The Experts below are selected from a list of 459 Experts worldwide ranked by ideXlab platform
José L. García Ruano - One of the best experts on this subject based on the ideXlab platform.
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1,3-dipolar cycloaddition of diazoalkanes to (S)-(+)-3-[(4-methylphenyl)sulfinyl]-5,6-dihydropyran-2-one. Synthesis of optically pure cyclopropanes by denitrogenation of sulfinyl and sulfonyl pyrazolines.
The Journal of organic chemistry, 2009Co-Authors: David Cruz Cruz, Amelia Tito, M. Rosario Martín, Francisco Yuste, José L. García RuanoAbstract:The addition of diazomethane and Diazoethane to enantiopure (S)-(+)-3-[(4-methylphenyl)sulfinyl]-5,6-dihydropyran-2-one (3) afforded the corresponding pyrazolines 4 and 6-exo in good yields and with almost complete π-facial selectivity. When the reaction is effected in the presence of Yb(OTf)3, the facial selectivity is inverted to give the pyrazolines 5 and 7-exo. The denitrogenation of optically pure sulfinyl pyrazolines 4−7-exo into the corresponding cyclopropanes with Yb(OTf)3 occurred with complete retention of configuration but moderate chemoselectivity and yields. These results were significantly improved starting from sulfonyl pyrazolines, which afforded optically pure 3-oxabicyclo[4.1.0]heptan-2-ones with yields ranging between 65% (17 and ent-17) and ≥95% (16 and ent-16).
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Synthesis of bicyclo[3.1.0]hexanones via 1,3-dipolar cycloaddition of diazoalkanes to homochiral α-sulfinyl-2-cyclopentenones
Tetrahedron, 2008Co-Authors: José L. García Ruano, Alberto Fraile, M. Rosario Martín, Marina Alonso, David De La Cruz, M. Teresa Peromingo, Amelia Tito, Francisco YusteAbstract:Abstract The reactions of diazomethane, Diazoethane, and (trimethylsilyl)diazomethane with (S)-2-p-tolylsulfinylcyclopent-2-en-1-one have been studied. The sulfinyl group increases the reactivity and controls the π-facial and endo/exo selectivities. The π-facial selectivity can be inverted in the presence of Yb(OTf)3, which makes possible the stereodivergent synthesis of both diastereoisomeric pyrazolines. Completely stereoselective denitrogenation of optically pure pyrazolines into cyclopropanes was achieved under substoichiometric Yb(OTf)3 catalysis.
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1,3-Dipolar Cycloadditions of Diazoalkanes to Activated Sulfoxides: Influence of Lewis Acids
The Journal of organic chemistry, 2005Co-Authors: José L. García Ruano, Alberto Fraile, M. Rosario Martín, Marina Alonso, M. Teresa Peromingo, Amelia TitoAbstract:The reactions of diazomethane and Diazoethane with (S)-3-p-tolylsulfinylfuran-2(5H)-one (3) and its 4-methyl derivative (4) have been studied. The sulfinyl group was able to completely control the π-facial selectivity of all these reactions, which decreased when the polarity of the solvent increased and could be inverted in the presence of Lewis acids, Yb(OTf)3 being the most efficient catalyst. This behavior made possible the stereodivergent synthesis of diastereoisomeric pyrazolines in almost quantitative yields and de's higher than 98%. The endo/exo selectivity was also complete in reactions of 3 with Diazoethane, whereas 4 afforded an easily separable 1:1 mixture of diastereoisomers. Steric factors accounts for the endo/exo selectivity, whereas electrostatic interactions must also be considered to explain the facial selectivity.
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The role of steric and electronic interactions in the stereocontrol of the asymmetric 1,3-dipolar reactions of 5-ethoxy-3-p-(S)-tolylsulfinylfuran-2(5H)-ones with diazoalkanes: theoretical calculations and experimental evidences.
Journal of Organic Chemistry, 2003Co-Authors: José L. García Ruano, Alberto Fraile, M. Rosario Martín, Gemma González, Fernando R. Clemente, Ruth GordilloAbstract:The addition of diazomethane and Diazoethane to (5S,SS)- and (5R,SS)-5-ethoxy-3-p-tolylsulfinylfuran-2(5H)-ones (1a and 1b) and their 4-methylderivatives (2a and 2b) proceeded in almost quantitative yields and complete regioselectivity. The observed π-facial selectivity is determined by the configurations at both C-5 and the sulfinyl group, the later being the most important. The syn adducts were almost exclusively obtained from 1a and 2a in apolar solvents but the π-facial selectivity was strongly decreased in more polar solvents. On the other hand, the major adducts from 1b and 2b were the anti ones and such predominance was slightly increased with solvent polarity. The exo-selectivity was complete in all the cases except for the anti approach to compounds 2a (in polar solvents) and 2b. The role of the sulfinyl group in this behavior was inferred by comparison of these results with those obtained in reactions of diazoalkanes with 5-methoxyfuran-2(5H)-one (3). Steric interactions seem to be the main ones...
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Asymmetric 1,3-dipolar cycloadditions of diazoalkanes to (5S, SS)-5-[(1R)-menthyloxy]-4-phenylsulfinyl (and phenylsulfonyl)furan-2(5H)-ones
Tetrahedron: Asymmetry, 2002Co-Authors: José L. García Ruano, Gemma González, Fernando Bercial, Ana M. Martin Castro, M. Rosario MartínAbstract:Abstract The behavior of the title compounds in their reactions with diazomethane and Diazoethane is reported. The reactivity of the 5-alkoxyfuran-2(5 H )-ones as dipolarophiles is dramatically enhanced by the presence of sulfur functionalities at C-4. The regioselectivity of the cycloadditions of diazomethane is opposite to that observed with Diazoethane, due to control by the carbonyl group in the first case and by the sulfur function in the second case, with the sulfonyl group exhibiting a higher regio-orientating ability than the sulfinyl one. The π-facial selectivity is moderate, being controlled mainly by steric factors in the reactions involving the formation of N dipole C(4) furanone bonds, whereas the predominant role of electronic factors, modulated by the polarity of the solvent, leads to high stereoselectivities in processes involving the formation of N dipole C(3) furanone bonds. Finally, the endo / exo ratios from reactions with Diazoethane can be rationalized on steric grounds.
M. Rosario Martín - One of the best experts on this subject based on the ideXlab platform.
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1,3-dipolar cycloaddition of diazoalkanes to (S)-(+)-3-[(4-methylphenyl)sulfinyl]-5,6-dihydropyran-2-one. Synthesis of optically pure cyclopropanes by denitrogenation of sulfinyl and sulfonyl pyrazolines.
The Journal of organic chemistry, 2009Co-Authors: David Cruz Cruz, Amelia Tito, M. Rosario Martín, Francisco Yuste, José L. García RuanoAbstract:The addition of diazomethane and Diazoethane to enantiopure (S)-(+)-3-[(4-methylphenyl)sulfinyl]-5,6-dihydropyran-2-one (3) afforded the corresponding pyrazolines 4 and 6-exo in good yields and with almost complete π-facial selectivity. When the reaction is effected in the presence of Yb(OTf)3, the facial selectivity is inverted to give the pyrazolines 5 and 7-exo. The denitrogenation of optically pure sulfinyl pyrazolines 4−7-exo into the corresponding cyclopropanes with Yb(OTf)3 occurred with complete retention of configuration but moderate chemoselectivity and yields. These results were significantly improved starting from sulfonyl pyrazolines, which afforded optically pure 3-oxabicyclo[4.1.0]heptan-2-ones with yields ranging between 65% (17 and ent-17) and ≥95% (16 and ent-16).
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Synthesis of bicyclo[3.1.0]hexanones via 1,3-dipolar cycloaddition of diazoalkanes to homochiral α-sulfinyl-2-cyclopentenones
Tetrahedron, 2008Co-Authors: José L. García Ruano, Alberto Fraile, M. Rosario Martín, Marina Alonso, David De La Cruz, M. Teresa Peromingo, Amelia Tito, Francisco YusteAbstract:Abstract The reactions of diazomethane, Diazoethane, and (trimethylsilyl)diazomethane with (S)-2-p-tolylsulfinylcyclopent-2-en-1-one have been studied. The sulfinyl group increases the reactivity and controls the π-facial and endo/exo selectivities. The π-facial selectivity can be inverted in the presence of Yb(OTf)3, which makes possible the stereodivergent synthesis of both diastereoisomeric pyrazolines. Completely stereoselective denitrogenation of optically pure pyrazolines into cyclopropanes was achieved under substoichiometric Yb(OTf)3 catalysis.
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1,3-Dipolar Cycloadditions of Diazoalkanes to Activated Sulfoxides: Influence of Lewis Acids
The Journal of organic chemistry, 2005Co-Authors: José L. García Ruano, Alberto Fraile, M. Rosario Martín, Marina Alonso, M. Teresa Peromingo, Amelia TitoAbstract:The reactions of diazomethane and Diazoethane with (S)-3-p-tolylsulfinylfuran-2(5H)-one (3) and its 4-methyl derivative (4) have been studied. The sulfinyl group was able to completely control the π-facial selectivity of all these reactions, which decreased when the polarity of the solvent increased and could be inverted in the presence of Lewis acids, Yb(OTf)3 being the most efficient catalyst. This behavior made possible the stereodivergent synthesis of diastereoisomeric pyrazolines in almost quantitative yields and de's higher than 98%. The endo/exo selectivity was also complete in reactions of 3 with Diazoethane, whereas 4 afforded an easily separable 1:1 mixture of diastereoisomers. Steric factors accounts for the endo/exo selectivity, whereas electrostatic interactions must also be considered to explain the facial selectivity.
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The role of steric and electronic interactions in the stereocontrol of the asymmetric 1,3-dipolar reactions of 5-ethoxy-3-p-(S)-tolylsulfinylfuran-2(5H)-ones with diazoalkanes: theoretical calculations and experimental evidences.
Journal of Organic Chemistry, 2003Co-Authors: José L. García Ruano, Alberto Fraile, M. Rosario Martín, Gemma González, Fernando R. Clemente, Ruth GordilloAbstract:The addition of diazomethane and Diazoethane to (5S,SS)- and (5R,SS)-5-ethoxy-3-p-tolylsulfinylfuran-2(5H)-ones (1a and 1b) and their 4-methylderivatives (2a and 2b) proceeded in almost quantitative yields and complete regioselectivity. The observed π-facial selectivity is determined by the configurations at both C-5 and the sulfinyl group, the later being the most important. The syn adducts were almost exclusively obtained from 1a and 2a in apolar solvents but the π-facial selectivity was strongly decreased in more polar solvents. On the other hand, the major adducts from 1b and 2b were the anti ones and such predominance was slightly increased with solvent polarity. The exo-selectivity was complete in all the cases except for the anti approach to compounds 2a (in polar solvents) and 2b. The role of the sulfinyl group in this behavior was inferred by comparison of these results with those obtained in reactions of diazoalkanes with 5-methoxyfuran-2(5H)-one (3). Steric interactions seem to be the main ones...
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Asymmetric 1,3-dipolar cycloadditions of diazoalkanes to (5S, SS)-5-[(1R)-menthyloxy]-4-phenylsulfinyl (and phenylsulfonyl)furan-2(5H)-ones
Tetrahedron: Asymmetry, 2002Co-Authors: José L. García Ruano, Gemma González, Fernando Bercial, Ana M. Martin Castro, M. Rosario MartínAbstract:Abstract The behavior of the title compounds in their reactions with diazomethane and Diazoethane is reported. The reactivity of the 5-alkoxyfuran-2(5 H )-ones as dipolarophiles is dramatically enhanced by the presence of sulfur functionalities at C-4. The regioselectivity of the cycloadditions of diazomethane is opposite to that observed with Diazoethane, due to control by the carbonyl group in the first case and by the sulfur function in the second case, with the sulfonyl group exhibiting a higher regio-orientating ability than the sulfinyl one. The π-facial selectivity is moderate, being controlled mainly by steric factors in the reactions involving the formation of N dipole C(4) furanone bonds, whereas the predominant role of electronic factors, modulated by the polarity of the solvent, leads to high stereoselectivities in processes involving the formation of N dipole C(3) furanone bonds. Finally, the endo / exo ratios from reactions with Diazoethane can be rationalized on steric grounds.
Amelia Tito - One of the best experts on this subject based on the ideXlab platform.
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1,3-dipolar cycloaddition of diazoalkanes to (S)-(+)-3-[(4-methylphenyl)sulfinyl]-5,6-dihydropyran-2-one. Synthesis of optically pure cyclopropanes by denitrogenation of sulfinyl and sulfonyl pyrazolines.
The Journal of organic chemistry, 2009Co-Authors: David Cruz Cruz, Amelia Tito, M. Rosario Martín, Francisco Yuste, José L. García RuanoAbstract:The addition of diazomethane and Diazoethane to enantiopure (S)-(+)-3-[(4-methylphenyl)sulfinyl]-5,6-dihydropyran-2-one (3) afforded the corresponding pyrazolines 4 and 6-exo in good yields and with almost complete π-facial selectivity. When the reaction is effected in the presence of Yb(OTf)3, the facial selectivity is inverted to give the pyrazolines 5 and 7-exo. The denitrogenation of optically pure sulfinyl pyrazolines 4−7-exo into the corresponding cyclopropanes with Yb(OTf)3 occurred with complete retention of configuration but moderate chemoselectivity and yields. These results were significantly improved starting from sulfonyl pyrazolines, which afforded optically pure 3-oxabicyclo[4.1.0]heptan-2-ones with yields ranging between 65% (17 and ent-17) and ≥95% (16 and ent-16).
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Synthesis of bicyclo[3.1.0]hexanones via 1,3-dipolar cycloaddition of diazoalkanes to homochiral α-sulfinyl-2-cyclopentenones
Tetrahedron, 2008Co-Authors: José L. García Ruano, Alberto Fraile, M. Rosario Martín, Marina Alonso, David De La Cruz, M. Teresa Peromingo, Amelia Tito, Francisco YusteAbstract:Abstract The reactions of diazomethane, Diazoethane, and (trimethylsilyl)diazomethane with (S)-2-p-tolylsulfinylcyclopent-2-en-1-one have been studied. The sulfinyl group increases the reactivity and controls the π-facial and endo/exo selectivities. The π-facial selectivity can be inverted in the presence of Yb(OTf)3, which makes possible the stereodivergent synthesis of both diastereoisomeric pyrazolines. Completely stereoselective denitrogenation of optically pure pyrazolines into cyclopropanes was achieved under substoichiometric Yb(OTf)3 catalysis.
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1,3-Dipolar Cycloadditions of Diazoalkanes to Activated Sulfoxides: Influence of Lewis Acids
The Journal of organic chemistry, 2005Co-Authors: José L. García Ruano, Alberto Fraile, M. Rosario Martín, Marina Alonso, M. Teresa Peromingo, Amelia TitoAbstract:The reactions of diazomethane and Diazoethane with (S)-3-p-tolylsulfinylfuran-2(5H)-one (3) and its 4-methyl derivative (4) have been studied. The sulfinyl group was able to completely control the π-facial selectivity of all these reactions, which decreased when the polarity of the solvent increased and could be inverted in the presence of Lewis acids, Yb(OTf)3 being the most efficient catalyst. This behavior made possible the stereodivergent synthesis of diastereoisomeric pyrazolines in almost quantitative yields and de's higher than 98%. The endo/exo selectivity was also complete in reactions of 3 with Diazoethane, whereas 4 afforded an easily separable 1:1 mixture of diastereoisomers. Steric factors accounts for the endo/exo selectivity, whereas electrostatic interactions must also be considered to explain the facial selectivity.
Juergen Seitz - One of the best experts on this subject based on the ideXlab platform.
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Ruthenium(I)-catalyzed cyclopropanation reactions with (trimethylsilyl)diazomethane and aryldiazomethanes
Tetrahedron Letters, 2001Co-Authors: Gerhard Maas, Juergen SeitzAbstract:The polymeric ruthenium(I) complex [Ru2(CO)4(μ-OAc)2]n is a suitable catalyst for the cyclopropanation of mono-, 1,1- as well as 1,2-disubstituted, and trisubstituted alkenes with (trimethylsilyl)diazomethane, phenyl-diazomethane, and (4-cyanophenyl)diazomethane. Trisubstituted alkenes are cyclopropanated with a remarkable degree of syn-selectivity.
Alberto Fraile - One of the best experts on this subject based on the ideXlab platform.
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Synthesis of bicyclo[3.1.0]hexanones via 1,3-dipolar cycloaddition of diazoalkanes to homochiral α-sulfinyl-2-cyclopentenones
Tetrahedron, 2008Co-Authors: José L. García Ruano, Alberto Fraile, M. Rosario Martín, Marina Alonso, David De La Cruz, M. Teresa Peromingo, Amelia Tito, Francisco YusteAbstract:Abstract The reactions of diazomethane, Diazoethane, and (trimethylsilyl)diazomethane with (S)-2-p-tolylsulfinylcyclopent-2-en-1-one have been studied. The sulfinyl group increases the reactivity and controls the π-facial and endo/exo selectivities. The π-facial selectivity can be inverted in the presence of Yb(OTf)3, which makes possible the stereodivergent synthesis of both diastereoisomeric pyrazolines. Completely stereoselective denitrogenation of optically pure pyrazolines into cyclopropanes was achieved under substoichiometric Yb(OTf)3 catalysis.
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1,3-Dipolar Cycloadditions of Diazoalkanes to Activated Sulfoxides: Influence of Lewis Acids
The Journal of organic chemistry, 2005Co-Authors: José L. García Ruano, Alberto Fraile, M. Rosario Martín, Marina Alonso, M. Teresa Peromingo, Amelia TitoAbstract:The reactions of diazomethane and Diazoethane with (S)-3-p-tolylsulfinylfuran-2(5H)-one (3) and its 4-methyl derivative (4) have been studied. The sulfinyl group was able to completely control the π-facial selectivity of all these reactions, which decreased when the polarity of the solvent increased and could be inverted in the presence of Lewis acids, Yb(OTf)3 being the most efficient catalyst. This behavior made possible the stereodivergent synthesis of diastereoisomeric pyrazolines in almost quantitative yields and de's higher than 98%. The endo/exo selectivity was also complete in reactions of 3 with Diazoethane, whereas 4 afforded an easily separable 1:1 mixture of diastereoisomers. Steric factors accounts for the endo/exo selectivity, whereas electrostatic interactions must also be considered to explain the facial selectivity.
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The role of steric and electronic interactions in the stereocontrol of the asymmetric 1,3-dipolar reactions of 5-ethoxy-3-p-(S)-tolylsulfinylfuran-2(5H)-ones with diazoalkanes: theoretical calculations and experimental evidences.
Journal of Organic Chemistry, 2003Co-Authors: José L. García Ruano, Alberto Fraile, M. Rosario Martín, Gemma González, Fernando R. Clemente, Ruth GordilloAbstract:The addition of diazomethane and Diazoethane to (5S,SS)- and (5R,SS)-5-ethoxy-3-p-tolylsulfinylfuran-2(5H)-ones (1a and 1b) and their 4-methylderivatives (2a and 2b) proceeded in almost quantitative yields and complete regioselectivity. The observed π-facial selectivity is determined by the configurations at both C-5 and the sulfinyl group, the later being the most important. The syn adducts were almost exclusively obtained from 1a and 2a in apolar solvents but the π-facial selectivity was strongly decreased in more polar solvents. On the other hand, the major adducts from 1b and 2b were the anti ones and such predominance was slightly increased with solvent polarity. The exo-selectivity was complete in all the cases except for the anti approach to compounds 2a (in polar solvents) and 2b. The role of the sulfinyl group in this behavior was inferred by comparison of these results with those obtained in reactions of diazoalkanes with 5-methoxyfuran-2(5H)-one (3). Steric interactions seem to be the main ones...