Osmium olefinic aldehydes

Oxidative cleavage of the olefin is accomplished by the method of ijemieux-Johnson.12 The process begins with dihydroxylation of the double bond using osmium tetroxide (see Chapter 3)T leading to a cis diol and osmium(VI) oxide. The added periodate has two functions first, it reoxidizes the osmium(VI) species to os-mium(VIII), but it also cleaves the glycol oxidatively to an aldehyde. This is the reason for utilizing several equivalents of periodate. The periodate is in turn reduced from the +VH to the +V oxidation state. 

Optically active 1,2-diol units are often observed in nature as carbohydrates, macrolides or polyethers, etc. Several excellent asymmetric dihydroxylation reactions of olefins using osmium tetroxide with chiral ligands have been developed to give the optically active 1,2-diol units with high enantioselectivities. However, there still remain some problems, for example, preparation of the optically active anti-1,2-diols and so on. The asymmetric aldol reaction of an enol silyl ether derived from a-benzyloxy thioester with aldehydes was developed in order to introduce two hydroxyl groups simultaneously with stereoselective carbon-carbon bond formation by using the chiral tin(II) Lewis acid. For example, various optically active anti-a,p-dihydroxy thioester derivatives are obtained in good yields with excellent diastereo-... 

Group Vin metals are well established oxidising agents for the functionalisation of olefinic compounds. Ruthenium and osmium catalysts promote the oxidative cleavage of the double bond in olefinic compounds to aldehydes or ketones which may undergo further reaction to form carboxylic acids in some cases. However selective epoxidation is influenced by the nature of the ligands which... 

This reaction was first reported by Lemieux and Johnson in 1956. It is a conversion of an olefin into two individual aldehydes by means of an oxidative cleavage of a carbon-carbon double bond with osmium tetraoxide-sodium periodate. Therefore, it is known as the Lemieux-Johnson oxidative cleavage, Lemieux-Johnson reaction, or simply Lemieux-Johnson oxidation." In addition, the combination of osmium tetraoxide and sodium periodate is referred to as Lemieux-Johnson reagent. It should be pointed out that a lactol may be obtained directly from the oxidation of the olefin with a hydroxyl group near the oleflnic bond." ... 

This reaction has been improved by addition of 2,6-lutidine to suppress the side reactions and increase the yields of aldehydes. In addition, this oxidation has been modified by using osmium tetraoxide and oxone as oxidants, which directly convert 1,2-disubstituted olefins into two individual carboxylic acids. On the basis of this modification, osmium tetraoxide has been made to be a three-dimensional networked nanomaterial that, in combination with oxone, forms a superior heterogeneous catalyst, which even oxidizes alkynes into carboxylic acids7... 

A ligand-independent, osmium-catalyzed aminohydroxylation of MBH adduct has been developed by Sharpless et al. (Scheme 3.202). The yield, rate and selectivity of this reaction are not affected by the addition of cinchona alkaloid ligands. The diastereoselectivity for the aminohydroxylation is influenced by the aldehyde-derived substituent, while the acrylate-derived substituent has a minimal effect. Various derivatives and close analogs of the MBH product-core failed to aminohydroxylate, emphasizing the unique reactivity of this class of olefins. 

It was reported [39] that osmium tetroxide promoted catalytic oxidative cleavage of ds-stilbene and other olefins. The ds-stilbene catalytic oxidative cleavage gave benzoic acid in 95% yield. The process for the preparation of substituted aromatic and heteroaromatic aldehydes and carboxylic acids by the oxidation of substituted stilbenes has been patented [40]. Stilbenes of various substituents (Ri, R2 = H, Cl-4 alkyl, Cl-4 alkoxy, OH, NO2, CN, COjH, CONH2, SO3H, halogen X = C, N Z = CHO, CO2H ... 

In 1985, Orchin and coworkers [1] raised the question, Is the hydroformylation reaction reversible . Indeed, several investigations give clear evidence that aldehydes can be degraded under hydroformylation conditions or at least by the effect of typical hydroformylation-active complexes based on rhodium, cobalt, palladium, ruthenium, iridium, or osmium [2, 3]. As the result of the decarbonylation, an alkane is formed (Scheme 8.1). In 2015, also a clean dehydroformylation protocol operating under smooth conditions was discovered, which afforded olefins [4]. 

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