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Volume 3, Issue 2 (Suppl)
Trends in Green chem
ISSN: 2471-9889
Environmental & Green Chemistry 2017
July 24-26, 2017
Page 90
5
th
International Conference on
6
th
International Conference on
July 24-26, 2017 Rome, Italy
Environmental Chemistry and Engineering
Green Chemistry and Technology
&
Solvent-free procedure for the synthesis of tetrahydrosalen (H4salen) ligands by a solid state reaction using
sodium borohydride as a reducing agent
Jaime Ríos-Motta, Augusto Rivera
and
Ingrid Miranda-Carvajal
Universidad Nacional de Colombia, Colombia
N
,N´-bis(2-hydroxybenzyl) and N,N´-dibenzyl derivatives of 1,2, and 1,3-diamines, also known as tetrahydrosalen or salan
ligands, are intimately involved with a number of metal coordination complexes, which include those elements located in groups
12, 13 and 14. These tetradentate ligands associated with metal centers display cis-octahedral coordination geometry, which can form
two possible diastereomers (cis
fac-mer
and cis
fac-fac
), forming octahedral chiral complexes of the type [{ONNO}MX
2
]. Different
methods have been developed for the preparation of this class of compounds but the reduction of the corresponding diimines offers
the possibility to produce a wide range of such diamines. A series of N,N´-dibenzyl or N,N´-(2-hydroxybenzyl)- ethane-1,2-diamine,
-propane-1,3-diamine and -1,3-diamino-2-propanol (TetrahydroSalen ligands) were prepared in good yield by an efficient and highly
eco-friendly protocol. The respective di-Schiff bases (Salen) precursors were prepared in good yield by using water as a solvent
without the need for catalysis or the azeotropic removal of water. The reduction with sodium borohydride of the respective di-Schiff
bases under catalyst-free and solvent-free conditions occurs readily and with good yields, ranging from 48% to 95%. The direct
solid-solid reductive aminations were carried out by grinding the corresponding di-Schiff base and sodium borohydride with an
agate mortar and pestle at room temperature. Then, the reactions were conducted by heating at 60-90°C on a hot plate and were
complete within 15 minutes, producing tetrahydro-di-Schiff bases compounds. Compared to the previously reported methodologies,
our protocol offers considerable benefits, including that it has a simple procedure, is environmentally benign, produces high yields,
does not require the use of a catalyst, and allows for the product to be synthesized on the gram scale.
Biography
Jaime Ríos-Motta has his expertise in synthesis of heterocyclic compounds based on the use of aminal cage as preformed Mannich reagents. He has completed
his PhD from the National University of Colombia. He belongs to the group of research in synthesis of heterocycles as Senior Investigator. He has published more
than 80 papers in reputed journals and has been serving as an Editorial Board Member of reputed journals.
jariosmo@unal.edu.coJaime Ríos-Motta et al., Trends in Green chem, 3:2
DOI: 10.21767/2471-9889-C1-003