A-Seleno carbanion

Synthesis of Organometallics Bearing an a-Seleno Carbanion by Selenium-Metal Exchange... 

Reaction of organometallics bearing an a-seleno carbanion with carboxylic acid derivatives and related... 

Only a few enantioselective reactions of a-seleno carbanions have been reported. First, Hoffmarm and coworkers observed, using Se-NMR spectral analyses, large equiUbrium constants for diastereomeric complexes derived from a-se-leno carbanions and various chiral diamines [67]. They studied the enantiose-... 

Thus a carbonyl group can be converted into a CHa group by conversion into u selenoacetal followed by reduction or into CHR by alkylation of the a-seleno-carbanion followed by reduction. 

The reaction of selenoacetals with butyllithiums allows the synthesis of a large variety of a-seleno-alkyllithiums whose carbanionic centers are unsubstituted, monoalkyl substituted or dialkyl substituted. 

P-Hydroxy selenides are conveniently prepared from epoxides by treatment with sodium phenylse-lenide (Scheme 32) and by the addition of benzeneselenenic acid and its derivatives to alkenes (Scheme 33), - -" although in some cases these reactions are not regioselective. Useful phenylseleno -etherification and -lactonization reactions have been developed which can be regioselective (equation 42 and Schemes 34 and 35). -" " Selenide- and selenoxide-stabilized carbanions have been used in addition reactions with aldehydes and ketones, - and the reduction of a-seleno ketones also provides a route to P-hydroxy selenides. ... 

Examples of organometallics bearing a selenium-stabilized carbanion include (i) a-selenoalkyl-hydroxylithiums bearing hydrogens or alkyl groups on the carbanionic 7-9,i3,i6,i7.33,36,4o,4s-so,54-56, 77,139,160,162,i63,i66,i77,i8s-206 center (ii) a-selenocyclopropyllithiums 77,104,139-161 gnj a-seleno-... 

REACTIONS OF a-THIO- AND a-SELENO-ALKYLLITHIUMS BEARING HYDROGENAND/OR HYDROCARBON SIDE CHAINS ON THEIR CARBANIONIC CENTER... 

This chapter is devoted exclusively to the alkylation of the above mentioned organometallic reagents with alkyl halides, epoxides and oxetanes. It includes a large variety of organosulfur- and organoselen-ium-stabilized carbanions derived from saturated and unsaturated sulfides, selenides, sulfoxides, selen-oxides and sulfones as well as those carbanions bearing another heteroatomic moiety. The chapter excludes, however, those organometallics which can be viewed as a-thio and a-seleno enolates. 

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