56857-08-0Relevant academic research and scientific papers
Site-Selective Acceptorless Dehydrogenation of Aliphatics Enabled by Organophotoredox/Cobalt Dual Catalysis
Zhou, Min-Jie,Zhang, Lei,Liu, Guixia,Xu, Chen,Huang, Zheng
supporting information, p. 16470 - 16485 (2021/10/20)
The value of catalytic dehydrogenation of aliphatics (CDA) in organic synthesis has remained largely underexplored. Known homogeneous CDA systems often require the use of sacrificial hydrogen acceptors (or oxidants), precious metal catalysts, and harsh reaction conditions, thus limiting most existing methods to dehydrogenation of non- or low-functionalized alkanes. Here we describe a visible-light-driven, dual-catalyst system consisting of inexpensive organophotoredox and base-metal catalysts for room-temperature, acceptorless-CDA (Al-CDA). Initiated by photoexited 2-chloroanthraquinone, the process involves H atom transfer (HAT) of aliphatics to form alkyl radicals, which then react with cobaloxime to produce olefins and H2. This operationally simple method enables direct dehydrogenation of readily available chemical feedstocks to diversely functionalized olefins. For example, we demonstrate, for the first time, the oxidant-free desaturation of thioethers and amides to alkenyl sulfides and enamides, respectively. Moreover, the system's exceptional site selectivity and functional group tolerance are illustrated by late-stage dehydrogenation and synthesis of 14 biologically relevant molecules and pharmaceutical ingredients. Mechanistic studies have revealed a dual HAT process and provided insights into the origin of reactivity and site selectivity.
Catalytic Allylic Oxidation of Cyclic Enamides and 3,4-Dihydro-2H-Pyrans by TBHP
Yu, Yang,Humeidi, Ranad,Alleyn, James R.,Doyle, Michael P.
, p. 8506 - 8513 (2017/08/23)
Allylic oxidation of heteroatom substituted cyclic alkenes by tert-butyl hydroperoxide (70% TBHP in water) using catalytic dirhodium caprolactamate [Rh2(cap)4] forms enone products with a variety of 2-substituted cyclic enamides and 3,4-dihyro-2H-pyrans. These reactions occur under mild reaction conditions, are operationally convenient to execute, and are effective for product formation with as low as 0.25 mol% catalyst loading. With heteroatom stabilization of the intermediate allylic free radical two sites for oxidative product formation are possible, and the selectivity of the oxidative process varies with the heteroatom when R = H. Cyclic enamides produce 4-piperidones in good yields when R = alkyl or aryl, but oxidation of 2H-pyrans also gives alkyl cleavage products. Alternative catalysts for TBHP oxidations show comparable selectivities but give lower product yields.
Superbase-promoted direct N-carbonylation of pyrrole with carbonic acid diesters
Carafa, Marianna,Distaso, Monica,Mele, Valentina,Trani, Francesca,Quaranta, Eugenio
, p. 3691 - 3696 (2008/09/20)
Carbonic acid diesters have been investigated as carbonylating agents in the direct reaction with pyrrole (HetNH). In the presence of superbases (DBU, P1-t-Bu, BTPP) as catalysts, the heteroaromatic substrate can be N-carbonylated by direct reaction with carbonic acid diesters under not-severe experimental conditions. The carbonylation reaction makes accessible pyrrole N-carbonyl derivatives (HetNC(O)OR, (HetN)2CO) selectively through a simple straightforward way, which offers a safe eco-friendly alternative to the traditional synthetic methods based on hazardous phosgene or phosgene-derivatives.
A new method to N-arylmethylenepyrroles from N-acylpyrroles
D'Silva, Claudius,Iqbal, Rifat
, p. 457 - 458 (2007/10/03)
An efficient general method for the preparation of N-arylmethylenepyrroles based on the reduction of N-acylpyrroles is reported. The reduction procedure described is sufficiently mild to make it applicable to a variety of sensitive acyl and heterocyclic acyl compounds where reduction results in cleavage of the C-N bond. The method can also be used in the preparation of pyrrole derivatives containing base sensitive protecting groups.
Synthesis of Highly Functionalized 7-Azabicycloheptadienes
Chen, Zhengming,Trudell, Mark L.
, p. 9649 - 9652 (2007/10/02)
Highly functionalized 7-azabicycloheptadiene derivatives have been synthesized via a cycloaddition reaction between N-acyl-3,4-disubstituted pyrroles and ethynyl p-tolyl sulfone 5.
High-pressure Synthesis, Structures, and Conformational Properties of Some Derivatives of 7-Azabicycloheptane. X-Ray Determination of endo-10-Benzoyl-4-phenyl-4,10-diazatricyclo2,6>dec-8-ene-3,5-dione and exo-10-Acetyl-4-phenyl-4,10-diazatricyclo2,6>decane-....
Drew, Michael G. B.,George, Adrian V.,Isaacs, Neil S.,Rzepa, Henry S.
, p. 1277 - 1284 (2007/10/02)
The syntheses, using pressures up to 1.4 GPa, and the properties of Diels-Alder adducts of some N-acylated pyrroles are described.Both exo and endo adducts may be obtained and purified and are, in general, unstable with respect to the retro reaction.Progress towards a general synthesis of the 7-azabicycloheptane system is described.Structures of two of the adducts, those between N-phenylmaleimide (2b) and N-benzoylpyrrole (1a) and the dihydro adduct of (2b) with N-acetylpyrrole (1b), have been determined by X-ray crystallographic analysis.Examination of these structures by means of 1H n.m.r. temperature-dependent spectra and nuclear Overhauser effect differences confirm that conformational isomerism is due to restricted rotation about the amide C-N bond, the energy barrier, 70 kJ mol-1, being similar to that in acyclic amides.
Electroorganic Chemistry. 60. Electroorganic Synthesis of Enamides and Enecarbamates and Their Utilization in Organic Synthesis.
Shono, Tatsuya,Matsumura, Yoshihiro,Tsubata, Kenji,Sugihara, Yoshihiro,Yamane, Shin-ichiro,et. al.
, p. 6697 - 6703 (2007/10/02)
A variety of enecarbamates and enamides were synthesized from α-methoxy carbamates and α-methoxy amides prepared by anodic methoxylation of amine derivatives.Some new carbon-carbon bond-forming reactions and hydroxylation at the β position of amines have been accomplished by using these enecarbamates and enamides as key intermediates.Also, new synthetic routes of nicotinaldehyde and pyrrole derivatives have been exploited by utilizing anodic dimethoxylation of carbamates of piperidine and pyrrolidine, respectively.
