PMGB

Case 1: using aluminium chloride and ethanethiol 

To a solution of the aromatic methyl ether (0.02 mol) in 40 mL dichloromethane and 40 mL ethanethiol cooled in a ice-salt bath was added aluminum chloride (0.06 mol) portion wise (Caution-exothermic). The resulting mixture was stirred at room temperature for two days (48 h). The reaction mixture was diluted with 250 mL of dichloromethane and washed with 250 mL saturated NaHCO₃ solution, dried (Na₂SO₄) and evaporated under reduced pressure to give the corresponding phenol which was purified by silica gel column chromatography using a gradient of hexane and ethylacetate (colorless oil, 98% yield).

Reference:

1. Node, M.; Nishide, K.; Fuji, K.; Fujita, E. J. Org. Chem. 1980, 45, 4275-4277.

2. US Patent 2006/0052463 A1 (AlCl3 as O-demethylating agent)

3. http://lego.chemistry.tripod.com/various/demethylation.html

Note: 2-(Diethylamino)ethanethiol has been used for the odorless deprotection of aromatic methyl ethers. Magano, J.; Chen, M. H.; Clark, J. D.; Nussbaumer, T. J. Org. Chem. 2006, 71, 7103-7105.

Case 2: using sodium ethanethiolate (suitable for pyridines)

To a solution of the aromatic methyl ether (0.006 mol) in 10 mL DMF in a sealed tube at room temperature was added sodium ethanethiolate (0.03 mol). The resulting mixture was heated at 50 ^oC for 2 h. The reaction mixture was diluted with 100 mL water, and the pH was adjusted to 7 by adding 8 mL of saturated aqueous citric acid solution. Solid NaCl was added to the above solution until saturation and then extracted with dichloromethane (3 × 250 mL). The combined organic layers was evaporated, the residual oil was triturated with ether to give the corresponding phenol (white solid, 46% yield).

Reference:

1. Li, A. et. al. Tetrahedron 2003, 59, 5737-5741.

2. Lal, K. et. al. J. Org. Chem. 1987, 52, 1072-1078.

Note: We observed cleavage of aromatic-S-alkyl linkage in the substrate to aromatic-SH group while using EtSNa for O-demethylation.