点击这里给我发消息
全部分类

产品详情

2555-29-5|8-乙酰-7-羟基-4-甲基-2H-色烯-2-色烯|8-acetyl-7-hydroxy-4-methyl-2H-chromen-2-one

8-乙酰-7-羟基-4-甲基-2H-色烯-2-色烯

CAS号：2555-29-5
产品编号 : CM285225 分子式 : C12H10O4
分子量 : 218.21 纯度 :
包装单位 可用库存 价格(￥) 数量
询单
* 凯曼尼的所有产品仅用作科学研究，我们不为任何个人用途提供产品和服务。
收藏

产品信息

8-乙酰-7-羟基-4-甲基-2H-色烯-2-色烯
  • CAS 号: 2555-29-5
  • 产品编号: CM285225
  • 分子式: C12H10O4
  • 分子量: 218.21
  • 熔点:
  • 沸点:
  • Smiles Code: CC(=O)C1=C(O)C=CC2=C1OC(=O)C=C2C
  • MDL 号:
  • 浓度: -
  • 存储方式:
  • 外观性状:

相关产品推荐

100343-98-4|7-(二乙氨基)香豆素-3-甲酰肼|7-(diethylamino)-2-oxo-2H-chromene-3-carbohydrazide
100343-98-4
7-(二乙氨基)香豆素-3-甲酰肼
103676-94-4|4-氯-7-甲氧基-2H-色烯-2-酮|4-chloro-7-methoxy-2H-chromen-2-one
103676-94-4
4-氯-7-甲氧基-2H-色烯-2-酮
10543-42-7|香豆素-6-磺酰氯|2-oxo-2H-chromene-6-sulfonyl chloride
10543-42-7
香豆素-6-磺酰氯
105738-24-7|4-甲基-2-氧代-2H-色烯-7-基氯乙酸酯|4-methyl-2-oxo-2H-chromen-7-yl 2-chloroacetate
105738-24-7
4-甲基-2-氧代-2H-色烯-7-基氯乙酸酯
105837-04-5|7-溴-2-氧代-2H-色烯-3-羧酸乙酯|ethyl 7-bromo-2-oxo-2H-chromene-3-carboxylate
105837-04-5
7-溴-2-氧代-2H-色烯-3-羧酸乙酯
1076-38-6|4-羟基香豆素|4-hydroxy-2H-chromen-2-one
1076-38-6
4-羟基香豆素
1084-45-3|7-羟基-2-氧代-2H-亚甲基-4-羧酸乙酯|ethyl 7-hydroxy-2-oxo-2H-chromene-4-carboxylate
1084-45-3
7-羟基-2-氧代-2H-亚甲基-4-羧酸乙酯
108530-10-5|2-氧代-2H-色烯-7-基三氟甲磺酸酯|2-oxo-2H-chromen-7-yl trifluoromethanesulfonate
108530-10-5
2-氧代-2H-色烯-7-基三氟甲磺酸酯
1100353-03-4|N-(3-(咪唑并[1,2-a]吡啶-2-基)苯基)-8-甲氧基-2-氧代-2H-苯并吡喃-3-酰胺|N-(3-{imidazo[1,2-a]pyridin-2-yl}phenyl)-8-methoxy-2-oxo-2H-chromene-3-carboxamide
1100353-03-4
N-(3-(咪唑并[1,2-a]吡啶-2-基)苯基)-8-甲氧基-2-氧代-2H-苯并吡喃-3-酰胺
128789-29-7|8-氟-4-羟基-2H-色烯-2-酮|8-fluoro-4-hydroxy-2H-chromen-2-one
128789-29-7
8-氟-4-羟基-2H-色烯-2-酮
13252-84-1|4-羟基-6-甲氧基-2H-色烯-2-酮|4-hydroxy-6-methoxy-2H-chromen-2-one
13252-84-1
4-羟基-6-甲氧基-2H-色烯-2-酮
1338937-12-4|7-羟基-6-甲氧基-3-(2-(2-甲氧基乙氧基)乙基)-4-甲基-2H-苯并吡喃-2-酮|7-hydroxy-6-methoxy-3-[2-(2-methoxyethoxy)ethyl]-4-methyl-2H-chromen-2-one
1338937-12-4
7-羟基-6-甲氧基-3-(2-(2-甲氧基乙氧基)乙基)-4-甲基-2H-苯并吡喃-2-酮
1338937-21-5|2-(7-羟基-6-甲氧基-4-甲基-2-氧代-2H-苯并吡喃-3-基)乙酸|2-(7-hydroxy-6-methoxy-4-methyl-2-oxo-2H-chromen-3-yl)acetic acid
1338937-21-5
2-(7-羟基-6-甲氧基-4-甲基-2-氧代-2H-苯并吡喃-3-基)乙酸
1357078-03-5|(2-氧-2H-色满-7-基)硼酸|(2-oxo-2H-chromen-7-yl)boronic acid
1357078-03-5
(2-氧-2H-色满-7-基)硼酸
136918-66-6|4-氯-7-(二乙氨基)-2-氧代-2H-亚甲基-3-甲醛|4-chloro-7-(diethylamino)-2-oxo-2H-chromene-3-carbaldehyde
136918-66-6
4-氯-7-(二乙氨基)-2-氧代-2H-亚甲基-3-甲醛
137215-27-1|7-巯基-4-甲基-2H-吡喃-2-酮|4-methyl-7-sulfanyl-2H-chromen-2-one
137215-27-1
7-巯基-4-甲基-2H-吡喃-2-酮
1408287-07-9|6-(四甲基-1,3,2-二氧硼杂环戊烷-2-基)苯并吡喃-2-酮|6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-2H-chromen-2-one
1408287-07-9
6-(四甲基-1,3,2-二氧硼杂环戊烷-2-基)苯并吡喃-2-酮
1438410-03-7|7-溴-2-氧代-2H-色烯-3-羧酸|7-bromo-2-oxo-2H-chromene-3-carboxylic acid
1438410-03-7
7-溴-2-氧代-2H-色烯-3-羧酸
1635-31-0|3-氨基香豆素|3-amino-2H-chromen-2-one
1635-31-0
3-氨基香豆素
142730-52-7|11-氧代-2,3,6,7-四氢-1H,5H,11H-吡喃并[2,3-f]吡啶并[3,2,1-ij]喹啉-10-甲醛|4-oxo-3-oxa-13-azatetracyclo[7.7.1.0²,⁷.0¹³,¹⁷]heptadeca-1,5,7,9(17)-tetraene-5-carbaldehyde
142730-52-7
11-氧代-2,3,6,7-四氢-1H,5H,11H-吡喃并[2,3-f]吡啶并[3,2,1-ij]喹啉-10-甲醛
163684-50-2|4-(氯甲基)-7-羟基-8-甲基-2H-苯并吡喃-2-酮|4-(chloromethyl)-7-hydroxy-8-methyl-2H-chromen-2-one
163684-50-2
4-(氯甲基)-7-羟基-8-甲基-2H-苯并吡喃-2-酮
17831-88-8|4-氯-2H-苯并吡喃-2-酮|4-chloro-2H-chromen-2-one
17831-88-8
4-氯-2H-苯并吡喃-2-酮
1883574-88-6|7-氟-2-氧代-2H-色烯-3-羧酸乙酯|ethyl 7-fluoro-2-oxo-2H-chromene-3-carboxylate
1883574-88-6
7-氟-2-氧代-2H-色烯-3-羧酸乙酯
20671-66-3|4-甲基伞形酮辛酸酯|4-methyl-2-oxo-2H-chromen-7-yl octanoate
20671-66-3
4-甲基伞形酮辛酸酯
17575-15-4|4-羟基-7-甲氧基-2H-苯并吡喃-2-酮|4-hydroxy-7-methoxy-2H-chromen-2-one
17575-15-4
4-羟基-7-甲氧基-2H-苯并吡喃-2-酮
19484-57-2|6-氯-4-羟基香豆素|6-chloro-4-hydroxy-2H-chromen-2-one
19484-57-2
6-氯-4-羟基香豆素
1846-76-0|香豆素-3-羧酸乙酯|ethyl 2-oxo-2H-chromene-3-carboxylate
1846-76-0
香豆素-3-羧酸乙酯
19088-73-4|3-氰基-7-羟基香豆素|7-hydroxy-2-oxo-2H-chromene-3-carbonitrile
19088-73-4
3-氰基-7-羟基香豆素
17695-48-6|4-甲基伞形基棕榈酸酯|4-methyl-2-oxo-2H-chromen-7-yl hexadecanoate
17695-48-6
4-甲基伞形基棕榈酸酯
20280-81-3|4-甲氧基-2H-色烯-2-酮|4-methoxy-2H-chromen-2-one
20280-81-3
4-甲氧基-2H-色烯-2-酮
1994-13-4|6-氟-4-羟基香豆素|6-fluoro-4-hydroxy-2H-chromen-2-one
1994-13-4
6-氟-4-羟基香豆素
19063-55-9|6-溴香豆素|6-bromo-2H-chromen-2-one
19063-55-9
6-溴香豆素
20300-59-8|7-甲氧基-2-氧代-2H-色烯-3-羧酸|7-methoxy-2-oxo-2H-chromene-3-carboxylic acid
20300-59-8
7-甲氧基-2-氧代-2H-色烯-3-羧酸
1890299-47-4|7-硝基-2-氧代-2H-色烯-3-羧酸钾|potassium 7-nitro-2-oxo-2H-chromene-3-carboxylate
1890299-47-4
7-硝基-2-氧代-2H-色烯-3-羧酸钾
201847-52-1|(R)-2-氨基-N-(4-甲基-2-氧代-2H-苯并吡喃-7-基)丙酰胺2,2,2-三氟乙酸盐|(2R)-2-amino-N-(4-methyl-2-oxo-2H-chromen-7-yl)propanamide; trifluoroacetic acid
201847-52-1
(R)-2-氨基-N-(4-甲基-2-氧代-2H-苯并吡喃-7-基)丙酰胺2,2,2-三氟乙酸盐
190605-10-8|3,3'-羰基双(7-(二丁基氨基)-2H-苯并吡喃-2-酮)|7-(dibutylamino)-3-[7-(dibutylamino)-2-oxo-2H-chromene-3-carbonyl]-2H-chromen-2-one
190605-10-8
3,3'-羰基双(7-(二丁基氨基)-2H-苯并吡喃-2-酮)
19225-17-3|4,7-二羟基-3-苯基-2H-吡喃-2-酮|4,7-dihydroxy-3-phenyl-2H-chromen-2-one
19225-17-3
4,7-二羟基-3-苯基-2H-吡喃-2-酮
2051-59-4|6-氯-2H-铬-2-酮|6-chloro-2H-chromen-2-one
2051-59-4
6-氯-2H-铬-2-酮
190788-61-5|7-(4,4,5,5-四甲基-1,3,2-杂硼杂环戊烷-2-基)-2H-吡喃-2-酮|7-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-2H-chromen-2-one
190788-61-5
7-(4,4,5,5-四甲基-1,3,2-杂硼杂环戊烷-2-基)-2H-吡喃-2-酮
20571-42-0|7-(二乙氨基)-2H-苯并吡喃-2-酮|7-(diethylamino)-2H-chromen-2-one
20571-42-0
7-(二乙氨基)-2H-苯并吡喃-2-酮
19063-54-8|7-氯-2H-色烯-2-酮|7-chloro-2H-chromen-2-one
19063-54-8
7-氯-2H-色烯-2-酮
18735-81-4|7-氯-4-羟基-2H-色烯-2-酮|7-chloro-4-hydroxy-2H-chromen-2-one
18735-81-4
7-氯-4-羟基-2H-色烯-2-酮
18735-82-5|7-溴-4-羟基-2H-色烯-2-酮|7-bromo-4-hydroxy-2H-chromen-2-one
18735-82-5
7-溴-4-羟基-2H-色烯-2-酮
2304622-97-5|(R)-2-((4-(2-氯-4-氟苯基)-2-氧代-2H-铬基-7-基)氧基)丙酸|(2R)-2-{[4-(2-chloro-4-fluorophenyl)-2-oxo-2H-chromen-7-yl]oxy}propanoic acid
2304622-97-5
(R)-2-((4-(2-氯-4-氟苯基)-2-氧代-2H-铬基-7-基)氧基)丙酸
2732-18-5|5,7-二羟基-2H-色烯-2-酮|5,7-dihydroxy-2H-chromen-2-one
2732-18-5
5,7-二羟基-2H-色烯-2-酮
2442-31-1|8-羟基-2H-苯并吡喃-2-酮|8-hydroxy-2H-chromen-2-one
2442-31-1
8-羟基-2H-苯并吡喃-2-酮
2725-81-7|6-硝基香豆素|6-nitro-2H-chromen-2-one
2725-81-7
6-硝基香豆素
2445-81-0|8-甲氧基-2H-苯并吡喃-2-酮|8-methoxy-2H-chromen-2-one
2445-81-0
8-甲氧基-2H-苯并吡喃-2-酮
26093-31-2|7-氨基-4-甲基香豆素|7-amino-4-methyl-2H-chromen-2-one
26093-31-2
7-氨基-4-甲基香豆素
2123485-87-8|(E)-2-(3-氰基-4-(2-(7-羟基-2-氧代-2H-3-(2-(3-甲基)铬)乙烯基)-5,5-二甲基呋喃-2(5H)-亚基)丙二腈|2-{3-cyano-4-[(1E)-2-(7-hydroxy-2-oxo-2H-chromen-3-yl)ethenyl]-5,5-dimethyl-2,5-dihydrofuran-2-ylidene}propanedinitrile
2123485-87-8
(E)-2-(3-氰基-4-(2-(7-羟基-2-氧代-2H-3-(2-(3-甲基)铬)乙烯基)-5,5-二甲基呋喃-2(5H)-亚基)丙二腈
24526-69-0|4-甲基-2-氧代-2H-色烯-3-甲腈|4-methyl-2-oxo-2H-chromene-3-carbonitrile
24526-69-0
4-甲基-2-氧代-2H-色烯-3-甲腈
2199-87-3|6-溴香豆素-3-甲酸|6-bromo-2-oxo-2H-chromene-3-carboxylic acid
2199-87-3
6-溴香豆素-3-甲酸
2199-90-8|6-溴香豆素-3-甲酸乙酯|ethyl 6-bromo-2-oxo-2H-chromene-3-carboxylate
2199-90-8
6-溴香豆素-3-甲酸乙酯
277309-33-8|7-((苄氧基)甲氧基)-4-(三氟甲基)-2H-苯并吡喃-2-酮|7-[(benzyloxy)methoxy]-4-(trifluoromethyl)-2H-chromen-2-one
277309-33-8
7-((苄氧基)甲氧基)-4-(三氟甲基)-2H-苯并吡喃-2-酮
28705-46-6|7-(二乙氨基)-2-氧代-2H-苯甲基-3-羧酸乙酯|ethyl 7-(diethylamino)-2-oxo-2H-chromene-3-carboxylate
28705-46-6
7-(二乙氨基)-2-氧代-2H-苯甲基-3-羧酸乙酯
2145-27-9|7-氟-4-羟基-2H-吡喃-2-酮|7-fluoro-4-hydroxy-2H-chromen-2-one
2145-27-9
7-氟-4-羟基-2H-吡喃-2-酮
2445-83-2|7-甲基-2H-色烯-2-酮|7-methyl-2H-chromen-2-one
2445-83-2
7-甲基-2H-色烯-2-酮
277313-50-5|7-羟基-2-氧代-2H-色烯-3-甲醛|7-hydroxy-2-oxo-2H-chromene-3-carbaldehyde
277313-50-5
7-羟基-2-氧代-2H-色烯-3-甲醛
24618-19-7|8-氨基-7-羟基-4-甲基-2H-苯并吡喃-2-酮|8-amino-7-hydroxy-4-methyl-2H-chromen-2-one
24618-19-7
8-氨基-7-羟基-4-甲基-2H-苯并吡喃-2-酮
2555-20-6|8-甲氧基-2-氧代-2H-色烯-3-羧酸|8-methoxy-2-oxo-2H-chromene-3-carboxylic acid
2555-20-6
8-甲氧基-2-氧代-2H-色烯-3-羧酸
385418-75-7|7-硝基-2-氧代-2H-色烯-3-羧酸乙酯|ethyl 7-nitro-2-oxo-2H-chromene-3-carboxylate
385418-75-7
7-硝基-2-氧代-2H-色烯-3-羧酸乙酯
36651-81-7|8-羟基-5-甲基-2H-吡喃-2-酮|8-hydroxy-5-methyl-2H-chromen-2-one
36651-81-7
8-羟基-5-甲基-2H-吡喃-2-酮
35231-44-8|4-溴甲基-7-甲氧基香豆素|4-(bromomethyl)-7-methoxy-2H-chromen-2-one
35231-44-8
4-溴甲基-7-甲氧基香豆素
305-01-1|秦皮乙素|6,7-dihydroxy-2H-chromen-2-one
305-01-1
秦皮乙素
38215-36-0|香豆素 6|3-(1,3-benzothiazol-2-yl)-7-(diethylamino)-2H-chromen-2-one
38215-36-0
香豆素 6
3949-36-8|3-乙酰香豆素|3-acetyl-2H-chromen-2-one
3949-36-8
3-乙酰香豆素
298-81-7|8-甲氧基补骨脂素|9-methoxy-7H-furo[3,2-g]chromen-7-one
298-81-7
8-甲氧基补骨脂素
4139-61-1|6-溴-4-羟基-2H-色烯-2-酮|6-bromo-4-hydroxy-2H-chromen-2-one
4139-61-1
6-溴-4-羟基-2H-色烯-2-酮
33491-30-4|8-溴-2H-1-苯并吡喃-2-酮|8-bromo-2H-chromen-2-one
33491-30-4
8-溴-2H-1-苯并吡喃-2-酮
575-03-1|4-(三氟甲基)伞形酮|7-hydroxy-4-(trifluoromethyl)-2H-chromen-2-one
575-03-1
4-(三氟甲基)伞形酮
531-81-7|香豆素-3-羧酸|2-oxo-2H-chromene-3-carboxylic acid
531-81-7
香豆素-3-羧酸
55977-10-1|3-溴-7-羟基-4-甲基-2H-铬-2-酮|3-bromo-7-hydroxy-4-methyl-2H-chromen-2-one
55977-10-1
3-溴-7-羟基-4-甲基-2H-铬-2-酮
487-06-9|柠美内酯5,7-二甲氧基香豆素|5,7-dimethoxy-2H-chromen-2-one
487-06-9
柠美内酯5,7-二甲氧基香豆素
53518-15-3|7-氨基-4-三氟甲基香豆素|7-amino-4-(trifluoromethyl)-2H-chromen-2-one
53518-15-3
7-氨基-4-三氟甲基香豆素
51069-90-0|6-溴-4-氯-2-氧代-2H-苯甲基-3-甲醛|6-bromo-4-chloro-2-oxo-2H-chromene-3-carbaldehyde
51069-90-0
6-溴-4-氯-2-氧代-2H-苯甲基-3-甲醛
57597-64-5|7-(二乙氨基)-2-氧代-2H-亚甲基-3-甲醛|7-(diethylamino)-2-oxo-2H-chromene-3-carbaldehyde
57597-64-5
7-(二乙氨基)-2-氧代-2H-亚甲基-3-甲醛
477-33-8|(+)-沙米丁|(9R,10R)-10-(acetyloxy)-8,8-dimethyl-2-oxo-2H,8H,9H,10H-pyrano[2,3-h]chromen-9-yl 3-methylbut-2-enoate
477-33-8
(+)-沙米丁
462094-45-7|2-((2-氧代-2H-色烯-4-基)氧基)乙酸|2-[(2-oxo-2H-chromen-4-yl)oxy]acetic acid
462094-45-7
2-((2-氧代-2H-色烯-4-基)氧基)乙酸
51069-75-1|4-氯-6-甲基-2H-色烯-2-酮|4-chloro-6-methyl-2H-chromen-2-one
51069-75-1
4-氯-6-甲基-2H-色烯-2-酮
54311-48-7|5-氯-4-羟基-2H-色烯-2-酮|5-chloro-4-hydroxy-2H-chromen-2-one
54311-48-7
5-氯-4-羟基-2H-色烯-2-酮
4281-40-7|6,7-二甲氧基-4-甲基香豆素|6,7-dimethoxy-4-methyl-2H-chromen-2-one
4281-40-7
6,7-二甲氧基-4-甲基香豆素
51473-74-6|7-(二乙氨基)-2-氧代苯并-3-甲腈|7-(diethylamino)-2-oxo-2H-chromene-3-carbonitrile
51473-74-6
7-(二乙氨基)-2-氧代苯并-3-甲腈
54711-38-5|7-(二乙氨基)-4-(羟甲基)-2H-铬-2-酮|7-(diethylamino)-4-(hydroxymethyl)-2H-chromen-2-one
54711-38-5
7-(二乙氨基)-4-(羟甲基)-2H-铬-2-酮
447398-67-6|N-[4-(氯甲基)-2-氧代-2H-色烯-7-基]乙酰胺|N-[4-(chloromethyl)-2-oxo-2H-chromen-7-yl]acetamide
447398-67-6
N-[4-(氯甲基)-2-氧代-2H-色烯-7-基]乙酰胺
5543-58-8|R-文拉法辛|4-hydroxy-3-[(1R)-3-oxo-1-phenylbutyl]-2H-chromen-2-one
5543-58-8
R-文拉法辛
5543-57-7|S-文拉法辛|4-hydroxy-3-[(1S)-3-oxo-1-phenylbutyl]-2H-chromen-2-one
5543-57-7
S-文拉法辛
55804-66-5|香豆素314|ethyl 4-oxo-3-oxa-13-azatetracyclo[7.7.1.0²,⁷.0¹³,¹⁷]heptadeca-1(17),2(7),5,8-tetraene-5-carboxylate
55804-66-5
香豆素314
6160-78-7|4-甲基-7-氧香豆素-β-D-吡喃半乳糖苷|4-methyl-7-{[(2S,3R,4S,5R,6R)-3,4,5-trihydroxy-6-(hydroxymethyl)oxan-2-yl]oxy}-2H-chromen-2-one
6160-78-7
4-甲基-7-氧香豆素-β-D-吡喃半乳糖苷
62935-72-2|7-甲氧基香豆素-4-乙酸|2-(7-methoxy-2-oxo-2H-chromen-4-yl)acetic acid
62935-72-2
7-甲氧基香豆素-4-乙酸
6950-82-9|7-羟基香豆素-4-乙酸|2-(7-hydroxy-2-oxo-2H-chromen-4-yl)acetic acid
6950-82-9
7-羟基香豆素-4-乙酸
6093-71-6|7-羟基香豆素-3-羧酸乙酯|ethyl 7-hydroxy-2-oxo-2H-chromene-3-carboxylate
6093-71-6
7-羟基香豆素-3-羧酸乙酯
6174-86-3|3-氯-7-羟基-4-甲基香豆素|3-chloro-7-hydroxy-4-methyl-2H-chromen-2-one
6174-86-3
3-氯-7-羟基-4-甲基香豆素
70384-83-7|5-氯-2-氧代-2H-色烯-3-羧酸乙酯|ethyl 5-chloro-2-oxo-2H-chromene-3-carboxylate
70384-83-7
5-氯-2-氧代-2H-色烯-3-羧酸乙酯
61636-28-0|3-(2-氨基噻唑-4-基)-2H-苯并吡喃-2-酮|3-(2-amino-1,3-thiazol-4-yl)-2H-chromen-2-one
61636-28-0
3-(2-氨基噻唑-4-基)-2H-苯并吡喃-2-酮
74696-96-1|3-乙酰基-7-(二乙基氨基)-2H-吡喃-2-酮|3-acetyl-7-(diethylamino)-2H-chromen-2-one
74696-96-1
3-乙酰基-7-(二乙基氨基)-2H-吡喃-2-酮
93-35-6|7-羟基香豆素|7-hydroxy-2H-chromen-2-one
93-35-6
7-羟基香豆素
92-48-8|6-甲基香豆素|6-methyl-2H-chromen-2-one
92-48-8
6-甲基香豆素
91-44-1|7-二乙氨基-4-甲基香豆素|7-(diethylamino)-4-methyl-2H-chromen-2-one
91-44-1
7-二乙氨基-4-甲基香豆素
905442-42-4|(2S)-2-氨基-4-(7-羟基-2-氧代-2H-铬-4-基)丁酸|(2S)-2-amino-4-(7-hydroxy-2-oxo-2H-chromen-4-yl)butanoic acid
905442-42-4
(2S)-2-氨基-4-(7-羟基-2-氧代-2H-铬-4-基)丁酸
939-18-4|3-溴-2H-苯并吡喃-2-酮|3-bromo-2H-chromen-2-one
939-18-4
3-溴-2H-苯并吡喃-2-酮