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[摘要]：Photoinduced three-component reactions between tetracyanobenzene (TCNB), an arom. olefin, and a b-dicarbonyl compd. afford products composed of the three components via formal elimination of hydrogen cyanide, leading to the vicinal dialkylation of the olefin and the a-alkylation of the b-dicarbonyl compds. It is shown that these reactions are initiated by photoinduced electron transfer (PET) from the olefin to the singlet excited TCNB and proceed by a nucleophile-olefin combination, arom. substitution (NOCAS) reaction sequence with the enolized b-dicarbonyl compd. as a nucleophile. Therefore, arom. olefins are suitable substrates in photo-NOCAS reactions when TCNB is used as the electron acceptor. In addn., these results show that the enol of b-dicarbonyl compd. serves as a carbon nucleophile to trap the alkene cation radical in PET reactions to lead to C-C bond formation. |
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