The Argentine finished second on the stage just 42 seconds behind his brother Marcos and he leads his sibling by a huge 1.19:18.
Thomas Maffei was a distant third in the stage – 13:54 back and he is now nearly two and half hours behind Alejandro in the overall standings.
"This really hasn't been an easy Dakar," said Alejandro Patronelli after the stage.
"It's even been a very hard Dakar. Normally, the last days are easier. The finishes in Argentina were simpler.
"Here, there are dunes and it's very hot. It was complicated, but we've not got long to go now and we're nearly there.
"What I mean to say that at the end of the Dakar in Argentina, the last two stages were a lot more relaxed. You could focus your mind on just finishing."