No financial details of the deal were disclosed.
"Dynamo's management express their gratitude to William for their joint work and wish him success at his new club," read a statement on Dynamo's official website.
Vainqueur, who previously played with Nantes in France and Standard Liege in Belgium before joining Dynamo in July, 2014, scored three goals in 42 matches for the Moscow club.
Dynamo finished fourth in the Russian Premier League last season, but in June the team were banned from participating in next season's Europa League for breaking UEFA's Financial Fair Play rules.
The verdict of the European football ruling body UEFA has caused an exodus of foreign footballers from the club.
Earlier this month French international midfielder Mathieu Valbuena left Dynamo for Lyon, while Dutch defender Douglas Franco Teixeira joined Turkish top flight side Besiktas.
Hungarian international Balasz Dzsudzsak has also left Dynamo for Turkish club Bursaspor.
Borini set for Sunderland transfer
Sunderland are poised to sign Fabio Borini from Liverpool with the Italian striker believed to be heading to the northeast for a medical to clear the way for a four-year deal.
If the deal, reported to be worth around £7million ($10.8million, 9.6million euros), goes through, it would end a dogged pursuit of a man who played a key role in Sunderland's remarkable escape from Premier League relegation at the end of the 2013/14 season when he was sent out on loan.
The Black Cats' former head coach Gus Poyet had wanted to sign Borini on a full-time contract last summer, but was unable to persuade him turn his back on his ambitions at Anfield.
However, he has been unable to force his way into Brendan Rodgers' plans, making just 18 appearances last season, and has been linked with a series of clubs this summer, several of them in his native Italy.
There had been speculation that Watford could tempt Borini to Vicarage Road, but Sunderland, who collected their second league point of a testing start to the new season in a 2-2 draw at Aston Villa on Saturday, hope to beat them to the punch with a lucrative deal.
Borini's capture would further appease Poyet's successor Dick Advocaat, who has spent recent weeks urging owner Ellis Short and sporting director Lee Congerton to deliver the five or six "quality" summer signings he believes are vital if the club is to avoid yet another scrap for top-flight survival.
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