A convenient method for the synthesis of dialkyl ethers by alkylation of alcohols using phosphinimidates in the presence of a catalytic amount of trimethylsilyl triflate

An alkylation reaction of alcohols with alkyl N-(methylsulfonyl)diphenylphosphinimidates proceeded smoothly in the presence of a catalytic amount of trimethylsilyl triflate (Me3SiOTf) in DME at room temperature and the corresponding ethers were afforded in good to high yields. An alkyl N-(methylsulfonyl)diphenylphosphinimidate can be prepared easily from an alkyl diphenylphosphinite and methanesulfonyl azide, and is isolated without tedious operation. Moreover, it is easy to handle and can be stored for several months at room temperature because of its air- and moisture-resistant character. Also, one-pot tertiary alkylations of alcohols by using t-alkyl diphenylphosphinites and diphenoxyphosphoryl azide proceeded efficiently in the presence of a catalytic amount of Me3SiOTf in cyclohexane/CH2Cl2 at 0 degrees C or -10 degrees C, and gave the corresponding tertiary alkyl ethers in good yields. By following these methods, various ethers having alkali-sensitive functional groups can be prepared easily.