The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Masatomo Iwao - One of the best experts on this subject based on the ideXlab platform.
-
asymmetric synthesis of 3 substituted 8 hydroxy 3 4 Dihydroisocoumarins from s 4 isopropyl 2 2 methoxy 6 methylphenyl oxazoline
Tetrahedron, 2007Co-Authors: Katsuya Uchida, Tsutomu Fukuda, Masatomo IwaoAbstract:Abstract Reaction of the laterally lithiated (S)-4-isopropyl-2-(2-methoxy-6-methylphenyl)oxazoline with p-tolualdehyde gave an inseparable mixture of the addition products in low diastereoselectivity. However, the (S,S)-product cyclized to the corresponding 3,4-dihydroisocoumarin faster than the (S,R)-product on silica gel, which allowed to be produced both enantiomers of 8-methoxy-3-(p-tolyl)-3,4-dihydroisocoumarin in moderate to good optical purity [S-enantiomer: 75% ee; R-enantiomer: 96% ee]. This procedure was applied to the short-step synthesis of optically active 3,4-dihydroisocoumarin natural products such as (R)-8-hydroxy-3-(1-tridecyl)-3,4-dihydroisocoumarin and (R)-phyllodulcin.
-
asymmetric synthesis of 3 substituted 3 4 Dihydroisocoumarins via stereoselective addition of laterally lithiated chiral 2 o tolyl oxazolines to aldehydes followed by diastereomer selective lactonization
Tetrahedron, 2005Co-Authors: Yuji Kurosaki, Tsutomu Fukuda, Masatomo IwaoAbstract:Lateral lithiation of (S)-4-isopropyl-2-(o-tolyl)oxazoline in diethyl ether followed by the reaction with aldehydes in the presence of TMEDA produced the addition products with stereoselectivities up to 84% de. Utilization of TMEDA as a ligand is essential for the good selectivity. Rationale for the stereoselectivity is proposed based on ab initio calculation of the lateral lithio species. The major (S,S)-products lactonized faster than the minor (S,R)-products to the corresponding 3,4-Dihydroisocoumarins under acidic conditions. Thus, (3S)-3,4-Dihydroisocoumarins were obtained in good optical purities up to 97% ee by sequential application of these matched stereoselective reactions.
-
synthesis of 3 substituted 8 hydroxy 3 4 Dihydroisocoumarins via successive lateral and ortho lithiations of 4 4 dimethyl 2 o tolyl oxazoline
Tetrahedron Letters, 2004Co-Authors: Naruki Tahara, Tsutomu Fukuda, Masatomo IwaoAbstract:Abstract Sequential treatment of 4,4-dimethyl-2-(o-tolyl)oxazoline in THF with sec-BuLi, aromatic or aliphatic aldehydes, sec-BuLi, B(OMe)3, and H2O2 produced the laterally alkylated and ortho-hydroxylated oxazolines in one-pot. Treatment of these products with TFA in aqueous THF provided 3-substituted 8-hydroxy-3,4-Dihydroisocoumarins in 44–75% overall yields. This procedure allowed the short synthesis of (±)-hydrangenol and (±)-phyllodulcin, naturally occurring 3,4-Dihydroisocoumarins of pharmacological interest. A more economical synthesis of (±)-phyllodulcin via the trianion intermediate is also described.
Frank Glorius - One of the best experts on this subject based on the ideXlab platform.
-
ruthenium nhc diamine catalyzed enantioselective hydrogenation of isocoumarins
Journal of the American Chemical Society, 2017Co-Authors: Wei Li, Mario P. Wiesenfeldt, Frank GloriusAbstract:A novel and practical chiral ruthenium–NHC–diamine system is disclosed for the enantioselective hydrogenation of isocoumarins, which provides a new concept to apply (chiral) NHC ligands in asymmetric catalysis. A variety of optically active 3-substituted 3,4-Dihydroisocoumarins were obtained in excellent enantioselectivities (up to 99% ee). Moreover, this methodology was utilized in the synthesis of O-methylmellein, mellein, and ochratoxin A.
-
Ruthenium–NHC–Diamine Catalyzed Enantioselective Hydrogenation of Isocoumarins
2017Co-Authors: Mario P. Wiesenfeldt, Frank GloriusAbstract:A novel and practical chiral ruthenium–NHC–diamine system is disclosed for the enantioselective hydrogenation of isocoumarins, which provides a new concept to apply (chiral) NHC ligands in asymmetric catalysis. A variety of optically active 3-substituted 3,4-Dihydroisocoumarins were obtained in excellent enantioselectivities (up to 99% ee). Moreover, this methodology was utilized in the synthesis of O-methylmellein, mellein, and ochratoxin A
Vicente Gotor - One of the best experts on this subject based on the ideXlab platform.
-
one pot synthesis of enantiopure 3 4 Dihydroisocoumarins through dynamic reductive kinetic resolution processes
Organic Letters, 2013Co-Authors: Juan Mangassanchez, Vicente Gotor, Eduardo Busto, Vicente GotorfernandezAbstract:A straightforward chemoenzymatic synthesis of enantiopure 4-alkyl-3-methyl-3,4-Dihydroisocoumarins through a ketoreductase-catalyzed one-pot dynamic reductive kinetic resolution is reported. E. coli/ADH-A cells have shown outstanding diastereo- and enantioselectivity toward the bioreduction of a series of racemic ketones, with the use of anion exchange resins or triethylamine being compatible in the same aqueous reaction medium. The so-obtained enantiopure alcohols were subsequently cyclized in acid media affording the corresponding lactones in good to excellent conversions (72–96%) and excellent selectivities (dr ≥99:1 and ee >99%).
-
enantiopure 3 methyl 3 4 Dihydroisocoumarins and 3 methyl 1 2 3 4 tetrahydroisoquinolines via chemoenzymatic asymmetric transformations
Catalysis Science & Technology, 2012Co-Authors: Juan Mangassanchez, Eduardo Busto, Vicente Gotorfernandez, Vicente GotorAbstract:A new divergent and asymmetric synthetic route has been developed for the production of enantiomerically pure isocoumarin and isoquinoline derivatives. Stereoselective formation of 2-(2-hydroxypropyl)benzonitriles has been identified as the key step. Rhizomucor miehei lipase has displayed from moderate to excellent selectivities in the acetylation of its (R)-enantiomers, while ADH-A from Rhodococcus ruber catalyzed the bioreduction of the corresponding ketones with excellent activities and stereopreferences. Enantiopure alcohols obtained in this manner have been used for the straightforward synthesis of a series of 3-methyl-3,4-Dihydroisocoumarins and 3-methyl-1,2,3,4-tetrahydroisoquinolines with good overall yields.
-
Synthesis of chiral 3-alkyl-3,4-Dihydroisocoumarins by dynamic kinetic resolutions catalyzed by a Baeyer-Villiger monooxygenase.
The Journal of organic chemistry, 2010Co-Authors: Ana Rioz-martínez, Marco W. Fraaije, Daniel Torres E. Pazmiño, Gonzalo De Gonzalo, Vicente GotorAbstract:Baeyer−Villiger monooxygenases have been tested in the oxidation of racemic benzofused ketones. When employing a single mutant of phenylacetone monooxygenase (M446G PAMO) under the proper reaction conditions, it was possible to achieve 3-substituted 3,4-Dihydroisocoumarins with high yields and optical purities through regioselective dynamic kinetic resolution processes.
Peter Langer - One of the best experts on this subject based on the ideXlab platform.
-
chelation control in the formal 3 3 cyclization of 1 3 bis silyloxy 1 3 butadienes with 1 hydroxy 5 silyloxy hex 4 en 3 ones one pot synthesis of 3 aryl 3 4 Dihydroisocoumarins
Tetrahedron, 2010Co-Authors: Ihsan Ullah, Muhammad Sher, Asad Ali, Rasheed Ahmad Khera, Muhammad Farooq Ibad, Alexander Villinger, Christine Fischer, Peter LangerAbstract:The [3+3] cyclization of 1,3-bis(silyloxy)-1,3-butadienes with 1-hydroxy-5-silyloxy-hex-4-en-3-ones resulted in the one-pot formation of 3-aryl-3,4-Dihydroisocoumarins. The reactions proceeded by regioselective cyclization to give 6-(2-aryl-2-chloroethyl)salicylates, which underwent a silica gel-mediated lactonization. The cyclizations of protected 1-amino-5-silyloxy-hex-4-en-3-ones proved to be not regioselective.
-
synthesis of 3 aryl 3 4 Dihydroisocoumarins by regioselective domino 3 3 cyclization lactonization reactions of 1 3 bis silyloxy 1 3 butadienes with 1 hydroxy 5 silyloxy 4 en 3 ones
Tetrahedron Letters, 2008Co-Authors: Muhammad Sher, Asad Ali, Helmut Reinke, Peter LangerAbstract:Abstract The [3+3] cyclization of 1,3-bis(silyloxy)-1,3-butadienes with 1-hydroxy-5-silyloxy-4-en-3-ones afforded 6-(2-aryl-2-chloroethyl)salicylates, which were transformed into 3-aryl-3,4-Dihydroisocoumarins by silica gel-mediated lactonization.
Muhammad Sher - One of the best experts on this subject based on the ideXlab platform.
-
chelation control in the formal 3 3 cyclization of 1 3 bis silyloxy 1 3 butadienes with 1 hydroxy 5 silyloxy hex 4 en 3 ones one pot synthesis of 3 aryl 3 4 Dihydroisocoumarins
Tetrahedron, 2010Co-Authors: Ihsan Ullah, Muhammad Sher, Asad Ali, Rasheed Ahmad Khera, Muhammad Farooq Ibad, Alexander Villinger, Christine Fischer, Peter LangerAbstract:The [3+3] cyclization of 1,3-bis(silyloxy)-1,3-butadienes with 1-hydroxy-5-silyloxy-hex-4-en-3-ones resulted in the one-pot formation of 3-aryl-3,4-Dihydroisocoumarins. The reactions proceeded by regioselective cyclization to give 6-(2-aryl-2-chloroethyl)salicylates, which underwent a silica gel-mediated lactonization. The cyclizations of protected 1-amino-5-silyloxy-hex-4-en-3-ones proved to be not regioselective.
-
synthesis of 3 aryl 3 4 Dihydroisocoumarins by regioselective domino 3 3 cyclization lactonization reactions of 1 3 bis silyloxy 1 3 butadienes with 1 hydroxy 5 silyloxy 4 en 3 ones
Tetrahedron Letters, 2008Co-Authors: Muhammad Sher, Asad Ali, Helmut Reinke, Peter LangerAbstract:Abstract The [3+3] cyclization of 1,3-bis(silyloxy)-1,3-butadienes with 1-hydroxy-5-silyloxy-4-en-3-ones afforded 6-(2-aryl-2-chloroethyl)salicylates, which were transformed into 3-aryl-3,4-Dihydroisocoumarins by silica gel-mediated lactonization.
-
synthesis of functionalized homophthalates salicylates diaryl ethers and Dihydroisocoumarins based on cyclocondensation reactions of 1 3 dicarbonyl compounds and 1 3 bis silyloxy 1 3 butadienes
2008Co-Authors: Muhammad SherAbstract:Regioselective cyclocondensation reactions of 1,3-bis(silyl enol ethers) with different mono(silyl enol ethers) provide an elegant approach for the synthesis of various complex carba- and heterocycles from simple starting materials. Salicylates, diarylethers, resorcins and 3-aryl-3,4-Dihydroisocoumarins are prepared based on regioselective [3+3] cyclocondensation reactions of 1,3-bis(silyl enol ethers) with 1,1,3,3-tetramethoxypropane, 2-aryloxy-3-(silyloxy)alk-2-en-1-ones, 3,3-dimethoxypentanoyl chloride and 1-hydroxy-5-silyloxy-4-en-3-ones respectively. In addition, 4,5-diaryl-1,2,3-benzenetricarboxylates are prepared by reaction of 4-hydroxycyclopent-2-en-1-one-2-carboxylates with dimethyl acetylenedicarboxylate. In addition, 1-(2,2-dimethoxyethyl)-1,2,3-triazoles are prepared by regioselective copper(I)-catalyzed [3+2] cyclization of 2-azido-2,2-dimethoxyethane with alkynes.