CONFORMATIONAL PREFERENCES AND RESTRICTED RING INVERSION IN THIANTHRENIUM YLIDES

References

• A boat-to-boat interconversion
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• In these unsubstituted systems ring inversion does not require bonds to pass by one another. Thus, bond angle distortions are assumed to be the significant contributors to the barriers. For example, we have been unable to significantly reduce the rate of ring inversion of thioxanthene even at –100°C, as studied by variable temperature nmr; unpublished results
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• Kluba , M. , Harwood , J. , Casey , P. K. and Ternay , A. L. Jr. 1985 . J. Heterocyclic Chem. , 22 : 1261 and references cited therein
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• Ternay , A. L. Jr. and Evans , S. A. 1974 . J. Org. Chem. , 39 : 2941
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• Ternay , A. L. Jr. , Herrmann , J. , Hayes , B. A. and Joseph-Nathan , P. 1980 . J. Org. Chem. , 45 : 189 Its preferred conformation can be altered to a' by hydrogen bonding
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• Ternay , A. L. Jr. , Ens , L. , Herrmann , J. and Evans , S. 1969 . J. Org. Chem. , 34 : 940 Substitution peri to sulfur can force substituents bonded to sulfur into the a' array and inhibit ring inversion
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• Deuteriochloroform; 25°C
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• Galloy , J. , Watson , W. H. , Craig , D. , Guidry , C. , Morgan , M. , McKellar , R. , Ternay , A. L. Jr. and Martin , G. 1983 . J. Heterocyclic Chem. , 20 : 399 and references cited therein. Typically e' methylide carbons resonate near 50 ppm while a' counterparts are found near 70 ppm
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• Additionally, the proton and 13C nmr spectra of thianthrenium bis(carboethoxy)methylide are rather independent of temperature over the range from – 25 to + 100°C, further supporting a rather rapid ring inversion at room temperature
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• Ternay , A. L. Jr. , Baack , J. C. , Chu , S. S. C. , Napoleone , V. , Martin , G. and Alfaro , C. 1982 . J. Heterocyclic Chem. , 19 : 833 Thianthrenium bis(carboethoxy)methylide is e' in the solid state
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• Probe temperature range –10 to + 60°C
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• Oxidants include (a) dinitrogen tetroxide (0°C); (b) m-chloroperoxybenzoic acid (-20 to + 25°C); (c) ceric ammonium nitrate; and (d) hydrogen peroxide/acetic acid
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• Hosoya , S. and Wood , R. G. 1957 . Chem. and Ind. , : 1042 For a presentation of X-ray results see
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• Hosoya , S. 1958 . Chem. and Ind. , : 159
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• This view stems from the rather minor effects of temperature change upon the nmr spectrum (-20°C to + 120°C)
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• Derivatives of such heterocycles are important in psychopharmacology and often are cataloged by the number of atoms in their fused ring systems
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• Our syntheses have inevitably produced the trans diylide in very large excess. However, we have a preliminary single crystal X-ray analysis of the corresponding cis-diylide (unpublished results) which shows that this isomer is e′,e′ (like the corresponding disulfoxide) and not a',a'
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• This represents the upper operating limit of the spectrometer
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• The VT experiment was done in duplicate and results were reproducible within 1°C. Copies of these spectra are available upon request
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• Oki , M. 1985 . Applications of Dynamic NMR Spectroscopy to Organic Chemistry , 407 Florida : VCH . Tc was taken as 402 K and v max as 115 Hz (the difference between the center peaks of the more downfield (1.17 ppm) and more upfield (0.60 ppm) triplets at 25°C in DMSO-d6
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• Melting points are uncorrected. IR spectra were obtained on a BIO-RAD FTS-40 FTIR spectrometer over a range of 4000–400 cm−1. Mass spectra were obtained on a Finnigan MAT TSQ 70 spectrometer operating in the chemical ionization (CI) mode using methane gas. Spectra were obtained using either a gas chromatography (GC) inlet or a solid probe (SP). NMR spectra were acquired using a Nicolet NT-200 spectrometer operating at approximately 200.067 MHz for 1H and 50.31 MHz for 13C observation. All non-VT spectra were acquired using a 12 mm probe operating at 25 ± 1°C employing 100–300 mg of compound/3 ml of CDCl3. Typical 90° pulses for 1H and 13C were 38 and 21.5 μs, respectively. Chemical shifts are reported relative to tetramethylsilane, using either the protiochloroform signal set to 77.26 ppm as internal reference for proton, or the center peak of the deuteriochloroform signal set to 77.00 ppm as internal reference for 13C spectra
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• m/z (relative intensity)
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• Bubbles of gas (presumed to be nitrogen) evolved during the course of heating. A white precipitate was observed after heating at 110°C for 15 min
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• The flash column (4.5 cm) was packed with 90 g of 200–235 mesh silica gel using chloroform
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• Separation was achieved with a Varian Model 5000 and the following: Alltech C8 column; methanol eluent; solvent flow rate: 1.0 and 0.5 mL/min; λ max: 254 nm; recorder: 1 au/mv; chart speed: 2 cm/min; chart input: 10 mv
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• 4” Silica plate; (acetonitrile/methylene chlorida, 5/95) eluent; UV visualization; Rf 0.28 (minor) and 0.13 (major)
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