2,2′,5,5′-Tetraphenyl-3,3′-bithiophene-4,4′-diol, the first member of a new class of chiral C2-symmetric atropisomeric diols based on a biheteroaromatic scaffold, has been synthesized. Dynamic enantioselective HPLC experiments revealed a racemization barrier of 22.9 kcal/mol at 25 °C, which is high enough to permit the chromatographic collection of both enantiomers on a semi-preparative scale, but at the borders of application as a promoter in asymmetric catalysis. The ground and transition states involved in the enantiomerization process have been identified through DFT calculations, which suggest the intermediacy of a tautomeric species in which a thiophen-3-ol unit and a 2,3-dihydrothiophen-3-one ring are present. The proposed racemization mechanism is supported by the results of dynamic HPLC experiments. Calculations also suggested which substituent groups at the 2,2′-positions of the thiophene rings could lead to an increase in enantiomerization barriers sufficient to confer full configurational stability on the 3,3′-bithiophene framework.
BITHIENOLs : Promising C2-Symmetric Biheteroaromatic Diols for Organic Transformation / S. Gabrieli, R. Cirilli, T. Benincori, M. Pierini, S. Rizzo, S. Rossi. - In: EUROPEAN JOURNAL OF ORGANIC CHEMISTRY. - ISSN 1434-193X. - 2017:4(2017), pp. 861-870.
Titolo: | BITHIENOLs : Promising C2-Symmetric Biheteroaromatic Diols for Organic Transformation |
Autori: | ROSSI, SERGIO (Corresponding) |
Parole Chiave: | Alcohols; Atropisomerism; Biaryls; Chiral resolution; Racemization; Physical and Theoretical Chemistry; Organic Chemistry |
Settore Scientifico Disciplinare: | Settore CHIM/06 - Chimica Organica |
Data di pubblicazione: | 2017 |
Rivista: | |
Tipologia: | Article (author) |
Digital Object Identifier (DOI): | http://dx.doi.org/10.1002/ejoc.201601353 |
Appare nelle tipologie: | 01 - Articolo su periodico |
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