Nitriles, alkane synthesis

Tosylhydrazones can be silylated with (fert-bufyldimethylsilyl)trifluoromethanesulfonate (Me2teriBuSi03SCF3) on the sulfonamide nitrogen. This is how the starting material for a broadly applicable alkane synthesis is produced ( Figure 1.49). Due to their ability to undergo reductive cyanization (Figure 17.69) mesitylene sulfonyl hydrazones allow for a two-step synthesis of nitriles from ketones. 

By-Products. Almost all commercial manufacture of pyridine compounds involves the concomitant manufacture of various side products. Liquid- and vapor-phase synthesis of pyridines from ammonia and aldehydes or ketones produces pyridine or an alkylated pyridine as a primary product, as well as isomeric aLkylpyridines and higher substituted aLkylpyridines, along with their isomers. Furthermore, self-condensation of aldehydes and ketones can produce substituted ben2enes. Condensation of ammonia with the aldehydes can produce certain alkyl or unsaturated nitrile side products. Lasdy, self-condensation of the aldehydes and ketones, perhaps with reduction, can lead to alkanes and alkenes. 

Although the unsaturated nitrile oxides 124 can be prepared via the aldoxime route (see Scheme 8), the older procedure suffers from the disadvantage that a tenfold excess of allyl alcohol and two additional steps are required when compared to Scheme 15. Therefore, unsaturated nitro ether 123 that can be prepared by condensation of an aldehyde 120 and a nitro alkane followed by Michael addition of alcohol 122, was a useful precursor to nitrile oxide 124 [381. The nitrile oxide 124 spontaneously cyclized to ether 125. This procedure is particularly suitable for the synthesis of tetrahydrofurans (125a-h) and tetrahydropyrans (125i-k) possessing Ar substituents in 72-95% yield (Table 12). The seven-membered ether 1251 was obtained only in 30% yield on high dilution. The acetylenic nitro ether 126 underwent INOC reaction to provide the isoxazole 127. 

Exercise 15-24 It is possible to prepare amides from tertiary alcohols and alkane-nitriles, RCN, in concentrated sulfuric acid as the catalyst (Ritter reaction), as illustrated in the equation for the synthesis of W-fe/f-butylethanamide ... 

Reaction of a four-carbon unit with sulfur sources such as hydrogen sulfide, carbon disulfide, and elemental sulfur is one of the traditional thiophene syntheses that belong to this category (Equation 18). A wide variety of hydrocarbons, for example, alkanes, alkenes, dienes, alkynes, and diynes, serve as four-carbon units. Another practical method is the sulfuration of 1,4-dicarbonyl compounds (Paal synthesis). The method has become very popular with development of sulfuration reagents such as Lawesson s reagent. The reaction of a,/3-unsaturated nitriles with elemental sulfur in basic media, Gewald synthesis, is also useful for the preparation of 2-aminothiophenes which are important compounds in dyestuff and pharmaceutical industries. 

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