TY - JOUR
T1 - Design of new N-polyether pyrazole derived ligands: Synthesis, characterization and regioselectivity
AU - Guerrero, Miguel
AU - Pérez, José A.
AU - Ros, Josep
AU - Branchadell, Vicenç
AU - Pellicer, Eva
AU - Sort, Jordi
AU - Pons, Josefina
PY - 2014/1/1
Y1 - 2014/1/1
N2 - In this paper, we present for the first time the synthesis in satisfactory yields and characterization of a new family of five Npolyetheralkyl- 3,5-pyrazole derived ligands (L1-L5) as well as regioselectivity studies by NMR techniques. Ligands L1, L2, L3/3', and L4/4' were obtained by N-alkylation reaction, whereas for L5 O-alkylation reaction was followed. In N-alkylation, the alkylating agent was 1-chloro-2-[2-(2-methoxyethoxy)ethoxy]ethane, NaOEt as base and dry toluene as solvent. In O-alkylation, the alkylating agent is 1- chloro-2-[2-(2-methoxyethoxy)ethoxy]ethane, metallic Na as a base and dry tetrahydrofurane as solvent. In general, the two methods lead to high yields (60-95%), with reaction times of 24 h, except for L2 (48 h). All synthesized ligands have been characterized by elemental analyses, electrospray mass spectra, infrared spectra, 1H, 13C{1H} and HSQC NMR spectroscopy. Furthermore, the different regioselectivity observed in the synthetic reactions of pyrazole precursors with one pyridyl substituent has been rationalized from theoretical calculations. All together proves that the different behavior depends on whether the rate determining step is the SN2 reaction or the formation of the precursor complexes between pyrazolide-Na+ chelates and the polyether chloride chain. The application of this new family in supramolecular crystal engineering is interesting due to the different bonding properties of the heteroatoms (N vs. O) present in the structure of the ligands. © 2014 Bentham Science Publishers.
AB - In this paper, we present for the first time the synthesis in satisfactory yields and characterization of a new family of five Npolyetheralkyl- 3,5-pyrazole derived ligands (L1-L5) as well as regioselectivity studies by NMR techniques. Ligands L1, L2, L3/3', and L4/4' were obtained by N-alkylation reaction, whereas for L5 O-alkylation reaction was followed. In N-alkylation, the alkylating agent was 1-chloro-2-[2-(2-methoxyethoxy)ethoxy]ethane, NaOEt as base and dry toluene as solvent. In O-alkylation, the alkylating agent is 1- chloro-2-[2-(2-methoxyethoxy)ethoxy]ethane, metallic Na as a base and dry tetrahydrofurane as solvent. In general, the two methods lead to high yields (60-95%), with reaction times of 24 h, except for L2 (48 h). All synthesized ligands have been characterized by elemental analyses, electrospray mass spectra, infrared spectra, 1H, 13C{1H} and HSQC NMR spectroscopy. Furthermore, the different regioselectivity observed in the synthetic reactions of pyrazole precursors with one pyridyl substituent has been rationalized from theoretical calculations. All together proves that the different behavior depends on whether the rate determining step is the SN2 reaction or the formation of the precursor complexes between pyrazolide-Na+ chelates and the polyether chloride chain. The application of this new family in supramolecular crystal engineering is interesting due to the different bonding properties of the heteroatoms (N vs. O) present in the structure of the ligands. © 2014 Bentham Science Publishers.
KW - N-alkylation
KW - N-polyether-3,5-pyrazole derived ligands
KW - O-alkylation
KW - Regioisomers
U2 - 10.2174/15701794113106660077
DO - 10.2174/15701794113106660077
M3 - Article
SN - 1570-1794
VL - 11
SP - 149
EP - 155
JO - Current Organic Synthesis
JF - Current Organic Synthesis
IS - 1
ER -