Organo-copper reagents

Treatment of bromocyclopropanes with four molar equivalents of lithium dibu-tylcuprate followed by excess alkyl halide leads to a stereospecific introduction of the alkyl group with retention of configuration. The stereochemical outcome can be understood by the intermediacy of a mixed cuprate (42) whose formation and reaction with alkyl halides proceeds with retention of configuration. Yields are good and no butylated products are formed. 

Most of the organocuprate -addition-a-alkylations of cyclopent-l-enones and cyclohex-2-enones have involved introduction of the nucleophilic -substituent and the electrophilic a-substituent preferentially in a trans-configuration. In contrast lithium diphenylcuprate addition to cyclopent-2-enone followed by a-alkylation involves attachment of the two new groups stereoselectively in a cis-relationship, even though such c/s-2-alkyl-3-phenylcyclopentanones are less stable than their trans-epimers [equation (14)].  

The lactone tosylate (43) reacts with dialkylcuprates or dialkenylcuprates selectively with tosylate displacement rather than ring opening to give (44).  

Reaction of the organobiscuprate (45) with chloroenones (46) gives the spiro-ketone (47) in about 50% yield. In contrast, reaction with 3-acetoxycyclohex-3- 

Direct substitution of the hydroxy-group of allyl alcohols with alkyl groups has been achieved [equation (15)]. Although the detailed structure of the alkylating 

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Alkynyl(phenyl)iodonium salts can be efficiently coupled with various organo-copper reagents. Direct coupling of alkynyliodonium tosylates 132 with vinyl-... 

R.D. Rieke, US Patent 5,490,952 (February 13, 1996) Assignee University of Nebraska Utility Organo Copper Reagents... 

Cyclopentenones Bis(acetonitrile)dichl4ropalladium(II). Bis(cyclopentadienyl)jdiiodozirconium. Dl-p,-carbonylhexacarbohyldicobalt. Organo-copper reagents. Tin(IV) chloride. 

Propanedithiol, 50,72 Propargyl bromide, coupling with an organo-copper reagent, 50, 98 a-Pyrone, irradiation of, 50, 23... 

The choice of the organo-copper reagent is important. Thus reaction of (1) with dimethylcopperlithium yields only the linear product corresponding to (4),Bu = CH3. 

Organo-copper Reagents.—The heterocuprate (29) reacts with the readily synthesized secondary allylic ether of 2-hydroxybenzothiazole (28) to give the substitution product (30) with almost complete regioselectivity and in high yield (75%). The E Z ratio in compound (30) is strongly influenced by temperature. 

Scheme 13). Conjugate addition of an organo copper reagent to... 

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