19731-71-6Relevant articles and documents
Metal-free, redox-neutral, site-selective access to heteroarylamine via direct radical?radical cross-coupling powered by visible light photocatalysis
Zhou, Chao,Lei, Tao,Wei, Xiang-Zhu,Ye, Chen,Liu, Zan,Chen, Bin,Tung, Chen-Ho,Wu, Li-Zhu
supporting information, p. 16805 - 16813 (2020/11/09)
Transition-metal-catalyzed C?N bond-forming reactions have emerged as fundamental and powerful tools to construct arylamines, a common structure found in drug agents, natural products, and fine chemicals. Reported herein is an alternative access to heteroarylamine via radical?radical cross-coupling pathway, powered by visible light catalysis without any aid of external oxidant and reductant. Only by visible light irradiation of a photocatalyst, such as a metal-free photocatalyst, does the cascade single-electron transfer event for amines and heteroaryl nitriles occur, demonstrated by steady-state and transient spectroscopic studies, resulting in an amine radical cation and aryl radical anion in situ for C?N bond formation. The metal-free and redox economic nature, high efficiency, and site-selectivity of C?N cross-coupling of a range of available amines, hydroxylamines, and hydrazines with heteroaryl nitriles make this protocol promising in both academic and industrial settings.
Scandium(III) catalysis of transimination reactions. Independent and constitutionally coupled reversible processes
Giuseppone, Nicolas,Schmitt, Jean-Louis,Schwartz, Evan,Lehn, Jean-Marie
, p. 5528 - 5539 (2007/10/03)
Sc(OTf)3 efficiently catalyzes the self-sufficient transimination reaction between various types of C=N bonds in organic solvents, with turnover frequencies up to 3600 h-1 and rate accelerations up to 6 × 105. The mechanism of the crossover reaction in mixtures of amines and imines is studied, comparing parallel individual reactions with coupled equilibria. The intrinsic kinetic parameters for isolated reactions cannot simply be added up when several components are mixed, and the behavior of the system agrees with the presence of a unique mediator that constitutes the core of a network of competing reactions. In mixed systems, every single amine or imine competes for the same central hub, in accordance with their binding affinity for the catalyst metal ion center. More generally, the study extends the basic principles of constitutional dynamic chemistry to interconnected chemical transformations and provides a step toward dynamic systems of increasing complexity.
Thermal decomposition of O-benzyl ketoximes; role of reverse radical disproportionation
Blake, Jessie A.,Ingold, Keith U.,Lin, Shuqiong,Mulder, Peter,Pratt, Derek A.,Sheeller, Brad,Walton, John C.
, p. 415 - 420 (2007/10/03)
Thermolyses of seven dialkyl, two alkyl-aryl and two diaryl O-benzyl ketoxime ethers, R1R2C=NOCH2Ph, have been examined in three hydrogen donor solvents: tetralin, 9,10-dihydrophenanthrene, and 9,10-dihydroanthracene. All the oxime ethers gave the products expected from homolytic scission of both the O-C bond (viz., R1R2C=NOH and PhCH3) and N-O bond (viz., R1R2C=NH and PhCH2OH). The yields of these products depended on which solvent was used and the rates of decomposition of the O-benzyl oxime ethers were greater in 9,10-dihydrophenanthrene and 9,10-dihydroanthracene than in tetralin. These results indicated that a reverse radical disproportionation reaction in which a hydrogen atom was transferred from the solvent to the oxime ether, followed by β-scission of the resultant aminoalkyl radical, must be important in the latter two solvents. Benzaldehyde was found to be an additional product from thermolyses conducted in tetralin. This, and other evidence, indicated that another induced decomposition mode involving abstraction of a benzylic hydrogen atom, followed by β-scission of the resulting benzyl radical, became important for some substrates. Participation by minor amounts of enamine tautomers of the oxime ethers was shown to be negligible by comparison of thermolysis data for the O-benzyloxime of bicyclo[3.3.1]nonan-9-one, which cannot give an enamine tautomer, with that of the O-benzyloxime of cyclohexanone.
N-nitroso-N,O-dialkylhydroxylamines: Preparation, structure, and mechanism of the hydronium ion catalysed solvolytic nitrous oxide extrusion reaction
Bhat, J. Ishwara,Clegg, William,Maskill, Howard,Elsegood, Mark R.J.,Menneer, Iain D.,Miatt, Peter C.
, p. 1435 - 1446 (2007/10/03)
Eleven N-nitroso-N,O-dialkylhydroxylamines, RN(NO)OR′, have been prepared and the mechanisms of their hydronium ion catalysed solvolyses in aqueous solution which liberate nitrous oxide have been investigated. All reactions are first-order in substrate and first-order in hydronium ion, and the second-order rate constants at 25°C vary over a range of less than 140 in spite of considerable variation in substrate structure (R ranges from methyl to 4-methoxybenzyl to 2-adamantyl, for example) and changes in solvent composition (water with up to 50% methanol or 66% acetonitrile). Enthalpies and entropies of activation are qualitatively similar throughout the range (ΔH?= 72-93 kJ mol-1 and ΔS? = -19 to -57 J K-1 mol-1) which, with the product analyses, are accommodated by a mechanism involving pre-equilibrium protonation of the substrates followed by rate-limiting dissociation to give RN2O+ and HOR′. The oxodiazonium ion intermediate, RN2O+, then dissociates further to give the carbenium ion intermediate, R+, or suffers direct nucleophilic displacement of N2O by solvent (the external nucleophile) or by R′OH (the internal nucleophile liberated in the initial fragmentation). The carbenium ion, R+ (if formed), suffers nucleophilic capture either by solvent or by R′OH. When acetonitrile is the co-solvent (rather than methanol) for the N-(2-adamantyl) substrate 3g, the product of the Ritter reaction, 2-acetamidoadamantane, is detected. These nitrous oxide liberating reactions are compared with the nitric oxide liberating reactions of related N-nitrosohydroxylamines, and the origin of the difference between them is identified. The N(1)-nitroso group in the N,O-dibenzyl compound 3c is shown by X-ray crystallography to be essentially coplanar with the C and O atoms also bonded to N(1).
Preparation of six membered carocycles by aryl-tellurium mediated free-radical cyclisation
Barton,Dalko,Gero
, p. 4713 - 4716 (2007/10/02)
Radical cyclisation of various telluro-compounds was examined. Olefins conjugated to an electron withdrawing group, (7, 8, 9, 10, and 11) gave high yields of the corresponding six membered products. Non-activating olefin 23 gave the corresponding thiopyridyl derivative 24 as the only product. The photolysis, using oxime 18 as radicophile for the cyclisation, proceeded slowly at room temperature, and gave only a low yield of products 19 and 20.
THERMAL REARRANGEMENT OF CYCLOHEXANONE OXIME O-BENZYL ETHER
Koyama, Junko,Sugita, Teruyo,Suzuta. Yukio
, p. 1291 - 1294 (2007/10/02)
Thermal rearrangement of cyclohexanone oxime O-benzyl ether under air gave 1,2,3,4,7,8,9,10-octahydro-6-phenyl-phenanthridine in 35percent isolated yield, which yielded 6-phenyl-phenanthridine by dehydrogenation reaction with palladium carbon.The structur
