Formation of S-alkyl thiophenium ionic liquids: mechanistic rationale and structural relationships (En revisión)

SCHIEL MARÍA A.; GARCÍA DE LA CONCEPCIÓN, J.; DOMINI, CLAUDIA E.; CINTAS MORENO, PEDRO

ORGANIC & BIOMOLECULAR CHEMISTRY

ROYAL SOC CHEMISTRY

Lugar: CAMBRIDGE; Año: 2019 vol. 2019 p. 7772 - 7781

1477-0520

The quaternization of thiophenes through S-alkylation reactions with iodoalkanes in presence of silver salts, opens the door to a new family of room-temperature ionic liquids, yet relatively unexplored in terms of chemical reactivity and applications. This computational study provides for the first time a mechanistic rationale that accounts for experimental observations and unveils in addition a series of structural correlations with predictive value. Results are otherwise consistent with the calculated energy barriers of the corresponding transition structures. Calculations indicate that geometry at the sulfur atom goes from flat to tetrahedral during salt formation, and electron delocalization of thiophene is greatly reduced, if not lost, as inferred from aromaticity indexes. Moreover, the rationale explains the influence of polarizable anions on S-alkylation and why alkyl substitution at the a-position of thiophenes gives rise to more stable species than unsubstituted derivatives.