Oxido compounds ketones

The reaction of 2-lithio-l,3-dithianes with oxido compounds has been used for the stereospecific substitution of steroids both epimers could be obtained via this route Syntheses through dihydro-1,3-oxa-zines, originally used for the preparation of various aldehydes have been extended to ketones and acids difficult to obtain otherwise. 

Cyclic ketones from oxido compounds with ring isomerization... 

Ketones from ethylene derivatives via oxido compounds... 

Dicobalt octacarbonyl dissolved in isopropanol, propylene oxide added under Ng when GO-evolution has ceased, cooled if the reaction becomes too vigorous after 15-20 min., and the mixture distilled after ca. 1 hr. -v acetone. Y 75%.— This method gives ketones whereas aldehydes are usually obtained from 1,2-oxido compounds. F. e. s. J. L. Eisenmann, J. Org. Ghem. 27, 2706 (1962). 

Partial formation of a-bromoketones from ketones with formation of bromohydrins from oxido compounds... 

Hydrogen peroxide potassium hydroxide Ketones hy cleavage of oxido compounds s. 13, 303... 

Keto steroids can be obtained in excellent yields via the Beckmann degradation of 17a-hydroxy-or 16a,17a-epoxy-20-ketopregnanes. In the case of the 17-hydroxy compounds, substituents at C-16 readily survive e.g., 16 -Br, 16jS-Cl, Iba-OAc). The 16,17-oxido-20-oximinopregnanes produce 16a-acetoxy-17-ketones. 

A one-carbon homologation of carbonyl compounds is an important and extensively used method for the preparation of desired carbonyl compounds . One-carbon ring-expansion or one-carbon homologation of ketones or aldehydes via a S-oxido car-benoid is a representative example of the homologation, but few methods have been reported . 

Chemical systems of relevance to the molybdenum and tungsten enzymes include synthetic pterins, a-phosphorylated ketones (as precursor models), and a variety of molybdenum and tungsten oxido, sulfido, and 1,2-enedithiolate complexes. These compounds have been used to (1) confirm the identity of MPT derivatives (2) define steps in MPT biosynthesis (3) calibrate spectroscopic observations (4) give precise geometries and reactivities that can be used as input for theoretical studies and (5) provide options for mechanistic consideration. 

Figure 45. Conformational variation attributed to the 5a-10a-cis-normal-clerodanes A. two favored conformational possibilities (15) B. probable conformation of compounds containing a 18,19-oxido linkage C. the effect of the shielding zone of the C-2 ketone on the H-NMR chemical shift of the C-9 methyl (H-20) of cis-clerodanes.

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