- Facile synthesis of 3,5-diaryl-1,2,4-triazoles via copper-catalyzed domino nucleophilic substitution/oxidative cyclization using amidines or imidates as substrates
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Two methods for the synthesis of 3,5-diaryl-1,2,4-triazoles, both domino reactions, are reported. The first procedure, the Cu(OTf)2-catalyzed reaction between two amidines using NaHCO3 as a base, 1,10-phenanthroline as an additive and K3[Fe(CN)6]/ atmospheric oxygen as the oxidant, delivers 3,5-diaryl-1,2,4-triazoles with yields up to 68%. The second procedure for the synthesis of 3,5-diaryl-1,2,4- triazoles with yields up to 64% rests on the Cu(OTf)2-catalyzed reaction between two imidates and ammonium carbonate. This method features the formation of three bonds in a single synthetic step.
- Sudheendran, Kavitha,Schmidt, Dietmar,Frey, Wolfgang,Conrad, Jürgen,Beifuss, Uwe
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p. 1635 - 1645
(2014/02/14)
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- Helicity-encoded molecular strands: Efficient access by the hydrazone route and structural features
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Control over the folding of molecular strands may be achieved by appropriate choice of the constituting subunits, in particular for chains of specific heterocycles such as sequences of directly connected pyridine (py) and pyrimidine (pym) rings, which are known to fold into extended helical structures. Since the hydrazone (hyz) group represents an isomorphic analogue of a py site, the condensation of hydrazine and carboxaldehyde derivatives of pym offers a very efficient approach to strands incorporating hyz instead of py units and constituted by sequences of alternating hyz and pym group. A. series of such strands of different lengths, up to ten hyz units, i.e., 1-7, were synthesized. Their spectral properties indicate that they fold indeed into helical shapes. Extensive characterization was performed in solution by IH-NMR spectroscopy and in the solid state by determination of the crystal structures of eight such strands. They all display the expected helical geometry with up to 3 1/3, turns and direct stacking contacts. The efficiency and flexibility of the synthetic approach as well as its wide potential for generation of diversity through lateral decoration make the (hyz - pym) subunit a particularly attractive helicity codon.
- Schmitt, Jean-Louis,Stadler, Adrian-Mihail,Kyritsakas, Nathalie,Lehn, Jean-Marie
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p. 1598 - 1624
(2007/10/03)
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