Saturated Sulfur Heterocycles

Thiiranes can be prepared by cyclisation of 2-halo-thiols, but the most common method is via reaction of an epoxide with thiocyanate, thiourea, a phosphine sulfide or with dimethylthioformamide.  

Thietanes, tetrahydrothiophenes and tetrahydrothiapyrans can all be prepared by the reaction of the appropriate 1,co-dihalide with sulfide anion. 

Yamashita, S., Nishikawa, T, Yokoyama, Y, Inaba, M. and Moriwake, T, Tetrahedron Lett., 1989, 30, 4153. 

Ungureanu, L, Klotz, P, Schoenfelder, A. and Mann, A., Tetrahedron Lett, 2001, 42, 6087. 

Derguini-Boumechal, F. and Linstrumelle, G., Tetrahedron Lett., 1979, 20, 1503. 

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In a study of synthetic routes to the phorbol class of compounds, Lautens cyclised the stannane 307 (with 5 equiv MeLi, to avoid stannane reincorporation) to the 7,5-fused ring system 3 0 8.138 This reaction also works in the synthesis of analogous saturated five-membered nitrogen and sulfur heterocycles (see below). 

The nonaromatic but fully-conjugated 1,4-dioxin and its sulfur analogues show absorption at quite long wavelengths. The spectra of saturated nitrogen heterocycles show amine n ->sulfur rings show transitions associated with sulfur. Saturated ethers are usually transparent down to 210 nm. 

Sulfur heterocycles, saturated sulfur and oxygen ring compounds ... 

The best-known cyclic sulfur imides are saturated sulfurnitrogen heterocycles, which are derived from cyclo-Sg by the replacement of one or more sulfur atoms by an amido (NH) group. Derivatives containing adjacent NH groups are not found. Thus, the members of this series consist of S7NH (70), three diimides 1,3-, 1,4- and 1,5-S6(NH)2, two triimides 1,3,5- and l,3,6-Ss(NH)3, and S4N4H4 (71). 

PREPRATION AND REACTIONS OF SATURATED PERFLUORINATED HETEROCYCLES CONTAINING OXYGEN, NITROGEN, SULFUR, SELENIUM, AND PHOSPHOROUS... 

Preparation of Saturated Perfluorinated Heterocycles Containing Oxygen, Nitrogen, Sulfur, Selenium, and Phosphorous... 

The results from the one-dimensional Py-GC-MS of Murchison meteorite are shown in Figure 18.1 the results are consistent with previous studies of Murchison and other CM2 chondrites [11]. As well as a number of well-resolved species such as alkylbenzenes, sulfur heterocyclic compounds, and naphthalenes in the chromatogram, there is a significant portion of products that are present as an unresolved complex mixture (UCM), which can be seen as a broad rising baseline or hump. From the main fragment ions present, the UCM appears to be dominated by saturated, unsaturated, and cyclic hydrocarbons and not aromatic species which dominate the resolved components. Compared with typical terrestrial samples, the main difference is the lack of n-alkanes/alkenes in the pyrolyzate [35]. 

Muller et al. used SCS derivatives to study the effects of hydrodesulfurization (HDS) on polycyclic aromatic sulfur heterocycles (PASHs) in bitumen residua. Their experiments concentrated on PASHs, which is a predominant class of SCS in vacuum residue bottoms. Asphaltenes were removed by precipitation, followed by the separation of aromatic fractions from saturated fractions by the saturates, aromatics, resins, and asphalts (SARA) method. Several methods can be deployed as the SARA method depending on the type of petroleum sample, one of the more common for more viscous oils is a combination of two methods ASTM D2007 and ASTM D893. Pentane-insoluble (PI) method ASTM D893 is used first to identify the asphaltene content then ASTM D2007 is used to calculate the saturates, aromatics, and resins. 

In Table 29 the u(C=0) and other characteristic bands are given for some saturated five-membered heterocycles, and compared with the corresponding absorption frequencies for cyclopentanone. Adjacent NH groups and sulfur atoms have the expected bathochromic effect on r (C=0), whereas an adjacent oxygen atom acts in the reverse direction. The CHa vibrations of cyclopentanone are repeated to a considerable extent in the heterocyclic analogs. 

Calculation of group increments for oxygen, sulfur and nitrogen compounds has allowed the estimation of conventional ring-strain energies (CRSE) for saturated heterocycles from enthalpies of formation. For 1,3-dioxolane, CRSE is about 20 kJ mol . In 2,4-dialkyl-l,3-dioxolanes the cis form is always thermodynamically the more stable by approximately 1 kJ mol" . 

The various, complex, cascade reactions described above converted simple saturated and aromatic heterocycles into polycyclic pentathiepins and their chlorinated and rearranged derivatives this strikingly illustrates the extensive reactivity of S2CI2 and its complexes with bases, particularly DABCO. This reactivity encompassed dehydrogenation of tetrahydroaromatics, chlorination and sulfuration of aromatics and their conversion into SSCl derivatives. 

Figure 1 Saturated heterocycles containing oxygen or sulfur atoms in the 1,2,3-positions.

The species which are unknown and have not been identified as one of the major chemical lump such as alkanes, phenols and aromatics are lumped together as unidentified. However, the species in this lump include saturated and unsaturated cycloalkanes with or without side chains, which resembles the naphthenes, a petroleum refinery product group. A number of well known species in coal liquid are not mentioned in this lumping scheme. Such as heterocyclic compounds with sulfur, nitrogen or oxygen as the heteroatom, and other heteroatora containing species. Some of these compounds appear with aromatics (e.g. thiophenes, quinolines) and with phenols (e.g. aromatic amines), and most of them are lumped with the unidentified species lump. 

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