Nucleophilicity of 4‐(Alkylthio)‐3‐imidazoline Derived Enamines

Hensinger, Magenta J.; Eitzinger, Andreas; Trapp, Oliver; Ofial, Armin R.

doi:10.1002/chem.202302764

Cited by 4 publications

References 76 publications

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2‐Methylene‐1,2‐dihydropyridines (2‐pyNHOs): Highly Nucleophilic Enamines

Behnke,

Eitzinger,

et al. 2024

Eur J Org Chem

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The high reactivity of 2‐methylene‐1,2‐dihydropyridines also known as 2‐methylpyridinium derived N‐heterocyclic olefins (2‐pyNHOs) has been recognized in organic synthesis, yet a quantification of their nucleophilicity is lacking. Herein we used stopped‐flow photometry to determine the nucleophilicity of a series of 2‐pyNHOs from the kinetics of their reactions with quinone methides and benzhydrylium ions as reference electrophiles in four organic solvents at 20 °C. The kinetic data was evaluated by using the Mayr‐Patz equation, lg k(20 °C) = sN(N + E), which gave nucleophilicity parameters N (and sN). With N in the range of 19.4 to 21.2 (in DMSO), 2‐pyNHOs exceed the reactivity of classical enamines, such as pyrrolidino‐cyclopent‐1‐ene. The addition of 2‐pyNHOs to quinone methides resulted in the formation of zwitterionic adducts with pyridinium and phenolate moieties. Subsequent tautomerization yielded entirely neutral pyridine‐2(1H)‐ylidene‐phenol species in several cases. Formation of the zwitterionic adducts from 2‐pyNHOs and neutral electrophiles was almost equally fast in the polar solvents acetonitrile and DMSO, but proceeded one to two orders of magnitude slower in the less polar solvents dichloromethane or THF.

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2‐Methylene‐1,2‐dihydropyridines (2‐pyNHOs): Highly Nucleophilic Enamines

Behnke,

Eitzinger,

et al. 2024

Eur J Org Chem

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Combined kinetic, and theoretical approaches for the study of the SEAr reactions of 2-(2′,4′,6′-trinitrophenyl)-4,6-dinitrobenzotriazole 1-oxide with 5-R-substituted indoles in acetonitrile

Amamou,

Hedhli,

Slama

et al. 2024

Chem. Pap.

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We present a kinetic and theoretical study of nucleophilic addition reactions involving 2-(2',4',6'-trinitrophenyl)-4,6-dinitrobenzotriazole 1-oxide 1 with a series of 5-R-substituted indoles 2a-e (R = CN, Cl, H, Me and NH2) in acetonitrile at 20 °C. Single electron transfer (SET) mechanism was proposed and confirmed by the agreement between the rate constants (k) and the oxidation potentials (Ep ox ) of these series of indoles. Using Mayr's equation, the electrophilicity parameter (E) of 1 at C-7 position is derived and compared with the same parameter estimate using empirical equation E vs. pKa. Density Functional Theory (DFT) calculations were performed to confirm the suggested reaction mechanisms and elucidate the origin of the electrophilic reactivity of 1. Notably, a linear correlation (R 2 = 0.9957) between the experimental nucleophilicity (N) and the theoretical model of nucleophilicity ( -1 ) determined in this work of various 5-R-substituted indoles has been obtained and discussed.

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TCFH–NMI Ketone Synthesis Inspired by Nucleophilicity Scales

Ho,

Miller,

Chung

et al. 2024

Org. Lett.

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Tetramethylchloroformamidinium hexafluorophosphate (TCFH) and N-methylimidazole (NMI) enable the facile and practical reaction of carboxylic acids with amines, alcohols, and thiols to form amides, esters, and thioesters. To develop a mild synthesis of ketones with TCFH−NMI directly from carboxylic acids at room temperature, the Mayr nucleophilicity scale was used to compare the N values of competent nucleophiles to potential carbon-centered nucleophiles, identifying pyrroles and indoles as successful substrates when N ≥ 10.

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Nucleophilicity of 4‐(Alkylthio)‐3‐imidazoline Derived Enamines

Cited by 4 publications

References 76 publications

2‐Methylene‐1,2‐dihydropyridines (2‐pyNHOs): Highly Nucleophilic Enamines

2‐Methylene‐1,2‐dihydropyridines (2‐pyNHOs): Highly Nucleophilic Enamines

Combined kinetic, and theoretical approaches for the study of the SEAr reactions of 2-(2′,4′,6′-trinitrophenyl)-4,6-dinitrobenzotriazole 1-oxide with 5-R-substituted indoles in acetonitrile

TCFH–NMI Ketone Synthesis Inspired by Nucleophilicity Scales

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