Wavelength (nm) Figure 2. Visible absorption spectra at 25 "C for the photodecomposition of 3-azido-9-[[4-(diethylamino)-l-methylbutyl]amino]-7-methoxyacridine. Spectra A-H correspond to 0, 5, 10, 20, 30,40, 50, and 60-s irradiations of a 1.078 X M solution of the azide in 30 mM phosphate, pH 3.0. The solutions were irradiated in a Rayonet RPR-100 photochemical reactor using four RPR-3500-A lamps. The inset plots show A357 (0) and the logarithm of the observed A357 minus A357 observed at 60-s irradiation time ( . ) against time.removed in this way. The yield of crystalline product was 50%: mp 161-162 OC, dec; u, , (CHC13) 2120 cm-I. Anal. Calcd for Displacement of the chloro substituent from VI11 to give the quinacrine azide analogue I1 was carried out by heating a mixture of the 2-amino-5-(diethylamino)pentane (1.33 equiv) with the chloroacridine (VIII) and phenol at 100 OC for 3 h. The mixture was then taken up in ether and dry hydrogen chloride gas bubbled through it to precipitate the hydrochloride salt: mp 173 OC, dec; u, (CHC13) 21 10 cm-I. Anal. Calcd for Cz3Hz~N60-2HC1. Hz0: C, 55.53; H, 6.89; N, 16.89; C1, 14.24. Found C, 55.37; H, 6.43; N, 16.44; C1, 13.78. Figure 2 shows the photosensitivity of the quinacrine azide product which appears to smoothly decompose in a 60-s irradiation with 350-nm light. The inset plot for Figure 2 shows the absorbance plotted for the 357-nm maximum and log (Ai -A) plotted against time. A tl/z.of 8-10 s is observed for the first-order photodecomposition. Similar data are obtained from the absorbances at 423 nm. An isosbestic point at 460 nm is also observed for the photodecomposition reaction. The photosensitivity of I1 is not pH dependent. Photodecomposition kinetics virtually identical with those seen in Figure 2 have been observed at pH 7.2 (30 mM phosphate). We have not investigated the photochemical products for the irradiation of I1 or any of the other azido intermediates all of which are comparably photosensitive. It is important to note that most biological systems are relatively insensitive to irradiation with 350-nm light of such intensity and duration as is needed to photodecompose 11. The photosensitivity of I1 appears to be comparable to other organic azides which have proven useful in photochemical labelingz6Both work in our laboratory and elsewhere suggest that these azides will prove useful in photochemical labeling experiments. Mair and Stevens6 have shown that azide in the 3-position on the acridine ring gives rise on irradiation to complex mixtures of products which they assumed to result from a variety of reactions of the generated reactive nitrene. In our more biologically interesting azidoacridines there is a similar photoproduct complexity. In contrast Mair and Stevens showed that the azide in the 9-position of the acridine ring results in a long-lived nitrene. Such nitrenes may survive many collisions with solvent and form an azo dimer as a principal product. Other positions of the acridine ring do not appear to have been investigated. (26) Chowdhry...
A more detailed insight into the structure of the 1‐azaallyl anion of a SAMP‐hydrazone has been made possible by the first X‐ray crystallographic study of a chiral monomeric azaenolate. The lithiated 2‐acetylnaphthalene‐SAMP‐hydrazone 1 exists as rubyred crystals; it has an η1‐structure with intramolecular methoxychelatization, while the lithium ion is solvated by two THF molecules.
The isomeric mixture of ethyl 5,6-dihydro-4H-pyrrolo[1,2-b]pyrazole-2- and −3-carboxylates (14 and 15), derived from a
proline meso-ionic synthon, demonstrated remarkably different
stabilities towards alkaline hydrolysis. On that basis, a nonchromatographic, highly efficient method for their large-scale
separation was developed. The desired isomer 14 was converted
into 5,6-dihydro-4H-pyrrolo[1,2-b]pyrazole-2-carbaldehyde, a
key intermediate in the synthesis of bicyclic heteroaryl-substituted 6-alkylidene penems.
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