title: Pursuing the active species in an aluminium-based Lewis acid system for catalytic Diels-Alder cycloadditions.
abstract: Several Al-based complexes supported by a bis(imino)aryl NCN pincer ligand have been prepared. Systematic structural and experimental evidence identified a cationic species, supported by a THF molecule, as the best Lewis acid precatalyst for a range of Diels-Alder cycloadditions. This highlighted the importance of fully isolating and characterizing the active species in any catalytic process especially when Lewis acids are used due to the presence of hidden Brønsted acids (HBAs). Finally, the control experiments conducted in order to eliminate HBA activity that involve a bulky pyridine base should be performed with caution as the corresponding protonated pyridinium salt could also serve as a proton source.
authors.affiliation: School of Physical and Mathematical Sciences, Division of Chemistry and Biological Chemistry, Nanyang Technological University, Singapore, 637371, Singapore. dvidovic@ntu.edu.sg.
authors.forename: Zhizhou
authors.initials: Z
authors.lastname: Liu
authors.affiliation: School of Physical and Mathematical Sciences, Division of Chemistry and Biological Chemistry, Nanyang Technological University, Singapore, 637371, Singapore. dvidovic@ntu.edu.sg.
authors.forename: Rakesh
authors.initials: R
authors.lastname: Ganguly
authors.affiliation: School of Physical and Mathematical Sciences, Division of Chemistry and Biological Chemistry, Nanyang Technological University, Singapore, 637371, Singapore. dvidovic@ntu.edu.sg.
authors.forename: Dragoslav
authors.identifier: http://orcid.org/0000-0003-4269-3995
authors.initials: D
authors.lastname: Vidović