Anisole inductive effects

Electron density is influenced by resonance (mesomerism), as well as by inductive effects, as seen in unsaturated molecules such as alkenes and aromatics. The donation of electrons through resonance by a methoxy group increases the electron density at the p position of a vinyl ether (3-1) and at the para position of anisole (C6H5OCH3). Thus, the... 

The pioneering work of a coupling of aromatic and heteroaromatic compounds with acetylenes was reported by Yamazaki et al. in 1979 [35]. Reaction of benzene with diphenylacetylene gives triphenylethene in 45% yield. In the case of the monosubstituted benzene, the reaction of toluene proceeds at the meta position selectively but the reaction of anisol takes place at the ortho position (Eq. 21). They proposed that the site-selectivity stems from an inductive effect of an elec-... 

Ether groups exert their ortho-directing action in the metallation of aromatic rings mainly via their electron-withdrawing inductive effect. Methoxybenzene has been lithiated with BuLi in Et20 or THF. The metallation in the latter solvent can be carried out in a reasonable time (2-3 h at 20 °C), but part of the butyllithium is consumed by reaction with the solvent, unless a considerable excess of anisole is used. The activating influence of two methoxy groups in 1,3-dimethoxybenzene renders the metallation easier. 

FIGURE 14.80 The carbon-oxygen bond in anisole is also electron-withdrawing, yet substitution is directed ortho/para and the reactions are fast. The resonance effect outweighs this inductive effect. 

Star and coworkers examined the effect of monosubsti-tuted benzenes including aniline, phenol, anisole, toluene, chlorobenzene, and nitrobenzene on NTFET device characteristics." These aromatic compounds presumably n-n stacked to the surface of the CNT their substituent group provided different inductive and resonance effects, which... 

A third possible explanation for the reduced reactivity of anisole and phenol compared to that of toluene could be that the former two substrates are deactivated towards electrophilic aromatic substitution by reaction of the alcohol or ether moiety with either the Lewis (BF3) - or Bronsted ( HBFV) acid. In this instance the first equivalent of acid would be consumed by reaction with the oxygen (Scheme 2.4), and the second equivalent effecting protonation of CO. Inductive deactivation of the aromatic ring by the cationic oxygen will result in reduced reactivity of the aromatic system. Since the positive charge resulting from complexation of phenol with BF3 on the phenolic entity could be neutralised by proton loss to the reaction medium, phenol is expected to be more reactive than anisole under the reaction conditions (Scheme 2.4). Additional support for this explanation is provided by the reported isolation of an anisole/HF/BFs complex containing a 1 1 2 ratio of reactants. 

The low PRF at the mef -position of anisole is noteworthy. At the raeta-position, there is no resonance effect, so we see the inductive withdrawal effect of the OMe group. At the ortho- and /2 ra-positions, this is masked by the much greater resonance donor effect. 

---