1,3-Oxazepane-4,7-Diones Compounds: 1H and 13C NMR High-Resolution Spectroscopy (1D and 2D)

The complete 1H and 13C NMR assignment of new 1,3-oxazepane-4,7-dione compounds has been obtained using one- and two-dimensional NMR techniques including COSY, HMQC, and HMBC experiments. The data deduced from this study show that the alkyl chain and the phenyl ring are in different planes compared to the oxazepine ring. 1. Introduction “Oxazepine” refers to any seven-membered ring containing an oxygen and nitrogen atom. The 1,3-oxazepine is a branch of many types of the heterocyclic oxazepine [1–7]. The core structure of 1,3-oxazepane-4,7diones consists of a seven-memebred ring along with two carbonyl group. Over the years, the syntheses of oxazepine derivatives have been investigated and documented. The result is important of heterocyclic compounds having significant biological uses [8–13]. Recently, we prepared a variety of 1,3-oxazepinediones in order to study the spectroscopic and liquid crystal properties [14]. In this paper, we present the structural elucidation by 1D and 2D NMR experiments of 3-alkyl-2-(3-hydroxyphenyl)-1,3-oxazepane-4,7-diones with general formula(HOC6H4)CONCnH2n+1CH-CH(CO)2 (where , 4, 6, 8, 10, 12, 14, 16, and 18). Here, the hydroxyphenyl and the terminal alkyl chain are attached to the oxazepane ring. 2. Experimental 2.1. Material The experimental part for the synthesized of 1,3-oxazepane-4,7-dione compounds and recording of CHN, FT-IR, and all proton and carbon NMR spectra have been reported elsewhere [15]. 2.2. Physical Measurements Melting points were recorded by GALLENKAMP digital melting point apparatus. The elemental microanalyses (CHN) were performed using a Perkin Elmer 2400 LS Series CHNS/O analyzer. The NMR spectra were recorded in deuterated methyl sulphoxide (DMSO-d6) at 298？K on a Bruker 400？MHz Ultrashied FT-NMR spectrometer equipped with a 5？mm BBI inverse gradient probe. Chemical shifts were referenced to internal tetramethylsilane (TMS). The concentration of solute molecules was 50？mg in 1.0？mL of (DMSO-d6). Standard Bruker pulse programs [16] were used throughout the entire experiment. The spectroscopic details of NMR are summarized in Table 1. Table 1: Acquisition parameter used in the NMR measurements. 3. Results and Discussion The data of the 1H and 13C NMR chemical shifts for title compounds in DMSO solution are listed in respective Tables 2 and 3. Table 2: 1H NMR chemical shifts (ppm) of compounds 2oxa–18oxa. Table 3: 13C NMR and DEPT135 chemical shifts (ppm) of compounds 2oxa–18oxa. 3.1. 1D and 2D 1H NMR Spectral Assignment A complete assignment for the title compounds can be given based on the