Secondary oxidants iodosobenzene

Oxidation of cyclic secondary amines such as pyrrolidine (351) and piperidine (353) with iodosobenzene in water leads to lactams 352 and 354, respectively (88TL6913, 88TL6917) (Scheme 90). Similar oxidation of 2-piperidinecarboxylic acid and 2-pyrrolidinecarboxylic acid is accompanied by decarboxylation. Cyclic tertiary amines 355, 357, and 359 (Eq. 48) are likewise oxidized to the corresponding lactams. Other examples include phencyclidine (360) to A-(l-phenylcyclohexyl)piperidone (361), N-(cyanocyclohexyl)piperidine (362) to A-(l-cyanocyclohexyl)piperidone (363) (Scheme 91), and 1,2,3,4-tetrahydroisoquinoline to 1,2,3,4-tetrahy-droisoquinolinone (Eq. 49). 

Iodosobenzene diacetate and iodine convert pentanol to 2-methyltetrahydrofuran by a similar mechanism. The secondary radical is most likely captured by iodine or oxidized to the carbocation prior to cyclization.271... 

Iodosobenzene diacetate [IBD, PhI(OAc)2] is able to oxidize benzylic alcohols to benzaldehydes when a solid mixture of iodosobenzene diacetate and the alcohol is irradiated with microwaves. Best results are obtained when iodosobenzene diacetate is supported on alumina.118 The use of polymer supported iodosobenzene diacetate (PSDIB) simplifies the work-up in the oxidation of benzylic alcohols to benzaldehydes.119 PSDIB can be employed in the presence of KBr and using water as solvent, resulting in the transformation of secondary alcohols into ketones and primary alcohols into carboxylic acids.117... 

The combination of iodosobenzene 5 and potassium bromide in water generates a powerful oxidant for the oxidation of alcohols. Primary alcohols are converted exclusively to the carboxylic acids in very high yields, whereas secondary alcohols lead to the corresponding ketones, Scheme 13 [73]. 

The epoxidation of simple olefins which cannot benefit from secondary interactions brings some formidable problems that were solved by sophisticated catalyst design, mainly by the groups of Jacobsen and Katsuki in the 1990 s. A class of square planar salen complexes was chosen (Figure 19, for example) capable of giving a metal-oxo derivative by reaction with monooxygen donors such as iodosobenzene or sodium hypochlorite (the preferred oxidant). A series... 

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