The Palladium Catalyzed Synthesis of Carboxylate-Substituted Imidazolines

Dhawan, Rajiv; Arndtsen, Bruce A.; Dghaym, Rania D.

doi:10.1201/9780203911013.ch39

Cited by 2 publications

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“…As we have previously reported, the addition of NEt( i -Pr) 2 base to the palladium-catalyzed reaction mixture can block the formation of imidazolinium carboxylates and instead allow the in situ formation of Münchnone 3a (Scheme ) . The addition of imines to Münchnones is known to lead to the formation of β-lactams, via reaction with the ketene tautomer of 3 , rather than the Münchnones undergoing dipolar cycloaddition to form imidazolinium carboxylates. , This can be circumvented by the addition of benzenesulfonic acid, which catalyzes the dipolar cycloaddition of an N-allyl-substituted imine with Münchnone 3a and forms 8a within hours at ambient temperature (Scheme ). A small amount of the inseparable homocoupled imidazoline product 4c is generated under these conditions.…”

Section: Resultsmentioning

confidence: 99%

A Palladium-Catalyzed Multicomponent Synthesis of Imidazolinium Salts and Imidazolines from Imines, Acid Chlorides, and Carbon Monoxide

Worrall

Bontemps

et al. 2010

J. Org. Chem.

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A palladium-catalyzed multicomponent synthesis of imidazolinium carboxylates and imidazolines is described. The palladium catalyst [Pd(CH(R(1))N(R(2))COR(3))Cl](2), or [Pd(allyl)Cl](2), with P(t-Bu)(2)(2-biphenyl) can mediate the simultaneous coupling of two imines, acid chloride, and carbon monoxide into substituted imidazolinium carboxylates within hours under mild conditions (45 °C, 4 atm of CO). The reaction proceeds in good yield with aryl-, heteroaryl-, and alkyl-substituted acid chlorides, as well as variously functionalized imines. Imidazolines are formed via the initial generation of Münchnone intermediates, followed by their cycloaddition with an in situ generated protonated imine. The addition of an amine base can intercept catalysis at Münchnone formation, which allows the subsequent cycloaddition of a second imine. The latter provides a route for the assembly of complex, polysubstituted imidazolinium carboxylates with independent control of all five substituents. The subsequent removal of the nitrogen substituent(s) provides an overall synthesis of imidazolines.

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Section: Resultsmentioning

confidence: 99%

A Palladium-Catalyzed Multicomponent Synthesis of Imidazolinium Salts and Imidazolines from Imines, Acid Chlorides, and Carbon Monoxide

Worrall

Bontemps

et al. 2010

J. Org. Chem.

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“…Control experiments demonstrate that these two fragments are ultimately coupled to generate 4, by 1,3-dipolar cycloaddition of the protonated imine to 8, followed by CÀO bond cleavage, which affords imidazoline 4 in near quantitative yield (step F). [24] On examining this mechanism, it was noted that the dynamic equilibrium between complex 2 and imine, acid chloride, and Pd 0 suggests that mixing these three reagents with carbon monoxide could allow the direct formation of imidazolines. Since Pd 0 is ultimately liberated after b-hydride elimination (step E), this process also holds the potential to be catalytic.…”

Section: The Direct Synthesis Of Peptide-based Productsmentioning

confidence: 98%

Metal‐Catalyzed One‐Step Synthesis: Towards Direct Alternatives to Multistep Heterocycle and Amino Acid Derivative Formation

Arndtsen

2008

Chemistry A European J

130

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The growing understanding of transition-metal catalysis has provided the opportunity to design reactions that convert simple, readily available building blocks in one step into an array of biologically relevant products. Described herein is the application of this approach to the construction of various biologically relevant products, including pyrroles, imidazoles, beta-lactams, oxazoles, alpha-amino acids, propargyl amides, functionalized pyridines, and others. These catalytic reactions rely upon several synthetic operations occurring in sequence, in which the reactivity of transition-metal complexes both activates basic building blocks towards reaction, and controls how multiple versions of these substrates come together. Overall, this allows the synthesis of each these products in one step, in high yield, with minimal waste, and with straightforward access to product diversity.

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The Palladium Catalyzed Synthesis of Carboxylate-Substituted Imidazolines

Cited by 2 publications

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A Palladium-Catalyzed Multicomponent Synthesis of Imidazolinium Salts and Imidazolines from Imines, Acid Chlorides, and Carbon Monoxide

A Palladium-Catalyzed Multicomponent Synthesis of Imidazolinium Salts and Imidazolines from Imines, Acid Chlorides, and Carbon Monoxide

Metal‐Catalyzed One‐Step Synthesis: Towards Direct Alternatives to Multistep Heterocycle and Amino Acid Derivative Formation

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