O. Maior

Excited states properties of some phenoxathiin derivatives

Abstract Several properties of the excited singlet state (natural lifetimes, fluorescence quantum yields, solvatochromicity, etc.) of some 3-substituted phenoxathiin derivatives (methyl, formyl, acetyl) were investigated by means of absorption and steady-state fluorescence spectroscopy. The results point out that the emission properties are dependent on the type of the substituent, the most efficient being 3-acetylphenoxathiin. The effect of the solvent polarity on the fluorescence maxima of 3-formyl- and 3-acetylphenoxathiin, rationalized in terms of the Lippert–Mataga equation, points at an increase in the dipole moment in the excited state. A specific behavior in protic solvents was also noticed. AMI calculations for the ground and excited states support the experimental data and explain the higher efficiency of the carbonyl containing derivatives in terms of a different nature of the first excited singlet. It was established that the enhanced radiative decay for these compounds is due to the presence of new low-lying vacant π -molecular orbital situated between the frontier orbitals of phenoxathiin. The theoretical results reflect also the charge transfer character of the excited states in agreement with the solvatochromicity already discussed.

Synthesis of New Thiazoles from α-Halohetaryl Ketones

Reactions of α-bromoacetylphenoxathiin, α-bromoacetylphenoxathiin 10,10-dioxide, or α-bromoacetylthianthrene with certain p-(arylsulfonyl)thiobenzamides lead to the formation of the corresponding 2,4-disubstituted thiazoles. The new compounds were characterized through elemental analysis and spectral data (IR, 1H NMR, and 13C NMR).

Spectral study of some phenoxathiin derivatives and their positive ions

Optical and e.s.r. spectra of some phenoxathiin derivatives and their positive ions are given and discussed. Charge-transfer complexes of the substituted derivatives were prepared and their ionisation potentials were estimated. MO calculations were used for the assignment of the electronic transitions and hyperfine splittings.

Syntheses of New Carbonyl Derivatives from α-Halohetaryl Ketones

The Kröhnke reaction of 2ω-bromoacetylphenoxathiin and 2-ω-bromophenoxathiin 10,10-dioxide, through N-ylide and S-ylide intermediates, leading to the corresponding glyoxals, was described. The condensation reaction of 2-ω-bromoacetylphenoxathiin with aromatic o-hydroxy aldehydes and further cyclization to new furan derivatives was also performed. The new compounds were characterized through elemental analysis and spectral data (IR, 1H NMR and 13C NMR).

Phenoxathin chemistry. Remarks concerning the benzoylation reaction of phenoxathin

Benzoylation of phenoxathiin leads to a mixture of 2- and 3-benzoylphenoxathiins. Starting from 3-phenoxathiincarbonyl chloride and benzene in the presence of anhydrous aluminum chloride, 2-benzoylphenoxathiin was obtained instead of the 3-substituted isomer. Treating 3-benzoylphenoxathiin with aluminum chloride and hydrogen chloride a rearrangement reaction took place, leading to 2-benzoylphenoxathiin.

Synthesis of n-(phenoxathiin-2-carbonyl)-or N-(thianthrene-2-carbonyl)-N′-arylthioureas

The reactions of phenoxathiin-2-carbonyl-or thianthrene-2-carbonyl-isothiocyanates with certain primary amines lead to the formation of corresponding N′-substituted-N-hetaroylthiocarbamides. The aforementioned isothiocyanates were obtained in situ by reactions of phenoxathiin-2-or thianthrene-2-carbonyl chlorides with KSCN. The new compounds were characterized by elemental analysis and spectral data (IR,1H and13C NMR).

Synthesis of 1H-pyrrolo[2,3-b]phenoxathiin-2,3-dione

The title compound was obtained using the Sandmeyer reaction starting from 2-aminophenoxathiine. A new synthesis of N-methylpyrrolo[2,3-b]phenoxathiin-2,3-dione was also presented. Chemical and spectral data supporting the structure of the newly synthesized compounds were given. The isatin analogue, 1-methylpyrrolo-[2,3-b]phenoxathiin-2,3-dione-10, 10-dioxide, could not be obtained.