Donoghue and Loe beat the British duo of Georgia Francis and Emily Carmichael by a four lengths, and will face the experienced Dutch combination of Marloes Oldenburg and Roos de Jong in tomorrow's final.
John Storey and Chris Harris took a classy win in the men's double sculls, setting them up for the final of the Double Sculls Challenge Cup.
The Olympian duo opened up a clear water advantage over the German lightweight crew of Konstantin Steinhuebel and Jonathan Rommelmann, and powered to a convincing win.
Storey and Harris will take on the French lightweight Olympic champions Pierre Houin and Jeremie Azou.
It was a sisterly duel in the semifinal of the women's pairs as Kerri Gowler lined up against younger sister Jackie.
The current world record holders Kerri and crewmate Grace Prendergast proved too strong for Jackie Gowler and Kirstyn Goodger, who are both racing their first elite season, winning with a clear water advantage.
Gowler and Prendergast will line up against Olympians Megan Kalmoe and Tracy Eisser of the USA in tomorrow's final.
The women's eight will contest the final of the Remenham Challenge Cup, after a superb win against the national crew from the Netherlands in today's semifinal.
The World Cup-winning eight pushed to an early lead and held their position the full length of the course to finish just over two lengths clear of the Dutch.
The final battle for the Cup will be between New Zealand and Leander/University of London.
The men's eight were forced out of contention for the Grand Challenge Cup, after coming up short against the German national crew.
Germany, who are the current world record-holders, snatched an early lead, but faced a sustained challenge from the New Zealand crew.
Cox Caleb Shepherd called an impressive race for New Zealand and the favoured German crew snatched victory by just three quarters of a length.
Hannah Osborne pushed Olympic silver medallist Vicki Thornley hard in the semifinal of the Princess Royal Challenge Cup for the women's single sculls.
Osborne, who is competing in her first year as an elite, held her own against the vastly experienced Thornley, pushing the pace down the course and finishing just over a length down on the British rower.