Protiodetritiation of benzene in trifluoroacetic acid

Electrophilic aromatic substitution. Part 36. Protiodetritiation of some annelated meta-cyclophanes: effect of ring-buckling on reactivity, and the first example of electrophilic substitution through a hole

“…The effect obtained was fairly small (2--3 fold), and comparable results are obtained here. The [6]naphthalenophane (1; n = 6 ) is much more severely distorted,' and the resultant loss of aromaticity is such that addition reactions, e.g. with bromine or potassium permanganate, occur readily.2 Addition does not take place in the higher homologues.…”

“…(v) Reactivity of Hexahydrophenanthrylene (3a) and Hexahydroaceanthryfene (3b).-We attempted to prepare [ 16-3H]- [6]( 1,3)naphthalenophane* by reaction of the 16-chloro precursor (4) with lithium metal followed by tritiated water.…”

“…In addition, strain in the five-membered side chain will facilitate C-C hyperconjugation. The enhanced reactivity is thus due to a combination of steric facilitation of C-H and C-C hyperconjugation, factors which have been shown previously to account for the high reactivity of acenaphthene as compared with 1,8-dimethylnaphthalene,' for the relative activation order of cycloalkyl substituents," and for the greater activation by the bicyclo[2.2.2]octyl substituent than by the adamantyl substituent.I3 Further attempts were made to prepare the [6]naphthalenophane. Reaction of (4) with n-butyl-lithium gave a trace of what appeared to be the 16-butyl derivative, but there was insufficient material for a full characterisation.…”

The quantitative electrophilic reactivity of annulenes. Part 2. Partial rate factors for hydrogen exchange of azulene, cycl[3,2,2]azine, indolizine, N-methylisoindole, indole, and pyrrolo[2,1-b]thiazole, and attempted exchange in trans-9,10-dimethyldihydropyrene: the dramatic effect of creating aromaticity in the transition state for electrophilic substitution, and the importance of valence bond theory

“…~ [The correlation between localization energies for naphthalene and (I) (calculated for the non-planar model by the SPO method)3 predicts 0 3 + for (I) to be -0.67. This is probably too high since the difference 0 , ' -' T ~+ for (I) should be greater than that for (11) because of the difference in inductive effects of CH, uersus CF,.]…”

“…To date there has been only one study of the quantitative electrophilic reactivity of an annulene. Detritiation and desilylation of 1,6-methano[lO]annulene (I) and its 11,ll-difluoro derivative (11) yielded the partial rate factors and o f values given in Table 1. The data showed that the annulene (I) was much more reactive than naphthalene to which it is formally similar (for detritiation,, 'T, + -0.35; 0 2 + -0.25).…”