Effect of the nature of the support on the enantioselective hydrogenation of 1-phenyl-1,2-propanedione over supported iridium catalysts

The enantioselective hydrogenation of 1-phenyl-1,2-propanedione at 298 K and 40 bar over modified supported iridium catalysts has been studied. Cinchonidine has been used as chiral inducer. The catalysts were obtained by impregnation of Ir(acac)3 on three different supports: SiO2, TiO2 and MoO3, fol...

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Autores principales:	MARZIALETTI,TERESITA, FIERRO,J.L.G., REYES,P
Lenguaje:	English
Publicado:	Sociedad Chilena de Química 2005
Materias:	Ir, 1-phenyl-1,2-propanedione cinchonidine hydrogenation enantioselectivity
Acceso en línea:	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072005000100005
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spelling	oai:scielo:S0717-970720050001000052005-05-27Effect of the nature of the support on the enantioselective hydrogenation of 1-phenyl-1,2-propanedione over supported iridium catalystsMARZIALETTI,TERESITAFIERRO,J.L.G.REYES,P Ir, 1-phenyl-1,2-propanedione cinchonidine hydrogenation enantioselectivity The enantioselective hydrogenation of 1-phenyl-1,2-propanedione at 298 K and 40 bar over modified supported iridium catalysts has been studied. Cinchonidine has been used as chiral inducer. The catalysts were obtained by impregnation of Ir(acac)3 on three different supports: SiO2, TiO2 and MoO3, followed by calcination in air and reduction under hydrogen at 773 K. All the solids were characterized by nitrogen adsorption-desorption isotherms at 77 K, H2 chemisorption, XRD, TEM, TPR and XPS. It was found that Ir/SiO2 and Ir/TiO2 catalysts reduced at high temperatures, 773 K, possess similar metal particle size, close to 2.0 nm, eventhough the H/Ir ratio obtained from H2 chemisorption showed larger differences, with the H/Ir ratio being lower for titania- and molybdenum-supported iridium catalysts. In these samples, migration of the partially reduced supports, TiOx and MoOx moieties, on the metal crystals induce the creation of Irdelta+ species. TPR and XPS results confirmed that the metal component was not completely reduced. The activity was influenced by the nature of the support, being more active those in the SMSI state such as Ir/TiO2 and Ir/MoO3 being more active. This has been attributed to the presence of electron deficient metal species, Irdelta+, which are responsible for the polarization of the carbonyl bond of the substrates, thus favoring the activity and enantioselectivity of the reaction. The effect of different solvents on the activity and the enantioselectivity of the reaction was also studied. The highest enantiomeric excess (ee) of (R)-1-phenyl-1-hydroxy-2-propanone (20%) was obtained with the Ir/TiO2 catalyst using acetic acid as solventinfo:eu-repo/semantics/openAccessSociedad Chilena de QuímicaJournal of the Chilean Chemical Society v.50 n.1 20052005-03-01text/htmlhttp://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072005000100005en10.4067/S0717-97072005000100005
institution	Scielo Chile
collection	Scielo Chile
language	English
topic	Ir, 1-phenyl-1,2-propanedione cinchonidine hydrogenation enantioselectivity
spellingShingle	Ir, 1-phenyl-1,2-propanedione cinchonidine hydrogenation enantioselectivity MARZIALETTI,TERESITA FIERRO,J.L.G. REYES,P Effect of the nature of the support on the enantioselective hydrogenation of 1-phenyl-1,2-propanedione over supported iridium catalysts
description	The enantioselective hydrogenation of 1-phenyl-1,2-propanedione at 298 K and 40 bar over modified supported iridium catalysts has been studied. Cinchonidine has been used as chiral inducer. The catalysts were obtained by impregnation of Ir(acac)3 on three different supports: SiO2, TiO2 and MoO3, followed by calcination in air and reduction under hydrogen at 773 K. All the solids were characterized by nitrogen adsorption-desorption isotherms at 77 K, H2 chemisorption, XRD, TEM, TPR and XPS. It was found that Ir/SiO2 and Ir/TiO2 catalysts reduced at high temperatures, 773 K, possess similar metal particle size, close to 2.0 nm, eventhough the H/Ir ratio obtained from H2 chemisorption showed larger differences, with the H/Ir ratio being lower for titania- and molybdenum-supported iridium catalysts. In these samples, migration of the partially reduced supports, TiOx and MoOx moieties, on the metal crystals induce the creation of Irdelta+ species. TPR and XPS results confirmed that the metal component was not completely reduced. The activity was influenced by the nature of the support, being more active those in the SMSI state such as Ir/TiO2 and Ir/MoO3 being more active. This has been attributed to the presence of electron deficient metal species, Irdelta+, which are responsible for the polarization of the carbonyl bond of the substrates, thus favoring the activity and enantioselectivity of the reaction. The effect of different solvents on the activity and the enantioselectivity of the reaction was also studied. The highest enantiomeric excess (ee) of (R)-1-phenyl-1-hydroxy-2-propanone (20%) was obtained with the Ir/TiO2 catalyst using acetic acid as solvent
author	MARZIALETTI,TERESITA FIERRO,J.L.G. REYES,P
author_facet	MARZIALETTI,TERESITA FIERRO,J.L.G. REYES,P
author_sort	MARZIALETTI,TERESITA
title	Effect of the nature of the support on the enantioselective hydrogenation of 1-phenyl-1,2-propanedione over supported iridium catalysts
title_short	Effect of the nature of the support on the enantioselective hydrogenation of 1-phenyl-1,2-propanedione over supported iridium catalysts
title_full	Effect of the nature of the support on the enantioselective hydrogenation of 1-phenyl-1,2-propanedione over supported iridium catalysts
title_fullStr	Effect of the nature of the support on the enantioselective hydrogenation of 1-phenyl-1,2-propanedione over supported iridium catalysts
title_full_unstemmed	Effect of the nature of the support on the enantioselective hydrogenation of 1-phenyl-1,2-propanedione over supported iridium catalysts
title_sort	effect of the nature of the support on the enantioselective hydrogenation of 1-phenyl-1,2-propanedione over supported iridium catalysts
publisher	Sociedad Chilena de Química
publishDate	2005
url	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072005000100005
work_keys_str_mv	AT marzialettiteresita effectofthenatureofthesupportontheenantioselectivehydrogenationof1phenyl12propanedioneoversupportediridiumcatalysts AT fierrojlg effectofthenatureofthesupportontheenantioselectivehydrogenationof1phenyl12propanedioneoversupportediridiumcatalysts AT reyesp effectofthenatureofthesupportontheenantioselectivehydrogenationof1phenyl12propanedioneoversupportediridiumcatalysts
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Effect of the nature of the support on the enantioselective hydrogenation of 1-phenyl-1,2-propanedione over supported iridium catalysts

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