2739-97-1Relevant articles and documents
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Johnson, M. D.,Tobe, M. L.,Wong, L. Y.
, (1968)
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σ-bonded organotransition-metal ions. Part IV. Kinetics and mechanism of the acid-catalysed decomposition of the 4- pyridiomethylpentacyanocobaltate(III) ion
Johnson,Tobe,Wong, Lai-Yoong
, p. 491 - 497 (1967)
Potassium 4-pyridylmethylpentacyanocobaltate(III) monohydrate, prepared by the reaction of cobaltous cyanide with 4-bromomethylpyridinium bromide, is stable to air in aqueous solution. In solutions of pH 9·2 and below the pyridine ring is protonated to form the 4-pyridiomethylpentacyanocobaltate(III) ion and in perchloric acid of ca. 4M a second proton is added, presumably to one of the cyanide ligands. The kinetics of decomposition of these species have been investigated. In > 1M-perchloric acid the rate of decomposition increases linearly with increasing acid concentration to a maximum in ≥ 7·5M-acid, owing to the unimolecular decomposition of the protonated 4-pyridiomethylpentacyanocobalate(III) ion to the 4-cyanomethylpyridinium ion. At lower acidities (pH 1-5) the kinetics are complicated by the slowly established equilibrium between the 4-pyridiomethylpentacyanocobaltate(III) ion and the 4-pyridiomethylaquotetracyanocobaltate(III) ion and by the further decomposition of the latter ion at a rate comparable with the initial rate of approach to equilibrium. The kinetics in this pH region can however be simplified by the addition of small quantities of HCN sufficient to suppress the formation of the aquotetracyano-complex so that only the acid-catalysed decomposition of the pentacyano-complex is observed.
Robust and Scalable Approach to 1,3-Disubstituted Pyridylcyclobutanes
Demchuk, Oleksandr P.,Hryshchuk, Oleksandr V.,Vashchenko, Bohdan V.,Radchenko, Dmytro S.,Kovtunenko, Volodymyr O.,Komarov, Igor V.,Grygorenko, Oleksandr O.
, p. 5937 - 5949 (2019)
An approach to all isomeric 3-pyridylcyclobutane-derived building blocks, i.e. ketones, alcohols and amines, is described. Synthesis of the title compounds relied on the five-step reaction sequence including alkylation of isomeric pyridyl acetonitriles with 1,3-dibromo-2,2-dimethoxypropane. Hydrolysis, decarboxylation and removal of the ketal moiety led to the key 3-pyridylcyclobutanones (obtained on up to 120 g scale in a single run), which were transformed into the corresponding alcohols and amines with high diastereoselectivity. The title cyclobutanone derivatives were used to synthesize three isomeric nicotine analogues, as well as for parallel synthesis of a small lead-like compound library via reductive amination.
Mechanistic study of carboxylic acid and phosphate ester cleavage by oximate metal complexes surpassing the limiting reactivity of highly basic free oximate anions
Flores-Alamo, Marcos,Gómez-Tagle, Paola,Lugo-González, José Carlos,Yatsimirsky, Anatoly K.
supporting information, p. 2452 - 2467 (2020/03/05)
Two tridentate and one tetradentate new ligands containing the terminal oxime group separated from secondary amino and pyridine groups as additional binding sites by two or three methylene groups have been prepared. Their acid-base properties, as well as the composition and stability of their complexes with Zn(ii) and Cd(ii) ions, were determined by potentiometric and spectrophotometric titrations. The X-ray structure of a Cd(ii) complex of a related tridentate oxime ligand previously studied in solution was determined. All oximate complexes show high reactivity in the cleavage of aryl acetates, paraoxon, parathion and 4-nitrophenyl diphenyl phosphate, with rate constants significantly surpassing the limiting rate constants observed for highly basic free oximate anions. The second-order rate constants for individual oximate complexes in solution are assigned to each ligand, metal cation and substrate. The results of the cleavage of 4-substituted phenyl acetates were analyzed in terms of Br?nsted correlations with the leaving group pKa, which demonstrated a change in the rate determining step from the nucleophilic attack to the leaving group departure upon an increase in the leaving group basicity. The zero slope of the Br?nsted correlation for the nucleophilic attack indicates transition state stabilization through electrophilic assistance by the metal ion. This interpretation is supported by metal selectivity in the relative efficiency of the cleavage of paraoxon and parathion. The existence of the alpha-effect in ester cleavage by coordinated oximates is confirmed by an analysis of the Br?nsted correlations with the nucleophile basicity for metal bound oximate and alkoxo or hydroxo nucleophiles. The very high reactivity of the oximate complexes of the new ligands is attributed to transition state stabilization and to the removal of the solvational imbalance of oximate anions that impedes the expected increase in the reactivity of highly basic free anions.
Mechanistic Insight Facilitates Discovery of a Mild and Efficient Copper-Catalyzed Dehydration of Primary Amides to Nitriles Using Hydrosilanes
Liu, Richard Y.,Bae, Minwoo,Buchwald, Stephen L.
supporting information, p. 1627 - 1631 (2018/02/17)
Metal-catalyzed silylative dehydration of primary amides is an economical approach to the synthesis of nitriles. We report a copper-hydride(CuH)-catalyzed process that avoids a typically challenging 1,2-siloxane elimination step, thereby dramatically increasing the rate of the overall transformation relative to alternative metal-catalyzed systems. This new reaction proceeds at ambient temperature, tolerates a variety of metal-, acid-, or base-sensitive functional groups, and can be performed using a simple ligand, inexpensive siloxanes, and low catalyst loading.