Selenoxides dialkyl

Selenoxides telluroxides. Diaryl or alkyl aryl sclcnidcs and diaryl or dialkyl tclluridcs arc oxidized to oxides in 40 95 yield by treatment with r-hutyl... 

Some dialkyl selenoxides (127a-c) were also resolved efficiently by complexation with 3 or 14b to give optically almost pure (+)-127a (154%), (-)-127b (79%), and (-)- 127c (74%) in the yields indicated.51... 

Selenoxide werden in essigsaurem Medium von Dialkyl- und Diaryl-sulfiden zu Seleniden reduziert ... 

Although unable to metallate selenides, dialkyl amides are sufficiently strong to metallate phenylselenoacetals39,46 51) as well as methyl48,52) and phenyl 46,47,52) selenoorthoesters. They are also able to metallate selenoxides 4 9,11 53 55) and selenones 14). Finally selenoacetals are readily available 4,711,12 S6) from carbonyl compounds and selenols in the presence of a Lewis acid and selenoorthoesters have been prepared from orthoesters, selenols, and boron trifluoride etherate47,48,52). 

The treatment of a,p-unsaturated ketones with organocopper reagents provides another method to access specific enolates of unsymmetrical ketones. Lithium dialkylcuprates (see Section 1.2.1) are used most commonly and the resulting enolate species can be trapped with different electrophiles to give a,p-dialkylated ketones (1.27). Some problems with this approach include the potential for the intermediate enolate to isomerize and the formation of mixtures of stereoisomers of the dialkylated product. The intermediate enolate can be trapped as the silyl enol ether and then regenerated under conditions suitable for the subsequent alkylation. Reaction of the enolate with phenylselenyl bromide gives the a-phenylseleno-ketone 12, from which the p-alkyl-a,p-unsaturated ketone can be obtained by oxidation and selenoxide elimination (1.28). 

Arylthallium bis(trifluoroacetate)s are converted by successive treatment with KF and BF3 into aryl fluorides.Thallium(iii) nitrate (TTN) readily oxidizes dialkyl sulphides and selenides to the corresponding sulphoxides or selenoxides, and 2-(alkylthio)-l-arylethanones (37) into compounds (38) in methanolic solution.In a modification of the TTN oxidative conversion of aryl alkyl ketones into arylacetic acids, enol ethers derived from the ketones are used instead of the ketones themselves. This reduces the formation of side products. Cyclic aralkyl ketones (39) may be ring-expanded and alkylated to give compounds (40) via treatment of their Wittig-derived alkenes with TTN/ an extrapolation of the basic reaction discovered previously. 

A variety of methods for the reduction of sulfoxides to sulfides are available. PI3 rapidly reduces aryl alkyl and dialkyl sulfoxides and selenoxides, usually at —78 °C (eq 3). For example, treatment of ethyl phenyl sulfoxide with 1 equiv of PI3 (CH2CI2, -78 °C, 15 min) affords ethyl phenyl sulfide in 91% yield. Others have successfully employed this procedure. Dialkyl sulfoxides generally react in somewhat lower yield. A phenyl vinyl sulfoxide (eq 3, entry c) requires ambient temperatures to react. Selenoxides behave similarly, and P2I4 can usually be used in place of PI3. Treatment of decyl phenyl selenone with PI3 (CH2CI2, 0 °C, 30 min) affords a mixture of the reduced product, decyl phenyl se-lenide (69%), and the substitution product, n-decyl iodide. ... 

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