Intramolecular Reactivity of trans [4+4] Photodimers of 2-Pyridones

Peiling Chen; Patrick J. Carroll; Scott Mc N. Sieburth

doi:10.1055/s-2007-983793

PAPER

Intramolecular Reactivity of trans [4+4] Photodimers of 2-Pyridones

Peiling Chen^a, Patrick J. Carroll^b, Scott McN. Sieburth*^a
^a Department of Chemistry, Temple University, 1901 N. 13th St., Philadelphia, PA 19122, USA
e-Mail: scott.sieburth@temple.edu;
^b Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104, USA

Abstract

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Abstract

Photodimers of 2-pyridones are cycloocta-1,5-dienes with two lactam bridges. These, and related structures, undergo halogenation to give rearranged products in which an amide nitrogen has intercepted an initial halonium ion. For the trans isomer, a transient four-membered azetidinium ion reacts via dealkylation, giving a dihalide-diamide product in high yield. This readily available intermediate reacts with nucleophiles in a process that begins with intramolecular amide N-alkylation, reforming the azetidinium intermediate. Reaction of this intermediate with the nucleophile can take two different paths, depending on the reversibility of the nucleophilic attack, with reversible nucleophiles giving N-dealkylation and irreversible nucleophiles reacting with the carbonyl group.

Key words

cycloadditions - dimerizations - ketones - photochemistry - pyridines

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References

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