Thio compounds, functional groups

The most important raw materials for the production of non-ferrous metals, such as copper, lead, zinc, nickel, cobalt, molybdenum, antimony and cadmium, are the sulfide minerals. The use of collectors containing various thio-type functional groups has proved to be the most successful in the flotation of these minerals. Some of these compounds are shown in Table 1. 

Osmylation of the chirally masked 2-alkoxypent-3-enal 1 and subsequent functional group manipulations furnished enantiopure 5-deoxy-L-lyxose and -xylose derivatives. A new preparation of 5-deoxyribonolactone derivative 2 from ribonolactone by tributyltin hydride reduction of a 5-chloro-5-deoxy intermediate has been published. Conversion of compound 2 to a 5 -deoxy-nucleoside analogue is covered in Chapter 20. A multistep synthesis of methyl 5-0-benzoyl-2,3-dideoxy-P-D-g/ycero-pentofuranose (4) from D-xylose involving Raney nickel desulfurization of compound 3 (see Chapter 11) has been described. Several deoxy-ketoses have been prepared by Raney nickel desulfurization of 1-thio-ketose derivatives obtained by enzyme-catalysed aldol condensations (see Vol. 29, Chapter 2, Scheme 1). An example is given in Scheme 1. ... 

Sn2 reactions are highly useful in organic synthesis because they enable us to convert one functional group into another—a process that is called a funcdonal group trausfonna-tion or a functional group interconversion. With the Sn2 reactions shown in Fig. 6.11, methyl, primary, or secondary alkyl halides can be transformed into alcohols, ethers, thiols, thioethers, nitriles, esters, and so on. Note. The use of the prefix thio- in a name means that a sulfur atom has replaced an oxygen atom in the compound.)... 

The reaction is selective for thiodiglycol, however there are some thiodiglycol related compounds which also give signals but at a much lower level. The compounds in this class are bis (2-chloroethyl) sulphide (H), ethyl-2-hydroxyethyl sulphide, 2-chloroethyl-2-hydroxyethyl sulphide (1/2 H), 1,2-bis (2-chloroethylthio) ethane (Q) and bis (2-chloroethylthioethyl)ether (T). The signal intensity is dependant upon the presence of a thio ether function and a group beta to the sulphur capable of being easily oxidised. 

More than a third part of all the described principal syntheses of pyrimidines bearing fluorinated alkyl at C-4 atom commences from fluorinated p-dicarbonyl compounds 699. The chemistry of these bis-electrophiles was reviewed recently [411, 412] therefore, their preparation is not discussed herein. This synthesis of pyrimidines is fairly general (Table 34) it allows for introducing aliphatic, alicyclic and aromatic p-diketones (Entries 1-10), p-ketoesters (Entries 11-16), and cyclic P-ketoamides (Entry 17). Presence of some functional groups, such as additional ester moiety (Entry 15), is more or less tolerated, whereas increasing steric hindrance results in lowered yields of the products (Entry 10). A scope of conunon NCN binucleophiles include amidines (Entries 1, 11, 12, 17), (thio)urea and its derivatives (Entries 2-4), guanidines (Entries 5,16) and biguanides (Entry 6). Electron-rich amino heterocycles e.g. aminoazoles and even 2,6-diaminopyridine) are excellent NCN binucleophiles for the principal synthesis of fused pyrimidine derivatives (Entries 7-10, 13-15). 

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