Synthesis and structure elucidation of 25,26,27,28-tetramethylcalix[4]arene tetraketone using 1D and 2D NMR spectroscopies.

The (1)H and (13)C NMR spectra of the new calix[4]arene-based tetraketone were completely assigned by one- and two-dimensional homo- and heteronuclear experiments ((1)H-(1)H COSY, (1)H-(13)C HMQC, and HMBC) at 400 and 100MHz, respectively, at 25 degrees C standard pulse sequence. (1)H and (13)C spectra were measured at room temperature for 25,26,27,28-tetramethylcalix[4]arene tetraketone (1). (13)C[(1)H], DEPT and NMR techniques were used to distinguish the methyl, methylene and methine carbon resonance signals of calix[4]arene 1. Correlation of 1D ((1)H, (13)C[(1)H], DEPT) and 2D (HMQC and HMBC) NMR data was used to completely assign various overlapping and broad signals of calix[4]arene 1. Heteronuclear multibond correlation (HMBC) studies were used to completely assign various carbon resonances. Our results show that the conformation of calix[4]arene 1 in the solution is very similar to the cone conformation reported in the literature