Fluorine induced pseudo-anomeric effects in methoxycyclohexanes through electrostatic 1,3-diaxial interactions
Abstract
We report counter‐intuitive axial preferences in non‐stereochemically biased, selectively fluorinated methoxycyclohexanes. These pseudo‐anomeric effects are apparent when electronegative CF2 groups are placed at the C‐2, C‐4 and C‐6 positions of the cyclohexane ring to render the C‐3/5 axial hydrogen atoms electropositive. The electrostatic interaction between these axial hydrogen atoms and the ‐OMe oxygen is stabilising. The effect is explored using high‐level ab initio and DFT calculations in the framework of NBO, QTAIM and NCI analysis across a range of derivatives, and experimentally (19F{1H}‐NMR at −80 °C) for some illustrative examples. The effect is significant in energy terms for a weak interaction, and illustrates a new stereoelectronic aspect attributed to selective fluorine substitution in organic chemistry.
Citation
Piscelli , B , Sanders , W , Yu , C , Al-Maharik , N , Lebl , T , Cormanich , R & O'Hagan , D 2020 , ' Fluorine induced pseudo -anomeric effects in methoxycyclohexanes through electrostatic 1,3-diaxial interactions ' , Chemistry - A European Journal , vol. 26 , no. 52 , pp. 11989-11994 . https://doi.org/10.1002/chem.202003058
Publication
Chemistry - A European Journal
Status
Peer reviewed
ISSN
0947-6539Type
Journal article
Rights
Copyright © 2020 The Authors. Published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Description
Authors thank FAPESP, CONFAP and The UK Academies for a São Paulo International Research Collaboration (FAPESP #2019/05028-7). FAPESP is also gratefully acknowledge for an undergraduate fellowship to BAP (#2019/03855-3), and a Young Research Award to RAC (#2018/03910-1). The Chinese Scholarship Council (CSC) is thanked for a Studentship (CY). Finally CENAPAD-SP, CESUP and SDumont are acknowledged for computational resources used in theory calculations.Collections
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