Abstract
In medicinal chemistry, benzyloxy-benzaldehyde is a valuable intermediate, to which the attachment of a five membered heterocycle may be advantageous from the point of view of drug design. The starting iodo-benzyloxy-benzaldehydes were synthesized by the Obenzylation of o-, m- and p-hydroxybenzaldehydes with 2-, 3- and 4-iodobenzylbromides in refluxing acetone or acetonitrile in the presence of potassium carbonate and potassium iodide. Starting from the corresponding iodo-benzyloxy-benzaldehydes, the Suzuki-Miyaura carboncarbon cross-coupling reaction was utilized to get five membered heteroaryl-substituted benzyloxy- benzaldehydes. Various methods for Suzuki cross-coupling were studied. The applied boronic acids were 2- and 3-thiophene-boronic acids, as well as 2- and 3-furan-boronic acids. The reactions were followed by TLC and HPLC-UV-MS analysis. The products were purified by column chromatography. The original Suzuki method comprising NaOEt/EtOH, tetrakis(triphenylphosphine) palladium, in toluene was applied only in a few cases, resulting in poor yields. In several cases, the Suzuki coupling of substituted aryl iodides with 2-furanboronic acid failed to result in the formation of the expected products using the palladium acetate/tri(o-tolyl)phosphine/aqueous tripotassium phosphate/dimethoxyethan system. But reacting 3-thiophene-boronic acids with the corresponding iodo-benzyloxybenzaldehydes, this method afforded the products in 76-99% yields. The more powerful tetrakis(triphenylphosphine)palladium/aqueous cesium carbonate/ dimethylformamide system seemed to be more successful in cases of 2-thiophene boronic acid as well as 2- and 3-furan-boronic acids, providing the desired products in 75-93% yield. Twenty-six new compounds were synthesized.
Graphical Abstract
[http://dx.doi.org/10.1021/jm970599m] [PMID: 9484507]
[http://dx.doi.org/10.1016/S0040-4020(97)10233-2]
[http://dx.doi.org/10.2174/1570180813666160804142245]
[http://dx.doi.org/10.2174/1570180816666181106123809]
[http://dx.doi.org/10.1016/S0040-4020(02)01188-2]
[http://dx.doi.org/10.1021/jm060519r] [PMID: 17125252]
[http://dx.doi.org/10.1021/ol0158866] [PMID: 11405684]
[http://dx.doi.org/10.1021/ol010060p] [PMID: 11440566]
[http://dx.doi.org/10.1016/j.tetlet.2006.04.039]
[http://dx.doi.org/10.1016/j.bmcl.2008.12.011] [PMID: 19111461]
[http://dx.doi.org/10.1021/jm100665z] [PMID: 21080629]
[http://dx.doi.org/10.1016/S0968-0896(02)00600-4] [PMID: 12537995]
[http://dx.doi.org/10.1016/j.bmc.2004.07.010] [PMID: 15358286]
[http://dx.doi.org/10.1016/S0960-894X(03)00353-6] [PMID: 12798326]
[http://dx.doi.org/10.1021/jm0601598] [PMID: 16789742]
[http://dx.doi.org/10.1002/jhet.5570450109]
[http://dx.doi.org/10.1016/j.tetlet.2003.10.080]
[http://dx.doi.org/10.1016/j.tetlet.2014.08.058]
[http://dx.doi.org/10.1016/S0040-4039(01)95429-2]
[http://dx.doi.org/10.1021/cr00039a007]
[http://dx.doi.org/10.1002/ejoc.200501004]
[http://dx.doi.org/10.1039/b211329e] [PMID: 12638952]
[http://dx.doi.org/10.3987/COM-04-10224]
[http://dx.doi.org/10.1080/00397919108021778]
[http://dx.doi.org/10.1021/jm0611004] [PMID: 17480064]