Inorganic Iodine V Reagents

This reaction can be performed in non-aqueous solvents, sueh as diethyl ether or THF and the workup generally requires a simple filtration of iodic acid followed by evaporation of the solvent. Application of this methodology is exemplified by a convenienf preparation of alkyl glyoxylates 908 in high yield (Seheme 3.367) [1318]. 

Secondary alcohols are oxidized by H5IO6 in the presence of various chromium catalysts to ketones [1321-1325], while primary alcohols can be oxidized to aldehydes or to carboxylic acids depending on the catalyst. Primary alcohols in the presence of pyridinium chlorochromate (PCC)[1322] or chromium (III) acetylacetonate, Cr(acac)3 [1321] are oxidized to aldehydes or ketones in excellent yields, while the use of CrOj [1326,1327] or pyridinium fluorochromate [1323] as catalysts results in the oxidation to carboxylic acids. The periodic acid promoted oxidation of primary and secondary alcohols to carbonyl compounds can also be catalyzed by Cu(II) derivatives [1328,1329], by bromide anion [1330] and by TEMPO [1331]. 

Chromium(VI) oxide is also an efficient catalyst for oxidation at the benzylic position with periodic acid as the terminal oxidant in acetonitrile. Substituted toluenes with an electron-withdrawing group at the 4- or 3-position and diarylmethanes such as Ph2CH2 and fiuorene are oxidized to the respective substituted benzoic acids and ketones in excellent yields [1332], Periodic acid in the presence of catalytic CrOj can be used for the oxidation of arenes, such as naphthalenes and anthracene, to the corresponding quinones for example, 

2- methylnaphthalene is oxidized to 2-methyl-1,4-naphthoquinone (vitamin K3) by this catalytic system in high yield and regioselectivity [1333], Sulfides can be oxidized by periodic acid to sulfoxides in the presence of catalytic FeCb [1334], or to sulfones in the presence of CrOs [1335]. 

Additional examples of synthetic application of periodic acid as an oxidant include the oxidative iodination of aromatic compounds [1336-1341], iodohydrin formation by treatment of alkenes with periodic acid and sodium bisulfate [1342], oxidative cleavage of protecting groups (e.g., cyclic acetals, oxathioacetals and dithioacetals) [1315, 1343], conversion of ketone and aldehyde oximes into the corresponding carbonyl compounds [1344], oxidative cleavage of tetrahydrofuran-substituted alcohols to -y-lactones in the presence of catalytic PCC [1345] and direct synthesis of nitriles from alcohols or aldehydes using HsIOe/KI in aqueous ammonia [1346], 

---