3972-25-6Relevant academic research and scientific papers
Synthesis and Reactivity of Low-Coordinate Titanium Synthons Supported by a Reduced Redox-Active Ligand
Clark, Kensha Marie
, p. 6443 - 6448 (2016)
To further explore the reactivity and redox capability of the bis-arylimino acenaphthylene ligand (BIAN) in early transition metal complexes, the coordinatively unsaturated titanium synthons, [(dpp-BAAN)Ti(R)2] ([dpp-BAAN]2- = N,N′-bis(2,6-diisopropylphenylamido)acenaphthylene and R = OtBu (2) or CH2C(CH3)3 (3)), in which the BAAN ligand is reduced by two electrons, were isolated in good yields via sterically induced radical elimination reactions. Addition of p-tolyl azide to complex 3 initiated reductive elimination of the neopentyl ligands to generate a putative imido species. The imido species was trapped by a second oxidative addition of chloride ligands to yield the titanium imido complex, [(dpp-BIAN)Ti[=N(4-C6H4Me)]Cl2 (4). These reactions demonstrate that the BAAN ligand can provide redox equivalents for enhanced reactivity that includes oxidative addition and reductive elimination at d0 metal centers.
Copper-catalyzed synthesis of CN-containing chroman-4-ones via intramolecular radical cascade acyl-cyanation reaction
Wang, Liang,Jiang, Min,Shi, Ming-qi
, (2021)
A copper-catalyzed intramolecular radical cascade acyl-cyanation to synthesize cyano-containing chroman-4-ones has been developed. A series of CN-substituted chroman-4-one derivatives can be prepared with moderate to good yields using green cyano source under mild conditions. Control experiments indicated this reaction involved an intramolecular acyl radical addition/cyanation process. Moreover, this protocol features step- and atom-economy, and the introduction of cyano group into the chroman-4-one is of great interest and importance.
Photolysis of solutions of 3-terf-butylperoxy-3-methyl-1-butyne
Shutova,Skakovskii,Agabekov,Murashko,Dikusar
, p. 627 - 632 (2001)
Photolysis of solutions of 3-tert-butyl-3-methyl-1-butyne in CD3OD and C6D12 was studied by means of 1H NMR spectroscopy, chemical nuclear polarization of the reaction products in the range 213-333 K, and kinetic measurements. It is shown that 3-tert-butyl-3-methyl-1-butyne decomposes primarily from a singlet electronic state. A scheme is proposed of the most probable reactions involving the radicals formed and solvent molecules. It is found that secondary processes play an important role in the initiation of the chemical nuclear polarization and the photolysis mechanism.
Photocatalytic Reductive Radical-Polar Crossover for a Base-Free Corey–Seebach Reaction
Crespi, Stefano,Donabauer, Karsten,K?nig, Burkhard,Murugesan, Kathiravan,Rozman, Ur?a
supporting information, p. 12945 - 12950 (2020/09/23)
A metal-free generation of carbanion nucleophiles is of prime importance in organic synthesis. Herein we report a photocatalytic approach to the Corey–Seebach reaction. The presented method operates under mild redox-neutral and base-free conditions giving the desired product with high functional group tolerance. The reaction is enabled by the combination of photo- and hydrogen atom transfer (HAT) catalysis. This catalytic merger allows a C?H to carbanion activation by the abstraction of a hydrogen atom followed by radical reduction. The generated nucleophilic intermediate is then capable of adding to carbonyl electrophiles. The obtained dithiane can be easily converted to the valuable α-hydroxy carbonyl in a subsequent step. The proposed reaction mechanism is supported by emission quenching, radical–radical homocoupling and deuterium labeling studies as well as by calculated redox-potentials and bond strengths.
Phosphonium Phenolate Zwitterion vs Phosphonium Ylide: Synthesis, Characterization and Reactivity Study of a Trimethylphosphonium Phenolate Zwitterion
Xiao, Jing,Li, Qiang,Shen, Ruwei,Shimada, Shigeru,Han, Li-Biao
supporting information, p. 5715 - 5720 (2019/11/22)
4-Methoxy-3-(trimethylphosphonio)phenolate was obtained from a regioselective addition of PMe3 to p-quinone monoacetal. This compound undergoes hydrogen isotope exchange with D2O or CD3CN, and is capable of catalyzing H/D exchange of CD3CN with substrates bearing weakly acidic hydrogens. It exhibits similar reactivity to phosphorus ylides for olefinations of aldehydes. A possible tautomerization between the phosphonium phenolate zwitterion and phosphonium ylide is proposed for the first time to rationalize the unique reactivity.
Iodine mediated deprotection of N-tert-butanesulfinyl amines: A functional group compatible method
Chen, Wen,Ren, Jian,Wang, Minshou,Dang, Lingjing,Shen, Xianfu,Yang, Xiaodong,Zhang, Hongbin
supporting information, p. 6259 - 6262 (2014/06/09)
In the presence of iodine, a functional group compatible method for the deprotection of tert-butanesulfinyl and p-toluenesulfinyl units was developed. This journal is the Partner Organisations 2014.
Catalysis in a porous molecular capsule: Activation by regulated access to sixty metal centers spanning a truncated icosahedron
Kopilevich, Sivil,Gil, Adria,Garcia-Rates, Miquel,Bonet-Avalos, Josep,Bo, Carles,Mueller, Achim,Weinstock, Ira A.
experimental part, p. 13082 - 13088 (2012/10/08)
The 30 cationic {MoV2O4(acetate)} + units linking 12 negatively charged pentagonal "ligands," {(MoVI)MoVI5O21(H 2O)6}6- of the porous metal-oxide capsule, [{MoVI6O21(H2O)6} 12{MoV2O4(acetate)} 30]42- provide active sites for catalytic transformations of organic "guests". This is demonstrated using a well-behaved model reaction, the fully reversible cleavage and formation of methyl tert-butyl ether (MTBE) under mild conditions in water. Five independent lines of evidence demonstrate that reactions of the MTBE guests occur in the ca. 6 × 10 3 A3 interior of the spherical capsule. The Mo atoms of the {MoV2O4(acetate)}+ linkers - spanning an ca. 3-nm truncated icosahedron - are sterically accessible to substrate, and controlled removal of their internally bound acetate ligands generates catalytically active {MoV2O4(H 2O)2}2+ units with labile water ligands, and Lewis- and Bronsted-acid properties. The activity of these units is demonstrating by kinetic data that reveal a first-order dependence of MTBE cleavage rates on the number of acetate-free {MoV2O 4(H2O)2}2+ linkers. DFT calculations point to a pathway involving both Mo(V) centers, and the intermediacy of isobutene in both forward and reverse reactions. A plausible catalytic cycle - satisfying microscopic reversibility - is supported by activation parameters for MTBE cleavage, deuterium and oxygen-18 labeling studies, and by reactions of deliberately added isobutene and of a water-soluble isobutene analog. More generally, pore-restricted encapsulation, ligand-regulated access to multiple structurally integral metal-centers, and options for modifying the microenvironment within this new type of nanoreactor, suggest numerous additional transformations of organic substrates by this and related molybdenum-oxide based capsules.
Selective Ru(0)-catalyzed deuteration of electron-rich and electron-poor nitrogen-containing heterocycles
Groell, Birgit,Schnuerch, Michael,Mihovilovic, Marko D.
experimental part, p. 4432 - 4437 (2012/06/30)
A highly selective Ru3(CO)12-catalyzed deuteration method using t-BuOD as deuterium source is reported. Electron-rich and electron-poor N-heteroarenes such as indoles, azaindoles, deazapurines, benzimidazole, quinolines, isoquinolines, and pyridines were efficiently deuterated at specific positions with high selectivity; in most cases, deuterium incorporation was close to the theoretically possible values. To further increase deuteration degrees, several cycles of the reaction protocol can be carried out which gave superior deuteration degrees employing a much lower excess of deuterating agent compared to established protocols. It was proved that the same protocol can in principle be applied to tritiation reactions important for radioactive labeling of bioactive molecules.
Catalysis of transesterification reactions by lanthanides - Unprecedented acceleration of methanolysis of aryl and alkyl esters promoted by La(OTf)3 at neutral sspH and ambient temperatures
Neverov, Alexei A.,McDonald, Todd,Gibson, Graham,Brown
, p. 1704 - 1710 (2007/10/03)
La3+ catalysis of the methanolysis of the esters p-nitrophenyl, 2,4-dinitrophenyl, and phenyl acetate (1-3), phenyl benzoate (4), and ethyl, i-propyl, cyclohexyl, and tert-butyl acetate (5, 6a, 6b, 7) was studied at 25°C as a function of sspH and [La(OTf)3]. The active form of the catalyst is attributed to a dimethoxy-bridged dimer of stoichiometry (La3+)2(-OCH3)2, having maximum activity atsspH 8 to 9. For preparative reactions, the active catalyst can be made in situ simply by adding 0.01 equiv of La(OTf)3, and 0.01 equiv of NaOCH3 to a methanol solution containing the ester (1 M). Strong catalysis of methanolysis of both aryl and alkyl esters was observed, although tert-butyl acetate was inert. At sspH 8.5, where the catalyst is maximally active, the transesterification reactions are accelerated by 40 000-fold to 18 000 000-fold in the presence of as little as 5 mM catalyst relative to the background reaction depending on the ester structure. A mechanism for catalysis of transesterification is presented wherein the reactive species is generated by breaking a single La-OCH3 bond of the dimethoxy-bridged dimer to reveal a nucleophilic metal-bound methoxide - Lewis acid La3+ electrophilic pair.
α-(Acyloxy)dialkylnitrosamines: Effects of structure on the formation of N-nitrosiminium ions and a predicted change in mechanism
Hongliang, Cai,Fishbein, James C.
, p. 1826 - 1833 (2007/10/03)
The decay of α-(acyloxy)dialkylnitrosamines in aqueous solutions has been studied with a view toward elucidating mechanistic details and effects of structure on mechanism and reactivity. Rate constants (k1) for the pH-independent decay of 43 α-(acyloxy)dialkylnitrosamines have been determined. Observations from these and other experiments rule out decomposition via an anchimeric assistance mechanism involving the Z isomer that had previously been suggested. All of the reported data for most of the compounds is consistent with a mechanism involving the formation of N-nitrosiminium ions in or before the rate-limiting step. Structure -reactivity correlations indicate that the stability of α-(acyloxy)dialkylnitrosamines is determined by electronic properties of substituents at RN and RC as well as by the ability of substituents RC to engage in hyperconjugative interactions of C-H bonds with the developing cationic center in the transition state for nitrosiminium ion formation. Attachment of substituents of sufficient electron-withdrawing power at RN and RC results in a predicted change in mechanism to what appears to be an acyl group attack mechanism.
