Abstract
The study of the reactivity of three 2-phenyl-3H-indole ligands of general formulae C8H3N-2-(C6H4-4-R1)-3-NOMe-5-R2 (1) [with R1 = H, R2 = OMe (a); R1 = R2 = H (b) or R1 = Cl, R2 = H (c)] with [Pd(η3-1-R3C3H4)(μ-Cl)]2 (R3 = H or Ph) has allowed us to isolate two sets of new Pd(II)-allyl complexes of general formulae [Pd(η3-1-R3C3H4)(1)Cl] {R3 = H (2) or Ph (3)}. Compounds 2a–2c and 3a–3c were characterized by elemental analyses, mass spectrometry and IR spectroscopy. The crystal structures of 2a, 3a and 3b were also determined by X-ray diffraction. 1H-NMR studies reveal the coexistence of two (for 2a–2c) or three (for 3a–3c) isomeric forms in CD2Cl2 solutions at 182 K. Additional studies on the catalytic activity of mixtures containing [Pd(η3-C3H5)(μ-Cl)]2 and the parent ligand (1a–1c) in the allylic alkylation of (E)-3-phenyl-2-propenyl (cinnamyl) acetate with sodium diethyl 2-methylmalonate as well as the stoichiometric reaction between compounds 3a and 3c with the nucleophile reveal that in both cases the formation of the linear trans- derivative is strongly preferred over the branched product. Computational studies at a DFT level on compound 3a allowed us to compare the relative stability of their isomeric forms present in solution and to explain the regioselectivity of the catalytic and stoichiometric processes.
Highlights
Indole is one of the most important heterocycles for its presence in bioactive natural products, pharmaceuticals, and agrochemicals [1,2,3,4,5,6,7,8,9]
9 of on synthesis, including the preparation of natural products [25,26,27,28,44] and, (b) there is a lack of studies the use of indoles in Pd(II) catalyzed allylic alkylations, we investigated the potential utility of lack of studies on in the use of indoles in Pd(II)
NMR studies at 182 K indicated: (a) the coexistence of two isomers and small amounts of other minor species; (b) that in the major components the arrangement of the Cα carbon of the allyl and the nitrogen occupied adjacent positions, the phenyl ring of the allyl unit was in the syn- site and differed in the conformation of the 1-PhC3 H5 ligand that is to say corresponding to isomers A and E
Summary
Indole is one of the most important heterocycles for its presence in bioactive natural products, pharmaceuticals, and agrochemicals [1,2,3,4,5,6,7,8,9]. In Medicinal Chemistry [1,2,3,4,6,10,11,12], due to their biological activity, and valuable reagents for the design and synthesis of compounds with interesting properties and applications in a variety of fields [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19]. Interesting applications of novel indole derivatives as dyes [1,2,3,13], as components of Dye Sensitized Solar Cells (DSSC) [1,2,3,5]
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