Some group IVB derivatives of 1,6-methano[10]annulene. Synthesis, substituent effects and reactivity

Stabilized and Destabilized Carbocations in the 1,6-Methano[10]annulene Series

“…A previous study on rates of protiodemetalation of substrates 18 and 19 showed that desilylation occurred 35 times faster in the 1,6-methano[10]annulene systems than in the analogous naphthyl systems 21. 6 Protiodestannylation of 19 occurred 700 times faster than in 22. 6 The implication is that the intermediate cations 20 in this electrophilic aromatic substitution reaction are more effectively stabilized by the annulene system than the cations 23 are stabilized by the naphthyl system.…”

“…6 Protiodestannylation of 19 occurred 700 times faster than in 22. 6 The implication is that the intermediate cations 20 in this electrophilic aromatic substitution reaction are more effectively stabilized by the annulene system than the cations 23 are stabilized by the naphthyl system. These findings complement our solvolysis rate data, which also suggest that 1,6-methano[10]annulene stabilization of carbocations greatly surpasses naphthyl stabilization.…”

“…A previous study on rates of protiodemetalation of substrates 18 and 19 showed that desilylation occurred 35 times faster in the 1,6-methano[10]annulene systems than in the analogous naphthyl systems 21 . Protiodestannylation of 19 occurred 700 times faster than in 22 …”

“…1,6-Methano[10]annulenyl Cations. The 2-substituted chloride 8 was prepared as previously described , from the corresponding alcohol 7 , and the isomeric 3-substituted chloride 10 was prepared in an analogous fashion from alcohol 9 . These chlorides were solvolyzed in methanol at 25.0 °C, where both of these substrates readily react.…”

“…Capture of the DMSO-d 6 solvent at sulfur gives product 45, whereas capture at oxygen gives the unstable oxosulfonium ion 47. This intermediate can lose dimethyl sulfide and fragment to naphthalene and the formyl cation, 48, which is the source of the formic acid via the trace of water present in the DMSO-d 6 . The formyl cation can also serve to produce the trace of 1-naphthaldehyde.…”