Alkenes osmium tetroxide-periodate

Osmium tetroxide used in combination with sodium periodate can also effect alkene cleavage.191 Successful oxidative cleavage of double bonds using ruthenium tetroxide and sodium periodate has also been reported.192 In these procedures the osmium or ruthenium can be used in substoichiometric amounts because the periodate reoxidizes the metal to the tetroxide state. Entries 1 to 4 in Scheme 12.18 are examples of these procedures. Entries 5 and 6 show reactions carried out in the course of multistep syntheses. The reaction in Entry 5 followed a 5-exo radical cyclization and served to excise an extraneous carbon. The reaction in Entry 6 followed introduction of the allyl group by enolate alkylation. The aldehyde group in the product was used to introduce an amino group by reductive alkylation (see Section 5.3.1.2). 

In summary, the reaction of osmium tetroxide with alkenes is a reliable and selective transformation. Chiral diamines and cinchona alkakoid are most frequently used as chiral auxiliaries. Complexes derived from osmium tetroxide with diamines do not undergo catalytic turnover, whereas dihydroquinidine and dihydroquinine derivatives have been found to be very effective catalysts for the oxidation of a variety of alkenes. OsC>4 can be used catalytically in the presence of a secondary oxygen donor (e.g., H202, TBHP, A -methylmorpholine-/V-oxide, sodium periodate, 02, sodium hypochlorite, potassium ferricyanide). Furthermore, a remarkable rate enhancement occurs with the addition of a nucleophilic ligand such as pyridine or a tertiary amine. Table 4-11 lists the preferred chiral ligands for the dihydroxylation of a variety of olefins.61 Table 4-12 lists the recommended ligands for each class of olefins. 

Osmium tetroxide used in combination with sodium periodate can also effect alkene cleavage.135 Successful oxidative cleavage of double bonds using ruthenium tetroxide and sodium periodate has also been reported.136 In these procedures, the osmium or ruthenium can be used in substoichiometric amounts because the periodate reoxidizes the metal to the tetroxide state. Entries 1 4 in Scheme 12.17 are examples of these procedures. 

Exercise 16-37 An elegant modification of the two-step procedure to prepare ketones from alkenes by hydroxylation and oxidative cleavage of the diol formed uses a small amount of potassium permanganate (or osmium tetroxide, 0s04) as the catalyst and sodium periodate as the oxidizing agent ... 

The conversion of tetrasubstituted double bonds to the coiresptxiding ketones is easily achieved using a number of oxidants. However, if one or more of the alkenic carbons is secondary, the product will be either an aldehyde or a carboxylic acid. Ozone and a combination of osmium tetroxide and sodium meta-periodate are recommended if the desired product is an aldehyde. Under carefully controlled conditions it is also possible to obtain good yields of the aldehyde when permanganate is used as the oxidant All methods that give aldehydes from secondary carbons can also be used to prepare ketones from tertiary carbons. 

Sodium periodate (sodium metaperiodate), NaI04 (mp 300 °C dec), which is commercially available, is applied mainly in aqueous or aqueous-alcoholic solutions. Like the free periodic acid, sodium periodate cleaves vicinal diols to carbonyl compounds [762], This reaction is especially useful in connection with potassium permanganate [763, 764] or osmium tetroxide [765], Such mixed oxidants oxidize alkenes to carbonyl compounds or carboxylic acids, evidently by way of vicinal diols as intermediates. Sulfides are transformed by sodium periodate into sulfoxides [322, 323, 766, 767, 768, 769, 770, 771, 772], and selenides are converted into selenoxides [773]. Sodium periodate is also a reoxidant of lower valency ruthenium in oxidations with ruthenium tetroxide [567, 774],... 

Gallc er and co-workers devised a formal enantioselective synthesis of ( — )-3 in wduch the stereogenic center at C-6 was derived fiom Cbz-protected (S)-2-amino-4-pentenoic acid (36) (44). Acylation of 3,3-dimethoxy-pyrrolidine (37) with this acid yielded amide 38, which was converted into aldehyde 39 by cleavage of the terminal alkene vnth osmium tetroxide and sodium periodate (Scheme 5). The indolizidine nucleus was constructed from 39 by a problematic intramolecular aldol condensation, which was eventually optimized by using 2,2,6,6-tetramethylpiperidine as base followed by adsorption onto, and elution from, silica gel (45). Diastereoselective reduction of the ketone group of the aldol product 40 was accomplished in better than 95% enantiomeric excess (ee) with the Corey... 

C.U. Sodium Periodate In section 3.7.A.ii, a mixture of osmium tetroxide and periodic acid oxidatively cleaved alkenes. Sodium periodate can cleave diols directly. In the Chida et al. synthesis of pironetin, for example, 371 was cleaved to dialdehyde 372 using an aqueous acetone solution of NalOq. l Sodium periodate in dichloromethane, in the presence of sodium bicarbonate, has also been used.5l9... 

Osmium tetroxide can be used in substoichiometric amounts because the periodate oxidizes the osmium back to the tetroxide. The periodate therefore plays two roles, one to cleave the diol and the other to re-oxidize the osmium(VI), although it does not itself react with alkenes or aldehydes. Reaction often occurs at the least-hindered alkene and therefore provides a selective method for the oxidative cleavage of, for example, a vinyl group in the presence of a di- or trisubstituted alkene. If potassium permanganate is used in place of osmium tetroxide, then any aldehyde products are usually oxidized to give the corresponding carboxylic acids. 

Overall, ozone compares favorably with other approaches for oxidative alkene cleavage involving Osmium Tetroxide, Potassium Permanganate, Ruthenium(VIII) Oxide, Sodium Periodate, or chromyl carboxylates which are costly, toxic, involve metal wastes, and may require detailed workup procedures. 

Osmium tetroxide used in combination with sodium periodate can also effect alkene cleavage cleanly.Successful oxidative cleavage of double bonds using ruthenium... 

For the same reasons as described for the ozonolysis of alkenes, the oxidative cleavage of vicinal diols by periodate is hmited as a synthetic method. The vicinal diol is seldom directly available, and it must be prepared from an aUtene. We also recall that the hydroxyl groups must be located in a cis configuration, or the molecule must have sufficient conformational freedom to bring the two hydroxyl groups into a gauche conformation. The vicinal diol is prepared from an alkene by oxidation with osmium tetroxide. 

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