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A Kinetic Study of the Intramolecular Nitroaldol (Henry) Reaction Giving 2-Nitroindan-1-ols

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Abstrakt

An intramolecular base-catalyzed nitroaldol reaction of three newly prepared 2-(2-nitroalkyl)benzaldehydes (1a-c) giving corresponding 2-nitroindan-1-ols (2a-c) was studied in water and five non-aqueous solvents. Whilst for the parent 2-(2-nitroethyl)benzaldehyde (1a) the reaction takes place in two kinetically discernible steps - deprotonation and cyclization, for 2-(2-nitropropyl)- and 2-(2-nitro-2-phenylethyl)benzaldehydes 1b and 1c general base-catalyzed formation of a reactive carbanion is rate-limitting. An unusually high Bronsted coefficient (beta(B)=1.12 +/- 0.03) was found for 1b indicating smaller imbalance of the transition state whose structure therefore resembles a nitronate. Cyclization products 2a-c prefer relative trans-configuration in ratios from 55:45 to 83:17 depending on the solvent. Mutual interconversion of the cis-/trans-diastereoisomers occurs either via nitronate species 2a(-) or via a reverse ring opening/ring closing pathway through the nitronate species 1b(-) and 1c(-). The mechanism was also supported by quantum calculations.

Rozsah stran

p. 3973–3979

ISSN

2365-6549

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Projekt

GA17-08499S/Recyklovatelné katalyzátory pro udržitelné technologie pokročilých organických intermediátů

Zdrojový dokument

ChemistrySelect, volume 4, issue: 13

Vydavatelská verze

https://onlinelibrary.wiley.com/doi/abs/10.1002/slct.201900481

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Klíčová slova

Cyclization, Epimerization, kinetics, nitroaldol reaction, reaction mechanism, Kinetika, nitroaldolová reakce, epimerizace, cyklizace, 2-nitroindan-1-ol

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