title: Comparison of Cu-ZSM-5 zeolites and Cu-MOF-505 metal-organic frameworks as heterogeneous catalysts for the Mukaiyama aldol reaction: a DFT mechanistic study.
abstract: The density functional theory (DFT) model ONIOM(M06L/6-311++G(2df,2p):UFF was employed to reveal the catalytic activity of Cu(II) in the paddle-wheel unit of the metal-organic framework (MOF)-505 material in the Mukaiyama aldol reaction compared with the activity of Cu-ZSM-5 zeolites. The aldol reaction between a silyl enol ether and formaldehyde catalyzed by the Lewis acidic site of both materials takes place through a concerted pathway, in which the formation of the CC bond and the transfer of the silyl group occurs in a single step. MOF-505 and Cu-ZSM-5 are predicted to be efficient catalysts for this reaction as they strongly activate the formaldehyde carbonyl carbon electrophile, which leads to a considerably lower reaction barrier compared with the gas-phase system. Both MOF-505 and Cu-ZSM-5 catalysts stabilize the reacting species along the reaction coordinate, thereby lowering the activation energy, compared to the gas-phase system. The activation barriers for the MOF-505, Cu-ZSM-5, and gas-phase system are 48, 21, and 61 kJ mol(-1) , respectively. Our results show the importance of the enveloping framework by stabilizing the reacting species and promoting the reaction.
authors: Laboratory for Computational and Applied Chemistry, Department of Chemistry, Faculty of Science and Center of Nanotechnology, Kasetsart University Research and Development Institute, Kasetsart University, Bangkok 10900, Thailand.
authors: Sudarat
authors: S
authors: Yadnum
authors: Saowapak
authors: S
authors: Choomwattana
authors: Pipat
authors: P
authors: Khongpracha
authors: Jakkapan
authors: J
authors: Sirijaraensre
authors: Jumras
authors: J
authors: Limtrakul
mesh_terms: D000447:Aldehydes / Q000737:chemistry*; D002384:Catalysis; D003300:Copper / Q000737:chemistry*; D005557:Formaldehyde / Q000737:chemistry; D058116:Lewis Acids / Q000737:chemistry; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000737:chemistry*; D011789:Quantum Theory; D017655:Silicon Compounds / Q000737:chemistry; D017641:Zeolites / Q000737:chemistry*
chemical_list: D000447:Aldehydes; D058116:Lewis Acids; D009942:Organometallic Compounds; D017655:Silicon Compounds; C570564:ZSM-5 zeolite; D017641:Zeolites; D005557:Formaldehyde; D003300:Copper; C116609:3-hydroxybutanal