Gold-catalyzed oxidation of arylallenes: Synthesis of quinoxalines and benzimidazoles

• Dong-Mei Cui,
• Dan-Wen Zhuang,
• Ying Chen and
• Chen Zhang

Beilstein J. Org. Chem. 2011, 7, 860–865, doi:10.3762/bjoc.7.98

• to form α-diketones and aldehydes in good yields is presented. Further directed synthesis of quinoxalines and benzimidazoles, via the condensation of the resulting α-diketones and aldehydes with benzene-1,2-diamine, was achieved in high yields. Keywords: allene; benzimidazole; gold-catalysis

• /hydration and oxidative cleavage of allenes to form α-diketones and aldehydes, and the synthesis of quinoxalines and benzimidazoles via the condensation of the resulting α-diketones and aldehydes with benzene-1,2-diamine [45][46][47][48][49][50][51][52][53][54][55][56]. Results and Discussion Our initial

• oxidative transformation under the same reaction conditions. Having prepared a variety of α-diketones and aldehydes successfully, we then undertook the synthesis of quinoxalines and benzimidazoles (Scheme 2). Thus, the treatment of the corresponding mixture of α-diketone 2 and aldehyde 3 with benzene-1,2

An overview of the key routes to the best selling 5-membered ring heterocyclic pharmaceuticals

• Marcus Baumann,
• Ian R. Baxendale,
• Steven V. Ley and
• Nikzad Nikbin

Beilstein J. Org. Chem. 2011, 7, 442–495, doi:10.3762/bjoc.7.57

• , with cimetidine being an exception. The use of such compounds has now been almost completely superseded by the prescription of alternative proton pump inhibitors such as esomeprazole. Imidazole containing drugs can be subdivided into two classes: monocyclic imidazoles and benzimidazoles. The former is

• ). This route has been used to prepare several ondansetron analogues based on different amine components. Benzimidazoles Nearly all benzimidazole containing drugs such as esomeprazole (190, Nexium), omeprazole (191, Prilosec), lansoprazole (192, Prevacid), pantoprazole (193, Protonix) and rabeprazole (194

• diaminobenzoates was obtained (Scheme 42) [64]. Telmisartan (217, Micardis) is a well known angiotensin II receptor antagonist used in the treatment of hypertension and, heart and bladder diseases. Its pharmacophore consists of two linked benzimidazoles and a biphenyl unit (Scheme 43). As shown previously, such

Palladium- and copper-mediated N-aryl bond formation reactions for the synthesis of biological active compounds

• Carolin Fischer and
• Burkhard Koenig

Beilstein J. Org. Chem. 2011, 7, 59–74, doi:10.3762/bjoc.7.10

• resulted in good yields [4][26]. Copper-diamine-catalysed N-arylation facilitated the arylation of pyrroles, pyrazoles, indazoles, imidazoles, triazoles, benzimidazoles and indoles [27][28][29]. Besides aryl halides as the aryl donor, arylsiloxanes [30], arylstannanes [31], iodonium salts [32], aryl lead

• ], benzimidazoles [40][41], sulfonamides [38], pyrroles [42] and lactams [43]. The three typical methods for N-arylation have been extensively reviewed concerning scope and limitation of these reactions [4][44][45][46][47][48]. However, the application of palladium- and copper-mediated N-arylation reactions in the

Enantiospecific synthesis of [2.2]paracyclophane- 4-thiol and derivatives

• Gareth J. Rowlands and
• Richard J. Seacome

Beilstein J. Org. Chem. 2009, 5, No. 9, doi:10.3762/bjoc.5.9

• recognition processes in biological systems as highlighted by Gmeiner [12][13][14] and as ligands or catalysts [43][44][45][46][47]. We have previously prepared planar chiral benzimidazoles [32] and wanted to extend the range of heterocycles that could be accessed. Diastereoisomer (Rp,RS)-5 was functionalised

ADDP and PS-PPh₃: an efficient Mitsunobu protocol for the preparation of pyridine ether PPAR agonists

• Paul S. Humphries,
• Quyen-Quyen T. Do and
• David M. Wilhite

Beilstein J. Org. Chem. 2006, 2, No. 21, doi:10.1186/1860-5397-2-21

• . As expected, oxazoles, thiazoles, pyrazoles, and pyridines are tolerated in this chemistry. In a limited number of cases, functionality (e.g. basic amines, benzimidazoles, indoles, etc.) caused no reaction to occur and only recovered starting materials were isolated (data not shown). We then shifted