Sonogashira reactions poly

Yamamoto and Plenio introduced ferrocene units into PAEs and prepared redox-active PAEs 70 [107,109]. Yamamoto coupled l,l -diiodoferrocene to a diethynylarene by either a Sonogashira reaction or by utilizing alkynylgrignard reagents (Scheme 6.25). Plenio reported poly(l,3-ferrocenyleneethyny-lene)s 70d (Scheme 6.26) by a clever metallation strategy. Polymers 70 are structurally novel but have not found any applications. They might be useful as active layers in transistor-types due to their ease of oxidation. 

Some drawbacks of the precursor routes mentioned above have been overcome by the use of polycondensation- and C-C-bond-coupling reactions. To produce soluble PPV-, poly(thiophene)-, or poly(pyrrol) derivatives for spin coating preparation, various types of transition metal catalyzed reactions, such as the Heck-, Suzuki-, and Sonogashira-reaction, Wittig- and Wittig-Horner-type coupling reactions, or the McMurry- and Knoevenagel-condensation have been utilized. 

Oligomerization on solid phase via the Sonogashira reaction has also been carried out by Hwang and Tour in the preparation of 24 tetrameric oligo(phenylene ethynylene)s [104], as well as by Diederich and coworkers [105,106], who prepared poly(triacetylene)-derived oligomers displaying high fluorescence intensities. Triazene linkers, to attach the scaffold to a polystyrene resin, were also employed in these two cases. On-bead homo-... 

It was also shown that poly(ethylene glycol) (PEG), but not ILs, was the suitable solvent for Sonogashira reaction using carbapalladacycle complex as catalyst, Scheme 2.12 [55]. Here, the influence of [BMIm][PF, ], [BMMIm][PFg], [BMImJCl, and PEG on the reaction of l-(4-bromophenyl)ethanone and phenylacetylene was compared with CsOAc as co-catalyst. Under optimized reaction conditions and with a solvent-to-substrate ratio of 50 (w/w), the yields to the coupling product were 0%, 52%, 2%, and 88% in these four solvents. In the case of using PEG as solvent, CsOAc can be well dissolved in PEG and an active Pd NPs/PEG catalyst system could be obtained during the first run. The whole catalyst system could be recovered and reused for the next run without deactivation. Meanwhile, although Pd NPs were also formed in [BMIm][PF5] and [BMIm]Cl, the poor solubility of CsOAc in ILs resulted in low catalytic activity. 

The Pd-catalyzed C-C coupling (Sonogashira coupling) was applied to polymer synthesis about 20 years ago [23-25], and has especially been developed for the synthesis of n-conjugated poly(aryleneethynylene)s (PAEs) (for reviews, see refs. [16,26-33]). Recently other synthetic routes for PAEs were also developed, e.g., the alkyne metathesis method [28, 34] and the coupling reaction of =C-MR3 with R X (M=Si [35, 36] or Sn [37, 38]). In this review, we are concerned with the synthesis and chemical properties of PAEs with heteroaromatic rings. 

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. 

Utesch, N. F., Diederich, F. Acetylenic scaffolding on solid support Poly(triacetylene)-derived oligomers by Sonogashira and Cadiot-Chodkiewicz-type cross-coupling reactions. Org. Biomol. Chem. 2003,1, 237-239. 

Another palladium-catalyzed coupling reaction performed successfully on soluble polymers is the Sonogashira coupling. In a more recent report it was reported that PEG 4000 acts simultaneously as polymeric support, solvent, and phase transfer catalyst (PTC) in both steps, coupling and hydrolysis [72]. Poly(ethylene glycol) (PEG)-bound 4-iodobenzoic acid was readily reacted with several terminal alkynes under rapid microwave conditions (Scheme 16.50). Cleavage of the coupling products from the PEG support was achieved efficiently by simple saponification with brief microwave irradiation in an open beaker in a domestic microwave oven. 

In catalytic Pd(0) reactions, this phosphonium salt was treated with a Pd(ll) source, base, and substrates to form an active catalyst for Sonogashira, Suzuki, and Heck coupling chemistry (Eq. 42, Eq. 43, Eq. 44). The reactions used 0.5 mol% of the Pd catalyst, >99.9% of which was recovered based on Pd analysis of the filtrate of a nanofiltration using UV-visible and total reflection X-ray fluorescence analysis. The spectroscopic analyses reportedly could detect as little as 0.05% of the 0.01 mmol of starting Pd catalyst in the leachate. The membrane used in this chemistry was a solvent-resistant nanofiltration membrane consisting of a porous poly(acrylonitrile) layer and a dense surface layer of poly(dimethylsiloxane). This membrane worked through nine cycles in the... 

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