2. BCl3, works for meta-carbonyl benzyl methyl ether.
other ether can also be removed.
4. Et3SiH/(C6F5)3B then TBAF
very gentle condition.
5.HBr 48% solution, tributylhexdecylphosphonium bromide.
6. HBr, AcOH
conclusion: halide is essential. an oxygen-philic element is also important( usually an element with empty atomic orbitals).
7. LiCl/DMF/ heat