Yamamoto coupling reactions

Lee and Hwang synthesized a PF with aryl side chains 6 via the Yamamoto coupling reaction [20]. The device fabricated therewith (ITO/PEDOT PSS/6/ Ca/Al) emits blue light with suppressed long tail emission but gives low performance with maximum efficiency of 0.03 cd A-1 and maximum luminance of 820 cd nr2. Note that the device could bear considerably high current density (>1.5 A cm-2). 

FIGURE 9.16 Syntheses of poly(3,6-carbazole)s by Grignard (A), electroreductive (B), and Yamamoto coupling reactions (C). 

Two approaches were available for the preparation of quaterrylene bisimides, taking advantage of either intramolecular cyclization or intermolecular dimerization reactions. These two methods were developed independently in Mullen s and Langhals groups. As shown in Scheme 7, Mullen s intramolecular approach started from bromination of perylene monoimide 74, which was subjected to Yamamoto coupling reaction to produce precursor 76, and the quaterrylene bisimide 77 was... 

By using a cocatalyst of Pd-Cu, aryl-alkenyl halides couple efficiently widi alkynes to generate die disubstituted alkynes (Scheme 9.6).8 This coupling reaction has been applied to die synthesis of polyphenyleneethynylenes by Yamamoto et al. in 1984 (Scheme 9.7).9a Due to the ready availability of diacetylenes and the mild coupling condition, this strategy has been widely used for die preparation of many poly(aryleneethynylene)s.9... 

The palladium-catalyzed multicomponent coupling reactions have attracted considerable interest.12,12a 12e A reaction using allylstannane 39 and allyl chloride 40 was applied to the three-component diallylation of benzylidenema-lonitrile and its congeners by Yamamoto et al 2 Analogous diallylation of isocyanate 41 was studied by Szabo et al. (Scheme 7).12a The reaction mechanism can be explained by formation of an amphoteric bis-allylpalladium intermediate 43 which undergoes an initial electrophilic attack on one of the allyl moieties followed by a nucleophilic attack on the other. 

In 1998, Yamamoto et al. reported the first catalytic enantioselective allylation of imines with allyltributylstannane in the presence of a chiral 7i-allylpalladium complex 23 (Scheme 9) [15]. The imines derived from aromatic aldehydes underwent the allylation with high ee values. Unfortunately, the allylation reaction of aliphatic imines resulted in modest enantioselectivities. They proposed that a bis-Jt-allylpalladium complex is a reactive intermediate for the allylation and reacts with imines as a nucleophile. The bis-Jt-allylpalladium complex seemed the most likely candidate for the Stille coupling [16]. Indeed, the Stille coupling reaction takes place in the presence of triphenylphosphine even if imines are present, whereas the allylation of imines occurs in the absence of the phosphine [17]. They suggested the phosphine ligand played a key role in controlling the... 

Palladium-mediated cydization based on the reactivity of o-alkynyl or alkenyl-phenyl isonitriles have been developed [105]. On the basis of their earlier studies on the three-component synthesis of allyl aryl cyanamides [106], Yamamoto and co-workers reported a palladium-catalyzed three-component coupling reaction of 2-alkynylisocyanobenzenes 122 with allyl methyl carbonate and trimethylsilylazide leading to N-cyanoindoles 125 [107]. One of the key steps of the proposed mechanism is the formation of 7i-allylpalladium carbodiimide 123 and its isomerization to rc-allylpalladium cyanamide complex 124 (Scheme 8.50). 

Yamamoto Y, Akiba K (1999) Ligand-Coupling Reactions of Compounds of Group 15 and Group 16 Elements. In Akiba K (ed) Chemistry of Hypervalent Compounds. Wiley-VCH,... 

Transition-metal-catalyzed synthesis of poly(arylene)s via carbon-carbon coupling reactions was started by Yamamoto et al. three decades ago [52,53] since then various carbon-carbon bond formation processes with transition-metal catalysts have been applied to polycondensation [54-57]. In recent years, Buchwald et al. and Hartwig et al. developed Pd-catalyzed amination and etherification of aromatic halides by using bulky, electron-rich phosphine ligands [58-60], and this chemistry has been applied to polycondensation for... 

K. Osakada, T. Yamamoto, Mechanism and Relevance of Transmetalation to Metal Promoted Coupling Reactions, Rev. Heteroatom Chem. 1999, 21, 163-178. 

Discoveries made in the late 1970s of electrical conductivity in conjugated polymers spawned a monumental interest in the study of these materials, which are ideally suited for synthesis via cross-coupling reactions. Yamamoto was the first to realize this possibility with a regiochemicahy defined synthesis of poly(/ -phenylene) formed via the Kumada-Corriu protocol. Since then, various cross-coupling reactions have been applied in condensation polymerization reactions,with the Suzuki and Sonogashira protocols gaining the most widespread use. 

Various carbon-carbon cross-coupling reactions are employed to arrive at oligomers from fluorene monomers, including nickel-cataylzed Yamamoto coupling between aryl halides [48], palladium(0)-catalyzed Suzuki coupling between boronic acids/esters and halides [49], and ferric-chloride-catalyzed Scholl reaction, also called Friedel-Crafts arylation, of bare fluorenes [50,51]. 

Scheme 1 Synthesis of polyfluorenes via Yamamoto and Suzuki coupling. With Suzuki coupling (AA-BB type coupling reaction), the synthesis of strictly alternating copolymers is possible...

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