Electrofugal group

As mentioned in Section II.B.5, the tert-butyldi phony I silyl group attached to the olefinic carbon is a poor electrofugal group and hence does not leave easily in electrophilic substitution reactions140. On the other hand, the epoxide 172, obtained from the corresponding vinylsilane having such a bulky silyl substituent, gives the carbonyl compound upon... 

The presence of a good electrofugal group (L + ), such as H+ or Me3Si +, makes elimination the predominant path (Scheme 10.14, pathways a and b). When R is an aromatic ring, pathway (a) is favorable and a benzylic proton is lost to form styrenes this results in a photochemical process analogous to the Heck reaction (Scheme 10.15) [12],... 

Finally, with a poor electrofugal group, the course of the reaction may be directed by choosing suitable conditions ... 

The benzyl radicals generated by efficient deprotonation or electrofugal group loss from the benzylic position of arene radical cations (Eq.4) have found interesting applications in organic synthesis [25]. Some of the examples pertaining to this class are exemplified in Sect. 2.5. A recent publication of Santamaria et al. [26] illustrates the use of PET generated benzylic radicals (via deprotonation step from arene radical cations) for selective and mild photo-oxidation of... 

Both nucleophilic and electrophilic attack on trigonal carbon can take place by two pathways (Fig. 5.4)—direct attack on one of the cr bonds attached to the double bond (path a), or by attack on the n bond (path b), with the formation of an ionic intermediate, followed by the loss, respectively, of a nucleofugal group X or an electrofugal group M. There are also formally unimolecular pathways, SN1 and SeI, with ionisation followed by capture by the nucleophile or electrophile, but the former is rare and the latter unknown. 

Open-chain SE2 reactions are special cases of electrophilic attack on a C=C double bond in the sense 5.132, with attack specifically at C-3, and followed by the loss of an electrofugal group from the stereogenic centre. The most studied of these are the electrophilic substitution reactions of stereodefined allylsilanes,... 

Mediods for overcoming these difficulties include the reaction in Scheme 64 and the corresponding Julia (Scheme 76) or Krief-Reich alkene syntheses, which are all selective for the synthesis of ( )-allylsilanes. These methods use phosphorus, sulfur or selenium as the electrofugal group another possibility is to use electrofugal carbon in a decarboxylative elimination, which can be carried out stereospecifically either anti or syn (Scheme 77). ... 

In a number of fragmentations, the electrofugal group is generated only after an initial addition of a nucleophilic species. Typical of this class of fragmentation are the reactions of /3-halogenocarbonyl compounds, e.g. ... 

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