Proton sponges chelated

The nitration of 1 with one equivalent of HNO3 in H2SO4 gave two products the 4-nitro derivative 108 and the binaphthyl proton sponge 36 in 70 and 10% yield, respectively164,187. The reaction proceeds even at —20 °C and is completed within 5 min. These conditions are essentially milder than those for the naphthalene nitration. This is somewhat astonishing, since in such an acidic medium the diamine 1 seems to exist entirely as cation 1 H+, which should be more inert towards electrophiles than the naphthalene itself. One of the reasonable explanations of this discrepancy is that the reaction proceeds via very small equilibrium amounts of the non-protonated 1 or the non-chelated cation l H+-c. Any of them, under the action of the nitronium cation, is oxidized to the radical cation 1+ , which either dimerises or reacts with N02 to give the reaction products 36 and 108 (Scheme 27). There are several indirect pieces of evidence in favour of this. One of them... 

This transformation is one of the most convenient syntheses of chelating polyfunctional ligands, studied extensively in organometallic chemistry. In this reaction, the practically non-coordinating nature of proton sponges (cf. equation 13) is effectively used. In the case of other bases, the process does not proceed (EtsN) or results in the formation of complex mixtures (f-BuOK). 

The H-bond complexes formed between phenol derivatives and bis-l,8-(dimethylamino)-naphthalene (175) in 1,2-dichloroethane and tetrachloroethylene solution were characterized by FTIR spectroscopy. Compound 175 acts as an effective proton sponge for its ability to form a six-membered chelate-type structure including aN H N moiety. The stability constants of the 1 1 and 2 1 complexes are strongly dependent on the pXa value of the phenols and increase also with the polarity of the solvent. No complex formation was detected in tetrachloroethylene when H was replaced by... 

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