Acylation Chapter silylation

Unfortunately, space does not permit a full review, so that many examples and important applications of derivatives in GC—MS have been omitted. However, some mass spectrometric properties and applications as well as detailed derivative preparation instructions are given in the specialist chapters on Esterification (Chapter 2), Acylation (Chapter 3), Silylation (Chapter 4), Formation of cydic derivatives (Chapter 7), and also in the respective chapters of the first edition of the handbook [12]. 

Typically, oc,0-unsaturated esters, a,0-unsaturated aldehydes and a,0-unsaturated nitriles are poor acceptors for the Lewis acid catalyzed silylallylation procedure, but they are excellent acceptors for the complementary fluoride ion mediated allylation procedure (cf. Volume 4, Chapter 1.2, Section 1.2.2.1.7). Other suitable acceptors include 1,4-quinones,70 a,0-unsaturated acyl cyanides (162),718 silyl ot,0-enoates (163)71b and nitroalkenes (Scheme 26) 72 reduction (titanium(III) trichloride) of the intermediate nitronates arising from nitroalkene allylation affords y,8-enones (166). 

It will not be possible to have a free OH group on the lactone during this step as the acid chloride would, of course, react there too. In practice, protection as a silyl ether (Chapter 24) was enSugh and the lithium enolate was then used for the acylation reaction. Aqueous ethanol work-up removed the silyl protection. 

The number of reagents that has been used for the identification of primary amines is possibly larger than for any other class of compounds [5], But most of these classical derivatives lie beyond the scope of this chapter. They are covered in other parts of the book acylation in Chapter 3, silylation in Chapter 4 and alkylation in Chapter 5. The different nitrophenyl derivatives are discussed in Chapter 8, and Chapter 9 presents the options for preparing fluorescent derivatives. The only derivatization fitting into the framework of this chapter is the condensation with carbonyls resulting in the formation of Schiff bases or, in the case of aromatic amines, anils. 

A method the determination of hydroxy groups in polyethylene glycols (PEG) has been described by Fritz and co-workers [9] (see Method 3.1 at the end of the chapter). The method consists of substituting the hydroxyl group with a chromophoric siloxy group, purification of the silylated polymer, and a photometric determination of the chromophor concentration. The silanisation of the primary hydroxyls with dimethylaminosilanes proceeds quantitatively under very mild conditions and elimination of the excess reagent by precipitation is easy. The precision of the method is 4.5% (95% confidence level) down to 5 X 10 " mol/kg. The method has about the same precision as acylation methods but yields a 1000 fold gain in sensitivity. 

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