The Steelmen got the ascendency early in the quarter-final replay after the meeting at Tannadice earlier this month ended 2-2 with a goal from Jamie Murphy inside the opening ten minutes.
The 21-year old midfielder received a neat flick-on from John Sutton after Darren Randolph’s long goalkick and hammered home a bouncing ball from about 18 yards to get things started.
Motherwell where then further ahead just after the half-hour mark when Chris Humphrey finished a good move with a volley from 10 yards before Francis Jeffers scored his second goal for his new club in the 63rd minute in sensational style. The former Everton and Arsenal starlet used some trickery on a defender 25 yards out before advancing and then smashing home into the corner to wrap up proceedings.
The ‘Well will now meet St Johnstone in the final four at Hampden Park on April 16, knocking out the defending cup winners in the process.