Iodine(iii) promoted ring-rearrangement reaction of 1-arylamino-2-oxocyclopentane-1-carbonitriles to synthesize N-aryl-δ-valerolactams.

The first example of N-aryl-δ-valerolactam synthesis via an intramolecular ring rearrangement reaction of 1-arylamino-2-oxocyclopentane-1-carbonitrile promoted by phenyliodine bis(trifluoroacetate) (PIFA) was reported. We show that this unprecedented regio-selective ring-rearrangement reaction driven by hypervalent iodine (PIFA) involves C5-H elimination, C1-C2 bond opening, and C1-N bond rearrangement steps and restraining the leaving tendency of the CN group. The structure of the lactam was further confirmed by single crystal X-ray diffraction (XRD) analysis. The present protocol showed a diverse array of functional group tolerance under the reaction conditions and offered good to excellent yields of lactams.