Heck coupling procedure

Dioxane is an equally suitable solvent for these Heck couplings (and is the solvent used in the published procedures) however, due to the lower cost and the lower toxicity of toluene, it was chosen as the solvent for these reactions. 

General procedure for Heck coupling. A mixture of POPd (16.0 mg, 6 mol%), quinoline derivative (0.56 mmol), tert-butyl acrylate (356 mg, 2.8 mmol), and base (0.61 mmol) was stirred in 5 mL of anhydrous DMF at 135 °C for 24 h. The reaction mixture was allowed to cool to room temperature, quenched with water, and extracted with Et20. The combined organic layers were washed with water, dried over MgS04, and the solvents were removed under vacuum. The crude products were purified by flash chromatography on silica gel. 

A very recent addition to the already powerful spectrum of microwave Heck chemistry has been the development of a general procedure for carrying out oxidative Heck couplings, that is, the palladium)11)-catalyzed carbon-carbon coupling of arylboronic acids with alkenes using copper(II) acetate as a reoxidant [25], In a 2003 publication (Scheme 6.6), Larhed and coworkers utilized lithium acetate as a base and the polar and aprotic N,N-dimethylformamide as solvent. The coupling... 

In a similar approach, p-phenylene vinylene oligomers containing 3- to 6-mers have been grown on DOPO-Br capped NCs by homocoupling of l-bromo-2,5-di-n-octyl-4-vinylbenzene.133 Finally, using a one-step procedure, vinyl-terminated poly(hexylthiophene) has been grafted onto DOPO-Br coated NCs via Heck coupling.134... 

The first step is to make an indole by Pd(II)-catalysed cyclization in the presence of benzoquinone as reoxidant. The nucleophilic nature of the 3-position of the indole (Chapter 43) was exploited to introduce the required iodine functionality. Rather than direct iodination, a high yielding two-step procedure involving mercuration followed by iodination was employed. The more reactive iodide was then involved in a Heck coupling with an unsaturated side chain in the absence of phosphine... 

Emmons reaction (Scheme 26). ° Horner-Wadsworth-Emmons reactions also feature in new routes to (diphenylphosphono)acetic acid esters and alkenes. The latter involve combining the Homer-Wadsworth-Emmons procedure with a Heck coupling reaction for the synthesis of tri-substituted alkenes. 

General procedure for a Heck coupling on a 2% cross-linked polystyrene support (Scheme 14) [9] ... 

Palladium-catalyzed cro.ss-coupling reactions were also reported. In Smith s synthesis of the lipoprotein-associated phospholipase A2 inhibitor discussed in Section 6.2.2.1, the cyclization precursor 23 was prepared by a Heck coupling between bromopyrimidine 55 and ethyl acrylate to give 56, which was then converted to 23 following conventional procedures <01BMCL701>. Yields were not reported. 

Orr/zc- em-Dihalovinylanilines 278 were also used in another example of a Buchwald-Hartwig-type/Mizoroki-Heck reaction for the synthesis of 2-vinylic indoles 279 (Scheme 8.69). Lautens and coworkers [140] recently illustrated a domino coupUng under Jeffery s condition where the aniline nitrogen undergoes an amination step followed by a Mizoroki-Heck coupling with various alkenes. In this process, electronic factors and steric hindrance of the different substituents had only a small effect on the yield however, in the formation of 3-substituted indoles using this method only very poor yields were obtained. The procedure can also be performed in an intramolecular mode leading to tricycUc compounds such as pyridino and azepino indoles 281 and 282 (Scheme 8.69). 

Reddy and collaborators reported a new one-pot, three-component procedure toward the synthesis of novel 4-phenyl-2-[3-(alkynyl/alkenyl/aryl) phenyl] pyrimidine libraries starting with the Michael addition of enaminone 64 with 3-bromobenzimidamide hydrochloride (65) (Scheme 28) (13S75). This was followed by a cyclization, an isomerization, a dehydration, and a subsequent Sonogashira reaction with terminal alkynes or a Suzuki reaction with arylboronic acids or a Heck coupling reaction with alkenes. 

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