy)-3,5-dihydroxy-4H-chromen-4-one (183067-65-4) + 2,5-difluorobenzoic acid (2991-28-8) → C36H24F2O8

Conditions	Yield
With dmap; 1-ethyl-(3-(3-dimethylamino)propyl)-carbodiimide hydrochloride In dichloromethane at 50℃; for 5h;	84%

oridonin (28957-04-2, 28957-10-0) + 2,5-difluorobenzoic acid (2991-28-8) → (1S,5S,6S,6aR,9S,11aS,11bS,14R)-1,5,6-trihydroxy-4,4-dimethyl-8-methylene-7-oxododecahydro-1H-6,11b-(epoxymethano)-6a,9-methanocyclohepta[a]naphthalen-14-yl 2,5-difluorobenzoate

Conditions	Yield
With dmap; 1-ethyl-(3-(3-dimethylamino)propyl)-carbodiimide hydrochloride In dichloromethane	83%

tert-butyl alcohol (75-65-0) + 2,5-difluorobenzoic acid (2991-28-8) → N-(tert-Butoxycarbonyl)-2,5-difluoroaniline (129589-71-5)

Conditions	Yield
With diphenylphosphoranyl azide; triethylamine for 2h; Heating;	81%

methyl 2-diazohydrocinnamate (51507-18-7) + 2,5-difluorobenzoic acid (2991-28-8) → (S)-3-methoxy-3-oxo-2-phenylpropyl 2,5-difluorobenzoate + C17H14F2O4

Conditions	Yield
With C2HF6NO4S2*C27H30BNO In dichloromethane at -78℃; for 1h; Inert atmosphere; enantioselective reaction;	A 75% B n/a

2,5-difluorobenzoic acid (2991-28-8) → 2,5-difluoro-3-nitro-benzoic acid (741721-49-3)

Conditions	Yield
With sulfuric acid; nitric acid	72%
With sulfuric acid; nitric acid at 0 - 20℃; for 1h;	31.3%
With sulfuric acid; nitric acid In water at 0 - 20℃;	31.3%
With sulfuric acid; nitric acid at 0 - 20℃;	31.3%
With sulfuric acid; nitric acid at 0 - 20℃;	31.3%

5-(propylthio)-1H-benzimidazol-2-ylamine (80983-36-4) + 2,5-difluorobenzoic acid (2991-28-8) → 2,4-difluoro-N-(5-(propylthio)-1H-benzo[d]imidazol-2-yl)benzamide

Conditions	Yield
Stage #1: 2,5-difluorobenzoic acid With potassium carbonate; 1,1'-carbonyldiimidazole In tetrahydrofuran for 0.5h; Stage #2: 5-(propylthio)-1H-benzimidazol-2-ylamine In tetrahydrofuran Reflux;	71%

ethyl acrylate (140-88-5) + 2,5-difluorobenzoic acid (2991-28-8) → ethyl 2-(4,7-difluoro-3-oxo-1,3-dihydroisobenzofuran-1-yl)acetate

Conditions	Yield
With silver hexafluoroantimonate; potassium acetate; dichloro[η5-1-(3,5-bis(trifluoromethyl)phenyl)-3-(2-(2,3,4,5-tetramethylcyclopentadienyl)ethyl)urea][(6-oxo-1,6-dihydropyridin-2-yl)diphenylphosphine]rhodium(III); copper(II) trifluoroacetate In toluene at 120℃; for 16h; Reagent/catalyst; Schlenk technique; Inert atmosphere;	70%

4-pyridin-2-yl-thiazol-2-ylamine (30235-26-8) + 2,5-difluorobenzoic acid (2991-28-8) → 2-[(2,5-difluorobenzoyl)amino]-4-(pyridin-2-yl)thiazole

Conditions	Yield
Stage #1: 2,5-difluorobenzoic acid With 1,8-diazabicyclo[5.4.0]undec-7-ene; 1,1'-carbonyldiimidazole In N,N-dimethyl-formamide at 23℃; for 0.5h; Inert atmosphere; Stage #2: 4-pyridin-2-yl-thiazol-2-ylamine In N,N-dimethyl-formamide at 23℃; for 16h; Inert atmosphere;	69%

tetrahydrofuran (109-99-9) + [Ru2II,III(CH3CO2)4(THF)2]BF4 + 2,5-difluorobenzoic acid (2991-28-8) → [Ru2II,II(2,5-F2PhCO2)4(THF)2]*0.5THF

Conditions	Yield
Stage #1: [Ru2II,III(CH3CO2)4(THF)2]BF4; 2,5-difluorobenzoic acid In N,N-dimethyl-aniline for 12h; Schlenk technique; Glovebox; Reflux; Stage #2: tetrahydrofuran	67%

{2‐azabicyclo[2.1.1]hexan‐1‐yl}methanamine + 2,5-difluorobenzoic acid (2991-28-8) → N‐({2‐benzyl‐2‐azabicyclo[2.1.1]hexan‐1‐yl}methyl)‐2,5‐difluorobenzamide

Conditions	Yield
Stage #1: 2,5-difluorobenzoic acid With 1-[(1-(cyano-2-ethoxy-2-oxoethylidenaminooxy)dimethylamino-morpholino)]-uronium hexafluorophosphate; N-ethyl-N,N-diisopropylamine In dichloromethane at 20℃; for 0.5h; Stage #2: {2‐azabicyclo[2.1.1]hexan‐1‐yl}methanamine In dichloromethane at 20℃; for 1h;	65%

4-(6-(4-amino-4-methylpiperidin-1-yl)pyridin-3-yl)-6-(2-hydroxy-2-methylpropoxy)pyrazolo[1,5-a]pyridine-3-carbonitrile + 2,5-difluorobenzoic acid (2991-28-8) → N-(1-(5-(3-cyano-6-(2-hydroxy-2-methylpropoxy)pyrazolo[1,5-a]pyridin-4-yl)pyridin-2-yl)-4-methylpiperidin-4-yl)-2,5-difluorobenzamide

Conditions	Yield
With N-[(dimethylamino)-1H-1,2,3-triazolo[4,5-b]pyridine-1-ylmethylene]-N-methylmethanaminium hexafluorophosphate N-oxide; N-ethyl-N,N-diisopropylamine In dichloromethane at 20℃; for 18h;	64%

5-chloro-2-benzoxazolinone (95-25-0) + 2,5-difluorobenzoic acid (2991-28-8) → 5-chloro-6-(2,5-difluoro-benzoyl)-3H-benzooxazol-2-one (230628-47-4)

Conditions	Yield
With PPA Acylation;	62%

N-(2-methylbenzoyl)-8-aminoquinoline (1182669-71-1) + 2,5-difluorobenzoic acid (2991-28-8) → 2-fluoro-7-methyl-5-(quinolin-8-yl)-5,6-dihydrophenanthridin-6-one

Conditions	Yield
Stage #1: 2,5-difluorobenzoic acid With sodium carbonate In N,N-dimethyl acetamide at 110℃; for 0.5h; Schlenk technique; Inert atmosphere; Stage #2: N-(2-methylbenzoyl)-8-aminoquinoline With nickel(II) acetate tetrahydrate; silver nitrate In N,N-dimethyl acetamide at 170℃; for 24h; Schlenk technique; Inert atmosphere;	62%

2-bromo-4-(methylsulfonyl)phenol (20951-43-3) + 2,5-difluorobenzoic acid (2991-28-8) → C14H10BrFO5S

Conditions	Yield
With potassium carbonate In N,N-dimethyl-formamide at 100℃; for 3h;	62%

tetraacetyl thioglucose (19879-84-6) + 2,5-difluorobenzoic acid (2991-28-8) → 2,3,4,6-tetraacetate-1-(2,5-difluorobenzoate) β-D-glucopyranose

Conditions	Yield
With copper acetylacetonate; silver carbonate at 130℃; for 0.25h; Microwave irradiation; Inert atmosphere; Sealed tube; stereoselective reaction;	62%

tert-butyl alcohol (75-65-0) + 2,5-difluorobenzoic acid (2991-28-8) → C11H12F2O2

Conditions	Yield
With sulfuric acid; magnesium sulfate In toluene at 20℃; Sealed tube;	62%

(R)-2-(3,8-diazabicyclo[3.2.1]octan-3-yl)-2-(4-cyanophenyl)-N-(cyclopropylmethyl)acetamide + 2,5-difluorobenzoic acid (2991-28-8) → (R)-2-(4-cyanophenyl)-N-(cyclopropylmethyl)-2-(8-(2,5-difluorobenzoyl)-3,8-diazabicyclo[3.2.1]octan-3-yl)acetamide

Conditions	Yield
With benzotriazol-1-ol; 1-ethyl-(3-(3-dimethylamino)propyl)-carbodiimide hydrochloride; N-ethyl-N,N-diisopropylamine In N,N-dimethyl-formamide at 20℃; for 18h;	59%

2-Benzoxazolinone (59-49-4) + 2,5-difluorobenzoic acid (2991-28-8) → 6-(2,5-difluoro-benzoyl)-3H-benzooxazol-2-one (230628-46-3)

Conditions	Yield
With PPA Acylation;	58%
With PPA
With PPA at 140 - 160℃;

2,5-difluorobenzoic acid (2991-28-8) → 2,5-difluorobenzohydrazide (265644-03-9)

Conditions	Yield
Stage #1: 2,5-difluorobenzoic acid With thionyl chloride In dichloromethane at 20℃; Reflux; Stage #2: With hydrazine In dichloromethane for 4h; Reflux;	56%
Multi-step reaction with 2 steps 1: sulfuric acid / Reflux 2: hydrazine hydrate / ethanol / Reflux View Scheme
Multi-step reaction with 2 steps 1: sulfuric acid / 10 h / Reflux 2: hydrazine hydrate / ethanol / 8 h / Reflux View Scheme

(Z)-N′-hydroxy-1H-benzo[d]imidazole-5-carboximidamide + 2,5-difluorobenzoic acid (2991-28-8) → 3-(1H-benzo[d]imidazol-6-yl)-5-(2,5-difluorophenyl)-1,2,4-oxadiazol

Conditions	Yield
Stage #1: 2,5-difluorobenzoic acid With 1,1'-carbonyldiimidazole In N,N-dimethyl-formamide at 20℃; for 1h; Stage #2: (Z)-N′-hydroxy-1H-benzo[d]imidazole-5-carboximidamide In N,N-dimethyl-formamide at 110℃;	47.6%

(R)-3-amino-N-(3-(cyclopropylmethyl)-7-fluoro-1-isopropyl-2,4-dioxo-1,2,3,4-tetrahydroquinazolin-6-yl)piperidine-1-carboxamide + 2,5-difluorobenzoic acid (2991-28-8) → (3R)-N-(3-(cyclopropylmethyl)-7-fluoro-1-isopropyl-2,4-dioxo-1,2,3,4-tetrahydroquinazolin-6-yl)-3-((2,5-difluorobenzoyl)amino)-piperidine-1-carboxamide

Conditions	Yield
With dmap; 2,4,6-tripropyl-1,3,5,2,4,6-trioxatriphosphinane-2,4,6-trioxide; N-ethyl-N,N-diisopropylamine In tetrahydrofuran at 70℃; for 6h;	39.5%

N-biphenyl-4-yl-3-oxo-3-piperazin-1-yl-propionamide hydrochloride (1187890-09-0) + 2,5-difluorobenzoic acid (2991-28-8) → N-Biphenyl-4-yl-3-[4-(2,5-difluoro-benzoyl)-piperazin-1-yl]-3-oxo-propionamide (1187889-55-9)

Conditions	Yield
With benzotriazol-1-ol; 1-ethyl-(3-(3-dimethylamino)propyl)-carbodiimide hydrochloride; N-ethyl-N,N-diisopropylamine In N,N-dimethyl-formamide at 10 - 20℃;	37%

Upstream product

• 32890-92-9 2,3,4,6-tetrafluorobenzoic acid 
• 367-23-7 1,2,4-trifluorobenzene 
• 2367-82-0 1,2,3,5-tetrafluorobenzene 
• 540-36-3 para-difluorobenzene 
• 1979-36-8 2',5'-difluoroacetophenone 
• 2358-29-4 2,3,6-trifluorobenzoic acid 
• 124-38-9 carbon dioxide 
• 399-94-0 2-bromo-1,4-difluorobenzene 

Downstream Products

• 52333-66-1 2-(2,5-difluoro-phenyl)-oxazolo[4,5-b]pyridine 
• 129589-71-5 N-(tert-Butoxycarbonyl)-2,5-difluoroaniline 
• 35730-09-7 2,5-difluorobenzoyl chloride 
• 1053624-65-9 C₅₉H₇₇F₂NO₁₄Si₂ 
• 230628-46-3 6-(2,5-difluoro-benzoyl)-3H-benzooxazol-2-one 
• 223444-58-4 N-t-Butyl-2,5-difluorobenzamide 
• 1275249-07-4 C₁₂H₇F₂N₃ 
• 129589-73-7 Methyl 4-(tert-butoxycarbonylamino)-2,5-difluorobenzoate 
• 129589-72-6 N-(tert-Butoxycarbonyl)-2,5-difluoro-N-(methoxycarbonyl)aniline 
• 129589-74-8 Methyl 2-(tert-butoxycarbonylamino)-3,6-difluorobenzoate 
• 79787-15-8 dimethyl 2,3-dihydro-5-(2,5-difluorophenyl)-1H-pyrrolizine-6,7-dicarboxylate 
• 79787-20-5 2,3-dihydro-5-(2,5-difluorophenyl)-6,7-bis(hydroxymethyl)-1H-pyrrolizine 
• 106588-52-7 2-(2,5-difluorophenyl)-4,4-dimethyl-2-oxazoline 

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