In the substituted ring

Achiral A,A-diisopropyl-ferrocenecarboxamide (440) was deprotonated by Snieckus and coworkers by n-BuLi/(—)-sparteine (11) (equation 119) . The base discriminates well between the enantiotopic protons H(2) and H(5) in the substituted ring to form the diastereomer 441 with high selectivity. Trapping the intermediate with a couple of different electrophiles afforded the substitution products 442a-d with 85 to 99%... 

The naphthalene ring is much less reactive. Polymethylnaphthalenes are more reactive than the parent molecule, and 1,2,3,4-tetramethylnaphthalene gives an adduct with maleic anhydride in 82% yield. Reaction occurs exclusively in the substituted ring.50 This is because the steric repulsions between the methyl groups, which are relieved in the nonplanar adduct, exert an accelerating effect. 

Relaxation rates depend both on correlation time and interproton distances ( 6.2). Look first at inter-proton distances in the substituted ring it should be clear which protons will relax most rapidly. The relaxation rates of corresponding protons in the two rings will tell you about the difference in effective correlation time. 

The protons in the unsubstituted ring relax slowly because ring rotation is fast. In the substituted ring, protons with one neighbour relax more slowly than those with two neighbours. Adapted from Adam, MJ. and Hall, L.D. (1980). J. organomet. chem., 186,289-96. 

The activating influence of the trimethylsilyl function is also apparent in the reduction of naphthalene derivatives (Scheme 40). The 1,4-disilyl derivative (201) is reduced exclusively in the substituted ring to give (202), while 2-trimethylsilylnaphthalene (203) affords a 4 1 mixture of (204) and (205), respectively. " As would be expected, the reduction of C-silylbenzoic acids and their esters is controlled by the carboxy function."... 

Figure 9. Isotropic shift vs. T1 for the ring protons in the substituted ring of mono-t-butyluranocene, 3 2...

The 2-substituted naphthalenes are not as straightforward, and tend to reduce in the substituted ring regardless of the nature of the substituent. For example, 2-methylnaphthalene was claimed to reduce exclusively in the methylated ring (26). Although a reinvestigation uncovered the presence of a second isomer (12, Scheme XI), the major product is, in fact, 11 (18). This... 

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