Condensation of Diacetyl with Alkyl Amines: Synthesis and Reactivity of p-Iminobenzoquinones and p-Diiminobenzoquinones

Diacetyl exposure disrupts iron homeostasis in animals and cells

OBJECTIVE

Several mechanisms have been proposed for the biological effect of diacetyl. We tested the postulate that animal and cell exposures to diacetyl are associated with a disruption in iron homeostasis.

MATERIALS AND METHODS

Male, Sprague-Dawley rats were intratracheally-instilled with either distilled water or diacetyl. Seven days after treatment, animals were euthanized and the lungs removed, fixed, and embedded. Sections were cut and stained for iron, collagen, and ferritin. Human epithelial (BEAS-2B) and monocytic (THP-1) cells were exposed in vitro to ferric ammonium citrate (FAC), diacetyl, and both FAC and diacetyl. Cell non-heme iron concentrations and ferritin levels were quantified using inductively coupled plasma optical emission spectroscopy and an immunoassay respectively.

RESULTS

After exposure of animals to diacetyl, there were airway polypoid lesions which stained positively for both iron and the intracellular storage protein ferritin. Trichrome stain showed a deposition of collagen immediately adjacent to accumulated metal following diacetyl exposure. In in vitro cell exposures, FAC increased non-heme iron concentration but co-incubations of FAC and diacetyl elevated levels to significantly greater values. Levels of ferritin were increased with exposures of BEAS-2B and THP-1 cells to FAC but were similarly greater after co-exposure with FAC and diacetyl.

CONCLUSIONS

Results of animal and cell studies support a disruption of iron homeostasis by diacetyl. It is proposed that, following internalization, diacetyl complexes intracellular sources of iron. The cell recognizes a loss of its requisite iron to diacetyl and imports greater concentrations of the metal.

M[TPP]Cl (M = Fe or Mn)-Catalyzed Oxidative Amination of Phenols by Primary and Secondary Anilines

Iron- and manganese-catalyzed para-selective oxidative amination of (4-R)phenols by primary and secondary anilines was developed. Depending on the identity of the R group, the products of this efficient reaction are either benzoquinone anils (C–N coupling) that are produced via a sequential oxidative amination/dehydrogenation (R = H), oxidative amination/elimination (R = OMe) steps, or N,O-biaryl compounds (C–C coupling) that are formed when R = alkyl through an oxidative amination/[3,3]-sigmatropic rearrangement (quinamine rearrangement) process.