Radical versus Non-Radical Reactivity in ortho- and para-Quinonedimethides and Implications for Cycloaddition Mechanisms.
Org Lett
; 26(38): 8110-8114, 2024 Sep 27.
Article
in En
| MEDLINE
| ID: mdl-39283019
ABSTRACT
The latent singlet diradical character of the parent ortho-quinonedimethide (o-QDM), as revealed by valence bond calculations, is demonstrated experimentally by trapping with the kinetically stable free radical TEMPO at room temperature. In the absence of TEMPO, the main pathway for decomposition at ambient temperature is not (as previously proposed in the literature) a radical reaction but instead a concerted Diels-Alder dimerization, which through ωB97X-D/aug-cc-pVTZ/SMD//M06-2X-D3/6-31+G(d,p)/SMD calculations is shown to proceed through an ambimodal bispericyclic transition state. The predominantly non-radical reactivity of o-QDM at room temperature differs from that of its isomeric para-quinonedimethide (p-QDM) congener, which self-reacts exclusively through radical pathways. These findings suggest the potential for tunable concerted/stepwise cycloadditions.
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1
Collection:
01-internacional
Database:
MEDLINE
Language:
En
Journal:
Org Lett
Journal subject:
BIOQUIMICA
Year:
2024
Document type:
Article
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