Electrophilic agents source

In this chapter, the recent progress in transition-metal-catalyzed C-H alkylation (until the end of 2011) will be presented. These reactions have been divided into three categories differing in the nature of the alkylating agent an electrophilic alkyl source (Scheme 19.2a, part 2), an alkyl metal (Scheme 19.2b, part 3), or an alkene (hydroarylation of alkenes. Scheme 19.2c, part 4). Reactions that do not involve the formation of a (hetero)arene-transition metal intermediate during the catalytic cycle have been excluded. Extensions to nonaromatic C(sp )-H bonds, that is, C(sp )-H of alkenes, and C(sp )-H bonds wiU also be reviewed. As for... 

Silicon presents an attractive option among eledrophilic activating and dehydrating agents of hemiacetals because of the wide commercial availability of eledrophilic silicon sources. The two main classes of silicon electrophiles used, namely silyl halides and silyl sulfonates, have been demonstrated to promote a variety of glycosylations including some examples of oligosaccharide synthesis. 

These complexes could exhibit different reactivities, since 219 is a potential CD and S-SCl source and could be an electrophilic chlorinating and sulfurating agent, while 220 should react only as the latter. 

Notes Mild oxidizing agent (See DMSO Oxidations in Aldehyde Syntheses). A source of the S-Me electrophile. For an odorless protocol 1 Instead of DMSO, dodecyl methyl sulfide is used in the reaction thus, eliminating the dimethylsulfide by-product. 

More recently, dithionylium salts (3.45A) have been explored for reactions with diols, amines and even azide [225], in the presence of fluoride sources, and an electrophilic brominating agent 5,5-dimethylhydantoin (DBH) to effect desulphurisation. High yields are obtained under very mild conditions (Figure 3.45). 

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