1,2,3-Dithiazolyl and 1,2,35-Dithiadiazolyl Radicals as Spin-Bearing ...

the mixture was filtered to remove the palladium on carbon and several milliliters of
concentrated HCl were added to afford the HCl salt of the primary amine. Preliminary
investigations into this reaction found that the free-base was quite tacky and exhibited
poor stability in the air. Converting this into the HCl salt gave 3,4-dioxo-3,4-
dihydronaphthalen-2-aminium chloride (V-12) as a dark red, free-flowing powder which
was stable in the air.
With the amine HCl in hand the Herz ring closure was attempted using sulfur
monochloride. The HCl salt was dissolved in acetonitrile and 6 equivalents of pyridine
were added to prevent the hydrochloric acid from decomposing the sulfur monochloride
and inhibiting the reaction. Six equivalents of sulfur monochloride were then added to the
reaction mixture resulting in the immediate appearance of a thick orange precipitate
which as the reaction flask was heated to reflux slowly gave way to a dark reddish,
homogenous solution. Over the course of an hour, a bright yellow precipitate was
formed, but was allowed to continue for a total of 90 minutes to ensure the reaction had
gone to completion. The yellow precipitate was filtered hot and washed with acetonitrile
before being dried under vacuum and later determined to be the 1,2,3-DTA chloride salt
(V-13) by proton NMR and FTIR. Only preliminary work has been put toward isolating
the radical V-9. Substantial sulfur impurities made isolation of this compound quite
difficult.
5.3.3 Infrared Spectroscopy
The spectrum for the starting material 1,2-naphthoquinone is not very complicated
due to the fact that the molecule has high symmetry. The most important piece of
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