Sulfur-containing six-membered

Space restrictions mean that the reactivity of multiheteroatom systems or fused systems where both rings are heterocyclic cannot be covered in this section - the reader is referred to the relevant CHEC volumes. Space again dictates that the chemistries of oxygen- and sulfur-containing six-membered heterocycles, and the chemistry of monocyclic six-membered heterocycles with more than one heteroatom, are only briefly indicated alongside the description of pyridine/quinoline/isoquinoline chemistry, but especially where these are not shown by the pyridine prototypes, but again the reader should study the CHEC volumes for a full discussion. The inclusion of an extra heteroatom in a six-membered system exaggerates the effect of the first and so often it is possible to predict properties by extrapolation however, the same is not true for the five-membered systems, so these heterocycles with more than one heteroatom are considered in detail and separately. 

Acetylation of the pyranose 227 gives crystalline tetra-O-acetyl-5-thio-/3-D-ribopyranose and the syrupy a-D anomer. Both compounds lack S-acetyl bands in their infrared spectra. Treatment of 227 with methanolic hydrogen chloride furnishes a mixture of anomeric methyl 5-thio-D-ribopyranosides which cocrystallize. Pure anomers are obtained on separation of the glycosides by use of a basic ion-exchange resin, or by separation of the triacetates on silica gel. The sulfur-containing, six-membered ring was established by periodate assay. 

Ring contraction of other sulfur-containing six-membered heterocyclic compounds... 

Calorimetric and computational study of sulfur-containing six-membered rings including saturated S- and O-heterocycles 05CSR347. 

Thermochemical data, and in particular the enthalpies of formation of oxygen-and sulfur-containing six-membered heterocycles, provide essential information on the factors responsible for the contrasting behaviour (structural, conformational and reactivity) between these types of compounds. Understanding of the experimental thermochemical observations has required theoretical modeling to confirm the relative importance of the steric, electronic, electrostatic and stereo-electronic interactions that are responsible for the enthalpies of formation for 1,3- and 1,4- dioxanes, 1,3,5-trioxane and their... 

Sulfur trioxide, SO3 (with boiling point 44.5° C) is monomeric in the vapor state, but several modifications of solid SO are recognized. There are at least two distinct polymeric forms, and a third solid form which has been found to contain six-membered rings ... 

Sulfur, Sj, is a dehydrogenating agent that converts compounds containing six-membered rings into their aromatic analogues. In the reaction, sulfur is reduced to hydrogen sulfide [491, 492], Such dehydrogenations occur at lower temperatures compared with those by selenium [493] or noble metals 495, 496, 497]. 

Naturally selenium contains six stable isotopes. Fifteen other isotopes have been characterized. The element is a member of the sulfur family and resembles sulfur both in its various forms and in its compounds. 

Sulfur containing heterocycles are also common Compounds m which sulfur is the heteroatom m three four five and six membered rings as well as larger rings are all well known Two interesting heterocyclic compounds that contain sulfur-sulfur bonds are hpoic acid and lenthiomne... 

The name of the parent six membered sulfur containing heterocycle is thiane It is num bered beginning at sulfur Multiple incorporation of sulfur in the ring is indicated by the prefixes di tri and so on... 

Part 2 (Volumes 2 and 3) deals with mono- and poly-cyclic compounds with one or more six-membered heterocyclic ring, with nitrogen, oxygen and sulfur as the heteroatoms. Volume 2 contains the six-membered rings with one nitrogen atom (Part 2A) and Volume... 

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