Reductions of Olefins

The sulfoxide directed reduction of olefin is known, so is sulfoxide reduction by chloroborane, but not simultaneous reduction of both by borane. 

The anion radical species formed by the electroreduction of aliphatic esters show interesting reactivities, and the reduction of olefinic esters gives bicyclic products with high regio- and stereoselectivity. The electroreduction of the ester in the presence of chlorotrimethylsilane affords a tricyclic product (Scheme 21) [35, 40]. The mechanism of this cyclization reaction seems to be the addition of anion radical species, formed by the reduction of the ester group, to the carbon-carbon double bond. 

SimplePHOX 7a proved a useful tool to force the diastereomeric reduction of olefin 31a to pseudopteroxazole precursor 31b in perfect diastereoselectivity and 90% yield with only trace amounts of over-reduced product. NeoPHOX catalyst from ligand 14b, a closely related system to 7a, furnished product 32b in 93% ee, which was then easily recrystallized to enantiopure material with 58% recovery. The R enantiomer of 33b was synthesized by the use of catalyst from ligand 8a in 90% ee and 98% yield with the fully aromatized naphthalene as 2% byproduct. A higher catalyst loading of 2 mol% of catalyst from 7a was used to produce the... 

Ideas regarding the mechanism of phytochemical reduction of olefins have been advanced by Fischer and Eysenbach. They also point out that just as in the case of the simple disproportionations in the course of sugar degradation (for example, the second and third forms of fermentation), saturation of the olefinic linkage is at an optimum in the weakly alkaline range, at about pH 8.5. 

Platinum dioxide, also known as Adams catalyst, is used commercially in many hydrogenation reactions at ordinary temperatures, such as reduction of olefinic and acetylenic unsaturation, aromatics, nitro, and carbonyl groups. 

Catalytic reduction of olefins by heavy metal catalysts probably involves metal hydride addition reactions also. If this is correct, the observed inhibition of the reduction by carbon monoxide, phosphines, sulfur compounds, and other materials with unshared electrons is exactly what would be expected if a vacant orbital on the hydride is required before addition can take place. 

Reduction of olefins and alkynes 5-10 Reduction of aromatic rings... 

The complete reduction of coal proceeds from aromatic rings through rings containing olefinic double bonds to saturated compounds. While reduction of the benzene ring takes place at a current efficiency of about 80% (8), current efficiency for reducing an olefin (1-decene) is only 27% as shown in this paper. The slow step in the coal reduction may very well be reduction of olefinic double bonds. An increase in the rate of olefinic double bond reduction may therefore lead to a considerable increase in current efficiency. 

Dicobalt octacarbonyl was one of the earliest known compounds believed to be capable of activating molecular hydrogen in homogeneous solution (48). The hydrogenation of organic substrates in the presence of this catalyst has been described in several earlier reviews (140a, 158). Reduction of olefins and aldehydes will be considered here. 

This reaction was investigated recently by Flynn and Hulburt 19,20) with the view to utilize such information to elucidate the role of metal catalysts in the heterogeneous reduction of olefins. 

Organocatalytic Enantioselective Reduction of Olefins, Ketones, and I mines... 

Asymmetric Organocatalytic Reduction of Olefins 395 Table 11.1 Organocatalytic reduction of conjugated aldehydes by Hantzsch ester 4 [14]. 

U. Kazmaier, J. M. Brown, A. Pfaltz, P. K. Matzinger, H. G. W. Leuenberger, Formation of C-H Bonds by Reduction of Olefinic Double Bonds Hydrogenation, in Methoden Org. Chem. (Houben-Weyl) 4th ed. 1952-, Stereoselective Synthesis (G. Helmchen, R. W. Hoffmann, J. Mulzer, E. Schaumann, Eds.), Vol. E21d, 4239, Georg Thieme Verlag, Stuttgart, 1995. 

M. Zaidlewicz, Formation of C—H Bonds by Reduction of Olefinic Double Bonds—Hydroboration and Hydroalumination, in Methoden Org. Chem. (Houben-Weyl) 4th ed. 1952-, Stere-... 

Two types of asymmetric reactions were conducted synthesis of styrene oxide and reduction of olefinic ketones. 

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