Synthesis and Spectroscopic Properties of 2,3-Diphenyl-1,3-thiaza-4-one Heterocycles

Abstract

Synthetic and spectroscopic data ( 1 H NMR, 13 C NMR, IR, UV/Vis) for a series of six 2,3-diphenyl-1,3-thiaza-4-one heterocycles which differ in ring size and substitution is reported. The results show that there are significant differences in spectroscopic signals common to all six compounds. Distinctions can be made among the compounds using the IR absorbance of the C4 carbonyl and the 1 H NMR signal at C2, and to a lesser extent the 13 C NMR signal at C4 and the UV/Vis spectrum.

Synthesis and spectroscopic properties of a series of novel 2-aryl-3-phenyl-2,3-dihydro-4H-1,3-benzothiazin-4-ones

“…Among the meta-and para-substituted compounds there was little variation in 1 H and 13 C NMR signals at C2, and the same was true of the 13 C NMR and IR signals at C4. The carbonyl (C4) IR signal of 1j (unsubstituted) was significantly different, however.…”

“…In its 13 C spectrum, the C2 carbon in the o-nitro compound 1a was significantly more upfield, at 61.0 ppm, than in the other nitro compounds,. This indicated a through-space interaction between the carbon and the positively charged nitrogen in the ortho position.…”

“…The shoulders ranged from approximately 314-326 nm. The side peak was not present in 2,3-diphenyl-2,3,5,6-tetrahydro-4H-1,3-thiazin-4-one, 13 so it is apparently due to the fused benzene ring. Figure 10.…”

“…Interestingly, the carbonyl (C4) in the unsubstituted compound 1j showed absorption at a much higher wavenumber, 1682 cm -1 , 13 than for any of the substituted compounds. This analysis was repeated in case of error, but the result was very close, 1684 cm -1 .…”

“…We had not previously noted the side peak when we recorded the spectrum of 1a in cyclohexane. 13 The spectrum of 1a was recorded again in cyclohexane, and there was in fact a shoulder as in the spectrum in acetonitrile. The wavelengths of λmax in CH3CN ranged from 272-287 nm (Figure 10).…”