中文名称 | 英文名称 | CAS号 | 化学式 | 分子量 |
---|---|---|---|---|
3-(氯甲基)-4-甲基-1,2,5-恶二唑 | 4-chloromethyl-3-methylfurazan | 62642-47-1 | C4H5ClN2O | 132.549 |
3-(溴甲基)-4-甲基-呋咱 | 3-(bromomethyl)-4-methyl-1,2,5-oxadiazole | 90507-32-7 | C4H5BrN2O | 177.0 |
3,4-双(氯甲基)-1,2,5-噁二唑 | 3,4-bis(Chlormethyl)furazan | 53601-88-0 | C4H4Cl2N2O | 166.995 |
The lithiation of various methyl substituted isoxazoles, isothiazoles, pyrazoles, oxadiazoles, and thiadiazoles using n-butyllithium has been studied. Three types of reactions, namely, lateral lithiation, ring cleavage, and addition of butyllithium to the ring, have been found. 3,5-Dimethylisoxazole, 3-phenyl-5-methylisoxazole, 3,4-dimethyl-1,2,5-oxadiazole, 2,5-dimethyl-1,3,4-thiadiazole, 3-phenyl-5-methyl-1,2,4-oxadiazole, and 3,5-dimethyl-1,2,4-thiadiazole all undergo lateral lithiation to give the respective acetic acids after carboxylation. 1-Methyl-3,5-disubstituted pyrazoles form the 1-lithiomethyl derivatives, while 1-phenyl-3,5-disubstituted pyrazoles are converted to the 1-ortholithiophenyl-3,5-disubstituted pyrazoles. 4-Methylisothiazole is lithiated mainly at C-5, but also suffers ring cleavage to form 1-n-butylthio-2-cyanoprop-1-ene. Heteroaromatic compounds containing an N—S bond, such as 3,4-dimeth yl-1,2,5-thiadiazole, 4-methyl-5-phenyl-1,2,3-thiadiazole, and 3,5-dimethylisothiazole, undergo nucleophilic attack at sulfur with resulting ring cleavage. 3,5-Dimethylisothiazole produces 2-n-butylthiopent-2-en-4-one. 3-Methyl-5-phenyl-1,2,4-oxadiazole gave 3-methyl-5-phenyl-5-n-butyl-1,2,4-dihydroöxadiazole by addition to the azomethine bond. The results of these lithiations are discussed. 3-Methyl-5-lithiomethylisoxazole was converted to various derivatives. Nuclear magnetic resonance spectral analysis was used to establish the identity of the products.