Stille coupling reactions, and

The mechanism " of the Suzuki reaction is closely related to that of the Stille coupling reaction, and is also best described by a catalytic cycle ... 

In particular, highly stable Pd nanoparticles, protected by an imidazolium based ionic polymer in a functionalized IL, can be easily prepared. These Pd nanoparticles are excellent pre-catalysts for Suzuki, Heck and Stille coupling reactions and can be stored without undergoing degradation for at least two years. 

Recently, transition metals and particularly palladium have found an increased use in C-synthesis. Reactions such as aromatic cyanation, the Stille-coupling reactions, and palladium-mediated carbonylation reactions using [ C] carbon monoxide are opening up new labeling pathways. 

Another fiiUy functionalized system is shown in Figure 8.21. It is synthesized following the Stille coupling reaction and is composed of an NLO chromophore... 

The Stille coupling reaction is very versatile with respect to the functionality that can be carried in both the halide and the tin reagent. Groups such as ester, nitrile, nitro, cyano, and formyl can be present, which permits applications involving masked functionality. For example, when the coupling reaction is applied to l-alkoxy-2-butenylstannanes, the double-bond shift leads to a vinyl ether that can be hydrolyzed to an aldehyde. 

Palladium(0)-catalyzed coupling reactions - i. e. the Heck and Sonogashira reactions, the carbonylative coupling reactions, the Suzuki and Stille cross-coupling reactions, and allylic substitutions (Fig. 11.1) - have enabled the formation of many kinds of carbon-carbon attachments that were previously very difficult to make. These reactions are usually robust and occur in the presence of a wide variety of functional groups. The reactions are, furthermore, autocatalytic (i.e. the substrate regenerates the required oxidation state of the palladium) and a vast number of different ligands can be used to fine-tune the reactivity and selectivity of the reactions. 

Wong reported that stoichiometric amounts of copper(I) chloride alone can promote the intramolecular Stille coupling (equation 138)243. In fact, copper(I)-mediated reaction was cleaner and faster compared with that catalysed by Pd(0) species. Selected examples of intermolecular Stille coupling reactions leading to dienes (Table 25)236a,242b 244, polyenes (Table 26)245 and macrocyclizations (Table 27)246 are given in the respective tables. 

The stereoselective synthesis of the 12-acetoxy enone 428, related to the limonoid azadiradione, has been achieved in 12 steps (16% overall yield), starting from tricyclic diester 429. The key steps involve an intramolecular 1,3-dipolar cycloaddition of a nitrile oxide and a Stille coupling reaction of vinyl iodide with stannylfuran (469). 

Oxazole compounds can also be produced by use of the Stille reaction. Clapham and Sutherland describe the use of tri-2-furylphosphine/Pd2(dba)3-catalyzed Stille coupling reactions (Scheme 12) to produce a range of oxazole-containing derivatives, including 58, with an 85% yield [56]. 

Dubac has employed a Stille coupling reaction to synthesize the pyrroles 88 and 89 from stannylpyrrole aldehyde 87 [71]. The latter tin compound was prepared as shown, and related stannylpyrroles were synthesized similarly [72] or using Muchowski s 6-dimethylamino-l-azafulvene dimer lithiation methodology [73]. 

The Stille reaction of 2-chloro-3,6-diisopropylpyrazine (7) and 2-chloro-3,6-diisopropylpyrazine 4-oxide (9) with tetra(p-methoxyphenyl)stannane (readily prepared in situ from the corresponding Grignard reagent and SnCU) led to the corresponding arylation products 8 and 10, respectively [9]. Additional Stille coupling reactions of chloropyrazines and their N-oxides have been carried out with tetraphenyltin [10] and aryl-, heteroaryl-, allyl- and alkylstannanes [11]. 

The heteroaromatic stannanes undergo the normal electrophilic substitution reactions of their protic precursors, and often to an enhanced degree. They are often prepared with the aim of a subsequent Stille cross-coupling reaction, and oligothiophenes with potentially useful optical and electron properties have been prepared by coupling between stannyl- and bromo-thiophenes, for example, Equation (63).204... 

In organic synthetic procedures, alkenyltin compounds are often prepared with a view to subsequent transmetalla-tion with lithium, or to the Stille coupling reaction with a palladium catalyst (Equations (70) and (71)). 

In 1994, Badone et al. reported that the Stille coupling of allenylstannane 77 and aryl triflates 78 resulted in formation of various aryl-substituted allenes 79 in moderate to good yield (Scheme 14.18) [39]. The choice of catalyst was certainly a crucial issue in this process for optimizing yield and rate. The best results could be obtained employing a catalyst cocktail of Pd2(dba)3-TFP-LiCl-CuI. Similar Stille coupling reactions with stannylated allenes and aromatic iodides as substrates were described by Aidhen and Braslau [40a] and Huang et al. [40b],... 

The 5-methyl-2(37f)-oxazolone sulfonamide derivatives 265 are obtained from the sulfonamides 263 via bromination and subsequent Stille coupling reaction with tetramethyltin in the presence of palladium catalyst (Fig. 5.64). °... 

Even though the governing phenomena of coupled reaction and mass transfer in porous media are principally known since the days of Thiele (1) and Frank-Kamenetskii (2), they are still not frequently used in the modeling of complex organic systems, involving sequences of parallel and consecutive reactions. Simple ad hoc methods, such as evaluation of Thiele modulus and Biot number for first-order reactions are not sufficient for such a network comprising slow and rapid steps with non-linear reaction kinetics. 

A number of Stille coupling reactions have been reported by Handy et al. [95], With PdCl2(PhCN)2/Ph3As/CuI in [BMIM][BF4], good yields and good catalyst recyclability (up to five times) were reported for the reachon between a-iodenones and vinyl and aryl stannanes (Scheme 5.2-19). However, the reported reaction rates were significantly lower than those obtained in NMP. 

The Stille coupling reaction has been performed in l-bntyl-3-methylimidazolium tetrafluoroborate. Use of this solvent system allows for facile recycling of the solvent and catalyst system, which can be used at least five times with little loss in activity. An interesting preference in starting catalyst oxidation state for nse with aryl bromides and aryl iodides was observed (Handy and Zhang, 2001). 

The cephalosporine analogue shown in 6.35. was also prepared in Stille coupling. Reaction of the allyl chloride moiety of chloromethylcephem and... 

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