Copper carbozincation

Palladium catalysed cyclic carbozincation of u>-iodoalkenes and copper promoted conjugate addition of alkylzincs to nitroalkenes preparation of 1-butyl-1-(3-nitro-2-phenylpropyl)cyclopentane60... 

A stereoselective synthesis of substituted pyrrolidines has been achieved by a sequential domino Michael addition and intramolecular carbozincation. The intermediate zinc-copper reagent obtained after cyclization can be trapped with an electrophile such as allyl bromide (Scheme 18).180 Addition of zincated hydrazones 52 on alkenyl boronates, followed by a trapping with an electrophile, provides adduct of type 53 with good yield and high diastereoselectivity (Scheme 19).181 By this addition/trapping sequence, several contiguous stereogenic centers are created in one step. 

Formation of the cyclopentane ring and concomitant arrangement of the two side chains in the cis fashion is another efficient approach to methyl < />/-jasmon ate as delineated in Scheme 9. In the upper sequence, nickel-catalyzed carbozincation of 17 with Et2Zn produced organozinc 18, which was converted to a copper reagent for coupling with 1-bromoacetylene to produce 19 efficiently.849 The ene reaction of 20 and 23 has afforded 21 and 24, respectively.858 859 In the latter case, 23 was generated in situ by retro Diels-Alder reaction of 22. 

Organometallic reagents of lithium, magnesium, zinc, aluminum, copper, etc. add to alkenes and alkynes.226 Carbozincation was reported to be improved by sonication. Perfluoroalkyl zinc reagents generated in situ add to alkynes in the presence of a copper salt (Fig. 39).227... 

Scheme 10.36 Similar features of the copper-catalyzed carbozincation in (a) conjugate additions case and (b) directed carbometallation of cyclopropenyl esters [33].

Scheme 10.37 Copper-catalyzed directed intermolecular carbozincation of cyclopropenecar-boxylates scope of the method [34].

Scheme 10.39 Copper-catalyzed carbozincation of substituted cyclopropenes directed by Evans chiral auxiliary [34].

Scheme 10.1Z7 Catalytic copper(l)-promoted carbozincation of chiral alkynylsulfoxides. followed by allylation/aldol-type addition sequence [107].

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