Arenes substituent groups

LG. Laing in Rodd s Chemistry of Carbon Compounds. A Modem Comprehensive Treatise. Vol. 3, Part C (2.) Aromatic Compounds. Nuclear substituted benzenoid Hydrocarbons with more than one nitrogen atom in the substituent group, S. 133 -215, Elsevier, Amsterdam 1973 A.J. Floyd, M. Sainsbury, Azo-Arenes in Supplement to Vol. 3, Part C, Elsevier Scientific Publishing Comp., S. 259-272, Amsterdam Oxford New York 1981. 

Figure 33. The steric demand of calix[4]arene blocking groups can be varied by attachment of different substituents, furthermore their complexation ability introduces interesting properties to rotaxanes.

In this section we shall be mainly interested in the reactions of arenes that involve attack on the carbon atoms of the aromatic ring. We shall not elaborate now on the reactions of substituent groups around the ring. 

When benzylic alcohols are the substrates, arenes behave as nucleophiles, as shown in equation (123) and for the analogs in the 1,4-addition.These reactions have been performed with alcohols that are activated by an arene substituent and another group that could be an olefin, an alkyne, or other arene (equation 140). In the case of dimerization reported by Hashmi (equation 141), primary benzylic alcohols produce dimers of the type in equation (141) that arise from the activation of this moiety, together with the expected cyclization products. In a very recently reported example, aryl-alkyl ethers are obtained by reaction with NaAuCU. ... 

Bridging substituent groups also influence the preference for either the arene oxide or the oxepin valence bond tautomer. Thus, when n = 3, indan 8,9-oxide 7 exists exclusively as the oxide form. With n = 4, tetralin 9,10-oxide 8 is dominant over its oxepin form while similar amounts of the arene oxide and oxepin are present when n = 5 (9). 

In addition to the NIH shift, the zwittcrionie species may nndergo direct loss of D to generate 4-hydroxyanisolc. in which there is no retention of deuterium (Fig. 4-6). The alternative pathway (direct loss of D ) may be more favorable than the NIH shift in some aromatic oxidation reactions. Therefore, depending on the substituent group on the arene.. some aromatic hydroxylation reactions do not di.splay any NIH. shift. 

Cr(CO)3 is an effective electron-withdrawing group. The coordination of this organometallic unit to the arene substituents of the isophthalamide in 89 increases the acidity of the NH protons and hence their affinity for anions. 

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