Methyl halide coupling reaction with

A practical method for preparation of fluorinated alkenyl copper reagents has been recently developed from cuprous halides metathesis of the corresponding zinc or cadmium reagents [180]. These copper reagents exhibit excellent stability at room temperature and undergo a variety of coupling reactions with methyl, allyl, vinyl, aryl and acid halides [180] (Scheme 63). More recently, preparation of cyclic perfluoroalkenyl copper reagents has been reported by the same route [156-158]. 

Although trimethyl(vinyl)silane undergoes the coupling reaction with aryl halides in the presence of TASF and a palladium catalyst as described in Section 1 (Eq. 3), those having an aliphatic substituent on vinyl fail to couple with aryl iodides under similar conditions, probably because they are not capable of affording pentacoordinate silicates efficiently owing to the electron-donating nature of the substituent. To assist the formation of the pentacoordinated intermediates, the methyl on silicon was replaced by fluorine [13]. The cou-... 

Prior to the Pd-catalyzed coupling reaction with a variety of aryl halides, a preliminary test was performed using a Pd(0) catalyst to find any effect of substituents in the C—C bond forming reactions. Several different types of 2-pyridylzinc bromides (Table 3.32, P1-P6) were coupled with 3-iodothiophene in the presence of 1 mol% of Pd(PPhs)4 in THF at rt, and the results are summarized in Table 3.32. In general, good yields (Table 3.32, entries 1, 3, and 4) were obtained from using 2-pyridylzinc bromide (PI), 4-methyl-2-pyridylzinc bromide (P3), and 5-methyl-2-pyridylzinc bromide (P4). Reactions with 3-methyl-2-pyridylzinc bromide (P2), 6-methyl-2-pyridylzinc bromide (P5), and 6-methoxy-2-pyridylzinc bromide (P6) resulted in moderate yields (Table 3.32, entries 2, 5, and 6). 

Pentacoordinated silicate TASF, one of the best activators of organosilicon compounds in the Pd-catalyzed cross-coupling reaction as we have seen, is found to be involved in the coupling reaction with aryl halides in the absence of other organosilanes to give methylated arenes (Scheme 24). Recently, DeShong and co-workers also reported that tetrabutylammonium triphenyldifluorosilicate, another pentacoordinated silicate, is applicable for the phenylation of aUyl benzoates and aryl halides in the presence of a palladium catalyst. 

Lithium enolates of ketones and esters undergo a coupling reaction with copper(II) halides to afford the corresponding 1,4-dicarhonyl compounds. Thus treating a 3 1 mixture of f-butyl methyl ketone and acetophenone with lithium diisopropylamide and CuCU gives a 60% yield of the cross-coupled product (eq 12). 

The Li compound 588 formed by the ort/io-lithiation of A. A -dimethylaniline reacts with vinyl bromide to give the styrene derivative 589(433]. The 2-phe-nylindole 591 is formed by the coupling of l-methyl-2-indolylmagnesium formed in situ from the indolyllithium 590 and MgBr2, with iodobenzene using dppb[434]. 2-Furyl- and 2-thienyllithium in the presence of MgBr2 react with alkenyl halides[435]. The arylallenes 592 and 1,2,4-alkatrienes are prepared by the coupling reaction of the allenyllithium with aryl or alkenyl halides[436]. 

Tributylstannyl)-3-cyclobutene-1,2-diones and 4-methyl-3-(tributylstan-nyl)-3-cyclobutene-l,2-dione 2-ethylene acetals undergo the palladium/copper-catalyzed cross coupling with acyl halides, and palladium-catalyzed carbon-ylative cross coupling with aryl/heteroaryl iodides [45]. The coupling reaction of alkenyl (phenyl )iodonium triflates is also performed by a palladium/copper catalyst [46],... 

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