Expansion by Contraction: Diversifying the Photochemical Reactivity Scope of Diazo-oxochlorins toward Development of in situ Alkylating Agents

Journal Article · Thu Apr 01 04:00:00 EDT 2010 · J. Am. Chem. Soc.

DOI:https://doi.org/10.1021/ja800094e· OSTI ID:1007020

Kopke, T; Pink, M; Zaleski, J M ^[1]

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1. Indiana

Irradiation of 2-diazo-3-oxochlorins (200 W, {lambda} {>=} 345 nm, 10 C) in the presence of nucleophilic and biomimetic substrates 1-butanol, tosylhydrazine, or tetrahydrofurfuryl alcohol generates Wolff-rearranged, pyrrole ring-contracted azeteoporphyrinoids in 11--34% yield, with the corresponding hydroxyporphyrins in up to 55% yield. For metalated diazo-oxochlorins, these products compete with intramolecular exocyclic ring formation by meso-phenyl ring addition, which occurs in up to 76% yield in the absence of substrate. The dependence of product distribution on substrate is established by photolysis in neat dichlorometane. Under these conditions, formation of the Wolff-rearranged product is inhibited and the phenyl addition product dominates (76%) due to the absence of a good nucleophile. A conceptually analogous dependence is also observed for the free-base derivative, with the exocyclic ring-containing dimerization product isolated in 42% yield. The third reaction pathway, formation of the hydroxyporphyrin, is enhanced by the presence of non-nucleophilic, oxidizable substrates such as 1,4-cyclohexadiene (M = Cu; 55%); however, in the presence of the bulky and oxidatively more stable tert-butyl alcohol, intramolecular exocyclic ring-quenching is observed in 51% yield with no detection of the hydroxyporphyrin. X-ray structure characterization of the azeteoporphyrinoids reveals a planar macrocycle, illustrating the strong influence of periphery contraction. Specifically, the copper-containing azeteoporphyrinoids show remarkably short Cu-N{sub azete} distances of 1.88--1.90 {angstrom}. All porphyrinoid photoproducts possess intense absorption bands throughout the visible spectral region, indicating that ring-contracted substrate adducts, as well as phenyl ring addition products, maintain porphyrinoid aromaticity. Overall, the ability of these chromophores to photochemically react under substrate control may make unimolecular porphyrinoid photoreagents such as these useful for applications in photobiology or O{sub 2}-independent photodynamic therapy.

• Research Organization: Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
• Sponsoring Organization: USDOE
• OSTI ID: 1007020
• Journal Information: J. Am. Chem. Soc., Journal Name: J. Am. Chem. Soc. Journal Issue: (47) ; 11, 2008 Vol. 130; ISSN JACSAT; ISSN 0002-7863
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ABSORPTION
ADDUCTS
ALCOHOLS
ALKYLATING AGENTS
CONTRACTION
CONTROL
DETECTION
DIMERIZATION
DISTRIBUTION
EXPANSION
IRRADIATION
PHOTOLYSIS
PYRROLES
REACTIVITY
RINGS
SUBSTRATES
THERAPY