Spurs are renowned for their last-minute forays into the transfer market. Last season they snapped up Scott Parker on deadline day and the year before they made a sensational swoop for Rafael van der Vaart.
Moutinho was expected to be the focus of their attention on deadline day tomorrow, but Tottenham appear unlikely to sign the 25-year-old due to a 40million euro (?31.7million) release clause in his contract.
"It's an impossible deal for the club," Villas-Boas told a press conference.
"You have to bear in mind that this is a player with a 40million euro release clause.
"This volume of money is out of Tottenham's possibility.
"Bearing in mind that this is a key player for club and country, you wouldn't say that you would get him at half the price and half the price is already bigger than Tottenham's record fee."
The Portuguese, who has added Jan Vertonghen, Gylfi Sigurdsson, Mousa Dembele and Emmanuel Adebayor this summer, also appears pessimistic about his chances of signing Brazil forward Willian from Shakhtar Donetsk for the same reason.
"We had initial contact with Shakhtar, (who) again (are) a club in a position with wealthy owners, (and are) not easy to deal with," Villas-Boas added.
"We can't say that it's over but we have approached the club and at the moment it's a deal that doesn't seem to be happening."
A last-minute bid for both players tomorrow cannot be ruled out given Daniel Levy's history of 11th-hour deals, but it is unclear whether Porto or Shakhtar will be willing to drop their asking price for the respective players.
What did become clear today is that Jermain Defoe is certain to stay at White Hart Lane.
Defoe has been linked with a number of clubs after Spurs chased a host of international strikers, but Villas-Boas has persuaded the 29-year-old that he is an integral part of his plans this term.
The former West Ham man, currently in his second spell at the north London club, has signed a new three-year deal.
Of the players who could leave Spurs tomorrow, Van der Vaart is the most high-profile.
Hamburg have bid around ?8million for Van der Vaart but Villas-Boas has told the German club they must up their bid significantly if they are to re-sign a player they sold to Real Madrid in 2008.
"We have had interest from Hamburg, but an offer of that dimension is not something the player deserves," Villas-Boas said.
"Tottenham should be respected as a club. (The transfer) doesn't seem to be happening."
Villas-Boas confirmed his interest in signing Lyon goalkeeper Hugo Lloris, with whom the Londoners have been in contact regularly for the last week or so.
"We are very comfortable with our goalkeepers, (but) we can take into account that there is a future that we have to prepare for," said the Spurs boss, whose current first choice, Brad Friedel, is 41.
"In that sense we have studied possibilities in that position as well and throughout the goalkeepers available, Hugo is one of the best."
Villas-Boas' plans for the season were dealt a major blow today when Younes Kaboul was ruled out for between three and four months after undergoing knee surgery.
The France defender excelled for the Londoners last term and was seen as Villas-Boas' first-choice centre-back - a stance which seemingly left Michael Dawson with no future at Spurs.
The club captain held talks with QPR but decided against moving to the west London outfit, but they may rekindle their interest tomorrow.
Kaboul's injury may mean the England centre-back remains at White Hart Lane even though Villas-Boas confirmed that he already knew Kaboul could be sidelined for some time when he told Dawson he was free to talk to QPR.
When asked whether he would consider a bid for Dawson, Villas-Boas replied: "I don't think so.
"We have known about this possibility (that Kaboul would be ruled out) for quite some time. It was even in the discussions I had with Michael.
"At the moment that leaves us with four (fit) central defenders, so we are happy with the situation as it stands.
"It is a massive blow to lose Younes."
