Thietane, structure

This phenomenon of bond lengthening seems to be a particular feature of strongly strained rings because other thietane structures exhibit such irregularities as well. The structural configuration and dimensions have been reviewed and described fully by White and Beeson. From microwave data, they calculate the dipole moment of thietane to be 1.85 D. 

A conformational analysis of thiacycloalkanes including 2-thiacyclobu-tane, utilizing molecular mechanics for the calculation of the geometries and energies, was made by Allinger and Hickey. The calculated C—C, C—S, C—S—C, C—C—C, and C—C—S bond parameters for the thietane structure, in comparison to those that were derived from electron diffraction, NMR, and microwave measurement, are reported. The experimental and calculated heat of formation of the thiacyclobutane are 14.49 and 14.58 kcal/mol, respectively. 

NMR studies of thiazetidine derivatives, " ) -sultones, and spiro compounds that contain the thietane structure have been carried out. With the help of Eu(fod)3 the AB pair of doublets of sultone 42 could be moved downfield. ... 

The literature describing theoretical studies on monocyclic thietanes and thietes until 1995 has been fully covered in CHEC-II(1996). However, the described papers were confined to semi-empirical or molecular orbital(MO) calculations. During the last decade, computational abilities have increased dramatically, and several papers have appeared dealing with ab initio calculations of thietane structures. Extensive ab initio calculations have been carried out in order to establish the isotropic shielding constant a and chemical shifts 8 of 14 variously substituted thietanes 1 <2000MRC468>. These values have been computed using the HF/6-31++G and geometries for this purpose... 

Hydroxythietanes are obtained by treating epichlorohydrins with hydrosulfide as illustrated by the preparation of 3-hydroxythietane itself/ Work reporting that an hydroxymethylthiirane is formed was reinvestigated and the thietane structure was confirmed. ... 

The proton spectra analysis of thietane, thietane oxide and thietane dioxide at 100 and 300 MHz in the temperature range — 140 to 190 °C confirmed the puckered structure for the oxide (5a) with the sulfinyl oxygen in the equatorial orientation, as inferred from chemical-shift considerations180. It appears that the repulsive-type 1,3-interactions between the oxygen and the 3-substituents184 are operating between oxygen and the axial proton on C-3 in the unsubstituted thietane oxide (5a). For the thietane dioxide (5b ... 

Interestingly, the crystal structures of 3-substituted thietane and thietane dioxides180 showed that in the solid state they exist in the puckered structure, with the S—O bond equatorial in the oxides and the 3-substituent axial for the trans-isomers, contrary to what has been quoted before66,195. Thus, the claim that conformer 5c is predominant in the solutions of the trans-isomer needs to be re-examined. 

The structures of four-membered rings are of considerable interest, owing in part to the low-frequency ring puckering vibration203. The comparison of the structures and conformational preferences of thietane oxides and dioxides discussed above with those of dithietane oxides and dioxides is therefore appropriate and will follow. 

The crystal structures of several thietane oxides have been determined. Bond lengths and angles are given in Table 6. 

The proton spectra of thietane oxide (5a) and thietane dioxide (5b) have been studied in order to evaluate whether the oxidation at the sulfur atom changes the established 35° puckering of the ring218, and whether a correlation is possible between structure and... 

Given any thietane, oxidation of the sulfur to a sulfone with peracids202,203 or H20 274c is straightforward and in most cases neither intervenes chemically with other sites nor alters the structural features or stereochemistry of the thietane ring. 

The preparation and investigation of the thietane oxide system (5a) is largely associated with stereochemical and conformational studies . The investigation of the thietane dioxides (5b) is substantially related to the chemistry of sulfenes , the [2 -I- 2] cycloaddition of which with enamines is probably the method of choice for the synthesis of 5b . The study of the thiete dioxide system (6) evolved, at least in part, from the recognition that the unstable thiete system 183 can be uniquely stabilized when the sulfur in the system is transformed into the corresponding sulfone , and that the thiete dioxide system is very useful in cycloadditions and thermolytic reactions. The main interest in the dithietane oxides and dioxides (7) appears to lie in the synthetic challenge associated with their preparation, as well as in their unique structural features and chemical behavior under thermolytic conditions . ... 

Wedged octahedral structure for 1 1 adduct of tristdi-pivalomethanato)-europium(III) and 3,3-dimethyl-thietane- 1-oxide... 

Scheme 3 shows the mechanism for the thietane formation, in which the six-membered 1,4-biradical BR is appropriate. There are two ways of cyclization to thietane 2, and each pathway gives an enantiomeric structure of thietanes, (1S,4R)- or (lR,4S)-2, respectively. The absolute structure of (-)-(M)-la and the major isomer (- -)-(lS,4R)-2a was determined by X-ray structural analysis using... 

Thietene is a liquid that polymerizes within an hour at room temperature. However, thietane, also a liquid, is more stable it exists as a puckered structure, similar to that of azetidine (note the sulfur atom and hence its lone-pair electrons occupy more space than those of oxygen). 

Thietane compounds could occur in space especially when one considers that sulfine, a commonly observed pyrolysis fragmentation product of thietane oxide, has been detected in the interstellar medium by microwave spectroscopy. Thietane derivatives have been isolated from the plant and animal kingdom, and it seems likely that much still remains untapped. In such plants as Tribus Arctotideae, the thioacetylene structure 13 containing a 3-... 

Crystallographic measurements have provided additional information about the structure of thietane. The ring of 2-(2,6-dimethylphenyl)imino-3,3-dimethyl-4,4-diphenylthietane is puckered, but in the crystal matrix the rings are more likely to be flattened. 2,4-Diphenylthietane 1-oxide molecules are closely packed with their S=0 bonds nearly parallel to the ring. No intermolecular hydrogen bonding was observed. ... 

The first thietane 1,1-dioxide to be analy2Ed by three-dimensional X-ray diffraction was trans-4-chloro-3-morpholino-2,2,4-trimethylthietane 1,1-dioxide (33), which has a monoclinic crystal structure with four molecules occupying a unit cell. 

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