Spain's Sanchez turned in a time of 4 hours, 50 minutes and 29 seconds on the 119-mile stretch from Limoux to Foix, 47 seconds better than a pack of four riders including Slovakia's Peter Sagan.
Britain's Wiggins, meanwhile, beat out defending champion Cadel Evans of Australia by one spot during the stage.
Evans sustained a punctured tire during the final climb up the Category 1 Mur de Peguere amid reports of tacks being scattered across the route in an attempted sabotage.
Wiggins finished the day with a 2:05 lead over fellow Briton Christopher Froome while Italy's Vincenzo Nibali was third, 2:23 behind, and Evans was in fourth overall, 3:19 behind Wiggins.
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