Argentine Primera Division leaders River defeated top-flight rivals Estudiantes 3-2 at the Estadio Monumental Antonio Vespucio Liberti.
River's second-leg win on home soil was enough to claim a 5-3 victory on aggregate.
Colombia international Teofilo Gutierrez opened the scoring for River - who boasted a 2-1 first-leg advantage - in the first minute, springing the offside trap and placing the ball underneath Estudiantes goalkeeper Hilario Navarro.
That sparked Estudiantes into action, with the visitors netting two unanswered goals by the 51-minute mark.
Uruguayan Diego Vera levelled proceedings on the night with a diving header three minutes before half-time and Guido Carrillo put Estudiantes ahead courtesy of a powerful penalty.
Estudiantes' lead lasted just 10 minutes as Uruguayan striker Rodrigo Mora headed home a corner at the near post.
And River defender Ramiro Funes Mori completed the comeback two minutes later, directing a low header beyond Navarro to set up a mouth-watering Superclasico against Boca.
Boca did not have it as tough, routing Paraguayan outfit Cerro Porteno 4-1 on the road.
Andres Chavez scored twice as Boca won 5-1 over two legs in the second-tier South American club competition.
Boca - Copa Sudamericana's most successful team with two trophies - hit the front via Jonathan Calleri, who side-footed into an empty net after 10 minutes.
Former Spain international Daniel Guiza poked home the equaliser 18 minutes later as Cerro Porteno went into the break on level terms.
But it was one-way traffic in the second half as Cerro Porteno pressed forward in search of goals.
Chavez put River 2-1 ahead in the 67th minute, capping a swift counter-attacking move, before substitute Emmanuel Gigliotti got in on the action seven minutes later.
And Chavez bagged his second of the match four minutes from time, making a darting run from the halfway line and curling the ball past goalkeeper Diego Barreto.
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