¹H and ¹³C NMR spectral assignments of some novel 2,4,6,8‐tetraaryl‐3,7‐diazabicyclo[3.3.1]nonan‐9‐one derivatives

Abstract

The (1)H and (13)C NMR spectra of 2,4,6,8-tetraaryl-3,7-diazabicyclo[3.3.1]nonan-9-ones (1-2), oximes (3-8) and O-benzyl oximes (9-12) were recorded. The chemical shifts were unambiguously assigned using 1D and 2D NMR spectral data. The results clearly indicate that the compounds exist in chair-boat conformation with equatorial and axial orientation of the aryl groups in the chair and boat forms, respectively. Since the molecules are flexible and dynamic in solution, the chair and boat forms are mutually interconvertible. In 3-12, because of the effect of oximation/oximination, all the protons in the heterobicyclic systems gave distinct signals except the benzylic protons of the boat form. In all synthesized compounds, the aryl group protons at C-6,8 are shielded by the aryl groups at C-2,4 and therefore appear in the lower frequency region than the aryl groups at C-2,4.

Synthesis, structure and conformational analysis of 2,4-diaryl-3-azabicyclo[3.3.1]nonan-9-one thiosemicarbazones and semicarbazones

“…On the other hand, the bicyclic compounds occupy a special place in the structural elucidation, conformation and stereochemistry. In connection with our earlier work on spectral [9] studies of variously substituted mono and bicyclic compounds, herein we report the characterization of bicyclic thiosemicarbazones and semicarbazones using spectral and single crystal X-ray analysis.…”

2,4,6,8-Tetrakis(2-fluorophenyl)-3,7-diazabicyclo[3.3.1]nonan-9-one

“…For the synthesis and stereochemistry of 3,7-diazabicyclo-[3.3.1]nonan-9-ones, see: Parthiban et al (2008). For the biological activity of 3,7-diazabicyclo[3.3.1]nonan-9-one derivatives and related structures, see: Park et al (2012); Parthiban et al (2009Parthiban et al ( , 2010; Asakawa (1995); Jeyaraman & Avila (1981).…”

“…The 2,4,6,8-tetrakis(2-fluorophenyl)-3,7-diazabicyclo[3.3.1] nonan-9-one was synthesized by successive Mannich condensations in one-pot, using 2-fluorobenzaldehyde (0.2 mol, 21 ml), acetone (0.05 mol, 3.7 ml) and ammonium acetate (0.1 mol, 7.7 g) in a 50 ml of absolute ethanol (Parthiban et al, 2008). The mixture was gently warmed on a hot plate at 303 K (30° C) with moderate stirring till the complete consumption of the starting materials, which was monitored by TLC.…”

2,4,6,8-Tetrakis(4-chlorophenyl)-3,7-diazabicyclo[3.3.1]nonan-9-oneO-benzyloxime acetone monosolvate

“…The 2,4,6,8-tetrakis(4-chlorophenyl)-3,7-diazabicyclo[3.3.1]nonan-9-one was synthesized by a modified Mannich condensation in one-pot, using 4-chlorobenzaldehyde (0.2 mol, 28.12 g), acetone (0.05 mol, 3.7 ml) and ammonium acetate (0.1 mol, 7.7 g) in a 50 ml of absolute ethanol (Parthiban et al, 2008). The mixture was gently warmed on a hot plate at 303 K (30° C) with moderate stirring till the complete consumption of the starting materials, which was monitored by TLC.…”