Peri-Methoxynaphthalenes

Selective demethylation of methoxyarenes. Boron trichloride is generally useful for selective cleavage of the more hindered methoxy group of polymethoxybenzenes and of peri-methoxynaphthalenes. 

Methoxynaphthalenes may be lithiated in their ortho or peri positions according to conditions (see Table 1 in Section LA). 1,4-Dimethoxynaphthalene, for example, perilithi-ates cleanly with f-BuLi (Scheme 67) ... 

The predominant lithiation at 3-position in 2-methoxynaphthalene may be due to steric factors. When one compares the two transition states corresponding to lithiation at 1-position and at 3-position, one may note that the alkyl group of the lithiating agent is hindered by the peri-H in 63, while no such hindrance is present in 64. 

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