Rate and equilibrium effects of tert-alkyl groups on rotamerization in 3,4-alkylenedioxy-, 3-alkoxy- and 3,4-dialkoxy-2-thienyl(di-tert-alkyl)methanols: an IR, NMR, kinetics and MM studyElectronic supplementary information (ESI) available: additional experimental data. See http://www.rsc.org/suppdata/p2/b2/b203714a/

In the last three decades, reacting sterically congested ortho-substituted arenes to form atropochiral biaryls is an appealing venture and a challenging subject that has garnered significant attention. Therefore, there is interest in developing methods to prepare these compounds. In this study, an efficient approach to produce a new class 2,2' disubstituted biaryls bridgehead phosphine oxides with an unusual topology and exceptional conformational stability is presented. Our methodology demonstrates that depending on the substitution pattern on the aryl moieties, the methanophosphocine backbone could be rigid enough to observe a double atropochirality, resulting in an under covered class of molecules. Notably, our studies revealed that replacing only one hydrogen at the ortho position by a fluorine atom led to sufficiently restricted rotation at temperatures below 80 °C, extending "far away" the limits of atropostability. Finally, our investigations, which employed variable-temperature NMR spectroscopy and DFT calculations, yielded unique insights into the isomerisation mechanism, indicating that the two biaryl motifs are fully independent in spite of their proximity.

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Beyond the Limits of Atropochirality: Design of Highly Conformationally Restrained Biaryls with Bridgehead Phosphine Oxide

Mele

Babouri

Pirat

et al. 2023

Chemistry A European J

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Recent Advances in Stereodynamics and Conformational Analysis by Dynamic NMR and Theoretical Calculations

2010

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Proton NMR and IR study of self‐association in pyridylalkanols: open or cyclic dimers? higher polymers?

Lomas

Adenier

Cordier

2006

J of Physical Organic Chem

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1 H NMR measurements indicate that (X-pyridyl)alkanols of the general formula (C 5 H 4 N)(CH 2 ) n OH, where n ¼ 1, 2 or 3, self-associate as open dimers, cyclic dimers, trimers and tetramers, with considerable variations depending on the position of the alkyl chain and its length. 2-(X-Pyridyl)propan-2-ols behave like the corresponding pyridylmethanols with, however, somewhat lower association constants. The IR spectra of 3-(X-pyridyl)-2,2,4,4tetramethylpentan-3-ols (X ¼ 3 or 4) in carbon tetrachloride suggest weak association, while the 2-pyridyl derivative occurs mainly as the intramolecularly hydrogen-bonded rotamer. The OH NMR shifts for the 3-and 4-pyridyl derivatives in benzene are concentration-dependent, but neither the equilibrium constants nor the degree of association can be evaluated. Benzyl alcohol in benzene associates as an open dimer and a cyclic tetramer, as does 2phenylpropan-2-ol, only more weakly. Rotation barriers for 3-(X-pyridyl)-2,2,4,4-tetramethylpentan-3-ols (X ¼ 2, 3 or 4) in DMSO or nitrobenzene are 20-21 kcal mol À1 .

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Cited by 8 publications

References 38 publications

Beyond the Limits of Atropochirality: Design of Highly Conformationally Restrained Biaryls with Bridgehead Phosphine Oxide

Beyond the Limits of Atropochirality: Design of Highly Conformationally Restrained Biaryls with Bridgehead Phosphine Oxide

Recent Advances in Stereodynamics and Conformational Analysis by Dynamic NMR and Theoretical Calculations

Proton NMR and IR study of self‐association in pyridylalkanols: open or cyclic dimers? higher polymers?

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