Heterocycles 2-iodoxybenzoic acid

Within the broad field of hypervalent iodine chemistry, five-membered iodine(V) heterocycles occupy a special place. There has been significant interest in the cyclic X -iodanes, mainly 2-iodoxybenzoic acid (IBX)... 

Organoiodine(V) heterocycles are represented by several typical classes 78—86 shown in Figure 15. The most important representative of these compounds, 2-iodoxybenzoic acid (IBX, 78), was originally reported in 1893 (1893CB1727). The cycHc structure of IBX derivatives was confirmed by an X-ray crystallographic study in the work of A. R. Katritzky and coworkers (1990JCS(P2)1657). 

In a convenient one-pot process, easily accessed propargyl vinyl ethers and aromatic amines are effectively converted into tetra- and pentasubstituted 5-methylpyrroles, which can fnrther be transformed into 5-formylpyrroles via 2-iodoxybenzoic acid (IBX)-mediated oxidation (Binder and Kirsch 2006). The cascade reaction proceeds through a silver(l)-catalyzed propargyl Claisen rearrangement, an amine condensation, and a gold(l)-catalyzed 5-exo-dig heterocyclization, as shown in Schane 11.4. 

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