Hypervalent iodine oxidative addition

The rhodium(II)-catalyzed intermolecular C(sp )—H amination reaction involves the use of the more soluble hypervalent iodine oxidant PhI(OCOiBu)2 which enables its slow addition over several hours, a protocol that increases the yield of the nitrene insertion. But contrary to the intramolecular process, it does not require the presence of magnesium oxide, a point that puts into question its presumed role of acid scavenger." It should be mentioned that these conditions have also proved appropriate to perform the... 

The oxidation of phenols with hypervalent iodine compounds has been used frequently and nucleophilic additions can be performed as well as cyclization reactions using this technique. The resulting quinone derivatives show high reactivity and they have been used in a various subsequent reactions. Substituted phenols like 32 [78] or 34 [79] have been oxidized by hypervalent iodine reagents and, depending on the substitution pattern, cyclizations have taken place as shown in Scheme 16. Product 33 is unstable and undergoes subsequent... 

Kim, D.Y, Mang, J.Y, and Oh, D.Y, Reaction of silyl enol ethers with phosphite using hypervalent iodine compound. A new synthesis of 2-aryl-2-oxoalkylphosphonates, Synth. Commun., 24, 629, 1994. Hohnquist, C.R., and Roskamp, E.J., Tin(II) chloride catalyzed addition of diazo sulfones, diazo phosphine oxides, and diazo phosphonates to aldehydes. Tetrahedron Lett., 33, 1131, 1992. 

Many of the steps employed eoncepts that we established earlier during the synthesis of simpler alkaloids therefore, they are not discussed in detail. However, some steps are noteworthy. First, it should be noted that the use of immobilized hypervalent iodine once again served us well in the oxidative formation of the spirodienone (54). The conjugate addition of the amidic nitrogen atom to complete the tricyclic scaffold (55) proceeded nicely when a Naflon-H fluorosulfonic acid resin was used as a source... 

Additional examples of synthetic applications of hypervalent iodine-induced heterocyclizations include the following the metal-free one-pot synthesis of 2-acylbenzothiazoles by oxidative cyclization of multiform substrates [434], iodine(III)-mediated tandem oxidative cyclization for construction of 2-nitrobenzo[ ]furans [435], hypervalent iodine mediated oxidative cyclization of o-hydroxystilbenes into benzo- and naphthofu-rans [436], PhI(OCOCF3)2-mediated synthesis of 3-hydroxy-2-oxindoles and spirooxindoles from anilides [437], synthesis of isoxazoles by hypervalent iodine-induced cycloaddition of nitrile oxides to alkynes [438],... 

The efficiency of this oxidation was also evaluated by comparison to other oxidations, such as the Dess-Martin, pyridinium dichromate and Swern oxidations. It was demonstrated that the hypervalent iodine(V)-catalyzed oxidation could be applied for almost all types of fluorinated alcohols and it was comparable to Dess-Martin oxidation, while pyridinium dichromate and Swern oxidations could not be employed for allylic and propargylic alcohols as well as the alcohols having an aliphatic side chain. Additionally, the hypervalent iodine-catalyzed oxidation could be applied for a larger scale reaction (Scheme 4.49) without any decrease in reaction efficiency [81]. 

DMP with high purity by the original procedure therefore, a few modifications have been suggested. In addition, DMP has been successfully used in the syntheses of polycyclic heterocyclesand in the removal of thioketals and thioacetals. It should be mentioned that other hypervalent iodine compounds can be used as oxidants as well, especially for the o-iodoxybenzoic acid (IBX), the precursor to DMP, which can oxidize tertiary cyclic allyl alcohol into O, y0-unsaturated cyclic ketones and secondary amines into imines and can convert epoxides or aziridines into corresponding of-hydroxy ketones or Q -amino ketones. 

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