Oxidation of styrene with permanganate
In the heterogenous permanganate oxidation of styrene, that is when the reaction is performed in dichloromethane with potassium permanganate on a solid support (such as aluminium oxide), the reaction stops at the stage of the aldehyde. 

The method was published in Synthesis 2001, 11, 1645-1648 and the authors report a yield of 90% for the oxidation of styrene to benzaldehyde.