TY - JOUR A1 - Bramborg, Andrea A1 - Linker, Torsten T1 - Regioselective synthesis of alkylarenes by two-step ipso-substitution of aromatic dicarboxylic acids JF - European journal of organic chemistry N2 - A strategy for the regioselective alkylation of arenes was developed, starting from commercially available and inexpensive terephthalic acid or naphthalene-1,4-dicarboxylic acid. The method entails a formal ipso-substitution of the carboxylate groups by a sequence of reductive alkylation under Birch conditions and subsequent acid-mediated rearomatization with loss of carbon monoxide and carbon dioxide. More than 20 different arenes with various side-chains were synthesized. With naphthalene-1,4-dicarboxylic acid as starting material, we were able to control the degree of alkylation by choosing the appropriate electrophile in the Birch reduction. Thus, bisalkylated naphthalenes and naphthoic acids became available chemoselectively. All reactions afforded a single regioisomer exclusively in high yields. Overall, aromatic dicarboxylic acids are suitable substrates for a two-step ipso-substitution that allows the selective synthesis of alkylated benzenes and naphthalenes. KW - Synthetic methods KW - Alkylation KW - Birch reduction KW - Arenes KW - Regioselectivity Y1 - 2012 U6 - https://doi.org/10.1002/ejoc.201200823 SN - 1434-193X IS - 28 SP - 5552 EP - 5563 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Schmidt, Bernd A1 - Elizarov, Nelli A1 - Riemer, Nastja A1 - Hölter, Frank T1 - Acetamidoarenediazonium Salts: Opportunities for Multiple Arene Functionalization JF - European journal of organic chemistry N2 - Unlike their ortho counterparts, meta- and para-acetamidoanilines can be converted into the corresponding acetamidoarenediazonium salts. These offer various opportunities for multiple Pd-catalyzed arene functionalization reactions, such as Matsuda-Heck-, Suzuki-Miyaura- or Fujiwara-Moritani couplings. KW - Arenes KW - Amides KW - C-C coupling KW - Cross-coupling KW - Palladium Y1 - 2015 U6 - https://doi.org/10.1002/ejoc.201500795 SN - 1434-193X SN - 1099-0690 IS - 26 SP - 5826 EP - 5841 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Schmidt, Bernd A1 - Riemer, Martin A1 - Schilde, Uwe T1 - Tandem Claisen Rearrangement/6-endo Cyclization Approach to Allylated and Prenylated Chromones JF - European journal of organic chemistry N2 - Allyl, dimethylallyl and prenyl ethers derived from o-acyl-phenols reacted upon microwave irradiation to form C-allylated or -prenylated chromone derivatives, depending on the substitution pattern of the arene and the allyl substituent. The reaction proceeds through a tandem Claisen rearrangement and 6-endo-trig or 6-endo-dig cyclization sequence. For prenyl ethers, the tandem sequence can be extended by a Cope rearrangement to furnish 6-prenylchromones. The method is potentially useful for the synthesis of natural products and drugs. KW - Allylic compounds KW - Arenes KW - Oxygen heterocycles KW - Microwave chemistry KW - Rearrangement KW - Michael addition Y1 - 2015 U6 - https://doi.org/10.1002/ejoc.201501151 SN - 1434-193X SN - 1099-0690 IS - 34 SP - 7602 EP - 7611 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Baier, Heiko A1 - Kelling, Alexandra A1 - Holdt, Hans-Jürgen T1 - PEPPSI-Effect on Suzuki-Miyaura Reactions Using 4,5-Dicyano-1,3-dimesitylimidazol-2-ylidene-Palladium Complexes: A Comparison between trans-Ligands JF - European journal of inorganic chemistry : a journal of ChemPubSoc Europe N2 - The PEPPSI (Pyridine Enhanced Precatalyst Preparation, Stabilization and Initiation) complexes 12-15 with the structure [PdCl2{(CN)(2)IMes}(3-R-py)] (12: R = H; 13: R = Cl; 14: R = Br; 15: R = CN) bearing the maleonitrile-based N-heterocyclic carbene (NHC) (CN)(2)IMes ({(CN)(2)IMes}: 4,5-dicyano-1,3-dimesitylimidazol-2-ylidene) were prepared. Solid state structures of 14 and 15 were obtained. Complexes 14 and 15 adopt a slightly distorted square-planar coordination geometry in the solid state with the substituted pyridine ligand trans to the NHC. Catalytic activities of precatalysts 12-15 were studied and subsequently compared to complexes [PdCl2{(CN)(2)IMes}(PPh3)] (4) and [PdCl(dmba){(CN)(2)IMes}] (5) recently reported by our group in the Suzuki-Miyaura reaction of various aryl halides and phenylboronic acid. Reactions using previously reported [PdCl2(IMes)(py)] (IMes: 1,3-dimesitylimidazol-2-ylidene) (1) were also carried out and their results contrasted to those involving 12-15, 4 and 5. Differences in initiation rates and the catalytically active species related to the seven complexes in regards to the throw away ligand were investigated. Poisoning experiments with mercury show that palladium nanoparticles are responsible for the catalytic activity. KW - Carbene ligands KW - Palladium KW - Cross-coupling KW - Arenes Y1 - 2015 U6 - https://doi.org/10.1002/ejic.201500010 SN - 1434-1948 SN - 1099-0682 IS - 11 SP - 1950 EP - 1957 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Schmidt, Bernd A1 - Schultze, Christiane T1 - A one-pot synthesis of pyranocoumarins through microwave-promoted propargyl claisen rearrangement/wittig olefination JF - European journal of organic chemistry N2 - The reaction between propargyl ethers of hydroxybenzaldehydes and the ylide ethyl (triphenylphosphoranylidene)acetate was carried out under microwave irradiation to regioselectively afford angular pyranocoumarins. The chromene and coumarin heterocyclic scaffolds were simultaneously formed in the same synthetic step without changing the reaction conditions. The natural products seselin, braylin, and dipetalolactone were among the products synthesized by this method. KW - Domino reactions KW - Alkynes KW - Arenes KW - Oxygen heterocycles KW - Microwave chemistry KW - Rearrangement Y1 - 2017 SN - 1434-193X SN - 1099-0690 VL - 2018 IS - 2 SP - 223 EP - 227 PB - Wiley-VCH Verl. CY - Weinheim ER - TY - JOUR A1 - Krüger, Tobias A1 - Linker, Torsten T1 - Synthesis of gamma-spirolactams by Birch reduction of arenes JF - European journal of organic chemistry N2 - A convenient method for the synthesis of gamma-spirolactams in only three steps is described. Birch reduction of inexpensive and commercially available aromatic carboxylic acids in the presence of chloroacetonitrile affords nitriles in moderate to good yields. Suitable precursors are methyl-substituted benzoic acids, naphthoic, and anthroic acid. Subsequent catalytic hydrogenation proceeds smoothly with PtO2 or Raney Ni as catalysts and lactams are isolated in excellent yields and stereoselectivities. Thus, up to 3 new stereogenic centers can be constructed as sole diastereomers from achiral benzoic acids. Furthermore, it is possible to control the degree of saturation at different pressures, affording products with 0, 1, or 2 double bonds. Overall, more than 15 new gamma-spirolactams have been synthesized in analytically pure form. KW - Arenes KW - Birch reduction KW - Hydrogenation KW - Lactams KW - Synthetic methods Y1 - 2021 U6 - https://doi.org/10.1002/ejoc.202100056 SN - 1099-0690 VL - 2021 IS - 10 SP - 1585 EP - 1591 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Krüger, Tobias A1 - Bramborg, Andrea A1 - Kelling, Alexandra A1 - Sperlich, Eric A1 - Linker, Torsten T1 - Birch Reduction of Arenes as an Easy Entry to γ-Spirolactones JF - European journal of organic chemistry N2 - A convenient method for the synthesis of γ-spirolactones in only 2–3 steps is described. Birch reduction of inexpensive and commercially available aromatic carboxylic acids in the presence of ethylene oxide affords hydroxy acids, which undergo direct lactonization during work-up. Suitable precursors are methyl-substituted benzoic acids, naphthoic, and dicarboxylic acids. Subsequent hydrogenation proceeds smoothly with Pd/C as catalyst and saturated γ-spirolactones are isolated in excellent yields and stereoselectivities. Thus, up to 3 new stereogenic centers can be constructed as sole diastereomers from achiral benzoic acids. Furthermore, it is possible to control the degree of saturation with Raney nickel or Wilkinson's catalyst to obtain products with 1 double bond. Overall, more than 30 new γ-spirolactones have been synthesized in analytically pure form. KW - Arenes KW - Birch reduction KW - Hydrogenation KW - Lactones KW - Synthetic methods Y1 - 2021 U6 - https://doi.org/10.1002/ejoc.202101018 SN - 1434-193X SN - 1099-0690 VL - 2021 IS - 46 SP - 6383 EP - 6391 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Sand, Patrick A1 - Schmidt, Bernd T1 - Ruthenium-catalyzed sulfoalkenylation of acetanilides and dual-use of the catalyst directing group JF - European journal of organic chemistry N2 - In contrast to vinylsulfonates and vinylsulfones, vinylsulfonamides are unreactive in Pd-catalyzed oxidative Heck-coupling reactions with acetanilides. This limitation has been resolved by using a C-H-activation protocol based on Ru-Cu-Ag-catalysis. Overall, the Ru-Cu-Ag-catalyzed conditions turned out to be more reliable and showed better reproducibility than the Pd-catalyzed C-H-activation. The coupling products thus obtained are functionalized styrenyl sulfones and -sulfonamides which can be used as starting materials for the synthesis of sulfonyl pyrroles and sulfonyl pyrrolo[2,3-c]quinolines. KW - Arenes KW - C-H activation KW - Heterocycles KW - Ruthenium KW - Sulfonamides Y1 - 2021 U6 - https://doi.org/10.1002/ejoc.202101216 SN - 1434-193X SN - 1099-0690 VL - 2021 IS - 40 SP - 5497 EP - 5506 PB - Wiley-VCH CY - Weinheim ER -