Hypervalent-Iodine(III)-Mediated Oxidative Methodology for the Synthesis of Fused Triazoles

The organic chemistry of hypervalent organoiodine compounds has been an area of unprecedented development. This surge in interest in the use of hypervalent iodine compounds has mainly been owing to their highly selective oxidizing properties, environmentally benign character and commercial availability. Hypervalent iodine reagents have also been used as an alternative to toxic heavy metals, owing to their low toxicity and ease of handling. Hypervalent organoiodine(III) reagents are versatile oxidants that have been successfully employed to extend the scope of selective oxidative transformations of complex organic molecules in synthetic chemistry. This Focus Review concerns the tandem in situ generation and 1,5-electrocyclization of N-heteroaryl nitrilimines into fused triazoles. We describe the importance of recently developed hypervalent-organoiodine(III)-catalyzed oxidative cyclization reactions, building towards the conclusion that hypervalent iodine chemistry is a promising frontier for oxidative cyclization, in particular of hydrazones, for the synthesis of fused triazoles.