Polarity-Mismatched Addition of Electrophilic Carbon Radicals to an Electron-Deficient Acceptor: Cascade Radical Addition--Cyclization--Trapping Reaction.

The polarity-mismatched perfluoroalkyl radical addition to electron-deficient alkenes was studied. For this study, several substrates having two polarity-different radical acceptors were employed to investigate the regiochemical courses of cascade reaction. In the case of substrate 1 having a methacryloyl moiety, we found polarity-mismatched perfluoroalkylation giving 15a-e as a major course over the polarity-matched perfluoroalkylation giving 16a-e. Moreover, in the case of substrates 2-7, perfluoroalkyl radicals selectively added to an electron-deficient alkene moiety of 2-7, to give polarity-mismatched perfluoroalkylation products without the formation of regioisomers. Next, the control of enantioselectivity was studied. In the case of substrates 1 and 3, the reaction proceeded with good enantioselectivities by employing a chiral Lewis acid, prepared from chiral box ligand 24 and Zn(OTf)2. For direct comparison, we also studied the reaction with other carbon radicals, derived from ICH2CO2Et, ICH2CN, BrC(CO2Et)2Me, and CCl3Br, which have electrophilic character. [ABSTRACT FROM AUTHOR]