化学
三氟甲基
三氟甲基化
溴化物
溴化锌
亚胺离子
药物化学
锌
光化学
激进的
有机化学
催化作用
烷基
作者
Marc Tordeux,C. Francèse,Claude Wakselman
出处
期刊:Journal of the Chemical Society
日期:1990-01-01
卷期号: (7): 1951-1951
被引量:61
摘要
A Barbier procedure, under moderate pressure, was used for the trifluoromethylation of various carbonyl compounds, starting from trifluoromethyl bromide and zinc in pyridine. Trifluoromethyl methanols were obtained from aldehydes and trifluoromethyl ketones from activated esters. Ethyl benzoate, or acetone, induced the formation of the solvated trifluoromethylzinc derivatives which did not react with carbonyl compounds. Consequently, the Barbier condensation in that case was considered to involve nascent organometallics reacting near the zinc surface. The reaction with sulphur dioxide, leading to trifluoromethanesulphinate, showed striking differences from that of carbonyl compounds. It was shown that the main pathway occurred in solution. This condensation was interpreted by the initial formation of sulphur dioxide radical anion, which reacts with trifluoromethyl bromide by a single-electron-transfer process. Attempts to condense iminium salts failed when a hydrogen atom was lacking in the α position. When the iminium ion can be transformed in situ to an enamine, a reaction occurred, leading to α-trifluoromethyl ketones. This condensation was interpreted by a chain mechanism involving trifluoromethyl radicals.
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