109-97-7Relevant articles and documents
1-pyrrole from Trimethyl(1-pyrrolyl)ammonium Ion
Zeltner, Peter,Bernauer, Karl
, p. 1860 - 1864 (1983)
Trimethyl(1-pyrrolyl)ammonium iodide (5a) and the corresponding p-toluenesulfonate 5b are transformed by strong bases into 1-pyrrole (9), i.e. into a N-Mannich base, a type of compound novel in the pyrrole series.In this reaction, which is very fast in DMSO the cation of compounds 5 is deprotonated to form the nitrogen ylide 6.The latter undergoes a Stevens-type rearrangement to 9.Several facts, namely the negative outcome of a cross-reaction experiment with 3,4-dimethylpyrrole and of an attempt to obtain 9 from pyrrole and dimethyl(methylidene)ammonium iodide in the presence of one equivalent of sodium methoxide, as well as unsuccessful CIDNP studies point to a rearrangement mechanism via the contact ion pair 12.
Devinylation of N-vinylpyrroles using mercury(II) acetate
Schmidt,Vasil'Tsov,Zorina,Ivanov,Mikhaleva,Trofimov
, p. 1300 - 1303 (2012)
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Haitinger
, p. 228 (1882)
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Tsukamoto,Lichtin
, p. 3798 (1960)
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Whitten et al.
, p. 322 (1966)
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Flash flow pyrolysis: Mimicking flash vacuum pyrolysis in a high-temperature/high-pressure liquid-phase microreactor environment
Cantillo, David,Sheibani, Hassan,Kappe, C. Oliver
, p. 2463 - 2473 (2012)
Flash vacuum pyrolysis (FVP) is a gas-phase continuous-flow technique where a substrate is sublimed through a hot quartz tube under high vacuum at temperatures of 400-1100 °C. Thermal activation occurs mainly by molecule-wall collisions with contact times in the region of milliseconds. As a preparative method, FVP is used mainly to induce intramolecular high-temperature transformations leading to products that cannot easily be obtained by other methods. It is demonstrated herein that liquid-phase high-temperature/high- pressure (high-T/p) microreactor conditions (160-350 °C, 90-180 bar) employing near- or supercritical fluids as reaction media can mimic the results obtained using preparative gas-phase FVP protocols. The high-T/p liquid-phase "flash flow pyrolysis" (FFP) technique was applied to the thermolysis of Meldrum's acid derivatives, pyrrole-2,3-diones, and pyrrole-2-carboxylic esters, producing the expected target heterocycles in high yields with residence times between 10 s and 10 min. The exact control over flow rate (and thus residence time) using the liquid-phase FFP method allows a tuning of reaction selectivities not easily achievable using FVP. Since the solution-phase FFP method does not require the substrate to be volatile any more -a major limitation in classical FVP-the transformations become readily scalable, allowing higher productivities and space-time yields compared with gas-phase protocols. Differential scanning calorimetry measurements and extensive DFT calculations provided essential information on pyrolysis energy barriers and the involved reaction mechanisms. A correlation between computed activation energies and experimental gas-phase FVP (molecule-wall collisions) and liquid-phase FFP (molecule-molecule collisions) pyrolysis temperatures was derived.
Chlorination of Pyrrole. N-Chloropyrrole: Formation and Rearrangement to 2- and 3-Chloropyrrole
Rosa, Michael De
, p. 1008 - 1010 (1982)
N-Chloropyrrole (2) was formed in 65-72percent yield when pyrrole (1) in CCl4 was chlorinated with aqueous NaOCl.This intermediate rearranged in methanol to give chloropyrroles by two distinct reactions: a thermal rearrangement which gave 2-chloropyrrole (3) and an acid-catalyzed intermolecular reaction which gave 2-chloropyrrole (3), 3-chloropyrrole (4), and 2,5-dichloropyrrole (5).Nucleophilic attack on the N-Cl bond of 2 was demonstrated by reactions in the presence of CN- and SCN-.In the latter case, 2-(thiocyano)pyrrole was formed.
Kinetics of elimination of several heterocyclic carbamates in the gas phase
Brusco, Yannely,Dominguez, Rosa M.,Rotinov, Alexandra,Herize, Armando,Cordova, Mary,Chuchani, Gabriel
, p. 796 - 800 (2002)
The kinetics of the gas-phase elimination of several heterocyctic carbamates were determined in a static system over the temperature range 190.0-409.7°C and the pressure range 26.5-125 Torr (1 Torr = 133.3 Pa). The reactions in seasoned vessels, with the free radical inhibitor cyciohexene and/or toluene always present, are homogeneous and unimolecular and obey a first-order rate law. The observed rate coefficients are represented by the following Arrhenius equations: for tert-butyl-1-pyrrolidine carboxylate, log k1 (s-1) = (11.36 ± 0.31) - (145.4 ± 3.1) kJ mol-1 (2.303RT)-1; for 1-(tert-butoxycarbonyl)-2-pyrrolidinone, log k1 (s-1) = (11.54 ± 0.29) - (140.8 ± 2.8) kJ mol-1 (2.303RT)-1; for tert-butyl-1-pyrrole carboxylate, log k1 (s-1): (12.12 ± 0.05) - (145.2 ± 1.0) kJ mol-1 (2.303RT)-1; and for 1-ethylpiperazine carboxylate, log k1 (s-1): (12.05 ± 0.19) - (188.2 ± 4.6) kJ mol-1 (2.303RT)-1 The saturated heterocyclic carbamates show a decrease in rates of elimination due to electronic factors. Heterocyclic carbamates with a nitrogen atom able to delocalize its electrons with π-bonds present in the ring were found to enhance the rates due to resonance interactions. Copyright
Decarboxylation via addition of water to a carboxyl group: Acid catalysis of pyrrole-2-carboxylic acid
Mundle, Scott O. C.,Kluger, Ronald
, p. 11674 - 11675 (2009)
(Chemical Equation Presented) The decarboxylation of pyrrole-2-carboxylic acid is subject to acid catalysis in strongly acidic solutions. Protonation of the pyrrole ring at C2 produces a potentially low-energy carbanion leaving group. Carbon dioxide forma
The benzyl can be selectively removed by visible light or near visible light. Method for protecting allyl and propargyl group
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Paragraph 0019, (2021/10/16)
The invention provides a method for selectively removing benzyl, allyl and propargyl protecting groups by visible light or near visible light, namely a substrate containing benzyl, allyl or propargyl protecting groups. The method has the advantages of simple operation, safe and clean visible light or near visible light as excitation conditions, cheap and easily available reagents, high reaction yield, high reaction chemistry and regional selectivity, and is suitable for selective removal of benzyl, allyl and propargyl protecting groups in various substrates.
Metal-Free Directed C?H Borylation of Pyrroles
Wang, Zheng-Jun,Chen, Xiangyang,Wu, Lei,Wong, Jonathan J.,Liang, Yong,Zhao, Yue,Houk, Kendall N.,Shi, Zhuangzhi
supporting information, p. 8500 - 8504 (2021/03/16)
Robust strategies to enable the rapid construction of complex organoboronates in selective, practical, low-cost, and environmentally friendly modes remain conspicuously underdeveloped. Here, we develop a general strategy for the site-selective C?H borylation of pyrroles by using only BBr3 directed by pivaloyl groups, avoiding the use of any metal. The site-selectivity is generally dominated by chelation and electronic effects, thus forming diverse C2-borylated pyrroles against the steric effect. The formed products can readily engage in downstream transformations, enabling a step-economic process to access drugs such as Lipitor. DFT calculations (wB97X-D) demonstrate the preferred positional selectivity of this reaction.
Transition-Metal-Free and Visible-Light-Mediated Desulfonylation and Dehalogenation Reactions: Hantzsch Ester Anion as Electron and Hydrogen Atom Donor
Heredia, Micaela D.,Guerra, Walter D.,Barolo, Silvia M.,Fornasier, Santiago J.,Rossi, Roberto A.,Budén, Mariá E.
supporting information, p. 13481 - 13494 (2020/12/15)
Novel approaches for N- and O-desulfonylation under room temperature (rt) and transition-metal-free conditions have been developed. The first methodology involves the transformation of a variety of N-sulfonyl heterocycles and phenyl benzenesulfonates to the corresponding desulfonylated products in good to excellent yields using only KOtBu in dimethyl sulfoxide (DMSO) at rt. Alternately, a visible light method has been used for deprotection of N-methyl-N-arylsulfonamides with Hantzsch ester (HE) anion serving as the visible-light-absorbing reagent and electron and hydrogen atom donor to promote the desulfonylation reaction. The HE anion can be easily prepared in situ by reaction of the corresponding HE with KOtBu in DMSO at rt. Both protocols were further explored in terms of synthetic scope as well as mechanistic aspects to rationalize key features of desulfonylation processes. Furthermore, the HE anion induces reductive dehalogenation reaction of aryl halides under visible light irradiation.