It was found that (E)-vinylic sulfones preferentially afford (Z)-allylic sulfones as kinetically-controlled products by treatment with a base under mild conditions, while (Z)-vinylic sulfones give (E)-allylic sulfones. Such stereochemical relationship was rationalized by “syn-effect”, and its relative degree for various substituents was determined by observation of E/Z ratios of the allylic sulfones resulted from the corresponding γ-mono- or γ,γ-disubstituted vinylic sulfones as follows: RO– (R = CH3, C2H5) ArO– (Ar = p-CH3OC6H4, p-CH3C6H4, C6H5, p-NO2C6H4) ≥ AcO– > Cl– ≥ Br– > CH3– > CH3S– ≥ –CH2– (cyclic and acyclic) > (CH3)2CH– >> (CH3)3C–, C6H5–. X-Ray crystallography was performed for some vinylic sulfones to reveal the origin of the “syn-effect”.
The relative degree of “syn-effect” for the γ-substituted vinylsulfones in their conversion to the corresponding allylsulfones with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) was determined by observing E/Z ratios of the resulting allylsulfones as follows: CH3O– ≥ AcO– > CH3– > –CH2– >> t-Bu– and Ph–.
SynopsisCorrelations between the crystal structures of polymers consisting of the hydrogen-bonded molecular sheets and anisotropy of the linear compressibility ( K O ) of the crystal were studied a t 2OoC under hydrostatic pressures up to 6 kbar. For nylon-6, it was found that K O is more than four times larger in the direction normal to the hydrogen-bonded sheet than in the parallel direction. The inversion of the sheet direction involved in the ay transition of nylon-6 was clearly reflected in the anisotropy of the linear compressibility. For atactic poly(viny1 alcohol), KO in the c-axis direction was 1.6 times larger than that in the a-axis direction, which is consistent with a structure model with the hydrogen-bonded sheet parallel to the a axis. Theoretical calculations by Tashiro et al. indicate, however, the anisotropy does not necessarily correspond to the sheet structure when the direction of the hydrogen bonds strongly deviates from the plane of the sheet.
It was revealed by X-ray crystallography that α-unsubstituted (E)-vinyl sulfones have syn-conformation which seems to be the cause of “syn-effect” found in the conversion of (E)-vinyl sulfones to the corresponding allyl sulfones with a base under mild conditions. Syn-conformation of a terminal olefin in solid state was also confirmed.
Syn-Effect" in the Conversion of (E)-Vinylic Sulfones to the Corresponding Allylic Sulfones.-Various γ-mono-and γ,γ-disubstituted (E)-vinylic sulfones are reacted under mild basic conditions to afford preferentially the isomeric (Z)-allylic sulfones as the kinetically controlled products. This outcome is rationalized by the "syn" effect and its relative degree for various substituents is evaluated by 1H NMR spectroscopic determination of the E/Z ratios of the resulting allylic sulfones. Thus, the following series are obtained: R-O (R: Me, Et) .simeq. Ar-O (Ar: p-anisyl, p-tolyl, phenyl, p-nitrophenyl) . gtoreq. Ac-O ¿ Cl ≥ Br ¿ Me ¿ MeS ≥ -CH2-(cyclic and acyclic) ¿ iPr tBu, phenyl. Some vinylic sulfones are submitted to X-ray crystal analyses in order to reveal the origin of the "syn" effect. -(HIRATA, T.; SASADA, Y.; OHTANI, T.; ASADA, T.; KINOSHITA, H.; SENDA, H.; INOMATA, K.; Bull. Chem. Soc. Jpn. 65 (1992) 1, 75-96; Dep. Chem., Fac. Sci., Kanazawa Univ., Kanazawa 920, Japan; EN)
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