Iodoarenes coupling

ROMP polymerization (Eq. 28) of norbornene esters containing SCS-Pd(II) pincer-type complexes useful in Heck, Suzuki, and Sonogashira couplings have been reported by Week s group [111, 112]. The SCS-Pd(II) complexes in the polymer 74 prepared by this chemistry are competent catalysts in iodoarene couplings. The product polymer 74 is soluble and recoverable by precipitation using hexanes. 

The protocol offers a direct and efficient method for the synthesis of the boronic ester in the solid phase, which hitherto met with little success using classical methodology (Scheme 1-42). A solid-phase boronate (113 [155], 114 [156]) is quantitatively obtained by treating a polymer-bound iodoarene with the diboron (82). The subsequent coupling with haloarenes furnishes various biaryls. The robot synthesis or the parallel synthesis on the surface of resin is the topic of further accounts of the research. 

Innumerable aryl- and heteroarylstannanes take part in Stille couplings with halopyridines. In one such example, the union of arylstannane 106 and 4-bromopyridine furnished arylpyridine 107 [90], Arylstannane 106 was prepared from the Pd-catalyzed reaction of hexabutylditin with iodoarene 105, which arose from aminobenzolactam 104 via a Sandmeyer reaction. 

The consecutive reaction of vinyl halides and alkenes with activated methylene systems [42] in the presence of a palladium catalyst and phase-transfer catalyst results from the addition of the methylene carbanion with the initially formed Heck product (Scheme 6.31) an intramolecular version of the reaction leads to the formation of bicycloalk-l-enes (Scheme 6.31) [42], The analogous combined coupling reaction of iodoarenes and activated methylene compounds with non-conjugated dienes under similar conditions forms the monoalkene (Scheme 6.31) [43]. 

Activated tiophenes were coupled with iodoarenes with phosphine-free Pd-catalysts in CH3CN/H2O 9/1 [29]. 

Immobilized Pd(II) pincer complexes were prepared as described previously (20-22). Heck couplings of iodoarenes and acrylates were carried out in DMF using tertiary amines as base and reaction kinetics were monitored as previously reported (20-22). 

Carbonylative cross-coupling of iodoarenes and aryl triflates with g< ///-fluorovinyltributylstannane takes place smoothly in a standard system, with triflate substrates requiring the addition of tetrabutylammonium iodide (Equation (4)). ... 

Besides, iodoarenes aryliodonium salts were used as electrophilic coupling partners in the synthesis of ynones. The carbonylative cross-coupling can be run in aqueous DME in the presence of Pd(OAc)2 and Gul as co-catalyst and NaHG03 as a base at 30 °G. ... 

In solution, (dichloroiodo)arenes have been shown to exist as an equilibrium mixture with dichlorine and iodoarenes [135]. Ligand coupling is probably responsible for the formation of dichlorine. 

Improvements of the old methods have been reported recently. For example, when iodoarenes were oxidized with Cr03 in acetic acid/acetic anhydride/sulfu-ric acid and then coupled with arenes, upon final addition of KBr(aq) several diaryliodonium bromides were obtained in good yield (Scheme 34) [102]. 

Ethynyl-3-pyridinols undergo coupling with iodoarenes, aryl triflates, and enol triflates in the presence of PdCl2(PPh3)2 and Cul. Nucleophilic attack of oxygen onto the arylated alkyne product occurs in situ to give... 

Spirocycles can be obtained from intramolecular radical biaryl coupling reactions when suitable substituents are present for an alternative stabilization of the cyclohexadienyl intermediate (c.f. 69, Scheme 25). Otherwise, rearomatization can occur by cleavage of one substituent from the quaternary center of the spirocycle, such as the C-P bond in 69. First examples for an alternative reaction course have been reported in studies on the photochemically induced cyclization of iodoarenes [134]. Recently, ferf-butyldimethylsilyl ethers [135] and azides [136] were identified as well-suited substituents to lead the ipso substitution into the pathway towards spirocycles (Scheme 27). 

The coupling of the tin-products obtained from SRN1 reactions with a iodoarene through a Pd(0)-catalyzed process has been developed to obtain polyarylated compounds in one-pot reactions as shown in Sch. 30 [105]. 

Iodoarenes may be oxidized in situ to an iodine(III) species which is subsequently coupled with the appropriate arene. Potassium persulphate [10] and chromium trioxide [11] were most suitable oxidants, notably for iodoarenes bearing electron-withdrawing substituents. 

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