中文名称 | 英文名称 | CAS号 | 化学式 | 分子量 |
---|---|---|---|---|
2-(3-苯基-1,2-恶唑-5-基)乙腈 | 5-cyanomethyl-3-phenylisoxazole | 129681-59-0 | C11H8N2O | 184.197 |
5-甲基-3-苯基异噁唑 | 5-methyl-3-phenylisoxazole | 1008-74-8 | C10H9NO | 159.188 |
5-(氯甲基)-3-苯基异噁唑 | 3-phenyl-5-chloromethyl-1,2,4-oxadiazole | 1011-37-6 | C10H8ClNO | 193.633 |
5-(溴甲基)-3-苯基异恶唑 | 5-bromomethyl-3-phenyl-isoxazole | 2039-50-1 | C10H8BrNO | 238.084 |
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.