N-Heterocyclic Olefin Catalysis for the Ring Opening of Cyclic Amidine Compounds: A Pathway to the Synthesis of ε-Caprolactam- and γ-Lactam-Derived Amines

Peixoto, Daniela; Malta, Gabriela; Cruz, Hugo; Barroso, Sónia; Carvalho, Ana Luı́sa; Ferreira, Luı́sa M.; Branco, Paula S.

doi:10.1021/acs.joc.8b02823

Cited by 15 publications

(10 citation statements)

References 48 publications

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“…In fact, the activation energy of ammonium ion formation is very low, [67] and thus we suppose a dynamic equilibrium between the quaternization of the terminal and the middle nitrogens. The nucleophilicity of DBU and related amidines DBN, TBD and MTBD has been used in their reactions with aldehydes, [68] carbonates, [69] imidazolides, [70] methyl-pyrazoles [71] and benzoxazinones [72] as electrophiles leading to caprolactams or substituted tetrahydropyrimidinones. Notably, cyclic amidines undergo ring-opening in the presence of water yielding aminopropyl lactams and pyrimidinones that readily react with halobenzenes [73][74][75] and esters.…”

Section: Resultsmentioning

confidence: 99%

Chromatography‐Free Multicomponent Synthesis of Thioureas Enabled by Aqueous Solution of Elemental Sulfur

et al. 2020

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The development of a new three-component chromatographyfree reaction of isocyanides, amines and elemental sulfur allowed us the straightforward synthesis of thioureas in water. Considering a large pool of organic and inorganic bases, we first optimized the preparation of aqueous polysulfide solution from elemental sulfur. Using polysulfide solution, we were able to omit the otherwise mandatory chromatography, and to isolate the crystalline products directly from the reaction mixture by a simple filtration, retaining the sulfur in the solution phase. A wide range of thioureas synthesized in this way confirmed the reasonable substrate and functional group tolerance of our protocol.

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Section: Resultsmentioning

confidence: 99%

Chromatography‐Free Multicomponent Synthesis of Thioureas Enabled by Aqueous Solution of Elemental Sulfur

et al. 2020

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“…A number of processes gathered in this review could most probably be extended to reactions with 1,5‐diazabicyclo[4.3.0]non‐5‐ene (DBN). Indeed, DBN display properties similar to those of DBU, and reports describing similar results are already available …”

Section: Conclusion and Remarksmentioning

confidence: 58%

“…Recently, Branco's team reported the synthesis of ε-caprolactam-derived imines from an organocatalyzed reaction of DBU with (hetero)aryl aldehydes (Scheme 20a). [46] Only traces of the coupling product were obtained with propionaldehyde. Scheme 20b which somewhat differs from the original, involves nucleophilic addition of DBU to the aldehyde giving 20A.…”

Section: Aldehydesmentioning

confidence: 99%

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DBU: A Reaction Product Component

Мuzart

2020

ChemistrySelect

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DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) is traditionally considered to be a non-nucleophilic base. Nevertheless, DBU possesses nucleophilic properties which mediate organic reactions and may lead to the formation of compounds containing the DBU scaffold. Participation of water to the processes affords there-component products. The review covers the reactions leading to DBU derivatives showing that the interest of this sterically hindered amidine is not limited to its basic role. Proposed mechanisms are described with, in some cases, personal comments.

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“…Recently the number of reports about the applications of nucleophilic behavior of DBU has increased tremendously . [11] As such an increasing number of reports in the literature that are more amenable to the in‐situ ring‐opening reaction of DBU with acetylenic esters, [12] 1, 4‐diaryl‐1, 3‐diynes, [13] aldehydes [14] and phenylboronic acids [15] forming N‐functionalised products have appeared. The extension of Chan‐Lam coupling was reported by our research group with DBU/DBN/TBD as reaction partners [15] .…”

Section: Methodsmentioning

confidence: 99%

Ullmann Coupling Reaction of Bicyclic Amidines DBU/DBN with Aryl Halides: A Pathway to the Synthesis of ϵ‐Caprolactam Derivatives

et al. 2021

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This paper demonstrates a selective, mild approach to Ullmann amination of aryl halides to synthesizeN‐alkylated derivatives of ϵ‐caprolactam. The synthetic route involves anin‐situring‐opening of 1,8‐diazabicyclo[5.4.0]undec‐8‐ene (DBU) followed by concurrent arylation with aryl halides in the presence of copper iodide as a catalyst under ligand‐free conditions. This method provides a new entry to a wide variety of ϵ‐caprolactam derivatives in good to excellent yields in a single synthetic sequence. Similarly, other bicyclic amidines such as 1, 5‐diazabicyclo‐[4.3.0]non‐5‐ene (DBN), and 1,5,7 triazabicyclo[4.4.0] dec‐5‐ene (TBD) also showed good to very high reactivity.Azepan‐2‐one, or Caprolactam, is an important synthon in polymer chemistry and has a global demand as it is employed to make Nylon 6 filament, fiber, and plastics.[1]The global caprolactam market size is expected to expand for the growing textile industry with rising demand for plastics in the construction of automotive, electrical, and electronic sectors. Additionally, technological advancements aimed at improving the cost‐effective manufacturing process of caprolactam, to minimize the release of hazardous waste into the environment is of vital necessity. Derivatives of ϵ‐caprolactam are of interest for the production of modified nylons[2]and nanogels.[3]Several Azepinones and their analogs play an important role in medicinal chemistry,[4]used in the synthesis of pharmaceutical drugs including Benazepril,[5]Telcagepant,[6]and Ivabradine.[7]

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N-Heterocyclic Olefin Catalysis for the Ring Opening of Cyclic Amidine Compounds: A Pathway to the Synthesis of ε-Caprolactam- and γ-Lactam-Derived Amines

Cited by 15 publications

References 48 publications

Chromatography‐Free Multicomponent Synthesis of Thioureas Enabled by Aqueous Solution of Elemental Sulfur

Chromatography‐Free Multicomponent Synthesis of Thioureas Enabled by Aqueous Solution of Elemental Sulfur

DBU: A Reaction Product Component

Ullmann Coupling Reaction of Bicyclic Amidines DBU/DBN with Aryl Halides: A Pathway to the Synthesis of ϵ‐Caprolactam Derivatives

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