The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
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 2 arylthio benzoates by 3 3 cyclocondensations of 3 arylthio 1 silyloxy 1 3 butadienes with 3 oxo orthoesters 1 1 3 3 tetramethoxypropane and 1 1 bis methylthio 1 en 3 ones
Tetrahedron, 2009Co-Authors: Muhammad Imran, Inam Iqbal, Christine Fischer, Nasir Rasool, Peter LangerAbstract:Abstract A variety of 2-arylthio-4-methoxybenzoates are regioselectively prepared by TiCl4-mediated [3+3] cyclocondensations of 3-arylthio-1-trimethylsilyloxy-1,3-butadienes with 3-oxo-orthoesters. Unsubstituted 2-(arylthio)benzoates were prepared by Me3SiOTf-catalyzed cyclization of 3-arylthio-1-trimethylsilyloxy-1,3-butadienes with 1,1,3,3-tetramethoxypropane. The TiCl4-mediated cyclization of 3-arylthio-1-trimethylsilyloxy-1,3-butadienes with 1,1-bis(methylthio)-1-en-3-ones results in regioselective formation of 2-arylthio-6-(methylthio)benzoates.
-
regioselective synthesis of2 arylthio 4 methoxybenzoates by formal 3 3 cyclocondensationsof 3 arylthio 1 trimethylsilyloxybuta 1 3 dienes with 3 oxo orthoesters
Synlett, 2009Co-Authors: Muhammad Imran, Inam Iqbal, Peter LangerAbstract:A variety of 2-arylthio-4-methoxybenzoates are regioselectively prepared by the first formal [3+3] cyclocondensations of 3-arylthio-1-trimethylsilytoxybuta-1,3-dienes with 3-oxo-orthoesters.
-
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.
-
efficient synthesis of salicylates by catalytic 3 3 cyclizations of 1 3 bis silyl enol ethers with 1 1 3 3 tetramethoxypropane
Journal of Organic Chemistry, 2007Co-Authors: Muhammad Sher, Christine Fischer, T Tam H Dang, Zafar Ahmed, Muhammad A Rashid, Peter LangerAbstract:Salicylic acid derivatives were prepared by Me3SiOTf-catalyzed [3 + 3] cyclization of 1,3-bis(silyl enol ethers) with 1,1,3,3-tetramethoxypropane.
Laura L Anderson - One of the best experts on this subject based on the ideXlab platform.
-
regioselective synthesis of 2 3 4 or 2 3 5 trisubstituted pyrroles via 3 3 or 1 3 rearrangements of o vinyl oximes
ChemInform, 2011Co-Authors: Heng Yen Wang, Daniel Mueller, Rachna M Sachwani, Rachel Kapadia, Hannah N Londino, Laura L AndersonAbstract:O-Vinyl oximes, generated by Ir-catalyzed isomerization of O-allyl oximes, undergo efficient cyclization to afford 2,3,4- trisubstituted pyrroles via [3,3] rearrangement or 2,5-di- and 2,3,5-trisubstituted pyrroles via [1,3] rearrangement.
-
regioselective synthesis of 2 3 4 or 2 3 5 trisubstituted pyrroles via 3 3 or 1 3 rearrangements of o vinyl oximes
Journal of Organic Chemistry, 2011Co-Authors: Heng Yen Wang, Daniel Mueller, Rachna M Sachwani, Rachel Kapadia, Hannah N Londino, Laura L AndersonAbstract:The regioselective synthesis of 2,3,4- or 2,3,5-trisubstituted pyrroles has been achieved via [3,3] and [1,3] sigmatropic rearrangements of O-vinyl oximes, respectively. Iridium-catalyzed isomerization of easily prepared O-allyl oximes enables rapid access to O-vinyl oximes. The regioselectivity of pyrrole formation can be controlled by either the identity of the α-substituent or through the addition of an amine base. When enolization is favored, a [3,3] rearrangement followed by a Paal-Knorr cyclization provides a 2,3,4-trisubstituted pyrrole; when enolization is disfavored, a [1,3] rearrangement occurs prior to enolization to produce a 2,3,5-trisubstituted pyrrole after cyclization. Optimization and scope of the O-allyl oxime isomerization and subsequent pyrrole formation are discussed and mechanistic pathways are proposed. Conditions are provided for selecting either the [3,3] rearrangement or the [1,3] rearrangement product with β-ester O-allyl oxime substrates.
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.
-
efficient synthesis of salicylates by catalytic 3 3 cyclizations of 1 3 bis silyl enol ethers with 1 1 3 3 tetramethoxypropane
Journal of Organic Chemistry, 2007Co-Authors: Muhammad Sher, Christine Fischer, T Tam H Dang, Zafar Ahmed, Muhammad A Rashid, Peter LangerAbstract:Salicylic acid derivatives were prepared by Me3SiOTf-catalyzed [3 + 3] cyclization of 1,3-bis(silyl enol ethers) with 1,1,3,3-tetramethoxypropane.
Ryo Akasaka - One of the best experts on this subject based on the ideXlab platform.
-
fundamental equations of state for cis 1 3 3 3 tetrafluoropropene r 1234ze z and 3 3 3 trifluoropropene r 1243zf
Journal of Chemical & Engineering Data, 2019Co-Authors: Ryo Akasaka, Eric W LemmonAbstract:New fundamental equations of state are presented for cis-1,3,3,3-tetrafluoropropene [R-1234ze(Z)] and 3,3,3-trifluoropropene (R-1243zf). The new equation for R-1234ze(Z), which is the main topic of this paper, is applicable to ranges at lower temperatures and higher pressures compared to the first published equation, and uncertainties in liquid-phase sound speeds are greatly improved. The equation is valid at temperatures from 238 to 440 K at pressures up to 34 MPa. Estimated uncertainties in this range are 0.1% for vapor pressures at temperatures above 300 K and 0.3% at lower temperatures, 0.1% for liquid-phase densities, 0.3% for vapor-phase densities, 0.02% for vapor-phase sound speeds, and 0.05% for liquid-phase sound speeds, except in the critical region where larger deviations up to about 1% are observed in density. The equation shows reasonable extrapolation behavior at extremely low and high temperatures, and at high pressures. The new equation for R-1243zf has a similar range of validity and unce...
-
thermodynamic property models for the difluoromethane r 32 trans 1 3 3 3 tetrafluoropropene r 1234ze e and difluoromethane 2 3 3 3 tetrafluoropropene r 1234yf mixtures
Fluid Phase Equilibria, 2013Co-Authors: Ryo AkasakaAbstract:Abstract Thermodynamic property models explicit in the Helmholtz energy are presented for the R-32/1234ze(E) and R-32/1234yf mixtures. The Helmholtz energy of the mixtures are expressed as the sum of the ideal mixture contribution and the contribution from mixing. The independent variables are the temperature, molar volume, and composition. The most accurate pure-fluid equations of state are incorporated to calculate the ideal mixture contribution. The contribution from mixing is determined by fitting to available experimental data. The estimated uncertainties in calculated properties from the models are 1% for the bubble point pressure and 0.25% for liquid density. The critical loci of the mixtures are reasonably represented with the models. The calculated critical temperatures correspond to experimental values within ±0.8 K.
-
new fundamental equations of state with a common functional form for 2 3 3 3 tetrafluoropropene r 1234yf and trans 1 3 3 3 tetrafluoropropene r 1234ze e
International Journal of Thermophysics, 2011Co-Authors: Ryo AkasakaAbstract:New fundamental equations of state explicit in the Helmholtz energy with a common functional form are presented for 2,3,3,3-tetrafluoropropene (R-1234yf) and trans-1,3,3,3-tetrafluoropropene (R-1234ze(E)). The independent variables of the equations of state are the temperature and density. The equations of state are based on reliable experimental data for the vapor pressure, density, heat capacities, and speed of sound. The equation for R-1234yf covers temperatures between 240 K and 400 K for pressures up to 40 MPa with uncertainties of 0.1 % in liquid density, 0.3 % in vapor density, 2 % in liquid heat capacities, 0.05 % in the vapor-phase speed of sound, and 0.1 % in vapor pressure. The equation for R-1234ze(E) is valid for temperatures from 240 K to 420 K and for pressures up to 15 MPa with uncertainties of 0.1 % in liquid density, 0.2 % in vapor density, 3 % in liquid heat capacities, 0.05 % in the vapor-phase speed of sound, and 0.1 % in vapor pressure. Both equations exhibit reasonable behavior in extrapolated regions outside the range of the experimental data.
Heng Yen Wang - One of the best experts on this subject based on the ideXlab platform.
-
regioselective synthesis of 2 3 4 or 2 3 5 trisubstituted pyrroles via 3 3 or 1 3 rearrangements of o vinyl oximes
ChemInform, 2011Co-Authors: Heng Yen Wang, Daniel Mueller, Rachna M Sachwani, Rachel Kapadia, Hannah N Londino, Laura L AndersonAbstract:O-Vinyl oximes, generated by Ir-catalyzed isomerization of O-allyl oximes, undergo efficient cyclization to afford 2,3,4- trisubstituted pyrroles via [3,3] rearrangement or 2,5-di- and 2,3,5-trisubstituted pyrroles via [1,3] rearrangement.
-
regioselective synthesis of 2 3 4 or 2 3 5 trisubstituted pyrroles via 3 3 or 1 3 rearrangements of o vinyl oximes
Journal of Organic Chemistry, 2011Co-Authors: Heng Yen Wang, Daniel Mueller, Rachna M Sachwani, Rachel Kapadia, Hannah N Londino, Laura L AndersonAbstract:The regioselective synthesis of 2,3,4- or 2,3,5-trisubstituted pyrroles has been achieved via [3,3] and [1,3] sigmatropic rearrangements of O-vinyl oximes, respectively. Iridium-catalyzed isomerization of easily prepared O-allyl oximes enables rapid access to O-vinyl oximes. The regioselectivity of pyrrole formation can be controlled by either the identity of the α-substituent or through the addition of an amine base. When enolization is favored, a [3,3] rearrangement followed by a Paal-Knorr cyclization provides a 2,3,4-trisubstituted pyrrole; when enolization is disfavored, a [1,3] rearrangement occurs prior to enolization to produce a 2,3,5-trisubstituted pyrrole after cyclization. Optimization and scope of the O-allyl oxime isomerization and subsequent pyrrole formation are discussed and mechanistic pathways are proposed. Conditions are provided for selecting either the [3,3] rearrangement or the [1,3] rearrangement product with β-ester O-allyl oxime substrates.
