Nucleophiles cross-coupling reactions

Recently, Baneijee et al. prepared a series of difluoro monomers with pendent trifluoromethyl groups using a Pd(0)-catalyzed cross-coupling reaction (Scheme 6.32).242,243 These monomers were converted to poly(arylene ether)s by nucleophilic displacement of the halogen atoms on the benzene ring with several... 

Palladium catalyzed cross-coupling reactions of arylhalides or halide equivalents with various nucleophiles have been shown to be highly effective and practical... 

The hydrosi(ly)lations of alkenes and alkynes are very important catalytic processes for the synthesis of alkyl- and alkenyl-silanes, respectively, which can be further transformed into aldehydes, ketones or alcohols by estabhshed stoichiometric organic transformations, or used as nucleophiles in cross-coupling reactions. Hydrosilylation is also used for the derivatisation of Si containing polymers. The drawbacks of the most widespread hydrosilylation catalysts [the Speier s system, H PtCl/PrOH, and Karstedt s complex [Pt2(divinyl-disiloxane)3] include the formation of side-products, in addition to the desired anh-Markovnikov Si-H addition product. In the hydrosilylation of alkynes, formation of di-silanes (by competing further reaction of the product alkenyl-silane) and of geometrical isomers (a-isomer from the Markovnikov addition and Z-p and -P from the anh-Markovnikov addition. Scheme 2.6) are also possible. 

The progress on S-C bond activation, which covers the reduction of a C-S bond to a C-H bond, cross coupling reaction of sulfides with main group organometaUic nucleophiles, ring opening reactions of thietanes and thiiranes, and desulfurization of thiols, sulfides, and thiophenes has already been reviewed elsewhere [6-10], and... 

A reverse cross-coupling reactions mediated by palladium was used to develop a colorimetric sensitive chemodosimeter for the detection of trace palladium (II) salts [93]. The decolorization of 4 is produced by a nucleophilic attack of ethanethiol in basic DMSO solutions. Palladium detection is done via thiol scavenging from the 4-ethanethiol complex leading to a color turn-on of the parent squaraine. Naked-eye detection of Pd(NC>3)2 is as sensitive as 0.5 ppm in solution, and the instrument-based detection can go as low as 0.1 ppm. 

Organomercuric compounds require nucleophilic assistance by soft iodide anions (cf. Section 9.6.3.2.2) for participation in cross-coupling reactions.158 The reaction is useful for aryl-aryl cross-coupling in those cases in which the organomercury species are obtained by direct mercuration of aromatic compounds (38).159... 

As described above, our synthetic strategy involves the convergent construction of the central cyclopentanone ring with a carbonylative cross-coupling reaction and a photo-Nazarov cyclization reaction (Chart 2.2). The electrophilic coupling component 51 was synthesized by an intramolecular Diels-Alder reaction [34] and the nucleophilic coupling component 52 by a vinyiogous Mukaiyama aldol reaction [35]. 

Scheme 6.20 Sequential one-pot nucleophilic aromatic substitution and Suzuki cross-coupling reactions.

Scheme 6.21 One-pot nucleophilic substitutions and Suzuki cross-coupling reactions for the synthesis of nAChR antagonists.

As shown in the previous sections, a (cr-allenyl)palladium species, which is formed from a propargyl electrophile and a Pd(0) catalyst, reacts with a hard carbon nucleophile in a manner analogous to the Pd-catalyzed cross-coupling reaction to give a substituted allene. The results indicate that the reactivity of the (cj-allenyl)palladium species is similar to that of an alkenylpalladium intermediate. Indeed, it was found that the (cr-allenyl)palladium species reacted with olefins to give vinylallenes, a reaction process that is similar to that of the Heck reaction of alkenyl halides [54]. 

Transition metal-catalyzed allylic substitution with phenols and alcohols represents a fundamentally important cross-coupling reaction for the construction of allylic ethers, which are ubiquitous in a variety of biologically important molecules [44, 45]. While phenols have proven efficient nucleophiles for a variety of intermolecular allylic etherification reactions, alcohols have proven much more challenging nucleophiles, primarily due to their hard, more basic character. This is exemphfied with secondary and tertiary alcohols, and has undoubtedly limited the synthetic utihty of this transformation. 

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