Heck-type process

Many reactions have been recently reported, which involve palladium migration along an aromatic skeleton. For example, a Heck-type process led to the anticipated 3-substituted pyridyl, Heck product as well as a crossover product (Equation (157)). 

Two important groups of reactions of the type outlined in equation (1) are not included in this chapter, as they are reviewed elsewhere in Comprehensive Organic Synthesis. Firstly, Heck-type processes (Y = H equation 1) are discussed in Volume 4, Chapter 4.3. A second way to effect the overall process indi-... 

Figure 4.17 Proof of concept for a Mizoroki-Heck-type process releasing carbon monoxide and water as the only waste.

In the Mizoroki-Heck reaction, the catalysis begins with the oxidative addihon of a C(sp )—X bond to a palladium(O) complex to give a C(sp )—Pd(II) complex common to almost all palladium(O)-catalyzed cross-coupling reachons (cf. Section 7.2.1). There are, however, alternative ways to generate the central o-aryl palladium(II) intermediate and to effect a Mizoroki-Heck-type process (Scheme 7.42). 

Transition metal enolate complexes have been prepared with most or all transition metals, and the enolate ligands have been shown to adopt a variety of bonding modes. Bofli early and late transition metal enolate complexes are intermediates in a number of important catalytic processes. Early transition metal enolates are important intermediates in asymmetric aldol reactions that exploit the Lewis acidic character of early metals. Late transition metal enolates are intermediates in aldol and Michael addition processes, -Saegusa oxidations,Heck-type processes, catalytic asymmetric conjugate additions, - and cross coupling of enolate nucleophiles. - ... 

Clearly, the promoter-less coupling discussed previously follows a pathway that is mechanistically distinct from all the other reported palladium-catalyzed silanol cross-couplings, namely, that of a Heck-type process. Another use of organosi-lanols in coupling reactions that proceed by a unique pathway has been reported by Sames et al. [48] In studies with the ortho-t-butylaniline substrate 75 (arising... 

A large number of nitrogen heterocycles can be synthesized by Pd -catalyzed cyclization of aminoalkenes. The first reported intramolecular aminopalladation of olefins mediated by Pd consisted of the cyclization of o-allylic anilines to 2-methylindoles. Both catalytic and stoichiometric procedures were developed using PdCl2(CH3CN)2 as catalyst (eq 14). This reaction features high yields, and tolerance toward functional groups and substitution on the allyl side chain. When the aniline substrate bears a methallyl side chain, palladium 8-hydride elimination is prevented and the cyclized alkylpalladium intermediate can be trapped by olefins in a Heck-type process (eq 15). Similar conditions have been used to convert o-amino styrenes into indoles. ... 

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