Abstract
Removal of methyl, benzyl, and methylene groups from alkyl aryl ethers is among the most popular deprotecting methods in organic synthesis. Alkali organoamides NaN(SiMe 3 ) 2 and LiN(i-Pr) 2 , often used as organic bases, have been developed as efficient deprotecting agents. Treatment of aryl methyl ethers with 1.5 equiv of NaN(SiMe 3 ) 2 or LiN(i-Pr) 2 in THF and 1,3-dimethyl-2-imidazolidinone in a sealed tube at 185 °C produced the corresponding phenol derivatives in good to excellent yields (80-97%). Removal of the methylene unit from benzodioxole derivatives was also accomplished by use of 2.5 equiv of these alkali organoamides. The corresponding catechols were obtained in 93-99% yields. The activity of NaN(SiMe 3 ) 2 was proven lower than that of LiN(i-Pr) 2 ; it is due to the steric congestion and the α-stabilizing effect of the silyl groups. Thus selective mono-O-demethylation of o-dimethoxybenzenes can be achieved by the use of NaN(SiMe 3 ) 2 but not LiN(i-Pr) 2 . O-Debenzylation of aryl benzyl ethers, however, can be accomplished by the use of LiN(i-Pr) 2 .