Zinc/Sulfuric Acid can also be used for the reduction of sulfonyl chlorides to thiophenols:
The following reaction is also a very vigorous one and must be performed in a well ventilated place. To a solution of 400 mL 25% H2SO4 (V/V) in a beaker at least 2 L in size, there was added 54 g of 2,5-dimethoxybenzenesulfonyl chloride, and the mixture was heated on a steam bath. The yellow crystals of the acid chloride floated on the surface of the aqueous layer. There should be 80 g of zinc dust at hand. A small amount of Zn dust was placed at one spot on the surface of this chapeau. With occasional stirring with a glass rod, the temperature was allowed to rise. At about 60 or 70 °C an exothermic reaction took place at the spot where the zinc was placed. Additional dollups of zinc were added, and each small exothermic reaction site was spread about with the glass stirring rod. Finally, the reaction spread to the entire solid surface layer, with a melting of the acid chloride and an apparent boiling at the H2O surface. The remainder of the 80 g of zinc dust was added as fast as the size of the reaction container would allow. After things subsided again, the heating was continued for 1 h on the steam bath. After the reaction mixture had cooled to room temperature, it was filtered through paper in a Buchner funnel, and the residual metal washed with 100 mL CH2Cl2. The two-phase filtrate was separated, and the lower, aqueous phase was extracted with 2x75 mL CH2Cl2. The addition of 2 L H2O to the aqueous phase now made it the upper phase in extraction, and this was again extracted with 2x75 mL CH2Cl2. The organic extracts were pooled (H2O washing is more trouble than it is worth) and the solvent removed under vacuum. The light amber residue (30.0 g) was distilled at 70-80 °C at 0.3 mm/Hg to yield 25.3 g 2,5-dimethoxythiophenol as a white oil.
Ref: Pihkal #40, http://www.erowid.org/library/books_online/pihkal/pihkal040.shtml (http://www.erowid.org/library/books_online/pihkal/pihkal040.shtml)