diethyl 1,2,5-oxadiazole-3,4-dicarboxylate 2-oxide

(4Z)-4-溴-4-己烯-3-酮

methyl 3-methyl-4-oxohex-2-enoate

2-trichlorostannylpentan-3-one

2-ethyl-3,4-dimethyl-2H-furan-5-one