Hypervalent‐Iodine‐Mediated Synthesis of 1,2‐Dispirodienones: Experimental and Theoretical Investigations

Abstract

The oxidation of phenol acetanilides mediated by hypervalent iodine is described. The transformation proceeds through the formation of a carbocationic species that evolves either into a [6,5,6]‐tricyclic compound (1,2‐dispirodienone) or a [6,6,6]‐tricyclic compound (aryl spirodienone). In most examples, the 1,2‐dispirodienones are obtained in good yields. In some cases, depending on the substitution pattern of the phenol acetanilides and the reaction conditions, aryl spirodienones are formed. We performed electrochemical experiments on a 1,2‐dispirodienone to study its redox properties. These data provide evidence that the 1,2‐dispirodienone can ring‐open and ring‐close under redox conditions. The hypervalent‐iodine‐mediated oxidation of phenol acetanilides to 1,2‐dispirodienones was rationalized on the basis of density functional theory (DFT) calculations. In addition, these DFT computations suggest that the formation of the aryl spirodienones occurs by a stepwise reaction pathway, which first involves an ipso attack to yield a [6,5,6]‐tricyclic carbocationic intermediate and then a 1,2‐sigmatropic shift of the bond that connects the two six‐membered rings.

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Recent Advances in Iodosobenzene‐Mediated Construction of Heterocyclic Scaffolds: Transition‐Metal‐Free Approaches and Scope

“…Synthetic organic chemists are involved in a continuous effort to reveal the excellent Lewis acidic oxidizing characteristics of these reagents from the last decade of the 20 th century to recent years. These reagents led to rapid development in the modern field of C–C/C–X (X = O, N, halogens) coupling and cyclization reactions . Some chiral hypervalent iodine reagents were also in the limelight for asymmetric synthesis .…”