Synthesis of monomers and polymers by the Heck reaction

Abstract

The Heck reaction allows the synthesis of monomers in a one-step reaction. Catalyzed by Pd, bromoarenes are reacted with ethylene to form substituted styrenes and symmetrical stilbenes. Unsymmetrical stilbenes are obtained from substituted bromoarenes and styrenes. Substituted hydroquinones and terephthalic acids are also available in high yields. Poly(l,4-phenylenevinylene) is obtained starting from 4-bromostyrene. Experimental partA typical procedure for the synthesis of a styrene and a stilbene derivative is given. Experimental conditions for other monomers are shown in Tab. 1.Reagents: DMF: distilled over 4,4 '-methylenedi(pheny1 isocyanate) and dibutyltin dilaurate as catalyst. Pd(OAc)2: used as received (Degussa). Tri-o-tolylphosphine: synthesized according to lit. '). Triethylamine, tributylamine: distilled over KOH. Styrene: used as received (stabilized with catechol). 4-Vinylbenzamide (6):A flame-dried pressure vessel of 100 ml volume was loaded under argon with 7 g (35 mmol) of p-bromobenzamide, 0,21 g (0,7 mmol) of tri-o-tolylphosphine, 0,078 g (0,35 mmol) of palladium acetate, 5,46 ml (40 mmol) of triethylamine, and a teflon@coated stir bar. 60 ml of DMF were added and a pressure of 72 bar ethylene (room temperature) applied. The autoclave was heated to 130°C for 24 h. The reaction mixture was precipitated with 400 ml of water and the solid dissolved in acetone. The filtered solution was concentrated and the residue was purified by sublimation. Yield: 3,7 g (72%), m.p. 176-177 "C, determined by DSC (lit.5): 170°C).

Poly(p-phenylene alkylene)s – A forgotten class of polymers

“…For example, Greiner and Heitz employed this useful organic chemistry tool to synthesize poly(p-phenylene vinylene) (PPV) and a variety of its derivatives, and other poly(arene vinylene)s from dibromoarenes and ethylene 57,[88][89][90] . Bao et al have also used the Heck reaction for the synthesis of PPVs, but in contrast to Greiner et al divinylbenzene was used as the olefin source 91) .…”

Soluble rigid-flexible polyethers containing bis(biphenyl)anthracene or bis(styryl)anthracene units in the main chain for light-emitting applications

“…9,10-Bis[p-acetoxystyryl] anthracene was synthesized in an onepot synthesis by the palladium-catalyzed Heck reaction 46 between 4-acetoxy-styrene and 9,10-dibromo-anthracene, as shown in Scheme 2. The coupling was easily carried out in DMF in the presence of a catalytic amount of Pd(OAc) 2 , a tertiary amine and triarylphosphine under a nitrogen atmosphere.…”

The Gilch Synthesis of Poly(p‐phenylene vinylenes): Mechanistic Knowledge in the Service of Advanced Materials

“…Examples are the Wessling, [26] sulfinyl, [27][28][29][30][31][32][33][34] sulfonyl, [35,36] xanthate, [37][38][39] dithiocarbamate, [40] Gilch, Heck, [69][70][71][72][73] Suzuki, [74,75] McMurry, [76] ring-opening metathesis, [77,78] acyclic diene metathesis, [79][80][81] Wittig, [82][83][84] Horner-Emmons, [85] Knoevenagel, [86] chemical vapor deposition, [87][88][89][90][91] and electropolymerization [92] methods. By assessing the pros and cons of all these approaches, the Gilch route stands out as one of the most powerful, versatile, and economically efficient approaches: simply by the treatment of a,a 0 -dihalogenated p-xylene derivatives 1 with potassium tert-butoxide (KO t Bu), high-molecular-weight PPVs 2 can be obtained in good to excellent yields (Scheme 1).…”