The 1,2,4-Triazolo[4,3-a]pyridin-3(2H)-one is an organic compound with the formula C₆H₅N₃O. The IUPAC name of this chemical is 2H-[1,2,4]triazolo[4,3-a]pyridin-3-one. With the CAS registry number 6969-71-7 and EINECS 230-191-8, it is also named as 3-Hydroxytriazolo[4,3-a]pyridine. The product's categories are APIs & Intermediate; Pyrimidine; Pyridines; Fused Ring Systems. It is pale yellow crystalline powder which is used as pharmaceutical intermediate.

The other characteristics of this product can be summarized as: (1)# of Rule of 5 Violations: 0; (2)ACD/BCF (pH 5.5): 1; (3)ACD/BCF (pH 7.4): 1; (4)ACD/KOC (pH 5.5): 18.995; (5)ACD/KOC (pH 7.4): 14.175; (6)#H bond acceptors: 4; (7)#H bond donors: 1; (8)#Freely Rotating Bonds: 0; (9)Polar Surface Area: 44.7 Å²; (10)Index of Refraction: 1.739; (11)Molar Refractivity: 36.01 cm³; (12)Molar Volume: 89.418 cm³; (13)Polarizability: 14.276×10^-24 cm³; (14)Surface Tension: 66.89 dyne/cm; (15)Density: 1.511 g/cm³; (16)Tautomer Count: 2; (17)Exact Mass: 135.043262; (18)MonoIsotopic Mass: 135.043262; (19)Topological Polar Surface Area: 44.7; (20)Heavy Atom Count: 10; (21)Complexity: 264.

Preparation of 1,2,4-Triazolo[4,3-a]pyridin-3(2H)-one: It can be obtained by 2-hydrazino-pyridine and urea. This reaction is a kind of cyclization at temperature of 200 °C. The reaction time is 2 hours. The yield is 57%.

Uses of 1,2,4-Triazolo[4,3-a]pyridin-3(2H)-one: It can react with carbonochloridic acid ethyl ester to get 1-Ethoxycarbonyl-3-oxy-sym.-triazolo[4,3-a]pyridin. This reaction needs heating. The reaction time is 3 hours and the yield is 71%.

When you are using this chemical, please be cautious about it as the following:
It is irritating to eyes, respiratory system and skin. In case of contact with eyes, rinse immediately with plenty of water and seek medical advice. If you want to contact this product, you must wear suitable protective clothing.

People can use the following data to convert to the molecule structure. 
1. SMILES:c1ccn2c(c1)n[nH]c2=O
2. InChI:InChI=1/C6H5N3O/c10-6-8-7-5-3-1-2-4-9(5)6/h1-4H,(H,8,10)
3. InChIKey:LJRXNXBFJXXRNQ-UHFFFAOYAU