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The 77Se, 13C and 'H NMR spectra of 57 mostly new compounds with phenylselenenyl groups attached to aeyc!lic alkanes, alkenes and phenylalkanes and of 10 corresponding selenoxides are reported. Substituent effects on the chemical shifts of these nuclei were determined and are discussed in terms of the conformation and configuration. The results suggest that, in contrast to PhSe-C-CSePh fragments, C -C --C S e chains prefer a gauche conformation. KEY WORDS -'Se NMR 13C NMR 'H NMR Phenylselenenylalkanes and -alkenes Selenoxides Substituent etrects Conformation I N T R O D U C T I O NRecently, we have published the NMR properties of a number of phenylselenenylcycloalkanes and discussed substituent effects on 77Se, 13C and 'H chemical shifts and conformational analyses of these compounds.' In this paper we describe an extension of this work to corresponding acyclic analogues. EXPERIMENTAL NMR measurements77Se NMR spectra were recorded at 76.3 MHz (Bruker AM-400) in 0.1-1 M CDCl, solution in 10 mm probes without ' H decoupling. Pulse widths were 30" and repetition rates 1-5 s. Spectral widths were 100 kHz and digital resolution was 6.1 Hz per point, i.e. less than 0.1 ppm. The reproducibility of 77Se chemical shifts is ca. kO.5 ppm if the temperature is kept constant carefully. 77Se chemical shifts are given relative to that of internal (or external) PhSeSePh (6 = 463), corresponding to CH,SeCH, (6 = 0).For all 'H and 13C NMR spectra including DEPT and COSY techniques standard Bruker software and parameters were used. 'H and I3C chemical shifts are referenced to tetramethylsilane (S = 0). IR spectra from CHCI, solutions were relcorded on Perkin-Elmer Model 221 and 13 10 spectrophotometers and electron impact (70 eV) mass spectra ton Varian MAT CH-5 and MAT 711 spectrometers; m/: values refer to fragments containing the "Se isotope. SynthesesSynthetic procedures were performed according to the Ether analogues (PhSeR; 1-29) . 2 diphenyl diselenide (PhSeSePh) was treated with sodium tetrahydroborate (NaBH,) and the respective alkyl halide (RX, X = CI, Br, I) or methanesulphonate (X = OSO,CH,) was added. The alkyl halides were commercially available and the methanesulphomates were prepared by reaction of alcohols with methanesulphonyl chloride. Acetal analogues [(PhSe),C(R,R'); 30-443 :3 diphenyl diselenide (PhSeSePh) was treated with NaBH, and boron tribromide (BBr,) was added to produce B(SePh), . After addition of the respective ketones the acetal analogues were isolated. Alkenyl derivatives [YhSeCH=CHR; 45-57] were obtained by elimination of PhSeH from the acetal analogues. The oxidation of selenides to form the selenoxides [PhSe(=O)R; 58-6714 was performed by bubbling ozone (from an ozone generator) through a solution of the respective selenide in chloroform at cu. -70°C and NMR spectra were recorded at -6O'C and higher until decomposition started. Only the selenoxides 58, 63 and 67 were stable enough to he isolated.
The results of 13C and (when pertinent) 77Se NMR spectra of thiophene and selenophene derivatives containing exocyclic selenium atoms are presented. The "Se spectra show an interaction between nitro or carbonyl groups and selenium when they are ortho to each other. The measurement of 'J(SeSe), 'J(SeSe) and 3J(SeSe) has been attempted on disymmetric diselenides; only 'J(SeSe) can be measured and values are very low, generally below 20 Hz. Other couplings cannot be observed and are smaller than the line width, which is 2 Hz. No theoretical interpretations can be advanced at present.The 13C and 77Se NMR of organic selenium and thiophene derivatives is becoming increasingly well especially in the selenophenic series. The 13C and 77Se NMR spectra of some new compounds are presented in this paper, including the selenium-selenium coupling constants. EXPERIMENTALThe NMR spectra were obtained on a Bruker W H 9 0 C and both 13C and 77Se were observed in the Fourier transform mode using a multi-nuclear probe.The 13C spectra were measured at 22.63MHz with a pulse width of 9 ps (90" pulse = 14 ps), a waiting time of 1 s between each scan and an exponential filtering of 3Hz. The sweep width was 6000Hz and the decay was stored in 4 K data points. The solvent, either deuterochloroform or acetone-d6, was used as * Author to whom correspondence should be addressed internal reference using i313c = 76.91 ppm for CDCl, and 6 1 3~ = 29.22 ppm for a~etone-d,.'~ Cr"' (acac), was used to observe the quaternary carbons; in this case there was no waiting time between each scan. No effects were observed on the chemical shifts which were measured with an error of kO.1 ppm.The 77Se spectra were observed at 17.19 MHz with the same solvent and lock as for I3C. The pulse width was 10 p s (90" pulse = 18.5 ps) and a waiting time of 2 s was used between each scan. The sweep widths were different according to the observed chemical shift, but 4 K data points were always used. The resonance frequencies were measured for each sample and compared to a reference sample of Se(CH,), in CDC1,. When the lock was deuteroacetone the appropriate correction was applied. The temperature was 26°C. According to the reference procedure, the chemical shifts are given with an estimated error of *0.5 ppm. J(77Se77Se) values were measured using a reduced sweep width of approximately 2000Hz and 8 K data points; 1000-30000 scans were stored. The error is ztO.5 Hz for the measurable values. The upper limits of the J values for the smaller coupling constants are given by the width at the base of the main line.Some of the compounds studied were prepared according to literature methods: 1,16 2,17 13,18 3,19 5,29 8, 11 and 12," 15 and 17.,' Compound 4, first prepared by Challenger et al.," was obtained by the action of sulphur and ethyl bromoacetate on 3-lithiothiophene.14 was obtained by a procedure similar to that used for 13. The bromide derivative was prepared from 2-nitro-3-thienyl selenocyanate in chloroform and an equimolar solution of phenylselenol in chloroform adde...
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