Preprint Review Version 1 This version is not peer-reviewed

Heteroatom Substitution at Amide Nitrogen — Resonance Reduction and HERON Reactions of Anomeric Amides

Named at the Third Heron Island Conference on Reactive Intermediates and Unusual Molecules, Heron Island 1994
Version 1 : Received: 6 October 2018 / Approved: 8 October 2018 / Online: 8 October 2018 (05:45:12 CEST)

A peer-reviewed article of this Preprint also exists.

Glover, S.A.; Rosser, A.A. Heteroatom Substitution at Amide Nitrogen—Resonance Reduction and HERON Reactions of Anomeric Amides. Molecules 2018, 23, 2834. Glover, S.A.; Rosser, A.A. Heteroatom Substitution at Amide Nitrogen—Resonance Reduction and HERON Reactions of Anomeric Amides. Molecules 2018, 23, 2834.

Journal reference: Molecules 2018, 23, 2834
DOI: 10.3390/molecules23112834

Abstract

This review describes how resonance in amides is greatly affected upon substitution at nitrogen by two electronegative atoms.  Nitrogen becomes strongly pyramidal and resonance stabilisation, evaluated computationally, can be reduced to as little as 50% that of N,N-dimethylacetamide.  However, this occurs without significant twisting about the amide bond, which is borne out both experimentally and theoretically.  In certain configurations, reduced resonance and pronounced anomeric effects between heteroatom substituents are instrumental in driving the HERON (Heteroatom Rearrangement On Nitrogen) reaction, in which the more electronegative atom migrates from nitrogen to the carbonyl carbon in concert with heterolysis of the amide bond, to generate acyl derivatives and heteroatom-substituted nitrenes.  In other cases the anomeric effect facilitates S­N1 and SN2 reactivity at the amide nitrogen.

Subject Areas

amide resonance; anomeric effect; HERON reaction; pyramidal amides; physical organic chemistry; reaction mechanism

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