Open AccessA Temperature-Controlled Switch between Fürst–Plattner Rule and Anti-Fürst–Plattner Rule Ring Opening of 2,3-Epoxy-steroids with Various Halide Sources in the Presence of Imidazolium Ionic Liquids
Author(s) -
Anita Horváth,
Kristóf Bolla,
Alexandra Wachtler,
Lilla Maksó,
Máté Papp,
Sándor Mahó,
Zsófia Dubrovay,
János Kóti,
Rita SkodaFöldes
Publication year - 2021
Publication title -
acs omega
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.779
H-Index - 40
ISSN - 2470-1343
DOI - 10.1021/acsomega.1c02470
Subject(s) - chemistry , halide , ionic liquid , ionic bonding , solvent , ring (chemistry) , ion , catalysis , inorganic chemistry , organic chemistry
The ring opening of 2α,3α- and 2β,3β-epoxy-5α-androstan-17-one with halide reagents (AlCl 3 , TMSCl, LiCl, and LiBr) was investigated using imidazolium ionic liquids in the dual role of solvent and catalyst. The application of the ionic liquid was shown to result in an increase in the amount of the unusual diequatorial halohydrins especially at temperatures above 100 °C. With a careful choice of reaction conditions, the latter derivatives could be produced with 43-96% selectivity depending on the nature of the halide ion. Moreover, the usual diaxial products could also be isolated in 70-85% yields by a proper change in the reaction conditions. The reusability of the ionic liquid was demonstrated in both types of reactions. The structures of the products were proved unequivocally by nuclear magnetic resonance (NMR) measurements including two-dimensional (2D) techniques as well as high-resolution mass spectrometry (HRMS). Based on quantum chemical calculations, the effect of the ionic liquid could be explained by the stabilization of the transition state leading to the diequatorial product.