Ap alladium-catalyzed cross-coupling between in situ generated allenyl/propargyl-lithium species and aryl bromides to yield highly functionalizeda llenes is reported. The direct and selective formation of allenic products preventing the corresponding isomeric propargylic product is accomplished by the choice of SPhos or XPhos based Pd catalysts. The methodology avoids the prior transmetalation to other transition metals or reverse approaches that required prefunctionalization of substrates with leaving groups,r esulting in af ast and efficient approach for the synthesis of tri-and tetrasubstituted allenes.E xperimental and theoretical studies on the mechanism showc atalyst control of selectivity in this allene formation.
Fullerene receptors prepared by a twofold CuI‐catalyzed azide‐alkyne cycloaddition reaction with π‐extended tetrathiafulvalene (exTTF) have been covalently linked to single‐walled carbon nanotubes and multi‐walled carbon nanotubes. The nanoconjugates obtained were characterized by several analytical, spectroscopic and microscopic techniques (TEM, FTIR, Raman, TGA and XPS), and evaluated as C60 receptors by using UV‐Vis spectroscopy. The complexation between the exTTF‐triazole receptor in the free state and C60 was also studied by UV‐Vis and 1H NMR titrations, and compared with analogous triazole‐based tweezer‐type receptors containing the electron‐acceptor 11,11,12,12‐tetracyano‐9,10‐anthraquinodimethane and benzene rings instead of exTTF motifs, providing in all cases very similar values for the association constant (log Ka≈3.0−3.1). Theoretical density functional theory calculations demonstrated that the enhanced interaction between the host and the guest upon increasing the size of the π‐conjugated arms of the tweezer is compensated by an increase in the energy penalty needed to distort the geometry of the host to wrap C60.
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