The Portuguese champions said in a statement Tuesday that Villas-Boas informed the club he is triggering the ¤15 million release clause to terminate his contract, which ends immediately.
Media in England and Portugal has widely reported that Villas-Boas is poised to join Chelsea on a three-year contract. At 33, he would be the youngest ever manager in the Premier League.
Porto said the club will sever the contract once a club pays the fee in the release clause.
"FC Porto ... was today notified of the intention of its coach, Andre Villas Boas, to terminate, without just cause, his contract with this company, using the release clause, with immediate effect," the Porto statement read.
Chelsea only reiterated what it said on Monday, that the club hopes to make an announcement "in the next few days." The Premier League club has been without a manager since Carlo Ancelotti was fired minutes after Chelsea's final match of last season, and had been heavily linked with current Turkey coach Guus Hiddink.
Villas-Boas is a former assistant of Mourinho at Chelsea and is regularly compared to the current Real Madrid coach.
He has been dubbed by many as the "Mini-Mourinho." Those comparisons were reinforced last month when Villas-Boas emulated his mentor by winning the Europa League, the second-tier European competition which Mourinho won with Porto in 2003 when it was called the UEFA Cup.
Villas-Boas became the youngest coach to win a UEFA club competition when Porto's unbeaten season ended with a 1-0 victory in Dublin over Portuguese rival Braga.
When Mourinho moved from Porto to Chelsea in 2004, he won back-to-back Premier League titles but failed to land the Champions League _ the trophy Chelsea owner Roman Abramovich craves the most.
Villas-Boas was a scout for Mourinho at Chelsea and followed him in 2008 to Inter Milan. A fluent English speaker, he was just a teenager when he started working with Bobby Robson during the former England manager's spell at Porto. At 21, Villas-Boas coached the British Virgin Isles.