1022-86-2Relevant articles and documents
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Jardine,Brown
, p. 2067,2069 (1963)
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Acid fluorides as acyl electrophiles in suzuki–miyaura coupling
Ogiwara, Yohei,Sakino, Daisuke,Sakurai, Yuka,Sakai, Norio
, p. 4324 - 4327 (2017)
The first palladium-catalyzed construction of ketones through Suzuki–Miyaura reaction by using acid fluorides is described. In contrast to typical acyl electrophiles such as acid chlorides, acid fluorides are uncommon acyl electrophiles to use in boron-based coupling reactions, probably due to a high level of stability toward nucleophiles. This first attempt to use acid fluorides as a coupling partner with boronic acids allowed highly functional group tolerance and a wide substrate scope while affording various ketones in effective yields.
Incvestigation of the possible role of arylamine formation in the ortho-substituted nitroarenes reductive cyclization reactions to afford heterocycles
Ragaini, Fabio,Sportiello, Paola,Cenini, Sergio
, p. 283 - 291 (1999)
Reductive carbonylation of nitroarenes with an unsaturated group in the ortho position generally affords high yields of heterocyclic compounds, including indoles, chalcones, quinolines, benzimidazoles, benzotriazoles, and indazoles. There is, however, no direct information on the organic intermediates formed during the reaction. In this paper, we have examined the possible formation of anilines as intermediates in the synthesis of indoles, acylindoles, quinolines, and quinolones with several catalytic systems based on palladium, ruthenium and rhodium. It transpired that, independent of the metal complex used as a catalyst, the formation of aniline as an intermediate is essential in the intra-molecular condensation reactions of nitroarenes involving an aldehydic or a keto group (including Michael addition reactions), but plays at best a very limited role in the addition reactions involving a C=C double bond.
Reaction of 3-(2-nitrophenyl)-1-arylprop-2-en-1-ones with triethylphosphite in microwave revisited: One-pot synthesis of 2-aroylindoles and 2-arylquinolines
Gupta, Annah,Khajuria, Rajni,Kapoor, Kamal K.
, p. 31 - 38 (2016)
One-pot synthesis of 2-aroylindoles and 2-arylquinolines has been achieved by the reductive cyclization of 3-(2-nitrophenyl)-1-arylprop-2-en-1-ones with triethylphosphite [P(OEt)3] under microwave irradiation. The formation of 2-arylquinolines by this method is unprecedented.
Diethoxymethyl protected indoles: Synthesis and regioselective transformations
Gmeiner, Peter,Kraxner, Johannes,Bollinger, Bernd
, p. 1196 - 1198 (1996)
Reaction of the indoles 1a-d with triethyl orthoformate gives access to the N-diethoxymethyl derivatives 2a-d. Convenient and mild removal of the diethoxymethyl substituent is possible by subsequent treatment of 2a-d with aqueous HCl and NaOH. Using 2a as an example, it could be shown that deprotonation followed by addition of an electrophile (Me3SiCl or Bu3SnCl) leads to substitution in position 2. Further functionalization was possible by palladium-catalyzed coupling reactions starting from the stannane 4. The diethoxymethyl protected η6-tricarbonylchromium complex 5 facilitated acylation in position 2 after deprotonation.
Synthesis of N-Heterocycles by Reductive Cyclization of Nitro Compounds using Formate Esters as Carbon Monoxide Surrogates
Formenti, Dario,Ferretti, Francesco,Ragaini, Fabio
, p. 148 - 152 (2018)
A series of alkyl and aryl formate esters were evaluated as CO sources in the Pd- and Pd/Ru-catalyzed reductive cyclization of substituted nitro compounds to afford heterocycles, especially indoles. Phenyl formate was found to be the most effective, and it allowed the desired products to be obtained in excellent yields, often higher than those previously reported with pressurized CO. Through detailed experiments and kinetic studies, we were able to discern between metal-catalyzed and base-mediated activation of phenyl formate and confirmed that just the base was effective in catalyzing its decarbonylation.
CARBON DIOXIDE: A REAGENT FOR THE PROTECTION OF NUCLEOPHILIC CENTRES AND THE SIMULTANEOUS ACTIVATION OF ALTERNATIVE LOCATIONS TO ELECTROPHILIC ATTACK. PART I. A NEW SYNTHETIC METHOD FOR THE 2-SUBSTITUTION OF 1-UNSUBSTITUTED INDOLES.
Katritzky, By Alan R.,Akutagawa, Kunihiko
, p. 5935 - 5938 (1985)
Indole was converted into several 2-substituted derivatives by using carbon dioxide both for N-protection and to give an intermediate carbanion stabilizing group. t-Butyllithium was used as a lithiating agent at the alpha-carbon atom of the indole enamino group.The resulting 2-substituted indole-1-carboxylic acids underwent smooth thermal decarboxylation under mild conditions.Alternatively, with longer reaction times the protecting group is lost during the reaction.
Palladium Complex-Catalyzed Reductive N-Heterocyclization of Nitroarenes: Novel Synthesis of Indole and 2H-Indazole Derivatives
Akazome, Motohiro,Kondo, Teruyuki,Watanabe, Yoshihisa
, p. 3375 - 3380 (1994)
The dichlorobis(triphenylphosphine)palladium (PdCl2(PPh3)2)-tin(II)chloride (SnCl2) system shows high catalytic activity for the reductive N-heterocyclization of various 2-nitrostyrene and N-(2-nitrobenzylidene)amine derivatives when employed at 100 deg C for 16 h under 20 kg cm-2 of initial carbon monoxide pressure, to give the corresponding indole and 2H-indazole derivatives in good yield.For example, 2-phenylindole was obtained in 75percent yield from the reductive N-heterocyclization of 2-nitrostilbene.Similarly, 2-propyl-2H-indazole was readily prepared in 83percent yield by the reductive N-heterocyclization of N-(2-nitrobenzylidene)propylamine.A nitrene intermediate for the present reaction is proposed on the basis of deuterium-labeling experiments and the investigation of alkyl rearrangement in the construction of the indole skeleton.Carbon monoxide effectively operates as a deoxygenating agent of the nitro group to afford a nitrene intermediate.
Rhodium-Catalyzed Reaction of Sulfoxonium Ylides and Anthranils toward Indoloindolones via a (4 + 1) Annulation
Wu, Xiaopeng,Xiao, Yan,Sun, Song,Yu, Jin-Tao,Cheng, Jiang
, p. 6653 - 6657 (2019)
A rhodium-catalyzed annulation between aroyl sulfoxonium ylides and anthranils has been developed to synthesize 10H-indolo[1,2-a]indol-10-one derivatives. This reaction started with an unpredented (4 + 1) annulation toward N-(2-formylphenyl) indolones, pr
Visible-light-driven Cadogan reaction
Qu, Zhonghua,Wang, Pu,Chen, Xing,Deng, Guo-Jun,Huang, Huawen
, p. 2582 - 2586 (2021/03/09)
Visible-light-driven photochemical Cadogan-type cyclization has been discovered. The organic D-A type photosensitizer 4CzIPN found to be an efficient mediator to transfer energy from photons to the transient intermediate that breaks the barriers of deoxygenation in Cadogan reaction and enables a mild metal-free access to carbazoles and related heterocycles. DFT calculation results indicate mildly endergonic formation of the intermediate complex of nitrobiarenes and PPh3, which corresponds with experimental findings regarding reaction temperature. The robust synthetic capacity of the photoredox Cadogan reaction systems has been demonstrated by the viable productivity of a broad range of carbazoles and related N-heterocycles with good tolerance of various functionalities.
Continuous Flow Synthesis of Quinolines via a Scalable Tandem Photoisomerization-Cyclization Process
Di Filippo, Mara,Baumann, Marcus
, p. 6199 - 6211 (2020/08/26)
A continuous photochemical process is presented that renders a series of quinoline products via an alkene isomerization and cyclocondensation cascade. It is demonstrated that a high-power LED lamp generates the desired targets with higher productivity and efficiency than a medium-pressure Hg-lamp. The scope of this tandem process is established and allows for the generation of various substituted quinolines in high yields and with throughputs of greater than one gram per hour. Finally, this effective flow process is coupled with a telescoped hydrogenation reaction to render a series of tetrahydroquinolines including the antimalarial natural product galipinine.
