Electron-withdrawing groups substitution

With electron-withdrawing groups substituted at the phenyl groups of the MePc macrocycles like tetra-nitro [Pc(N02)4] and perchloro-phthallocyanine (PcCli4), the metal-oxo species of the MePc complex becomes considerably more active, also as... 

The reaction of 1,3-dibromopropene with carbonyl compounds mediated by indium in water gives 3,3-disubsti-tuted propene 63 (Scheme 55). In the formation of 63, 1,3-dibromopropene acts as a w-allyl dianion synthon. Aromatic aldehydes generally have a higher selectivity than aliphatic ones in the product formation. Unsubstituted and electron-withdrawing group-substituted benzaldehydes give mainly 3,3-disubstituted propene 63. For electron-rich benzaldehydes, the formation of both 3,3- 63 and 1,3-disubstituted propene 64 is dramatically decreased and the selectivity is reversed completely to give diene 65 and homoallylic alcohol 66.219... 

Fioravanti, S. Colantoni, D. Pellacani, L. TardeUa, P.A. Aziridines versus vinyl carbamates from the direct amination of electron-withdrawing group-substituted trifluoromethyl enoates. J. Org. Chem. 2005, 70, 3296. 

Tropones unsubstituted at C(2,7) but having electron-withdrawing groups substituted elsewhere in the ring may also undergo ready rearrangement, for example tropone-4-carboxylic acid reacts with aqueous alkali at room temperature to give terephthalic acid [195]. 

Ease of elimination of alkyl groups is in the order methyl > n-propyl > ethyl, and electron-withdrawing groups substituted in the aromatic ring increase the rate of displacement. 

A -Disubstituted amides are characterized by the strong C=0 stretching at 1680-1630 cm . Strong electron withdrawing groups substituted on the nitrogen atom will reduce the tendency for the carbonyl oxygen to draw electrons (N=C—O) and thus raise the carbonyl frequency. ... 

The thermodynamic acidities have been measured for iV-sulphonyl-thioamides (pATa = 3.31—4.99) and for thioamides with electron-withdrawing groups substituted at the a-carbon atom [XYCHC(S)NR2 X,Y = ArSOa, HjNCO, PhCO, etc.] in these cases one has to discriminate among CH-, NH-, OH-, and SH-acidity. ... 

However, haloarenes that also bear electron-withdrawing groups substitute much more readily. The process involves two steps, addition followed by elimination (Figure 13.14). The intermediate, negatively charged, species is called a Meisenheimer complex. 

---