Oxidation of Ketones to Lactones or Enones

TO PALLADIUM-CATALYZED ASYMMETRIC BAEYER-VILUGER OXIDATION OF PROCHKAL CYCLOBUTANONES. 256 

Catalysts for Fine Chemical Synthesis, Vol. 5 Regio- and Stereo-Controlled Oxidations and Reductions Edited by S. Roberts and J. VWiittall 2007 John Wiley Sons, Ltd 

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Baeyer- Villiger reaction the oxidation of a ketone to an ester or lactone, nsnally by means of a peroxy acid Enone an unsaturated ketone, usually a, f relative to the carbonyl group... 

Diketene similarly reacts readily with tributyltin oxide in THF at room temperature47 to give the stannyl 3-stannyloxybut-3-enoate which rearranges to the 2-enolate this enolate will then give an ene reaction with an aldehyde,48 or react with an alkyl halide,49 followed by decarboxylation, providing a route to ketones, enones, and ketoaldehydes. Similar reactions with bromomethyl P- or y-lactones result in the formation of P-hydroxy-y-lactones or y-hydroxy-5-lactones. 

Selenenyl halides are relatively stable, though moisture sensitive, compounds that are generally prepared by the reactions shown in Scheme 7 and behave as electrophihc selenium species. " They react with ketones and aldehydes via their enols or enolates to afford a-seleno derivatives (e.g. (17) in equation 11). Similar a-selenenylations of /3-dicarbonyl compounds, esters, and lactones can be performed, although the latter two types of compounds require prior formation of their enolates. Moreover, the a-selenenylation of anions stabilized by nitrile, nifro, sulfone, or various types of phosphorus substituents has also been reported (equation 12). In many such cases, the selenenylation step is followed by oxidation to the selenoxide and spontaneous syn elimination to provide a convenient method for the preparation of the corresponding a ,/3-unsaturated compound (e.g. 18 in equation 11). Enones react with benzeneselenenyl chloride (PhSeCl) and pyridine to afford a-phenylselenoenones (equation 13). 

From enolates via selenoxidesA Lithium enolates derived from ketones, lactones, and esters react with PhSe-SePh or with phenylselenyl bromide or chloride (PhSeX) to form a-(phenylseleno)carbonyl compounds. These can be oxidized to the corresponding selenoxides with subsequent 5yn-elimination of benzeneselenic acid to form enones. 

Warren has used a variation of his phosphine oxide-based olefination method to synthesise single isomers (E or Z) of unsaturated carboxylic acids.23 a-Diphenylphosphinoyl ketones (32) are reduced by sodium borohydride to give diastereomeric mixtures of the corresponding alcohols (33) and (34). These alcohols can be converted to the lactones (35) and (36) which can be separated and individually converted stereospecifically into (Z)-(37) and (E)-(38) alkenes by base treatment (Scheme 6). In many cases it is possible to reduce p-ketophosphine oxides (39) and enones (41) stereoselectively to the ery/Aro-alcohols (40) and (42), respectively, using sodium borohydride in the presence of cerium chloride (Scheme 7).24 An earlier report that reduction in the presence of cerium salts did not cause reversal of stereochemistry compared to reduction with borohydride alone appears to be true only of the compounds studied in that report. The carbanions of 3-hydroxypropylphosphine oxides (43) have been reported to undergo O- to C-acyl transfer to give the p-ketoalkylphosphine oxides... 

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