INCAPE   05401
INSTITUTO DE INVESTIGACIONES EN CATALISIS Y PETROQUIMICA "ING. JOSE MIGUEL PARERA"
Unidad Ejecutora - UE
artículos
Título:
“Gas-phase reduction of cyclic and acyclic alfa,beta-unsaturated ketones by hydrogen transfer on MgO. Effect of the ketone structure”
Autor/es:
J.J. RAMOS; V. K. DÍEZ; C. FERRETTI; P.A. TORRESI; C. R. APESTEGUÍA; J.I. DI COSIMO
Revista:
CATALYSIS TODAY
Editorial:
ELSEVIER SCIENCE BV
Referencias:
Año: 2011 vol. 172 p. 41 - 47
ISSN:
0920-5861
Resumen:
The gas-phase hydrogen transfer reduction (HTR) of cyclic and acyclic ,-unsaturated ketones to the corresponding unsaturated alcohols (UOL) using 2-propanol as hydrogen donor was studied on MgO as an alternative to the less selective conventional hydrogenation using high pressure H2. The HTR of 2- cyclohexenone and mesityl oxide were used as model reactions. The MgO activity and selectivity toward the unsaturated alcohol depended on the ketone chemical structure. Cyclic 2-cyclohexenone was in fact less reactive but more selective to UOL formation than acyclic mesityl oxide, yielding about 85% UOL (91% selectivity) at 573 K. The rigid structure of 2-cyclohexenone enforces a s-trans conformation that favors selective reduction of the C O bond and thereby enhances the UOL formation. In contrast, the less rigid structure of the acyclic ketone affords the simultaneous reduction of both unsaturated bonds, C C and C O, forming also the saturated alcohol; as a consequence, maximum UOL yields of about 45% (47% selectivity) were obtained at 573 K from HTR of mesityl oxide. The unsaturated ketone conversion pathways toward UOL and other compounds also depended on the ketone structure. UOL formed on MgO as a primary product from both reactants 2-cyclohexenone and mesityl oxide, via a cyclic six-membered intermediate according to the Meerwein–Ponndorf–Verley mechanism. However the saturated alcohol was produced by consecutive UOL reduction in 2- cyclohexenone reactions but directly from mesityl oxide reduction. Reduction of the C C bond toward the saturated ketone was negligible regardless of the reactant structure whereas competing reactions such as the C C bond shift were more likely to contribute during reduction of the acyclic reactant.-unsaturated ketones to the corresponding unsaturated alcohols (UOL) using 2-propanol as hydrogen donor was studied on MgO as an alternative to the less selective conventional hydrogenation using high pressure H2. The HTR of 2- cyclohexenone and mesityl oxide were used as model reactions. The MgO activity and selectivity toward the unsaturated alcohol depended on the ketone chemical structure. Cyclic 2-cyclohexenone was in fact less reactive but more selective to UOL formation than acyclic mesityl oxide, yielding about 85% UOL (91% selectivity) at 573 K. The rigid structure of 2-cyclohexenone enforces a s-trans conformation that favors selective reduction of the C O bond and thereby enhances the UOL formation. In contrast, the less rigid structure of the acyclic ketone affords the simultaneous reduction of both unsaturated bonds, C C and C O, forming also the saturated alcohol; as a consequence, maximum UOL yields of about 45% (47% selectivity) were obtained at 573 K from HTR of mesityl oxide. The unsaturated ketone conversion pathways toward UOL and other compounds also depended on the ketone structure. UOL formed on MgO as a primary product from both reactants 2-cyclohexenone and mesityl oxide, via a cyclic six-membered intermediate according to the Meerwein–Ponndorf–Verley mechanism. However the saturated alcohol was produced by consecutive UOL reduction in 2- cyclohexenone reactions but directly from mesityl oxide reduction. Reduction of the C C bond toward the saturated ketone was negligible regardless of the reactant structure whereas competing reactions such as the C C bond shift were more likely to contribute during reduction of the acyclic reactant.2. The HTR of 2- cyclohexenone and mesityl oxide were used as model reactions. The MgO activity and selectivity toward the unsaturated alcohol depended on the ketone chemical structure. Cyclic 2-cyclohexenone was in fact less reactive but more selective to UOL formation than acyclic mesityl oxide, yielding about 85% UOL (91% selectivity) at 573 K. The rigid structure of 2-cyclohexenone enforces a s-trans conformation that favors selective reduction of the C O bond and thereby enhances the UOL formation. In contrast, the less rigid structure of the acyclic ketone affords the simultaneous reduction of both unsaturated bonds, C C and C O, forming also the saturated alcohol; as a consequence, maximum UOL yields of about 45% (47% selectivity) were obtained at 573 K from HTR of mesityl oxide. The unsaturated ketone conversion pathways toward UOL and other compounds also depended on the ketone structure. UOL formed on MgO as a primary product from both reactants 2-cyclohexenone and mesityl oxide, via a cyclic six-membered intermediate according to the Meerwein–Ponndorf–Verley mechanism. However the saturated alcohol was produced by consecutive UOL reduction in 2- cyclohexenone reactions but directly from mesityl oxide reduction. Reduction of the C C bond toward the saturated ketone was negligible regardless of the reactant structure whereas competing reactions such as the C C bond shift were more likely to contribute during reduction of the acyclic reactant.via a cyclic six-membered intermediate according to the Meerwein–Ponndorf–Verley mechanism. However the saturated alcohol was produced by consecutive UOL reduction in 2- cyclohexenone reactions but directly from mesityl oxide reduction. Reduction of the C C bond toward the saturated ketone was negligible regardless of the reactant structure whereas competing reactions such as the C C bond shift were more likely to contribute during reduction of the acyclic reactant.