Photoinduced Alkyl/Aryl Radical Cascade for the Synthesis of Quaternary CF₃-Containing Oxindoles and Indoline Alkaloids

Abstract

Metal-and additive-free, photoinduced decarboxylative radical alkylation−cyclization of CF 3 -acrylamides with alkyl redox-active esters provided the corresponding quaternary CF 3 -oxindole derivatives in good yields. Notably, diaryliodonium salts also efficiently participated in the arylation−cyclization of CF 3 -acrylamides in environmentally benign H 2 O as a solvent. The present approach has been extended for the concise synthesis of CF 3 -attached indoline alkaloid analogues, i.e., CF 3 -(±)-desoxyeseroline, CF 3 -(±)-esermethole, and CF 3 -(±) progesterone receptor antagonists. The preliminary mechanistic studies revealed that the reaction is likely to proceed through initial photoexcitation of redox-active ester/diaryliodonium salts followed by the SET process with acrylamide.

Generation and Application of Aryl Radicals Under Photoinduced Conditions

“…However, there was a decrease in yield when utilizing aryl radicals containing substituents such as 4-OMePh, 2-OMePh, 4-FPh, 4-NO 2 Ph, and 4-COMePh (Figure 42, Table 3G). [63] By using isocyanides (9H and 9'H) and acyl peroxides (8H), Moorthy et al established a straightforward, visible lightmediated synthesis of heteroarenes, including isoquinolines (10Ha), benzothiazoles (10Hb), and quinazolines (10Hc). All the isocyanide-based starting materials and acyl peroxides studied showed high to exceptional yield, regardless of whether the functional groups are electron-rich or electron-deficient in nature.…”

“…However, there was a decrease in yield when utilizing aryl radicals containing substituents such as 4‐OMePh, 2‐OMePh, 4‐FPh, 4‐NO 2 Ph, and 4‐COMePh (Figure 42, Table 3G). [63] …”