840-04-0Relevant academic research and scientific papers
Direct C-H bond activation: Palladium-on-carbon as a reusable heterogeneous catalyst for C-2 arylation of indoles with arylboronic acids
Bhattacharjee, Prantika,Bora, Utpal,Boruah, Purna K.,Das, Manash R.
, p. 7675 - 7682 (2020/06/09)
Direct C(sp2)-H bond functionalization of indoles with arylboronic acids is achieved using palladium supported on carbon as a reusable heterogeneous catalyst in the presence of an oxidant under mild conditions. The current protocol formed exclusive C-2 selective products without the aid of any ligand or directing group. The catalyst is reusable for up to four catalytic cycles with the retention of catalytic efficiency.
Phosphine-Free Palladium-Catalyzed Direct Bisarylation of Pyrroles with Aryl Iodides on Water
Cho, Beom Shin,Bae, Hyun Jung,Chung, Young Keun
, p. 5302 - 5307 (2015/05/27)
(Chemical Presented). The Pd-catalyzed bisarylation of pyrroles with aryl iodides on water is described. The reaction proceeds under mild reaction conditions, i.e., relatively low temperature (40 C) and phosphine-free.
Synthesis of 2,5-diarylpyrroles by ligand-free palladium-catalyzed ch activation of pyrroles in ionic liquids
Ehlers, Peter,Petrosyan, Andranik,Baumgard, Jens,Jopp, Stefan,Steinfeld, Norbert,Ghochikyan, Tariel V.,Saghyan, Ashot S.,Fischer, Christine,Langer, Peter
, p. 2504 - 2511 (2013/08/23)
The palladium-catalyzed CH activation and arylation of N-methylpyrrole and N-phenylpyrrole allowed a convenient synthesis of diarylpyrroles. The reactions were performed by using tetrabutylammonium acetate as an ionic solvent, which allowed for the application of a ligand-free catalytic system by using simple palladium salts or polyvinylpyrrolidone-stabilized palladium nanoparticles as the catalyst.
Room temperature palladium-catalyzed 2-arylation of indoles
Deprez, Nicholas R.,Kalyani, Dipannita,Krause, Andrew,Sanford, Melanie S.
, p. 4972 - 4973 (2007/10/03)
This communication describes the rational development of a PdII-catalyzed method for the direct 2-arylation of indoles using [Ar-IIII-Ar]BF4. These reactions proceed under remarkably mild conditions (often at room temperature and in the presence of ambient air and moisture), and these features are believed to be the result of a PdII/IV mechanism operating in these systems. These transformations can be used to prepare functionally diverse 2-arylated indoles and pyrroles, and their potential utility has been expanded by the development of an in situ procedure for generating the iodine(III) arylating reagents. Copyright
5(4H)-oxazolones. Part XI. Cycloaddition reaction of oxazolones and munchnones to triphenylvinylphosphonium salts as synthetic equivalents of alkynes
Clerici, Francesca,Gelmi, Maria Luisa,Trimarco, Pasqualma
, p. 5763 - 5774 (2007/10/03)
5(4H)-Oxazolones 1 and milnchnones 3 are reacted with triphenylvinylphosphonium bromide 2a to give, through a cycloaddition reaction, pyrrole derivatives 4a-d and 7a-c unsubstituted at C-3 and C-4. The use of substituted vinylphosphonium salts 2b,c and dipoles 1 and 3 allows the isolation of 3-methylpyrroles 4e, f and 7d,e and 3-pyrrolecarboxylic acids 9a-c, respectively. The cycloaddition reactions proceed with high regionelectivity because of the positive interaction of phosphonium group of 2 and carbonyl group of dipoles 1 and 3.
Conversion of pyrroles into bi-1,2,5-thiadiazoles: A new route to biheterocycles
Duan, Xiao-Guang,Rees, Charles W.
, p. 3189 - 3196 (2007/10/03)
Trithiazyl trichloride 1 converts 1,2,5-triphenylpyrrole 5 into its 3,4-dichloro derivative together with the isothiazole imine 6 and the imine hydrolysis product, the ketone 3. The best yield of the isothiazole 6 is obtained in the presence of 4 A molecular sieves (Table 1). Conversion of the pyrrole 5 into the isothiazole 6 is exactly analogous to the reaction of 1 with 2,5-diphenyl-furan and -thiophene. Other N-aryl and the related 2,5-diphenylpyrroles 8 give similar results (Table 2). However, 1-methyl-2,5-diphenylpyrrole 11 reacts with 1 in an entirely different way to give 4,4′-diphenyl-3,3′-bi-1,2,5-thiadiazole 12, in which two thiadiazole rings have been fused onto the pyrrole and the CH3N unit has been excised as HCN. The same product 12 is formed, in similar yields, by reaction of 1 with 1,4-diphenylbuta-1, 3-diyne and 1,4-diphenylbut-1-en-3-yne. Other N-alkyl 2,5-diphenylpyrroles 16 react similarly (Table 3), giving the best yield (70%) of bi-thiadiazole 12 in the presence of 4 A molecular sieves (Table 4). 1-Methyl- and 1-ethyl-3,4-dibromo-2,5-diphenylpyrrole also give 12, together with 3-(benzoyldichloromethyl)-4-phenyl-1,2,5-thiadiazole 21 in high combined yield. The formation of bi-1,2,5-thiadiazole 12 from N-alkylpyrroles represents a new dissection of the pyrrole ring and a new and very short route to an aromatic biheterocyclic system. Mechanisms which rationalise the different pathways observed are proposed for all of these reactions.
Intermediates in the Paal-Knorr Synthesis of Pyrroles
Amarnath, Venkataraman,Anthony, Douglas C.,Amarnath, Kalyani,Valentine, William M.,Wetterau, Lawrence A.,Graham, Doyle G.
, p. 6924 - 6931 (2007/10/02)
The mechanism of Paal-Knorr reaction between a 1,4-dicarbonyl compound and ammonia or a primary amine to form a pyrrole is explored.In aprotic solvents and in aqueous solutions near neutrality, d,l diastereomers of 3,4-dimethyl- and 3,4-diethyl-2,5-hexanediones (1r and 2r) formed pyrroles 1.3-57.0 times faster than the corresponding meso diastereomers (1m and 2m).This contradicts any intermediate, such as the enamine 15, which does not remain saturated at both the 3- and 4-positions through the rate-determining step.The demonstrated stereoisomeric difference in reactivity coupled with the following results support the hemiaminal (9) as the intermediate undergoing cyclization in the rate-limiting step of the Paal-Knorr reaction: (1) The reaction rate was adversely affected by increase in the size of the alkyl substituents on the dione. (2) Racemic 2,3-dimethyl-1,4-diphenyl-1,4-butanedione (3r) was more reactive toward ammonium acetate (2.2:1) and 2-aminoethanol (11.2:1) than the meso isomer (3m), ruling out the involvement of the less substituted enamine 14. (3) The relative rate of pyrrole formation of 1,4-diphenyl-1,4-butanedione (5) and its dimethoxy (6) and dinitro (7) derivatives (1:0.3:6) does not support cyclization of the imine (11) to the pyrrolinium ion (12). (4) The rates of reaction of 2,2,3,3-tetradeuterio-1,4-diphenyl-1,4-butanedione (5D) and perdeuterio-2,5-hexanedione (4D) were very close to those of unlabeled diketones, indicating the absence of a primary isotope effect in the reaction. (5) Neither the isomerization of the unreacted diastereomers of 1, 2, and 3 nor hydrogen exchange of 4D and 5D was detected during the reaction.
The regioselective elaboration of η-pyrrolyl ligands in (η-pyrrolyl)bis(triphenylphosphine)rhenium complexes: a way to 2,5-diphenylpyrrole and some of its N-derivatives
Zakrzewski, Janusz
, p. 71 - 76 (2007/10/02)
The η-pyrrolyl complexe (η-C4H4N)(Ph3P)2ReH2 (I) was prepared from (Ph3P)2ReH7, 3,3-dimethyl-1-butene and pyrrole, and treated with I2-K2CO3 to give (η-C4H4N)(Ph3P)2ReHI (2).This was treatede with PhLi to give (η-2-PhC4H3N)(Ph3P)2ReH2 (3) in high yield.Re
THERMAL HETEROCYCLIZATION OF METHYL ARYL KETAZINES. I. REACTIONS OF THE TAUTOMERIC DIENEHYDRAZINE FORM
Shurukhin, Yu. V.,Klyuev, N. A.,Grandberg, I. I.
, p. 1883 - 1888 (2007/10/02)
The thermal reactions of methyl aryl ketazines in the range of 150-350 deg C were studied.Thermolysis is represented by three types of parallel-consecutive reactions of various tautomeric forms of the initial compounds, i.e., the dienehydrazine, the enehydrazine, and azine forms.The chemical transformations of the first type lead to the cyclization of the azines into derivatives of 2,5-diarylpyrrole and 3,6-diarylpyridazine.The formation of pyrroles under the conditions of uncatalyzed thermolysis and at temperatures excluding the possibility of processes involvingthe participation of radicals is consistent with the mechanism of a -sigmatropic shift.
