Heck-coupling polymerization

The coupling reaction of aryl-alkenyl halides with alkenes in the presence of a palladium catalyst and a base is known as the Heck coupling (Scheme 9.4).6 Since the early 1980s, this type of coupling reaction has been used for die syndiesis of poly(arylenevinylene) and related polymers by polymerization of AB- or AA/BB-type of monomers (Scheme 9.5).7... 

Most commercial palladium scavengers are designed for use after a reaction - thus at low temperatures. Is the solid poison being considered stable at the temperatures of the reaction Many Heck couplings are used at well over 100°C and some polymeric poisons may bre down under these conditions. This could lead to ineffective poisoning of solution species as well as unwanted interaction of small molecule degradation products with supported palladium species. 

Tab. 6.5 Selected Heck coupling experiments with polymeric amphiphiles (experimental data are listed in Scheme 6.6, reaction time=7 h).

A sequence of an inter- and an intramolecular Heck coupling has been used to construct the 26-membered carbocyclic compound 60 from an acyclic precursor 59, which presents half of the target molecule (Scheme 20). The first step of this twofold coupling is favored to occur inter- rather than intramolecularly, because the latter would lead to a highly strained 13-membered ring system with a biaryl unit and a frans-configmed double bond. In the cyclizing second step, polymerization is disfavored by the orientation of the two side arms in the 3- and 3 -positions of the initially formed 1,1 -biaryl derivative. 

Mizoroki-Heck reaction, for cross-coupling polymerization,... 

Without reporting actual catalysis data, Scarpello et al. screened several commercial polymeric membranes for the separation of the Jacobsen catalyst, Pd-BI-NAP and Wilkinson catalyst out of relevant reaction solvents [21]. Turlan et al. even used zeolite membranes with a pore radius of 0.55 nm (silicalite) to separate Pd complexes from a DM Ac-dissolved Heck coupling product [22]. 

After impregnation of the polymeric support material with paUadium(II) tri-(o-tolyl)phosphine complexes the resulting catalyst material was tested in the Heck coupling of bromobenzene with butyl acrylate in DMF to yield 75% of -3-phenylacrylic... 

Different polystyrene-bound biscyclopentadienyl complexes have been prepared. One example is shown as 69 in Eq. 5-9 [180]. Treatment of soluble copolymers of styrene and methacrylic acid with dichlorotitanocene resulted in soluble titanium-containing copolymers 70 (Eq. 5-10] [181]. Finally polymeric organometallic mesogens 71 with [l,3-(diethynyl)cyclobutadiene]cyclopentadi-enyl Co(II) moieties were prepared by Heck coupling of a corresponding cyclobutadiene monomer with 2,5-diiodothiophene [182],... 

Cyclobutadiene moieties in the main chain provide a useful site for the attachment of metals to polymeric structures. For example, a variety of wellwith complexed cyclobutadiene units in the main chain have been prepared by Pd-catalyzed Heck coupling (Eq. 4.7),... 

Other examples involve Mizoroki-Heck couplings of aryl bromides using a sulfur linker cleaved nnder very mild conditions in the presence of samarium iodide [17, 18], the solid-supported hyperbranched polymerization of phenylacetylene derivatives [19] or a... 

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