Yamamoto coupling

Two pyrene-based oligomers (dimer 59 a, trimer 59 b) were generated by Mullen et al. [72] via Yamamoto coupling of mixtures of 2- (mono)- and 2,7-dibromo-pyrene. 

SCHEME 2.51 Synthesis of perylene-fluorene and a-cyanostilbene-fluorene copolymers via Yamamoto coupling. (From Klarner, G., Lee, J.-I., Davey, M.H., and Miller, R.D., Adv. Mater., 11, 115, 1999.)... 

The methods that have been examined for producing polarised EL include the use of liquid crystalline chiral oligomers and polymers. - Promising results have been obtained using conjugated polymers where fluorene makes up the backbone, e.g. (5.6), which was synthesised from the dibromo monomer via Yamamoto coupling. These types of material exhibit LC behaviour at transition temperatures of 100-200 °C, and produce blue polarised EL (425 nm) from thin flhns. °... 

TABLE 2. Spirobifluorene Copolymers Prepared by Yamamoto Coupling of... 

Random copolymers 596a-d synthesized by Yamamoto coupling of a fluorene and thiophene-base (02MI199 02MM1224). 

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). 

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]. 

Consequently, by combining the synthetic procedure of Yamamoto [26] with the introduction of more extended solubilizing substituents, advantageous results were expected. Accordingly, alkyl-substituted dihydrophenanthrenes or tetrahy-dropyrenes offered themselves as starting monomers for the preparation of soluble step-ladder PPPs of this type. 2,7-Dibromo-4,9-dialkyl-4,5,9,10-tetrahydro-pyrenes (10) represent suitable starting monomers for the realization of this synthetic route. These difunctionalized tetrahydropyrene monomers were first prepared by Mullen et al. and reacted in a Yamamoto coupling [27]. 

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

This type of polymerization is referred to as Yamamoto coupling. Polymers prepared by Yamamoto coupling exhibit a higher degree of polymerization than those prepared by the Heck reaction. ... 

One of these was aimed at the elaboration of a precursor route. Kaeriyama et al. [12] reported on the Yamamoto coupling of l,4-dibromo-2-methoxycarbonylben-zene to poly(2-methoxycarbonyl-l,4-phenylene) (2) as a processable PPP precursor. The aromatic polyester precursor 2 is then saponified and thermally decarboxylated to 1 with CuO catalysts. However, the reaction conditions of the final step are quite drastic and cannot be carried out in the solid state (film). 

Figure 1.32 Schematic for formation oifully conjugated D-A-D TBC (P3HT-b-PPyPh-b-P3HT, i.e., P13) via sequential polymeri2ation approach using Yamamoto coupling and subsequent cyclization. Reprinted from [452] with permission from ACS.

Thus, the Yamamoto coupling of monobrominated perylene monoimide 71 provided N-alkyl and N-arylbiperylenyls 72 in 83-89% yield. In contrast... 

Example 6.6 Synthesis of Poly[9,9-bis(2-Ethylhexyl)Fluorene] Via Yamamoto Coupling... 

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