Heck reaction palladium-catalyzed reactions involving

A similar palladium-catalyzed process involving an intramolecular Heck-type reaction in the first step was developed by Grigg and co-workers [70], The resulting seven-membered ring vinylpalladium(II) intermediate 54 reacts with the allene to... 

As observed in Heck reactions, in the reactions performed in 1,3-dialkylimidazolium ILs, the formation of carbenes that may be involved in the stabilization of catalytically active species is not uncommon. The in situ formation of a mixed phosphine-imidazolylidene palladium complex, in [G4GiIm]BF4, has been observed under conditions employed in many palladium-catalyzed coupling reactions (Scheme 40). ... 

Intramolecular arylations are also involved in catalytic processes that are mediated by palladacycles [119-122]. In the case of 4-arylpyridines 102, a palladium-catalyzed reaction in the presence of biphenylene leads to tetraphenylenes 103 (Scheme 11.34) [123]. Consistent with previous results on the Heck reaction of substrates 102 [120], palladacycles 104 were proposed as reasonable intermediates in the reaction with biphenylene. 

Palladium-catalyzed carbon-carbon cross-coupling reactions are among the best studied reactions in recent decades since their discovery [102, 127-130], These processes involve molecular Pd complexes, and also palladium salts and ligand-free approaches, where palladium(O) species act as catalytically active species [131-135]. For example, the Heck reaction with aryl iodides or bromides is promoted by a plethora of Pd(II) and Pd(0) sources [128, 130], At least in the case of ligand-free palladium sources, the involvement of soluble Pd NPs as a reservoir for catalytically active species seems very plausible [136-138], Noteworthy, it is generally accepted that the true catalyst in the reactions catalyzed by Pd(0) NPs is probably molecular zerovalent species detached from the NP surface that enter the main catalytic cycle and subsequently agglomerate as N Ps or even as bulk metal. 

An efficient synthesis of functionalized carbazoles was developed by the palladium-catalyzed annulation of a variety of internal alkynes. This reaction involves arylpalladation of the alkyne, followed by intramolecular Heck olefination, and double bond isomerization. The iodoindole 588 reacts with the alkyne 589 in the presence of a catalytic amount of palladium(O) to give substituted carbazoles 590. In this reaction two new C-C bonds are formed in a single step. Higher reaction temperatures were necessary due to the low reactivity of the iodoindole (566) (Scheme 5.29). 

Palladium-catalyzed coupling reactions of the Heck type have in many instances involved indole and pyrrole derivatives. Although the mechanisms are complex, organopalladium species are implicated (84H(22)1493). Vinylation of A-substituted-3 -iodoindoles with amidoacrylate groups provides a useful functionalization of indoles (Scheme 81) (90JOM(39l)C23). Yields are improved in intramolecular reactions, e.g. (406 — 407) and (408 — 409) <92H(34)219,91CPB2830). 

Palladium/silver-catalyzed Heck reactions have usually involved vinyl or aryl halides and alkenes, but these reaction conditions were also extended to allenes. Indeed, Zenner and Larock65 showed that simple alkyl allenes readily reacted with aryl and vinyl iodide derivatives in the presence of palladium acetate or chloride and silver phosphate. Moreover, the reaction could be rendered asymmetric using chiral ligands the best one was a bisoxazolidine derivative (Scheme 10.37). 

Abstract This review gives an insight into the growing field of transition metal-catalyzed cascades. More particularly, we have focused on the construction of complex molecules from acyclic precursors. Several approaches have been devised. We have not covered palladium-mediated cyclizations, multiple Heck reactions, or ruthenium-catalyzed metathesis reactions because they are discussed in others chapters of this book. This manuscript is composed of two main parts. In the first part, we emphasize cascade sequences involving cycloaddition, cycloisomerization, or ene-type reactions. Most of these reaction sequences involve a transition metal-catalyzed step that is either followed by another reaction promoted by the same catalyst or by a purely thermal reaction. A simple change in the temperature of the reaction mixture is often the only technical requirement to go from one step to another. The second part covers the cascades relying on transition metalo carbenoid intermediates, which have recently undergone tremendous... 

A commercial synthesis (Albemarle) of naproxen (a 2-aryl propionic acid anti-inflammatory related to ibuprofen) involves palladium catalyzed hydroxycarbonylation of an aryl olefin which is itself made in a palladium catalyzed Heck coupling reaction (Figure 6b). Resolution is needed to obtain the (5)-enantiomer of naproxen since its optical isomer is a liver toxin. 

Related to the Heck reaction is the Larock annulation of internal alkynes, which is a general route to heterocyclic and carbocyclic systems. Especially attractive is the construction of the pharmaceutically important indole ring system via palladium-catalyzed coupling of 2-iodo-aniline and the corresponding V-methyl, acetyl, and tosyl derivatives with a wide variety of internal alkynes. The catalytic process appears to involve arylpalladium formation, regioselective addition to the carbon-carbon triple bond, and subsequent intramolecular palladium displacement.- ... 

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