Chemistry and Physics Faculty Articles

Title

Reactivity of Nucleophiles Toward a p‐Benzyne Derived from an Enediyne

Document Type

Article

Publication Date

2-2013

Publication Title

Journal of Physical Organic Chemistry

Keywords

Enediyne, Cycloaromatization, p-Benzyne, Diradical, Nucleophilic addition, Selectivity, Solvation

ISSN

0894-3230

Volume

26

Issue/No.

2

First Page

206

Last Page

210

Abstract

Enediynes undergo cycloaromatization to p‐benzyne diradicals. A new reaction of p‐benzynes is here presented. Instead of their usual radical reactivity, they add nucleophiles, followed by protonation. Kinetic evidence showed that the rate‐limiting step is the cycloaromatization, followed by rapid addition of a nucleophile. The unusual feature of nucleophilic addition to a radical center in a singlet diradical is discussed. Calculations that ignore solvation suggest that the addition has no activation barrier, but one is created by the necessity for desolvation of the anionic nucleophile. Relative reactivities of several nucleophiles have been measured under competition conditions. The observation of deuterium incorporation from DMSO‐d6 or CD3CN shows that the species that is protonated is the aryl anion, not the p‐benzyne. The extent of deuterium incorporation increases as the nucleophile is changed from iodide to bromide to chloride. This remarkable instance of selectivity is discussed. These studies of p‐benzyne reactivity are exploring the nonradical chemistry of this diradical.

Comments

©2012 John Wiley & Sons, Ltd.

Additional Comments

NSF grant #s: CHE07-42801, CHE97-09183, 0742551; ACS-PRF grant #: 48388-AC4

ORCID ID

0000-0002-0566-0820

ResearcherID

V-6501-2018

DOI

10.1002/poc.2994

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