Structure of thietanes

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... 

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 structure of thietane 1-oxide has been investigated by microwave spectroscopy dihedral angle 145.1°, C-S, 1.836A C-C, 1.542A C-S-C 75.7°, C-C-C, 95.9° S-C-C, 89.6°. The sulfoxide oxygen prefers the equatorial position. The ring-puckering has also been studied by infrared spectroscopy the barrier to interconversion between a stable equatorial form and an axial conformer is about 3440 cal/mole. ... 

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... 

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-... 

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. 

Heating of thietanes can often lead to a ring contraction. Thermal treatment (150°C, in vacuo) of the tosylhydrazide salt 213 gives the allene epi-sulfide 214, a unique synthesis for this molecule. The mechanism is suggested to proceed either via the intermediate bicyclobutane ylide 215 or the mesomeric structure 216. Dodson et al. have noticed the rearrangement... 

The very useful lanthanide shift reagents, which facilitate analysis of molecular stereochemistry because of their line-broadening characteristics in NMR spectra, were studied when bound as a chelate complex to thietanes. X-Ray analysis of the adduct 3,3-dimethylthietane 1-oxide with tris(dipivalo-methanato)europium(III) [Eu(dpm)3] revealed the structure of a seven-coordinate complex (271). ... 

Cyclization of y, -unsaturated sulfenic acids to give thietan 1-oxide derivatives. Crystal structure of rei-(l/ ,2S,3/ ,4/ )-3-hexyl-2-hydroxy-methy 1-4-methylthietan 1 -oxide. ... 

Thietane 1-oxide is nonplanar with a pucker angle of 34.9° and with oxygen occupying an equatorial position. The other structural parameters of thietane 1-oxide and several of... 

Among the variations in chemical structure of these triblock copolymers developed in our laboratories were the use of poly(a-methyl styrene)(43, 44) as end blocks, and poly(alkylene sulfides) (42, 45 ) 311 d polydimethylsiloxanes (43, 46) as center blocks. The reactions of cyclic sulfides with organolithium is illustrated in Figure 10. Both the propylene sulfide and the methyl thietane can be used for the center block with styrene or a-methylstyrene end blocks, but the chemistry shown in Figure 10... 

In this reaction, achiral A-methacryloylthiobenzanilide 39 gave chiral crystals by spontaneous crystallization, and absolute asymmetric synthesis was performed by the solid-state photoreaction leading to optically active thietane-fused 3-thiolactam. The reaction mechanism for the cyclization was elucidated on the basis of the correlation between the absolute structures of both the prochiral starting monothioimide and the photoproduct. 

This chapter continues this work covering the literature of the last 10 years, that is, from 1996 until 2005. The preparation of this review was based on a literature search through SCOPUS and the Beilstein Database, which revealed 104 important papers published within this period. This chapter is organized in accordance with the general structure of CHEC-III, which includes a division into 12 sections including the same aspects as in CHEC-II(1996). For some aspects of thietane and thiete chemistry, such as their synthesis from six- and seven-membered rings, no new papers were published within the discussed period. 

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... 

The mass spectral fragmentation patterns of a variety of fused and spiro thietanes and thietes were presented in CHEC(1984) and CHEC-II(1996). Only more recent data are included here. The mass spectrometry (MS) spectra of thietanes 10 and 11 show molecular ion peaks at m/z 330 and 270, respectively, corresponding to the molecular weights of thiobarbiturates used for their preparation by photolysis in acetonitrile <2003H(59)303>. The structures of different derivatives (substituted in the thietane ring by CH3, Ph, or OC2H5 groups) of 5,7,7,9-tetramethyl-l-thia-... 

Data on the separation of thietane by gas chromatography have been reported along with data on other sulfur compounds. Thin-layer chromatographic separation of thietane from 1,2-dithiolane and 1,2.3-trithiane works well on silica gel. Thietane forms a hydrate (dec 11.7°) with water. Its clathrate structure was investigated by use of the nmr line shapes of the deuterium oxide hydrate. ... 

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