Suzuki symmetrically substituted

Thus, for our present purposes a similar approach was followed using Suzuki cross-coupling reactions as the key steps in the synthesis of our target compounds. Symmetrically substituted compounds were synthesized in a twofold Suzuki crosscoupling reaction from commercially available p-substituted phenylboronic acids or esters and 4,4 -dibromobiphenyl or 4,4 -biphenyl-bis-boronic acid ester and a p-substituted arylhalide, respectively, using tetrakis (triphenylphosphino) palladium as catalyst together with cesium fluoride as base in dry tetrahydrofurane as shown in Scheme 8.1. The desired products were obtained in respectable yields after heating at reflux for 50 h. 

Suzuki and co-workers first published on the topic of enantioselective transesterification in 2004 [140, 141]. This process exploits C -symmetric imidazolium salts with various substitutions. When vinyl propionate 281 acts as the acyl donor, ester 282 is isolated in 68% ee at 19% conversion, corresponding to an s value of 6.1 (Eq. 27). 

Product 117 is a convenient starting compound for the subsequent modification of photochromes. Publication (09TL1614) gives an efficient synthetic route to both symmetrical 118 and unsymmetrical 119 phenyl-substituted dihetarylethenes bearing amino, hydroxy, or carboxy groups based on a Suzuki reaction of dichloride 117 with commercially available substituted boronic acids (or their pinacol esters) in a dimethyl ether (DME)-H20 mixture (4 1). For the symmetrical products, the yields are 85-95% for the unsymmetrical products, they are 60%. 

In the following the development is presented of a general approach for the synthesis of symmetrically and differently l,4" -substituted p-quaterphenylenes by application of a reliable Suzuki cross-coupling strategy. Experimental details are not given here but can be found elsewhere [51-53]. Note that organic synthesis is a key step for the bottom-up nanotechnology approach. 

Yang X, Don X, Mullen K (2008) Efficient synthesis of symmetrically and unsymmetrically substituted hexaphenylbenzene analogues by Suzuki-Miyaura coupling reactions... 

Treatment of a benzyl-substituted and symmetrical bis-enol tri-flate with various aryl boronic acids in the presence of Pd(OAc)2 results in a Suzuki-Miyaura cross-coupling reaction, then an intramolecular Heck reaction between the remaining triflate residue and the benzyl group and so as to give the illustrated product (eq 96).i i... 

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