Coupling reactions with aryl compounds

The perfluoroacetylenic copper compounds undergo coupling reactions with aryl iodides and provide a useful synthetic route to the perfluoroalkyl aryl alkynes [147, 255] (equation 170) Coupling of these copper reagents with the 1-iodo-perfluoroalkynes gives the perfluorodiynes [747 255] (equation 171)... 

Triarylbismuth compounds can be used in cross-coupling reactions with aryl iodides, bromides, or triflates in the presence of Pd(PPh3)4 and CsF or K2C03.174... 

When the metallic additive to the intermediate 374 was zinc dihalide (or another Lewis acid, such as aluminum trichloride, iron trichloride or boron trifluoride), a conjugate addition to electrophilic olefins affords 381 . In the case of the lithium-zinc transmetallation, a palladium-catalyzed Negishi cross-coupling reaction with aryl bromides or iodides allowed the preparation of arylated componnds 384 ° in 26-77% yield. In addition, a Sn2 allylation of the mentioned zinc intermediates with reagents of type R CH=CHCH(R )X (X = chlorine, bromine) gave the corresponding compounds 385 in 52-68% yield. ... 

Hypervalent organobismuth compounds 1 bearing a 2,6-pyridinedialkoxide ligand [43] were used for the cross-coupling reaction with aryl triflates (Scheme 28) [44], Phenylation using phenylbismuth compounds smoothly proceeded for the reactive... 

Aryl chlorides can also be used as coupling partners for azabismocine reagents 2. In the coupling reaction with aryl chlorides, Pd(PPh3)4 was not an efficient catalyst, and Pd(OAc)2/l,l,-bis(diphenylphosphino)ferrocene (dppf) combination was found to be effective [54]. Not only the arylation, but also methylation, alkenylation and alkynylation reactions can be accomplished by using the corresponding bismuth compounds (Scheme 35). The addition of CsF improved the product yields. However, electron-rich aryl chlorides were unable to be coupled efficiently under these reaction conditions. 

Hegedus and Varaprath studied the reactions of various bromodienes with Ni(CO)4 and with bis(cyclooctadiene)nickel. l-Bromo-2,5-hexadiene and 2-bromomethyl-1,3-butadiene give the stable products 62 and 63, respectively, which resemble allyl nickel halides in their properties (217). Similar compounds had been prepared several years previously from geranyl halides (218). l-Bromo-2,4-pentadiene and l-bromo-2,4-hexadiene, however, formed intractable materials which could not be isolated and purified. In these cases the red color of the solution which was first produced faded and NiBr2 was deposited. The desired compounds, however, could be generated in situ at — 30° C and used in coupling reactions with aryl, alkenyl, and allyl halides (217). 

Highly regioselective radical addition of the indium hydride reagent HInCl2 to alkynes has been achieved. Various functionalities are tolerant under the reaction conditions. The reaction proceeds with complete // -stereoselectivity. Alkenylindium compounds obtained by this hydroindation can be employed for the subsequent cross-coupling reactions with aryl halides in one pot (Scheme 109).374,375... 

Lithiation of compound 560 with s-BuLi-TMEDA in THF at —78 °C following an inverse addition protocol provided the anion 561. It reacts with primary alkyl iodides and triflates, silyl chlorides, diphenyl disulfide, epoxides, aldehydes, ketones, imines, acyl chlorides, isocyanates and sulfonyl fluorides to yield the expected compounds 562 (Scheme 152). The transmetallation of compound 561 with ZnBr2 allowed the palladium-catalyzed cross-coupling reaction with aryl and vinyl bromides837. When the reaction was quenched with 1,2-dibromotetrafluoroethane, the corresponding bromide 562 (X = Br) is obtained838. 

An example prepared by tin-lithium transmetallation is compound 637, which reacts with enolizable ketones, after transmetallation with cerium(III) chloride895. This intermediate was transformed into the corresponding vinylzinc reagent and, after palladium(O)-catalyzed cross-coupling reactions with aryl iodides, was used in the synthesis of the antitumor antibiotic rineomycinone B2 methyl ester940,941. The vinyllithium 627 has also been transformed into the corresponding vinyl iodide by stannylation followed by reaction with iodine. The arylation has been performed in this case by a palladium(0)-catalyzed... 

Castro et al. 44) found that the order of reactivity of various halides in coupling reactions with ethynylcopper compounds in DMF is ArSX, ArX > RCOX ArCHaX, RCH=CHCH2X, ArCOCHaX > RCH= CHX, Alkyl-X. A somewhat different order is observed for the reactivity of some organic halides towards perhaloarylcopper reagents in THF (97, 147) Allyl Aryl > Alkyl and perfluoroaryl, perfluoro-vinyl > aryl > perfluoroalkyl. Acid halides were also far more reactive than aryl iodides in ethereal solvents 146). The ease of halide displacement is I > Br > Cl. 

TRIORGANOINDIUM COMPOUNDS AS EFFICIENT REAGENTS FOR PALLADIUM-CATALYSED CROSS-COUPLING REACTIONS WITH ARYL AND VINYL ELECTROPHILES... 

Oxidative addition [1, 38] of 1-alkenyl, 1-alkynyl, allyl, benzyl, and aryl halides to a palladium(O) complex affords a stable trans-o-p al 1 adi u m( 11) complex (11). The reaction proceeds with complete retention of configuration for alkenyl halides and with inversion for allylic and benzylic halides. Alkyl halides having /5-hydrogens are rarely useful because the oxidative addition step is very slow and may compete with /5-hydride elimination from the <7-organopalladium(II) species. However, it has been recendy shown that iodoalkanes undergo the cross-coupling reaction with organoboron compounds (Section 2.4.5). 

Pentacoordinated silicate TASF, one of the best activators of organosilicon compounds in the Pd-catalyzed cross-coupUng reaction as we have seen, is found to be involved in the coupling reaction with aryl hahdes in the absence of other organosilanes to give methylated arenes (Scheme 1A)S Recently, DeShong and co-workers also reported that tetrabutylammonium triphenyldifluorosilicate, another pentacoordinated silicate, is applicable for the phenylation of allyl benzoates and aryl haUdes in the presence of a palladium catalyst. 

These cross-coupling reactions are coupling reactions of aryl compounds with aryl compounds, aryl compounds with olefins, olefins with olefins, etc., as shown in Fig. 8.4. The cyclometalation reactions of aryl substrates with aryl compounds give aryl-aryl coupling reaction products, as shown in Eq. (8.29). Stanford et al. [138]... 

The use of BusSnH in 5-exo-6fig-cyclization has further advantages. For example, the high reactivity tributylstannyl group in fulvene -3.631 (X = H, Ar = Ph) makes it possible to perform a Stille coupling reaction with aryl iodides to afford compounds 3.633a,b (yields 60-70%), whereas an electrophile such as iodine affords iodide 3.634 (yield 82%). The XRD analysis confirmed the structures and the regio- and stereoselectivity of the reaction (Scheme 3.56) [308]. 

Another area of interest to the industrial sector is the development of a more efficient synthesis of biaryl compounds. This has been accompHshed using a Ni(II)-cataly2ed Grignard coupling reaction with an aryl haUde (86—89). 

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