Solvent‐Free Synthesis of Pyrroles: An Overview

Rakendu, Pramod N.; Aneeja, Thaipparambil; Anilkumar, Gopinathan

doi:10.1002/ajoc.202100436

Cited by 30 publications

(17 citation statements)

References 87 publications

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“…Pyrrole derivative monomers are a common class of heterocyclic compounds 1–3 and are widely used as important intermediates in fine chemicals, such as pharmaceuticals, food, pesticides, daily chemicals and polymeric materials 4–9 . Pyrroles themselves are found in large quantities in natural foods, such as roasted nuts, coffee, tea, cooked beef and mushrooms, 10 and thus pyrroles can be added to foods as edible flavours to greatly improve the characteristic taste and texture of enhanced foods 11,12 .…”

Section: Introductionmentioning

confidence: 99%

Synthesis and pyrolysis of various novel pyrrole ester fragrance precursors

Tian

Han

et al. 2023

Flavour & Fragrance J

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Due to the disadvantages of low fragrance threshold and high volatility of pyrrole monomer under high‐temperature process in tobacco or food, it cannot meet the market requirements. In order to develop pyrrole flavour precursors, 2,5‐dimethyl‐N‐pyrroleacetic acid was synthesized by the Paal–Knorr reaction using 2,5‐hexanedione and glycine as raw materials. Various pyrrole fragrance precursors such as 2‐ethyl‐4‐oxo‐4H‐pyran‐3‐yl 2‐(2,5‐dimethyl‐1H‐pyrrol‐1‐yl)acetate (5a), 4‐formyl‐2‐methoxyphenyl 2‐(2,5‐dimethyl‐1H‐pyrrol‐1‐yl)acetate (5b), pyridine‐2‐ylmethyl 2‐(2,5‐dimethyl‐1H‐pyrrol‐1‐yl)acetate (5c) and thiophen‐2‐ylmethyl 2‐(2,5‐dimethyl‐1H‐pyrrol‐1‐yl)acetate (5d) were synthesized by esterification from 2,5‐dimethyl‐N‐pyrroleacetic acid with ethyl maltol, vanillin, 2‐pyridinemethanol and 2‐thiophenemethanol, respectively. As part of the study, IR, NMR and HRMS were used to characterize the target compounds. Using gas chromatography–mass spectrometry‐olfactometer (GC–MS‐O), the pyrrole esters obtained were evaluated for the characteristics of their aromas. The thermal stability was analysed using thermogravimetric analysis and pyrolysis gas chromatography/mass spectrometry. In addition, the pyrolysis mechanism was speculated. With TG‐DTG results, the main mass loss phase of 5a occurred between 108°C and 450°C, with a dramatic mass loss reduction of 83.07%. At 118.60°C and 450°C, 5b showed a mass loss reduction of 60.80%. Furthermore, according to the Py‐GC/MS analysis results, compounds 5a and 5b formed 8 and 7 pyrolysis products. The main pyrolysis products of 5a and 5b were 1‐ethyl‐2,5‐dimethyl‐1H‐pyrrole, ethyl maltol, and vanillin, which are all aroma components used to blend cigarette smoke, can slow down the rate at which aromas are lost and mask unpleasant smoke. Study results provide a reference for the tobacco industry to further develop new high‐temperature release aroma ingredients.

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Section: Introductionmentioning

confidence: 99%

Synthesis and pyrolysis of various novel pyrrole ester fragrance precursors

Tian

Han

et al. 2023

Flavour & Fragrance J

View full text Add to dashboard Cite

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“…Moreover, solvent-free reactions are often more rapid and violent, and because of the lack of organic solvent dilution, the product tends to be viscous, which can easily cause the system to accumulate heat and become dangerous. 31,[47][48][49][50][51] Finally, if the reaction is not isochemical, 31,45 it is often necessary to use organic solvents for dissolution, extraction, and other methods to separate the products.…”

Section: Introductionmentioning

confidence: 99%

“…To solve this problem, researchers have pioneered the solid‐state grinding method, which uses an external intervention such as grinding, light, heat, microwave, or ultrasound to cause the molecules to bond more tightly, increasing the chance of collision and increasing the likelihood of the reaction occurring. Moreover, solvent‐free reactions are often more rapid and violent, and because of the lack of organic solvent dilution, the product tends to be viscous, which can easily cause the system to accumulate heat and become dangerous 31,47–51 . Finally, if the reaction is not isochemical, 31,45 it is often necessary to use organic solvents for dissolution, extraction, and other methods to separate the products.…”

Section: Introductionmentioning

confidence: 99%

An efficient catalytic and solvent‐free method for the synthesis of mono‐organofunctionalized polymethylhydrosiloxane derivatives

Gui

Dong

et al. 2023

Polymers for Advanced Techs

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Synthetic reactions with distinctive physicochemical properties and the study of functional groups during synthesis provide an effective way to design polymers on an individual basis. The functionalization of polymethylhydrosiloxane (PMHS) has been performed via hydrosilylation of PMHS with selected alkenes with different active functional groups. In the reaction of PMHS with selected CC bond‐containing olefins in solvent‐free systems, the most efficient catalyst system can be selected to obtain the PMHS reagents to introduce the desired functional groups while generating only regional isomeric products. On‐line real‐time monitoring techniques, in situ Fourier‐transform infrared (FT‐IR), were utilized to determine the chemical reaction rates and reaction conversions for each chemical reaction, and to assess the merits of the reaction systems. In addition, the structures of the functionalized polymers were characterized using FT‐IR spectroscopy, nuclear magnetic resonance (NMR), and gel permeation chromatography (GPC). The kinetic parameters of typical chemical reaction processes were calculated using Kissinger's equation and Ozawa's equation. The comparisons between solvent and solvent‐free systems were carried out under the same conditions, and the statistics revealed that the solvent‐free system was more efficient than its solvent‐based counterpart. This research on the introduction of monofunctional groups into PMHS side chains might pave the way for a variety of diverse functional groups, thus allowing for the further application of PMHS and its derivatives.

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“…Functionalized pyrroles represent a class of synthetic intermediates that are essential for accessing other valuable compounds for medicinal and advanced material applications . The synthesis of these fundamental structural building blocks has received significant attention, and various elegant methods have been developed to construct functionalized pyrroles . Most methods to construct pyrrole skeletons rely on condensation–cyclization reactions, including traditional Paal–Knorr-type and Clauson–Kaas-type reactions for the synthesis of N -substituted pyrroles or 2,5-substituted pyrroles.…”

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confidence: 99%

Flexible Construction Approach to the Synthesis of 1,5-Substituted Pyrrole-3-carbaldehydes from 5-Bromo-1,2,3-triazine

Ambre

Lee

et al. 2022

Org. Lett.

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We report an efficient and mild tandem catalytic process for the synthesis of functionalized pyrrole-3-carbaldehydes. These compounds were obtained by a one-pot three-component reaction of 5-bromo-1,2,3-triazine, terminal alkynes, and primary amines via a palladium-catalyzed Sonogashira coupling reaction, and then annulation through a silver-mediated reaction of the resulting alkynyl 1,2,3-triazines allowed for access to the multifunctionalized pyrrole-3-carbaldehydes.

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Solvent‐Free Synthesis of Pyrroles: An Overview

Cited by 30 publications

References 87 publications

Synthesis and pyrolysis of various novel pyrrole ester fragrance precursors

Synthesis and pyrolysis of various novel pyrrole ester fragrance precursors

An efficient catalytic and solvent‐free method for the synthesis of mono‐organofunctionalized polymethylhydrosiloxane derivatives

Flexible Construction Approach to the Synthesis of 1,5-Substituted Pyrrole-3-carbaldehydes from 5-Bromo-1,2,3-triazine

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