摩熵化学
数据库官网
小程序
打开微信扫一扫
首页 分子通 化学资讯 化学百科 反应查询 关于我们
请输入关键词

三唑并嘧啶类

中文名称 英文名称 CAS号 化学式 结构式图片
—— ethyl (7R)-7-(4-bromophenyl)-5-(trifluoromethyl)-4,7-dihydro-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxylate —— C15H12BrF3N4O2
ethyl (7R)-7-(4-bromophenyl)-5-(trifluoromethyl)-4,7-dihydro-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxylate
—— (5R,7S)-7-(5-bromo-2-fluorophenyl)-5-(3-chloro-4-ethoxyphenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine —— C19H17BrClFN4O
(5R,7S)-7-(5-bromo-2-fluorophenyl)-5-(3-chloro-4-ethoxyphenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine
—— ethyl (7S)-7-(4-bromophenyl)-5-(trifluoromethyl)-4,7-dihydro-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxylate —— C15H12BrF3N4O2
ethyl (7S)-7-(4-bromophenyl)-5-(trifluoromethyl)-4,7-dihydro-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxylate
—— (5S,7S)-5-(3-chloro-4-ethoxyphenyl)-7-[4-(difluoromethoxy)phenyl]-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine —— C20H19ClF2N4O2
(5S,7S)-5-(3-chloro-4-ethoxyphenyl)-7-[4-(difluoromethoxy)phenyl]-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine
—— (5R,7R)-5-(4-iodophenyl)-7-(2-methoxyphenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine —— C18H17IN4O
(5R,7R)-5-(4-iodophenyl)-7-(2-methoxyphenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine
—— (5S,7S)-5-(3-chloro-4-ethoxyphenyl)-7-(2-chlorophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine —— C19H18Cl2N4O
(5S,7S)-5-(3-chloro-4-ethoxyphenyl)-7-(2-chlorophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine
—— (5R,7S)-7-(5-bromo-2-fluorophenyl)-5-(3-bromophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine —— C17H13Br2FN4
(5R,7S)-7-(5-bromo-2-fluorophenyl)-5-(3-bromophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine
—— (5R,7R)-7-(2-chloro-6-fluorophenyl)-5-(4-chlorophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine —— C17H13Cl2FN4
(5R,7R)-7-(2-chloro-6-fluorophenyl)-5-(4-chlorophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine
—— (5S,7R)-7-(5-bromo-2-fluorophenyl)-5-(4-bromophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine —— C17H13Br2FN4
(5S,7R)-7-(5-bromo-2-fluorophenyl)-5-(4-bromophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine
—— (5S,7R)-7-(5-bromo-2-fluorophenyl)-5-(3-chloro-4-ethoxyphenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine —— C19H17BrClFN4O
(5S,7R)-7-(5-bromo-2-fluorophenyl)-5-(3-chloro-4-ethoxyphenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine
—— (5S,7S)-7-(2-chloro-6-fluorophenyl)-5-(4-chlorophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine —— C17H13Cl2FN4
(5S,7S)-7-(2-chloro-6-fluorophenyl)-5-(4-chlorophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine
—— (5S,7S)-7-(2-fluorophenyl)-5-(4-iodophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine —— C17H14FIN4
(5S,7S)-7-(2-fluorophenyl)-5-(4-iodophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine
—— ethyl (7S)-7-(4-methylphenyl)-5-(trifluoromethyl)-4,7-dihydro-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxylate —— C16H15F3N4O2
ethyl (7S)-7-(4-methylphenyl)-5-(trifluoromethyl)-4,7-dihydro-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxylate
—— (5R,7R)-5-(3-chloro-4-ethoxyphenyl)-7-[4-(difluoromethoxy)phenyl]-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine —— C20H19ClF2N4O2
(5R,7R)-5-(3-chloro-4-ethoxyphenyl)-7-[4-(difluoromethoxy)phenyl]-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine
—— (5S,7S)-7-(2-chloro-6-fluorophenyl)-5-(3,4-dimethylphenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine —— C19H18ClFN4
(5S,7S)-7-(2-chloro-6-fluorophenyl)-5-(3,4-dimethylphenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine
—— (5R,7S)-7-(5-bromo-2-fluorophenyl)-5-(4-chlorophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine —— C17H13BrClFN4
(5R,7S)-7-(5-bromo-2-fluorophenyl)-5-(4-chlorophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine
—— (5S,7S)-7-(5-bromo-2-fluorophenyl)-5-(4-chlorophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine —— C17H13BrClFN4
(5S,7S)-7-(5-bromo-2-fluorophenyl)-5-(4-chlorophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine
—— (5R,7S)-5-(3-chloro-4-ethoxyphenyl)-7-(2-chlorophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine —— C19H18Cl2N4O
(5R,7S)-5-(3-chloro-4-ethoxyphenyl)-7-(2-chlorophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine
—— (5R,7R)-5-(3-chloro-4-ethoxyphenyl)-7-(2-chlorophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine —— C19H18Cl2N4O
(5R,7R)-5-(3-chloro-4-ethoxyphenyl)-7-(2-chlorophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine
—— (5S,7S)-7-(5-bromo-2-fluorophenyl)-5-(3-bromophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine —— C17H13Br2FN4
(5S,7S)-7-(5-bromo-2-fluorophenyl)-5-(3-bromophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine
—— (5R,7R)-7-(5-bromo-2-fluorophenyl)-5-(3-chloro-4-ethoxyphenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine —— C19H17BrClFN4O
(5R,7R)-7-(5-bromo-2-fluorophenyl)-5-(3-chloro-4-ethoxyphenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine
—— (5R,7S)-7-(5-bromo-2-fluorophenyl)-5-(4-bromophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine —— C17H13Br2FN4
(5R,7S)-7-(5-bromo-2-fluorophenyl)-5-(4-bromophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine
—— (5R,7R)-7-(5-bromo-2-fluorophenyl)-5-(3-bromophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine —— C17H13Br2FN4
(5R,7R)-7-(5-bromo-2-fluorophenyl)-5-(3-bromophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine
—— (7S)-N-(4-methoxyphenyl)-5-methyl-7-(2,3,4-trimethoxyphenyl)-4,7-dihydro-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxamide —— C23H25N5O5
(7S)-N-(4-methoxyphenyl)-5-methyl-7-(2,3,4-trimethoxyphenyl)-4,7-dihydro-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxamide
—— (5R,7S)-5-(4-bromophenyl)-7-(2-fluorophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine —— C17H14BrFN4
(5R,7S)-5-(4-bromophenyl)-7-(2-fluorophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine
—— (5S,7S)-7-(5-bromo-2-fluorophenyl)-5-(3-chloro-4-ethoxyphenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine —— C19H17BrClFN4O
(5S,7S)-7-(5-bromo-2-fluorophenyl)-5-(3-chloro-4-ethoxyphenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine
—— (5R,7S)-5-(3-chloro-4-ethoxyphenyl)-7-[4-(difluoromethoxy)phenyl]-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine —— C20H19ClF2N4O2
(5R,7S)-5-(3-chloro-4-ethoxyphenyl)-7-[4-(difluoromethoxy)phenyl]-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine
—— (5R,7R)-5-(4-bromophenyl)-7-(2-fluorophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine —— C17H14BrFN4
(5R,7R)-5-(4-bromophenyl)-7-(2-fluorophenyl)-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine
—— methyl 12-methyl-4-[(5R,7S)-5-thiophen-2-yl-7-(trifluoromethyl)-1,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidin-2-yl]-10-thia-3,5,6,8-tetrazatricyclo[7.3.0.02,6]dodeca-1(9),2,4,7,11-pentaene-11-carboxylate —— C21H16F3N7O2S2
methyl 12-methyl-4-[(5R,7S)-5-thiophen-2-yl-7-(trifluoromethyl)-1,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidin-2-yl]-10-thia-3,5,6,8-tetrazatricyclo[7.3.0.02,6]dodeca-1(9),2,4,7,11-pentaene-11-carboxylate
—— methyl 4-[(5S,7S)-5-(3,4-dimethylphenyl)-7-(trifluoromethyl)-1,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidin-2-yl]-12-methyl-10-thia-3,5,6,8-tetrazatricyclo[7.3.0.02,6]dodeca-1(9),2,4,7,11-pentaene-11-carboxylate —— C25H22F3N7O2S
methyl 4-[(5S,7S)-5-(3,4-dimethylphenyl)-7-(trifluoromethyl)-1,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidin-2-yl]-12-methyl-10-thia-3,5,6,8-tetrazatricyclo[7.3.0.02,6]dodeca-1(9),2,4,7,11-pentaene-11-carboxylate
—— methyl 12-methyl-4-[(5S,7R)-5-thiophen-2-yl-7-(trifluoromethyl)-1,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidin-2-yl]-10-thia-3,5,6,8-tetrazatricyclo[7.3.0.02,6]dodeca-1(9),2,4,7,11-pentaene-11-carboxylate —— C21H16F3N7O2S2
methyl 12-methyl-4-[(5S,7R)-5-thiophen-2-yl-7-(trifluoromethyl)-1,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidin-2-yl]-10-thia-3,5,6,8-tetrazatricyclo[7.3.0.02,6]dodeca-1(9),2,4,7,11-pentaene-11-carboxylate
—— methyl 12-methyl-4-[(5S,7S)-5-thiophen-2-yl-7-(trifluoromethyl)-1,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidin-2-yl]-10-thia-3,5,6,8-tetrazatricyclo[7.3.0.02,6]dodeca-1(9),2,4,7,11-pentaene-11-carboxylate —— C21H16F3N7O2S2
methyl 12-methyl-4-[(5S,7S)-5-thiophen-2-yl-7-(trifluoromethyl)-1,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidin-2-yl]-10-thia-3,5,6,8-tetrazatricyclo[7.3.0.02,6]dodeca-1(9),2,4,7,11-pentaene-11-carboxylate
—— methyl 4-[(5R,7R)-5-(3,4-dimethylphenyl)-7-(trifluoromethyl)-1,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidin-2-yl]-12-methyl-10-thia-3,5,6,8-tetrazatricyclo[7.3.0.02,6]dodeca-1(9),2,4,7,11-pentaene-11-carboxylate —— C25H22F3N7O2S
methyl 4-[(5R,7R)-5-(3,4-dimethylphenyl)-7-(trifluoromethyl)-1,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidin-2-yl]-12-methyl-10-thia-3,5,6,8-tetrazatricyclo[7.3.0.02,6]dodeca-1(9),2,4,7,11-pentaene-11-carboxylate
—— methyl 4-[(5S,7R)-5-(3,4-dimethylphenyl)-7-(trifluoromethyl)-1,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidin-2-yl]-12-methyl-10-thia-3,5,6,8-tetrazatricyclo[7.3.0.02,6]dodeca-1(9),2,4,7,11-pentaene-11-carboxylate —— C25H22F3N7O2S
methyl 4-[(5S,7R)-5-(3,4-dimethylphenyl)-7-(trifluoromethyl)-1,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidin-2-yl]-12-methyl-10-thia-3,5,6,8-tetrazatricyclo[7.3.0.02,6]dodeca-1(9),2,4,7,11-pentaene-11-carboxylate
—— methyl 4-[(5R,7S)-5-(4-chlorophenyl)-7-(trifluoromethyl)-1,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidin-2-yl]-12-methyl-10-thia-3,5,6,8-tetrazatricyclo[7.3.0.02,6]dodeca-1(9),2,4,7,11-pentaene-11-carboxylate —— C23H17ClF3N7O2S
methyl 4-[(5R,7S)-5-(4-chlorophenyl)-7-(trifluoromethyl)-1,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidin-2-yl]-12-methyl-10-thia-3,5,6,8-tetrazatricyclo[7.3.0.02,6]dodeca-1(9),2,4,7,11-pentaene-11-carboxylate
—— (13S)-13-tert-butyl-4-[(1S,2S)-2-(4-methylphenyl)cyclopropyl]-10-thia-3,5,6,8-tetrazatetracyclo[7.7.0.02,6.011,16]hexadeca-1(9),2,4,7,11(16)-pentaene —— C25H28N4S
(13S)-13-tert-butyl-4-[(1S,2S)-2-(4-methylphenyl)cyclopropyl]-10-thia-3,5,6,8-tetrazatetracyclo[7.7.0.02,6.011,16]hexadeca-1(9),2,4,7,11(16)-pentaene
—— methyl 12-methyl-4-[(5R,7R)-5-thiophen-2-yl-7-(trifluoromethyl)-1,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidin-2-yl]-10-thia-3,5,6,8-tetrazatricyclo[7.3.0.02,6]dodeca-1(9),2,4,7,11-pentaene-11-carboxylate —— C21H16F3N7O2S2
methyl 12-methyl-4-[(5R,7R)-5-thiophen-2-yl-7-(trifluoromethyl)-1,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidin-2-yl]-10-thia-3,5,6,8-tetrazatricyclo[7.3.0.02,6]dodeca-1(9),2,4,7,11-pentaene-11-carboxylate
—— methyl 4-[(5R,7R)-5-(4-chlorophenyl)-7-(trifluoromethyl)-1,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidin-2-yl]-12-methyl-10-thia-3,5,6,8-tetrazatricyclo[7.3.0.02,6]dodeca-1(9),2,4,7,11-pentaene-11-carboxylate —— C23H17ClF3N7O2S
methyl 4-[(5R,7R)-5-(4-chlorophenyl)-7-(trifluoromethyl)-1,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidin-2-yl]-12-methyl-10-thia-3,5,6,8-tetrazatricyclo[7.3.0.02,6]dodeca-1(9),2,4,7,11-pentaene-11-carboxylate
—— 7-[1-(2,6-Dimethylphenoxy)ethyl]-[1,2,4]triazolo[1,5-a]pyrimidin-2-amine —— C15H17N5O
7-[1-(2,6-Dimethylphenoxy)ethyl]-[1,2,4]triazolo[1,5-a]pyrimidin-2-amine
—— 1-[7-(2,4-dichlorophenyl)-5-phenyl-1,7-dihydro-[1,2,4]triazolo[1,5-a]pyrimidin-2-yl]pyrrolidine-2,5-dione —— C21H15Cl2N5O2
1-[7-(2,4-dichlorophenyl)-5-phenyl-1,7-dihydro-[1,2,4]triazolo[1,5-a]pyrimidin-2-yl]pyrrolidine-2,5-dione
—— 1-[7-(4-methylphenyl)-5-phenyl-1,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidin-2-yl]pyrrolidine-2,5-dione —— C22H21N5O2
1-[7-(4-methylphenyl)-5-phenyl-1,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidin-2-yl]pyrrolidine-2,5-dione
—— N-[5-(4-chlorophenyl)-7-(2-methoxyphenyl)-1,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidin-2-yl]acetamide —— C20H20ClN5O2
N-[5-(4-chlorophenyl)-7-(2-methoxyphenyl)-1,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidin-2-yl]acetamide
—— 4-{[9-(Tert-butyl)-8,9,10,11-tetrahydro[1]benzothieno[3,2-E][1,2,4]triazolo[1,5-C]pyrimidin-2-YL]methyl}phenyl methyl ether —— C23H26N4OS
4-{[9-(Tert-butyl)-8,9,10,11-tetrahydro[1]benzothieno[3,2-E][1,2,4]triazolo[1,5-C]pyrimidin-2-YL]methyl}phenyl methyl ether
—— 8,10-diphenyl-10,11-dihydro-8H-thiopyrano[4',3':4,5]thieno[3,2-e][1,2,4]triazolo[4,3-c]pyrimidine —— C22H16N4S2
8,10-diphenyl-10,11-dihydro-8H-thiopyrano[4',3':4,5]thieno[3,2-e][1,2,4]triazolo[4,3-c]pyrimidine
—— 2-[(4-methyl-5-oxo-4,5,6,7,8,9-hexahydro[1]benzothieno[3,2-e][1,2,4]triazolo[4,3-a]pyrimidin-1-yl)sulfanyl]-N-(4-phenylbutan-2-yl)acetamide —— C24H27N5O2S2
2-[(4-methyl-5-oxo-4,5,6,7,8,9-hexahydro[1]benzothieno[3,2-e][1,2,4]triazolo[4,3-a]pyrimidin-1-yl)sulfanyl]-N-(4-phenylbutan-2-yl)acetamide
—— N-[7-(4-methoxyphenyl)-5-phenyl-1,7-dihydro-[1,2,4]triazolo[1,5-a]pyrimidin-2-yl]-3-nitrobenzamide —— C25H20N6O4
N-[7-(4-methoxyphenyl)-5-phenyl-1,7-dihydro-[1,2,4]triazolo[1,5-a]pyrimidin-2-yl]-3-nitrobenzamide
—— N-(5,7-diphenyl-1,7-dihydro-[1,2,4]triazolo[1,5-a]pyrimidin-2-yl)-4-methylbenzamide —— C25H21N5O
N-(5,7-diphenyl-1,7-dihydro-[1,2,4]triazolo[1,5-a]pyrimidin-2-yl)-4-methylbenzamide
—— 3-methyl-8,10-diphenyl-10,11-dihydro-8H-thiopyrano[4',3':4,5]thieno[3,2-e][1,2,4]triazolo[4,3-c]pyrimidine —— C23H18N4S2
3-methyl-8,10-diphenyl-10,11-dihydro-8H-thiopyrano[4',3':4,5]thieno[3,2-e][1,2,4]triazolo[4,3-c]pyrimidine
—— N-(5,7-diphenyl-1,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidin-2-yl)methanesulfonamide —— C18H19N5O2S
N-(5,7-diphenyl-1,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidin-2-yl)methanesulfonamide
—— 8-methyl-4-phenyl-1-(propan-2-ylsulfanyl)-6,7,8,9-tetrahydro[1]benzothieno[3,2-e][1,2,4]triazolo[4,3-a]pyrimidin-5(4H)-one —— C21H22N4OS2
8-methyl-4-phenyl-1-(propan-2-ylsulfanyl)-6,7,8,9-tetrahydro[1]benzothieno[3,2-e][1,2,4]triazolo[4,3-a]pyrimidin-5(4H)-one