Issue in Honor of Prof Rosalinda Contreras Theurel ARKIVOC 2008 (v) 153-171
Experimental Section
General Procedures. All syntheses and manipulations were carried out under argon using standard Schlenk line and glove box techniques. Solvents for general use (toluene, hexane, THF, Et2O) were dried over sodium or potassium/benzophenone and freshly distilled prior to use. Deuterated solvents were obtained from Aldrich, vacuum distilled and stored over molecular sieves. Triethylamine, and chlorotrimethylsilane were purchased from Aldrich and distilled before use. tert-butyl hydroperoxide 5.0-6.0M in decane was used as received from Aldrich. The bicyclophosphane 1 and dioxazaphosphocane 2 were synthesized according to literature methods.7 NMR spectra (1H, 13C and 31P) were recorded on Varian-Inova-400 MHz and VarianGemini- 200 MHz instruments and chemical shifts are reported relative to SiMe4 for 1H and 13C and are in ppm. Infrared spectra were recorded as KBr pellets on a Brucker Equinox 55 Spectrometer and are reported in cm-1. Microanalyses were obtained on an Elementar Vario EL III instrument operating in the CHN mode. Single-crystal X-Ray diffraction data for 4b, 4c and 5a were collected using the program SMART20 on a Brucker APEX CCD diffractometer with monochromatized Mo-Ka. radiation (. = 0.71073 .). Cell refinement and data reduction were carried out with the use of the program SAINT, the program SADABS was employed to make incident beam, decay and absorption corrections in the SAINT-Plus v. 6.0 suite21. Then, the structures were solved by direct methods with the program SHELXS and refined by full-matrix least-squares techniques with SHELXL in the SHELXTL v. 6.1 suite22. Hydrogen atoms were generated in calculated positions and constrained with the use of a riding model. The final models involved anisotropic displacement parameters for all non-hydrogen atoms. All the refinements were straightforward.
1,3-Dioxa-6-aza-2(O-trimethylsilyl ester)s3.3phosphacyclooctane (3). Chlorotrimethylsilane (0.565g, 5.2 mmol) was slowly added at room temperature to a stirred mixture of 2 (1g, 5.2 mmol) and 1 equivalent of triethylamine (0.524g, 5.2mmol) in 10 ml of toluene. The reaction mixture was then left under stirring for one night before the white precipitate of triethylamine hydrochloride was filtered off over Celite. A 31P NMR analysis of the crude solution showed the presence of only one resonance at 129 ppm. The filtrate was used in the following reactions without further purification considering that the formation of 3 is quantitative. A solution of a crude sample was concentrated and dissolved in deuterated benzene to perform 1H and 13C NMR analysis. 1H NMR (400 MHz, C6D6): d 0.19 (s, 9H, SiMe3), 1.67 (s, 3H, CH3CO) 2.49 (m, 1H)
2.79 (m, 1H) 2.96 (m, 1H) 3.37 (m, 1H) 3.46 (m, 1H) 3.84 (m, 1H) 3.96 (m, 1H) 4.09 (m, 1H) [N(CH2CH2O)2]. 13C NMR (100MHz, C6D6): d 1.98 (s, SiMe3), 22.22 (s, CH3CON), 50.32 (s, NCH2), 51.38 (s, NCH2), 60.17 (d, 2J31P13C=3.1 Hz, CH2O), 61.66 (d, 2J31P13C=10.6 Hz, CH2O), 170.01 (s, C=O). MS-FAB+ m/z (%): 266 (100) [MH+], 194 (54) [(C6H12NO4P)H+]. Oxidation of (3) with tert-butylhydroperoxide. One equivalent of commercial tertbutylhydroperoxide in decane solution (Aldrich) was added drop by drop via a syringe to a
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