15451-35-1Relevant articles and documents
Controllable Isomerization of Alkenes by Dual Visible-Light-Cobalt Catalysis
Meng, Qing-Yuan,Schirmer, Tobias E.,Katou, Kousuke,K?nig, Burkhard
supporting information, p. 5723 - 5728 (2019/04/03)
We report herein that thermodynamic and kinetic isomerization of alkenes can be accomplished by the combination of visible light with Co catalysis. Utilizing Xantphos as the ligand, the most stable isomers are obtained, while isomerizing terminal alkenes over one position can be selectively controlled by using DPEphos as the ligand. The presence of the donor–acceptor dye 4CzIPN accelerates the reaction further. Transformation of exocyclic alkenes into the corresponding endocyclic products could be efficiently realized by using 4CzIPN and Co(acac)2 in the absence of any additional ligands. Spectroscopic and spectroelectrochemical investigations indicate CoI being involved in the generation of a Co hydride, which subsequently adds to alkenes initiating the isomerization.
Beyond classical reactivity patterns: Hydroformylation of vinyl and allyl arenes to valuable β- And γ-aldehyde intermediates using supramolecular catalysis
Dydio, Pawe?,Detz, Remko J.,De Bruin, Bas,Reek, Joost N. H.
supporting information, p. 8418 - 8429 (2014/06/24)
In this study, we report on properties of a series of rhodium complexes of bisphosphine and bisphosphite L1-L7 ligands, which are equipped with an integral anion binding site (the DIM pocket), and their application in the regioselective hydroformylation of vinyl and allyl arenes bearing an anionic group. In principle, the binding site of the ligand is used to preorganize a substrate molecule through noncovalent interactions with its anionic group to promote otherwise unfavorable reaction pathways. We demonstrate that this strategy allows for unprecedented reversal of selectivity to form otherwise disfavored β-aldehyde products in the hydroformylation of vinyl 2- and 3-carboxyarenes, with chemo- and regioselectivity up to 100%. The catalyst has a wide substrate scope, including the most challenging substrates with internal double bonds. Coordination studies of the catalysts under catalytically relevant conditions reveal the formation of the hydridobiscarbonyl rhodium complexes [Rh(Ln)(CO)2H]. The titration studies confirm that the rhodium complexes can bind anionic species in the DIM binding site of the ligand. Furthermore, kinetic studies and in situ spectroscopic investigations for the most active catalyst give insight into the operational mode of the system, and reveal that the catalytically active species are involved in complex equilibria with unusual dormant (reversibly inactivated) species. In principle, this involves the competitive inhibition of the recognition center by product binding, as well as the inhibition of the metal center via reversible coordination of either a substrate or a product molecule. Despite the inhibition effects, the substrate preorganization gives rise to very high activities and efficiencies (TON > 18‰000 and TOF > 6000 mol mol-1 h-1), which are adequate for commercial applications.
Cyclic Siloxanes with Mesogenic Side Groups
Kreuzer, F.-H.,Andrejewski, D.,Haas, W.,Haeberle, N.,Riepl, G.,Spes, P.
, p. 345 - 378 (2007/10/02)
Cyclic liquid crystalline siloxanes (CLCS) are optical uniaxial positive (SA, N) and negative (N*) materials in accordance with calamitic structures.X-Ray measurements indicate, that the distances of SA layers correspond with the length of the monomer unit.In the case of mesogens with high polarity the distance is 1.7 fold the length of the monomer unit.A bundle model is proposed for CLC siloxanes.
