Reactions at Methoxyl Groups

Pyrogallol trimethyl ether was selectively demethylated in dichloromethane 

By contrast, 2,3,4-tris(2-ethylhexyloxy)benzaldehyde in 1,2-dichloroethane was monodealkylated selectively at the 2-position by the dropwise addition over 30 mins, of titanium tetrachloride at 8-12°C with continued stirring for a further 30 mins, and then at ambient temperature for 2 hours prior to quenching with dilute hydrochloric acid to afford 2-hydroxy-3,4-bis(2-ethylhexyloxy)benzaldehyde in 73% yield (ref.24). 

4- dihydroxy-4, 5-dimethoxystilbene by refluxing for 6.5 hours in benzene containing lithium aluminium hydride (ref.25). 

2-Hydroxy-3,4-dimethoxyacetophenone with benzaldehyde (1.5 moles) in ethanol containing 30% aqueous potassium hydroxide and a catalytic quantity of benzyltrimethylammonium chloride, the inclusion of which was essential, after being stirred at 30°C for 24 hours was cooled to 0°C and gassed with sulphur dioxide to give a 93% yield of benzylidene 2-hydroxy-3,4-dimethoxyacetophenone (ref.26). 

By treatment of structures such as the above with oxidising agents 

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