Dundee United booked their ticket for Monday's Scottish Cup semi-final draw with a deserved 2-1 victory over Dundee at Dens Park.
The home side, 15 points adrift at the bottom of the SPL, could not recover from the concession of two soft first-half goals, despite Jim McAlister offering a brief glimmer of hope.
United took the lead when Brian McLean (11) was given the freedom of the penalty area to glance home a header from Barry Douglas's inswinging free-kick.
Dundee levelled as John Baird helped the ball into the path of McAlister (19), who drilled a low first-time strike into the corner from 15 yards.
The equaliser heralded the best spell of the match for the Dark Blues as Baird headed over before the home striker saw his low shot saved by the feet of Radoslaw Cierzniak.
United were promptly back in front as Stuart Armstrong teed up the lively Gary Mackay-Steven (35) with a shrewd pass and the midfielder did not have to break stride before drilling in a snap-shot from 18 yards.
Michael Gardyne worked Rab Douglas at his near post while Lewis Toshney's risible free-kick from 30 yards underlined the hosts' growing frustration.
A flurry of Dundee corners yielded nought until Davide Grassi made some space eight yards out but his header was tame.
Jon Daly was inches away from poking home a third goal for United, but it was not to matter, the final stages pockmarked only by a flurry of needless yellow cards.