Oxygen-containing six-membered

In some situations, dialkylation is desired and there are several useful applications of this technique reported. 1,4-Dibromobutane [24] and 1,5-dibromopentane [24] alkylate phenylacetonitrile according to equation 10.12 to give 1-cyano-l-phenyl-cyclopentane or -hexane in 88% and 40% yields respectively [24]. Alkylation with 2,2 -dichlorodiethyl ether affords the oxygen containing six-membered ring in almost... 

Anionic five-coordinated silicates have been prepared also with oxygen-containing six- and seven-membered chelate rings (16-18), using suitable aromatic diols, 1,8-dihydroxynaphthalene and 2,2 -dihydroxybiphenyl, respectively37. However, spirosilicates... 

More complex, but still discrete silicate groupings have been found to exist in the minerals benitoite and beryl the former, BaTiSi309, contains six-membered silicon-oxygen rings, whereas the latter, BesAUSieOig, contains twelve-membered rings (Fig. 17-3). 

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. 

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... 

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... 

In the field of nucleosides, an interesting example of a cleavage of a nonfluor-inated six-membered cyclic ether containing oxygen and nitrogen atoms to give a fluoro nucleoside has been reported [5] (equation 5)... 

Thus, the reaction of 4-dialkylaminobut-3-yn-2-ones with various bifunctional reagents makes it possible to carry out a targeted synthesis of five- and six-membered nitrogen-, oxygen-, and sulfur-containing heterocycles having two heteroatoms. 

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