Abstract
This review summarizes data on the reactions of chromones and activated alkenes with trimethyl(trifluoromethyl)silane (Ruppert’s reagent), which occures as a nucleophilic 1,4-trifluoromethylation with high regioselectivity and good yields. The most important chemical properties of the formed products are also considered.
Highlights
The nucleophilic trifluoromethylation of organic compounds is complicated by the instability of free trifluoromethyl anion, which breaks down into the fluoride anion and difluorocarbene [1]
Monitoring using 19F NMR spectroscopy showed that chromones 1 in the presence of the nucleophilic initiator Me4NF (THF, 0 °C, 4 h) almost quantitatively and with high regioselectively react with CF3SiMe3 towards the way of 1,4-addition, giving trimethylsilyl ethers 2
When processing of the reaction mixture with diluted HCl only the products of 1,4-addition 2 are subjected to hydrolysis to give 2-trifluoromethyl-2-perfluoroalkylchroman-4-ones 4
Summary
It is important to note that in the case of α, β-unsaturated ketones, the formation of products of nucleophilic 1,4-trifluoromethylation (Michael addition) was not observed (Scheme 1). Monitoring using 19F NMR spectroscopy showed that chromones 1 in the presence of the nucleophilic initiator Me4NF (THF, 0 °C, 4 h) almost quantitatively and with high regioselectively react with CF3SiMe3 towards the way of 1,4-addition, giving trimethylsilyl ethers 2 (the content in the reaction mixture of 1,2-addition products 3 does not exceed 5–10 %).
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