6969-71-7

Basic information

• Product Name: 1,2,4-Triazolo[4,3-a]pyridin-3(2H)-one
• Synonyms: 1,2,4-TRIAZOLO-[4,3-A]PYRIDINE-3(2H)-ONE;1,2,4-TRIAZOLE(4,3)PYRIDIN-3-(2H)-ONE;1,2,4-TRIAZOL-(4,3-A)-PYRIDINE 3 (2H)-ONE;3-HYDROXYTRIAZOLO[4,3-A]PYRIDINE;3-HYDROXY-1,2,4-TRIAZOLO[4,3-A]PYRIDINE;1,2,4-Triazolopyridin-3-one;1,2,4-Triazole-(4,3-alpha)pyri;1,2,4-Triazole-(4,3-a) Pyridine-3 (2H) - One
• CAS NO: 6969-71-7
• Molecular Formula: C₆H₅N₃O
• Molecular Weight: 135.12
• EINECS: 230-191-8
• Product Categories: APIs & Intermediate;Pyrimidine;Pyridines;Fused Ring Systems;Heterocycles;intermediate for some organic synthesis
• Mol File: 6969-71-7.mol
• Article Data: 10

Chemical Properties

• Melting Point: 231°C
• Appearance: Powder
• Density: 1.511 g/cm³
• Refractive Index: 1.739
• Storage Temp.: 2-8°C
• Solubility: DMSO (Slightly), Methanol (Slightly, Heated, Sonicated)
• PKA: 7.86±0.20(Predicted)
• Stability: Light Sensitive
• BRN: 607433
• CAS DataBase Reference: 1,2,4-Triazolo[4,3-a]pyridin-3(2H)-one(CAS DataBase Reference)
• NIST Chemistry Reference: 1,2,4-Triazolo[4,3-a]pyridin-3(2H)-one(6969-71-7)
• EPA Substance Registry System: 1,2,4-Triazolo[4,3-a]pyridin-3(2H)-one(6969-71-7)

Safety Data

• Hazard Codes: Xi
• Statements: 36/37/38
• Safety Statements: 26-36
• WGK Germany: 3
• Hazardous Substances Data: 6969-71-7(Hazardous Substances Data)

Usage

Chemical Properties

Beige Solid

Uses

1,2,4-Triazolo[4,3-a]pyridin-3(2H)-one was used to prepare a congener of Trazodone (T718500) which was found to be a potent and selective inhibitor of synaptosomal uptake of 5-hydroxytryptamine.

InChI:InChI=1/C6H5N3O/c10-6-8-7-5-3-1-2-4-9(5)6/h1-4H,(H,8,10)

Synthetic route

N'-(pyridin-2-yl)formic hydrazide → [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7)

Conditions	Yield
In N,N-dimethyl-formamide at 140℃; for 24h; Reagent/catalyst; Temperature; Solvent; Schlenk technique; Sealed tube;	81%

pyrid-2-ylhydrazine (4930-98-7) + urea (57-13-6) → [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7)

Conditions	Yield
In neat (no solvent) for 0.0138889h; Microwave irradiation;	75%
at 200℃; for 2h; Cyclization;	57%
at 130℃; for 3h;	15%
at 120 - 160℃; for 4h; Temperature;

N'-(pyridin-2-yl)formic hydrazide → [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7)

Conditions	Yield
In N,N-dimethyl-formamide at 140℃; for 24h; Reagent/catalyst; Temperature; Solvent; Schlenk technique; Sealed tube;	81%

2-benzyl-[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (4231-61-2) → [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7)

Conditions	Yield
With trifluorormethanesulfonic acid In toluene at 150℃; for 0.25h; Microwave irradiation;	72%

pyrid-2-ylhydrazine (4930-98-7) + urea (57-13-6) → [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7)

Conditions	Yield
In neat (no solvent) for 0.0138889h; Microwave irradiation;	75%
at 200℃; for 2h; Cyclization;	57%
at 130℃; for 3h;	15%
at 120 - 160℃; for 4h; Temperature;

2-benzyl-[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (4231-61-2) → [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7)

Conditions	Yield
With trifluorormethanesulfonic acid In toluene at 150℃; for 0.25h; Microwave irradiation;	72%

2-chloropyridine (109-09-1) + semicarbazide hydrochloride (563-41-7) → [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7)

Conditions	Yield
With sulfuric acid In 2-ethoxy-ethanol for 24h; Reflux;	51%
With sulfuric acid In 2-ethoxy-ethanol for 0.0333333h; Microwave irradiation;	48%
With sulfuric acid In 2-ethoxy-ethanol; water	35.0 g (59%)

2-chloropyridine (109-09-1) + semicarbazide hydrochloride (563-41-7) → [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7)

Conditions	Yield
With sulfuric acid In 2-ethoxy-ethanol for 24h; Reflux;	51%
With sulfuric acid In 2-ethoxy-ethanol for 0.0333333h; Microwave irradiation;	48%
With sulfuric acid In 2-ethoxy-ethanol; water	35.0 g (59%)

diethylamine (109-89-7) + 1-acetyl-1,2,4-triazolo<4,3-a>pyridinium-3-olate (51330-53-1) → diethylacetamide (685-91-6) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7)

Conditions	Yield
In tetrahydrofuran at 25℃; Rate constant;

diethylamine (109-89-7) + 1-acetyl-1,2,4-triazolo<4,3-a>pyridinium-3-olate (51330-53-1) → diethylacetamide (685-91-6) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7)

Conditions	Yield
In tetrahydrofuran at 25℃; Rate constant;

1-acetyl-1,2,4-triazolo<4,3-a>pyridinium-3-olate (51330-53-1) → acetic acid (64-19-7) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7)

Conditions	Yield
With water at 25℃; Rate constant;

1-acetyl-1,2,4-triazolo<4,3-a>pyridinium-3-olate (51330-53-1) → acetic acid (64-19-7) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7)

Conditions	Yield
With water at 25℃; Rate constant;

2-bromo-pyridine (109-04-6) + <1,3>dioxolan-2-ylidene-malonodinitrile → [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7)

Conditions	Yield
Multi-step reaction with 2 steps 1: 100 percent / NH2NH2 / 2 h / 100 °C 2: 57 percent / 2 h / 200 °C View Scheme

2-bromo-pyridine (109-04-6) + <1,3>dioxolan-2-ylidene-malonodinitrile → [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7)

Conditions	Yield
Multi-step reaction with 2 steps 1: 100 percent / NH2NH2 / 2 h / 100 °C 2: 57 percent / 2 h / 200 °C View Scheme

2-chloropyridine (109-09-1) + hydrazine carboxamide (4426-72-6, 51433-48-8) → [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7)

Conditions	Yield
With sulfuric acid In 2-ethoxy-ethanol; water

2-chloropyridine (109-09-1) + hydrazine carboxamide (4426-72-6, 51433-48-8) → [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7)

Conditions	Yield
With sulfuric acid In 2-ethoxy-ethanol; water

2-bromo-pyridine (109-04-6) → [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7)

Conditions	Yield
Multi-step reaction with 2 steps 1: hydrazine hydrate / 1,4-dioxane / Reflux 2: 3 h / 130 °C View Scheme
Multi-step reaction with 2 steps 1: hydrazine / N,N-dimethyl-formamide / 0.03 h / Microwave irradiation 2: neat (no solvent) / 0.01 h / Microwave irradiation View Scheme

2-bromo-pyridine (109-04-6) → [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7)

Conditions	Yield
Multi-step reaction with 2 steps 1: hydrazine hydrate / 1,4-dioxane / Reflux 2: 3 h / 130 °C View Scheme
Multi-step reaction with 2 steps 1: hydrazine / N,N-dimethyl-formamide / 0.03 h / Microwave irradiation 2: neat (no solvent) / 0.01 h / Microwave irradiation View Scheme

2-chloropyridine (109-09-1) → [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7)

Conditions	Yield
Multi-step reaction with 3 steps 1: hydrazine hydrate / ethanol / 12 h / Reflux 2: Triethoxysilane / N,N-dimethyl-formamide / 20 °C 3: N,N-dimethyl-formamide / 24 h / 140 °C / Schlenk technique; Sealed tube View Scheme
Multi-step reaction with 2 steps 1: hydrazine / N,N-dimethyl-formamide / 25 h / Heating; Microwave irradiation 2: neat (no solvent) / 0.01 h / Microwave irradiation View Scheme

2-chloropyridine (109-09-1) → [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7)

Conditions	Yield
Multi-step reaction with 3 steps 1: hydrazine hydrate / ethanol / 12 h / Reflux 2: Triethoxysilane / N,N-dimethyl-formamide / 20 °C 3: N,N-dimethyl-formamide / 24 h / 140 °C / Schlenk technique; Sealed tube View Scheme
Multi-step reaction with 2 steps 1: hydrazine / N,N-dimethyl-formamide / 25 h / Heating; Microwave irradiation 2: neat (no solvent) / 0.01 h / Microwave irradiation View Scheme

pyrid-2-ylhydrazine (4930-98-7) → [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7)

Conditions	Yield
Multi-step reaction with 2 steps 1: Triethoxysilane / N,N-dimethyl-formamide / 20 °C 2: N,N-dimethyl-formamide / 24 h / 140 °C / Schlenk technique; Sealed tube View Scheme

pyrid-2-ylhydrazine (4930-98-7) → [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7)

Conditions	Yield
Multi-step reaction with 2 steps 1: Triethoxysilane / N,N-dimethyl-formamide / 20 °C 2: N,N-dimethyl-formamide / 24 h / 140 °C / Schlenk technique; Sealed tube View Scheme

2-bromo-pyridine (109-04-6) + semicarbazide hydrochloride (563-41-7) → [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7)

Conditions	Yield
With sulfuric acid In 2-ethoxy-ethanol for 0.0333333h; Microwave irradiation;

2-bromo-pyridine (109-04-6) + semicarbazide hydrochloride (563-41-7) → [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7)

Conditions	Yield
With sulfuric acid In 2-ethoxy-ethanol for 0.0333333h; Microwave irradiation;

[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) + methyl iodide (74-88-4) → 2-methyl-2H-[1,2,4]triazolo[4,3-a]pyridin-3-one (4231-60-1)

Conditions	Yield
In acetone at 40℃; Alkylation;	100%

[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) + methyl iodide (74-88-4) → 2-methyl-2H-[1,2,4]triazolo[4,3-a]pyridin-3-one (4231-60-1)

Conditions	Yield
In acetone at 40℃; Alkylation;	100%

[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) + phenylacetyl chloride (103-80-0) → 2-phenylacetyl-1,2,4-triazolo<4,3-a>pyridin-3(2H)-one

Conditions	Yield
In chloroform Heating;	96%

[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) + phenylacetyl chloride (103-80-0) → 2-phenylacetyl-1,2,4-triazolo<4,3-a>pyridin-3(2H)-one

Conditions	Yield
In chloroform Heating;	96%

phosgene (75-44-5) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → 2-chloroformyl-1,2,4-triazolo<4,3-a>pyridin-3-(2H)-one (50993-36-7)

Conditions	Yield
In tetrahydrofuran for 2h; Heating;	93%

phosgene (75-44-5) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → 2-chloroformyl-1,2,4-triazolo<4,3-a>pyridin-3-(2H)-one (50993-36-7)

Conditions	Yield
In tetrahydrofuran for 2h; Heating;	93%

acetyl chloride (75-36-5) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → 2-acetyl-1,2,4-triazolo<4,3-a>pyridin-3(2H)-one (27191-52-2)

Conditions	Yield
In chloroform for 4h; Heating;	92%

acetyl chloride (75-36-5) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → 2-acetyl-1,2,4-triazolo<4,3-a>pyridin-3(2H)-one (27191-52-2)

Conditions	Yield
In chloroform for 4h; Heating;	92%

1,3-chlorobromopropane (109-70-6) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → 2-(3-chloropropyl)-1,2,4-triazolo<4,3-a>pyridin-3-one (19666-40-1)

Conditions	Yield
With tetrabutylammomium bromide; potassium carbonate In acetonitrile for 0.0222222h; Solvent; Microwave irradiation;	92%
With potassium carbonate In acetonitrile for 8h; Heating / reflux;	70%

1,3-chlorobromopropane (109-70-6) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → 2-(3-chloropropyl)-1,2,4-triazolo<4,3-a>pyridin-3-one (19666-40-1)

Conditions	Yield
With tetrabutylammomium bromide; potassium carbonate In acetonitrile for 0.0222222h; Solvent; Microwave irradiation;	92%
With potassium carbonate In acetonitrile for 8h; Heating / reflux;	70%

1-(3-chloropropyl)-4-(3-chlorophenyl)piperazine hydrochloride (52605-52-4) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → trazodone (19794-93-5)

Conditions	Yield
With sodium hydroxide In isopropyl alcohol for 26h; Reagent/catalyst; Inert atmosphere; Reflux;	92%
With tetrabutylammomium bromide; potassium carbonate In acetonitrile for 0.0222222h; Time; Microwave irradiation;	92%

1-(3-chloropropyl)-4-(3-chlorophenyl)piperazine hydrochloride (52605-52-4) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → trazodone (19794-93-5)

Conditions	Yield
With sodium hydroxide In isopropyl alcohol for 26h; Reagent/catalyst; Inert atmosphere; Reflux;	92%
With tetrabutylammomium bromide; potassium carbonate In acetonitrile for 0.0222222h; Time; Microwave irradiation;	92%

bromoacetic acid tert-butyl ester (5292-43-3) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → tert-butyl 2-{3-oxo-2H,3H-[1,2,4]triazolo[4,3-a]pyridin-2-yl}acetate

Conditions	Yield
With potassium carbonate In acetonitrile at 60℃; for 1.5h;	70%

bromoacetic acid tert-butyl ester (5292-43-3) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → tert-butyl 2-{3-oxo-2H,3H-[1,2,4]triazolo[4,3-a]pyridin-2-yl}acetate

Conditions	Yield
With potassium carbonate In acetonitrile at 60℃; for 1.5h;	70%

1,1-dideutero-3-[4-(3-chlorophenyl)piperazin-1-yl]propan-1-ol (1181578-67-5) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → 2-(1,1-dideutero-3-(4-(3-chlorophenyl)piperazin-1-yl)propyl)-[1,2,4]triazolo[4,3-a]pyridin-3(2H)one (1181577-82-1)

Conditions	Yield
With triphenylphosphine; diethylazodicarboxylate In tetrahydrofuran at 0 - 20℃;	69%

1,1-dideutero-3-[4-(3-chlorophenyl)piperazin-1-yl]propan-1-ol (1181578-67-5) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → 2-(1,1-dideutero-3-(4-(3-chlorophenyl)piperazin-1-yl)propyl)-[1,2,4]triazolo[4,3-a]pyridin-3(2H)one (1181577-82-1)

Conditions	Yield
With triphenylphosphine; diethylazodicarboxylate In tetrahydrofuran at 0 - 20℃;	69%

4-chlorobutyl bromide (6940-78-9) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → 2-(4-chlorobutyl)-[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one

Conditions	Yield
With potassium carbonate In N,N-dimethyl-formamide at 20℃; Cooling with ice;	69%

4-chlorobutyl bromide (6940-78-9) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → 2-(4-chlorobutyl)-[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one

Conditions	Yield
With potassium carbonate In N,N-dimethyl-formamide at 20℃; Cooling with ice;	69%

1-(3-bromopropyl)-4-(3-chlorophenyl)-piperazine (142944-48-7) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → trazodone (19794-93-5)

Conditions	Yield
Stage #1: 1-(3-bromopropyl)-4-(3-chlorophenyl)-piperazine With sodium hydride In 1,4-dioxane for 1h; Reflux; Stage #2: [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one In 1,4-dioxane for 20h; Reflux;	65%

1-(3-bromopropyl)-4-(3-chlorophenyl)-piperazine (142944-48-7) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → trazodone (19794-93-5)

Conditions	Yield
Stage #1: 1-(3-bromopropyl)-4-(3-chlorophenyl)-piperazine With sodium hydride In 1,4-dioxane for 1h; Reflux; Stage #2: [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one In 1,4-dioxane for 20h; Reflux;	65%

benzyl bromide (100-39-0) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → 1-benzyl-[1,2,4]triazolo[4,3-a]pyridinium-3-olate (42238-98-2) + 2-benzyl-[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (4231-61-2)

Conditions	Yield
With potassium carbonate In 1,4-dioxane at 80℃; for 10h; Alkylation;	A 60% B 32%

benzyl bromide (100-39-0) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → 1-benzyl-[1,2,4]triazolo[4,3-a]pyridinium-3-olate (42238-98-2) + 2-benzyl-[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (4231-61-2)

Conditions	Yield
With potassium carbonate In 1,4-dioxane at 80℃; for 10h; Alkylation;	A 60% B 32%

3-chloropropyl p-toluenesulfonate (632-02-0) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → 2-(3-chloropropyl)-1,2,4-triazolo<4,3-a>pyridin-3-one (19666-40-1)

Conditions	Yield
Stage #1: [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one With sodium hydride In DMF (N,N-dimethyl-formamide) for 0.5h; Stage #2: 3-chloropropyl p-toluenesulfonate In DMF (N,N-dimethyl-formamide) at 50℃; for 4h;	58%

3-chloropropyl p-toluenesulfonate (632-02-0) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → 2-(3-chloropropyl)-1,2,4-triazolo<4,3-a>pyridin-3-one (19666-40-1)

Conditions	Yield
Stage #1: [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one With sodium hydride In DMF (N,N-dimethyl-formamide) for 0.5h; Stage #2: 3-chloropropyl p-toluenesulfonate In DMF (N,N-dimethyl-formamide) at 50℃; for 4h;	58%

tert-butyl 2-bromopropionate (39149-80-9, 54631-38-8, 98104-35-9, 32821-07-1) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → tert-butyl 2-{3-oxo-2H,3H-[1,2,4]triazolo[4,3-a]pyridin-2-yl}propanoate

Conditions	Yield
With potassium carbonate In acetonitrile at 60℃; for 20h;	58%

tert-butyl 2-bromopropionate (39149-80-9, 54631-38-8, 98104-35-9, 32821-07-1) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → tert-butyl 2-{3-oxo-2H,3H-[1,2,4]triazolo[4,3-a]pyridin-2-yl}propanoate

Conditions	Yield
With potassium carbonate In acetonitrile at 60℃; for 20h;	58%

ethylene dibromide (106-93-4) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → 2-(2-bromoethyl)-[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one

Conditions	Yield
With sodium hydride In N,N-dimethyl-formamide at 20℃; for 6h;	54.7%

ethylene dibromide (106-93-4) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → 2-(2-bromoethyl)-[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one

Conditions	Yield
With sodium hydride In N,N-dimethyl-formamide at 20℃; for 6h;	54.7%

benzyl chloroformate (501-53-1) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → 1-benzyloxycarbonyl-1,2,4-triazolo<4,3-a>pyridinium-3-olate (50739-45-2)

Conditions	Yield
at 90℃; for 1h;	52%

benzyl chloroformate (501-53-1) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → 1-benzyloxycarbonyl-1,2,4-triazolo<4,3-a>pyridinium-3-olate (50739-45-2)

Conditions	Yield
at 90℃; for 1h;	52%

[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) + (1S,2R,5S)-2-(4'-Chloro-biphenyl-4-ylsulfanyl)-5-methanesulfonyloxymethyl-cyclopentanecarboxylic acid tert-butyl ester → 2-(4'-chloro-biphenyl-4-ylsulfanyl)-5-(3-oxo-[1,2,4]triazolo[4,3-a]pyridin-2-ylmethyl)-cyclopentanecarboxylic acid tert-butyl ester

Conditions	Yield
With 15-crown-5; sodium hydride In N,N-dimethyl-formamide at 40℃; for 12h;	46%

[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) + (1S,2R,5S)-2-(4'-Chloro-biphenyl-4-ylsulfanyl)-5-methanesulfonyloxymethyl-cyclopentanecarboxylic acid tert-butyl ester → 2-(4'-chloro-biphenyl-4-ylsulfanyl)-5-(3-oxo-[1,2,4]triazolo[4,3-a]pyridin-2-ylmethyl)-cyclopentanecarboxylic acid tert-butyl ester

Conditions	Yield
With 15-crown-5; sodium hydride In N,N-dimethyl-formamide at 40℃; for 12h;	46%

C17H16BrF2NO (1084812-30-5) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → 2-(5-(3,5-difluorophenoxy)-2-methyl-2,3,4,5-tetrahydro-1H-benzo[c]azepin-8-yl)-[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (1084811-05-1)

Conditions	Yield
With potassium phosphate; N,N`-dimethylethylenediamine; copper(l) iodide In 1,4-dioxane at 110℃; for 16h; Product distribution / selectivity;	46%

1,3-dibromo-1,1,3,3-d4-propane (64528-94-5) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → 2-(1,1,3,3-tetradeutero-3-bromopropyl)-[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (1181578-69-7)

Conditions	Yield
With potassium carbonate In acetonitrile at 60℃; for 18h;	31%

C17H16BrF2NO (1084812-30-5) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → 2-(5-(3,5-difluorophenoxy)-2-methyl-2,3,4,5-tetrahydro-1H-benzo[c]azepin-8-yl)-[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (1084811-05-1)

Conditions	Yield
With potassium phosphate; N,N`-dimethylethylenediamine; copper(l) iodide In 1,4-dioxane at 110℃; for 16h; Product distribution / selectivity;	46%

3-chloro-1-[4-(3-chlorophenyl)piperazin-1-yl]propan-1-one (349097-88-7) + [1,2,4]triazolo[4,3-a]pyridin-3(2H)-one (6969-71-7) → 1-(3-chloro-phenyl)-4-[3-(3-oxo-[1,2,4]triazolo[4,3-a]pyridin-2-yl)-propionyl]-piperazine (53689-32-0)

Conditions	Yield
With tetrabutylammomium bromide; potassium hydroxide In toluene at 110℃; for 16h;	30%

Upstream product

• 4231-61-2 2-benzyl-[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one 
• 109-04-6 2-bromo-pyridine 
• 563-41-7 semicarbazide hydrochloride 
• 4930-98-7 pyrid-2-ylhydrazine 
• 109-09-1 2-chloropyridine 
• 4426-72-6 hydrazine carboxamide 
• 57-13-6 urea 
• 51330-53-1 1-acetyl-1,2,4-triazolo<4,3-a>pyridinium-3-olate 
• 109-89-7 diethylamine 

Downstream Products

• 25332-39-2 trazodone hydrochloride 
• 19794-93-5 trazodone 
• 1000932-43-3 2-(2-bromoethyl)-[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one 
• 1360440-43-2 2-(5-(4-chlorophenyl)-2,5-ethano-2,3,4,5-tetrahydro-1H-benzo[c]azepin-8-yl)-[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one 
• 1334297-40-3 2-(2-chloro-5-((2S,3R,4R,5S,6R)-3,4,5-trihydroxy-6-(hydroxymethyl)tetrahydro-2H-pyran-2-yl)benzyl)-[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one 
• 19666-40-1 2-(3-chloropropyl)-1,2,4-triazolo<4,3-a>pyridin-3-one 
• 1094305-62-0 2-(3-bromopropyl)[1,2,4]triazolo[4,3-a]pyridine-3(2H)-one 
• 1181577-82-1 2-(1,1-dideutero-3-(4-(3-chlorophenyl)piperazin-1-yl)propyl)-[1,2,4]triazolo[4,3-a]pyridin-3(2H)one 
• 53689-32-0 1-(3-chloro-phenyl)-4-[3-(3-oxo-[1,2,4]triazolo[4,3-a]pyridin-2-yl)-propionyl]-piperazine 
• 1084811-05-1 2-(5-(3,5-difluorophenoxy)-2-methyl-2,3,4,5-tetrahydro-1H-benzo[c]azepin-8-yl)-[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one 
• 137540-95-5 2-(2-{4-[Bis-(4-fluoro-phenyl)-methylene]-piperidin-1-yl}-ethyl)-2H-[1,2,4]triazolo[4,3-a]pyridin-3-one 
• 89762-47-0 C₁₅H₁₃N₃O₄ 
• 88754-51-2 1-phenylacetic-1,2,4-triazolo<4,3-a>pyridinium-3-olate 

Relevant articles and documents

Preparation method of pyridine triazolone

The invention discloses a preparation method of pyridine triazolone. The method comprises the following steps: 1) adding 2-chloropyridine and hydrazine hydrate into a first reaction flask, stirring, heating to 90-110 DEG C, and keeping the temperature to react for 6-8 hours to obtain a first mixed solution; 2) adding the first mixed solution into a second reaction bottle, extracting, recovering hydrazine hydrate under reduced pressure, cooling and adjusting alkali, and performing secondary extraction to obtain 2-pyridine hydrazine; 3) adding the 2-pyridylhydrazine and urea into the reaction kettle, heating to 150-160 DEG C, carrying out heat preservation reaction for 3-4 hours, cooling, adding water for dissolving, cooling, carrying out stirring reacting for 1 hour, and performing suctionfiltration, washing and drying on the reaction system to obtain a crude product; and 4) adding the crude product and DMSO into a third reaction flask, heating, stirring, filtering, cooling, carrying out heat preservation reaction for 1-2 hours, filtering, and drying to obtain pyridinetriazolone. The preparation method of pyridinetriazolone provided by the invention has the advantages that the total yield can reach 70% or above, and the purity of the obtained product can reach 99.2% or above.

The Base-Promoted Annulation of 2-Hydrazinyl Pyridine and CO2 toward Triazolones

A base-promoted annulation of 2-hydrazinyl pyridine and atmospheric pressure of CO2 has been developed in the presence of silane as reducing reagent, affording a series of triazolones in moderate to excellent yields. CO2 served as a carbonyl source in this transfomation. Moreover, benzamidrazones also worked well under this procedure. Thus, it represents a green, sustainable and straightforward pathway to access triazolone frameworks. (Figure presented.).

Microwave-assisted N-debenzylation of amides with triflic acid

A new and facile microwave-assisted protocol for the debenzylation of N-benzylamides with triflic acid has been developed. Both secondary and tertiary aliphatic or aromatic amides are obtained in moderate to good yields.