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|
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|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.1002/ejoc.201601353|
|Appare nelle tipologie:||01 - Articolo su periodico|
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