Nickel-catalyzed reactions zinc reagents

The electrosynthesis of /Miydroxy esters (220), 2,3-epoxy esters (221) and /Miydroxy nitriles (222) was achieved under nickel-catalyzed conditions, obviating Reformatsky reaction 70(equation 112-114). The reaction proceeds in excellent yield when a sacrificial zinc rod is used as the anode. A mechanism has been proposed which involves reduction of a Ni(II) complex to a Ni(0) complex, oxidative addition of the a-chloroester to the Ni(0) complex, and a zinc (II)/Ni(II) exchange, leading to an organozinc reagent, in analogy to the Reformatsky reactions. 

Nickel- or palladium-catalyzed coupling reactions of alkyl Grignard or zinc reagents can be applied to heteroaromatic halides and sulfides. The characteristic features are, therefore, based on those described in the preceding sections and hence details are not repeated in this section. Aspects are summarized by the types of heteroaromatic compounds NiCh(DPPP) is used as catalyst, unless stated otherwise hereafter. 

Progress from a synthetic point of view has been achieved in the selective oxidation of alkyl zinc reagents with oxygen in perfluoro-hexane solutions to give good yields of either hydroperoxides or alcohols. [28] As many zinc organometallics are easily obtained from olefins via a hydroboration/boron-zinc exchange sequence or by a nickel catalyzed hydro- or carbozincation reaction, this method may proof its synthetic potential in the future development. 

General Considerations and Mechanism In 1977, Fauvarque/Jutand reported the first palladium- and nickel-catalyzed cross-coupling reaction of aiyl halides with a zinc ester enolate the Reformatsky reagent (Scheme 19.29) [26b, 32]. When PdCljCPPhj) and NiCljjPPhj) are used... 

Two examples for nickel-catalyzed cross-coupling reactions of triflales and mesylates with the requisite zinc and boron species are outlined in Scheme 12.26. In 1994, Snieckus reported the Ni(0)-catalyzed reaction of aryl zinc reagents with aryl triflates and obtained the desired biaryl compounds in... 

Aryl chlorides are known to undergo nickel-catalyzed cross-coupling reaction of aryl Grignard reagents in the presence of zinc [59[. Vinylphosphates [60] and sulfoxides or sulfones [61] behave similarly to yield the corresponding coupling products. 

Reversal of the absolute configuration of the product 6 by addition of a zinc salt was observed in the cross-coupling of 2a with 4a catalyzed by 51/Ni [38,39] (Scheme 8F.7). Thus, the cross-coupling of the Grignard reagents 2a with 4a in the presence of nickel catalyst coordinated with aminoalkylphosphine (S)-51a gave (S)-6 with 61% ee, whereas the reaction of the... 

Oguni has reported asymmetric amplification [12] ((-i-)-NLE) in an asymmetric carbonyl addition reaction of dialkylzinc reagents catalyzed by chiral ami-noalcohols such as l-piperidino-3,3-dimethyl-2-butanol (PDB) (Eq. (7.1)) [13]. Noyori et al. have reported a highly efficient aminoalcohol catalyst, 2S)-3-exo-(dimethylamino)isobomeol (DAIB) [14] and a beautiful investigation of asymmetric amplification in view of the stability and lower catalytic activity of the het-ero-chiral dimer of the zinc aminoalcohol catalyst than the homo-chiral dimer (Fig. 7-5). We have reported a positive non-linear effect in a carbonyl-ene reaction [15] with glyoxylate catalyzed by binaphthol (binol)-derived chiral titanium complex (Eq. (7.2)) [10]. Bolm has also reported (-i-)-NLE in the 1,4-addition reaction of dialkylzinc by the catalysis of nickel complex with pyridyl alcohols [16]. 

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