Photochemical pincer-catalyzed reductive cyclisation towards indolines and oxindoles.

An organophotocatalytic method has been described towards the synthesis of indolines and oxindoles starting from unusual α -chloro amide and N -(2-chlorophenyl)- N -alkyl methacrylamide substrates. This marks a notable improvement since the earlier syntheses utilized iridium and gold catalysts, and involved C-I or C-Br bond cleavage as the initial step. Our photocatalyst is a pincer ligand that can be easily deprotonated to make a very strong reducing agent. The reductive cleavage of the carbon-chloride bond, and subsequent 5- exo -trig ring cyclization, followed by hydrogen atom abstraction, prepare the desired heterocycles under very mild reaction conditions. An atom economic use of KO t Bu has been shown to demonstrate the unusual trifunctional role of the latter.